Fix some more warnings

[taylor/freespace2.git] / src / ship / aicode.cpp

/*
 * Copyright (C) Volition, Inc. 1999.  All rights reserved.
 *
 * All source code herein is the property of Volition, Inc. You may not sell 
 * or otherwise commercially exploit the source or things you created based on
 * the source.
 */

/*
 * $Logfile: /Freespace2/code/Ship/AiCode.cpp $
 * $Revision$
 * $Date$
 * $Author$
 * 
 * AI code that does interesting stuff
 *
 * $Log$
 * Revision 1.6  2002/07/13 19:47:02  theoddone33
 * Fix some more warnings
 *
 * Change demo building, edit Makefile if you want the demo.
 *
 * Revision 1.5  2002/06/17 06:33:10  relnev
 * ryan's struct patch for gcc 2.95
 *
 * Revision 1.4  2002/06/09 04:41:26  relnev
 * added copyright header
 *
 * Revision 1.3  2002/06/01 07:12:34  relnev
 * a few NDEBUG updates.
 *
 * removed a few warnings.
 *
 * Revision 1.2  2002/05/03 13:34:33  theoddone33
 * More stuff compiles
 *
 * Revision 1.1.1.1  2002/05/03 03:28:10  root
 * Initial import.
 *
 * 
 * 107   9/15/99 4:42a Mikek
 * Make any big ship attacking Colossus, or Colossus attacking any large
 * ship not use big cruiser movement code.
 * 
 * 106   9/15/99 3:28a Jimb
 * Make all big ships in sm3-08 not do cruiser chase code when attacking
 * Colossus.  Added so Beast doesn't swerve away from Colossus.
 * 
 * 105   9/14/99 4:18p Andsager
 * hack for mission sm3-08 to abort cruiser_chase as sathanas is about to
 * begin circling colossus.
 * 
 * 104   9/08/99 10:44p Andsager
 * Make HUGE ships not die when warping out, after warp effect started.
 * 
 * 103   9/03/99 11:40p Mikek
 * Comment out an annoying nprintf().
 * 
 * 102   9/01/99 11:26p Dave
 * Fixed release build warnings.
 * 
 * 101   9/01/99 9:12p Mikek
 * Make it a boatload harder to become a traitor from hitting a large
 * ship.
 * 
 * 100   9/01/99 4:01p Andsager
 * Make sure BIG|HUGE ships do not respond to shockwaves
 * 
 * 99    9/01/99 10:09a Dave
 * Pirate bob.
 * 
 * 98    8/31/99 4:24p Andsager
 * Reduce collisions when attacking big ships.
 * 
 * 97    8/31/99 7:33a Mikek
 * Improvements in formation flying, less silly behavior, especially when
 * leader is moving very slowly.
 * 
 * 96    8/31/99 5:48a Mikek
 * Making ships not overshoot so much in formation flying.  Intermediate
 * checkin.
 * 
 * 95    8/30/99 12:03a Mikek
 * Make guard behavior much less annoying.  Guarders don't get quite so
 * close and they try to avoid striking the target they are guarding.
 * 
 * 94    8/29/99 4:18p Andsager
 * New "burst" limit for friendly damage.  Also credit more damage done
 * against large friendly ships.
 * 
 * 93    8/28/99 7:29p Dave
 * Fixed wingmen persona messaging. Make sure locked turrets don't count
 * towards the # attacking a player.
 * 
 * 92    8/26/99 10:46p Andsager
 * Apply shockwave damage to lethality.
 * 
 * 91    8/26/99 8:52p Dave
 * Gave multiplayer TvT messaging a heavy dose of sanity. Cheat codes.
 * 
 * 90    8/26/99 5:14p Andsager
 * 
 * 89    8/24/99 8:55p Dave
 * Make sure nondimming pixels work properly in tech menu.
 * 
 * 88    8/23/99 6:21p Jefff
 * added "no traitor" option to missions (and fred)
 * 
 * 87    8/20/99 3:36p Andsager
 * Make sure we don;t miss stealth sweep points.
 * 
 * 86    8/16/99 8:21a Andsager
 * fix link error
 * 
 * 85    8/16/99 8:19a Andsager
 * Add project_point_onto_bbox() to fvi and include in aicode
 * 
 * 84    8/15/99 1:30p Dave
 * Removed some bounding box code because of link errors. Assuming needed
 * function just needs to get checked in by DaveA.
 * 
 * 83    8/15/99 11:59a Andsager
 * For targing big/huge ships, find nearest distance to bbox, not center.
 * 
 * 82    8/13/99 2:20p Andsager
 * Add speed modification to chances turret will find stealth ship
 * 
 * 81    8/13/99 10:49a Andsager
 * Knossos and HUGE ship warp out.  HUGE ship warp in.  Stealth search
 * modes dont collide big ships.
 * 
 * 80    8/10/99 5:02p Andsager
 * Fix bug where AI gets stuck in SM_EVADE_WEAPON with no target.
 * 
 * 79    8/10/99 11:58a Andsager
 * Allow turrets to sometimes see stealth.
 * 
 * 78    7/31/99 2:57p Dave
 * Scaled flak aim and jitter by weapon subsystem strength.
 * 
 * 77    7/27/99 10:33p Andsager
 * improve ai for attacking stealth.  reduced jitter in aim.  reduced
 * error in position when avoiding.  skill level support for attacking
 * stealth.  Made target error same for team vs. team.
 * 
 * 76    7/27/99 10:49a Andsager
 * Make turret fire rate independent of team for HUGE turrets, and also
 * for mult team vs. team.
 * 
 * 75    7/26/99 12:14p Andsager
 * Apply cap to how much slower a transport flies with cargo.  Remove
 * limit on waypoint speed for training.  Enemy ai get stealth exact pos
 * when stealth fires
 * 
 * 74    7/20/99 1:49p Dave
 * Peter Drake build. Fixed some release build warnings.
 * 
 * 73    7/19/99 2:13p Dave
 * Added some new strings for Heiko.
 * 
 * 72    7/19/99 12:02p Andsager
 * Allow AWACS on any ship subsystem. Fix sexp_set_subsystem_strength to
 * only blow up subsystem if its strength is > 0
 * 
 * 71    7/15/99 9:20a Andsager
 * FS2_DEMO initial checkin
 * 
 * 70    7/14/99 1:44p Andsager
 * modify ai_guard for BIG ships to circle around the long axis
 * 
 * 69    7/09/99 5:54p Dave
 * Seperated cruiser types into individual types. Added tons of new
 * briefing icons. Campaign screen.
 * 
 * 68    7/08/99 4:32p Andsager
 * fix bug with turret-tagged-only
 * 
 * 67    7/08/99 12:06p Andsager
 * Add turret-tagged-only and turret-tagged-clear sexp.
 * 
 * 66    7/02/99 3:49p Andsager
 * Remove debug code.  Allow targeting of stealth from any weapon it
 * fires.
 * 
 * 65    7/02/99 2:01p Andsager
 * Fix bug where big ship tries to evade dumpfire weapon.
 * 
 * 64    7/02/99 10:58a Andsager
 * Put in big ship - big ship attack mode.  Modify stealth sweep ai.
 * 
 * 63    6/30/99 5:53p Dave
 * Put in new anti-camper code.
 * 
 * 62    6/28/99 3:22p Anoop
 * Fix turret optimization, where ship may not have any valid subsystems
 * (all blown off).
 * 
 * 61    6/25/99 5:56p Andsager
 * First real pass on stealth ai.
 * 
 * 60    6/25/99 3:08p Dave
 * Multiple flyby sounds.
 * 
 * 59    6/25/99 1:12p Danw
 * DKA:  Make sure big ship has subsystems before trying to target them.
 * 
 * 58    6/25/99 10:56a Johnson
 * Fixed dumb ai code.
 * 
 * 57    6/24/99 5:15p Dave
 * Make sure stride is always at least one for checking turret subsystem
 * targets.
 * 
 * 56    6/24/99 4:59p Dave
 * Significant speedups to turret firing.
 * 
 * 55    6/23/99 5:51p Andsager
 * Add waypoint-cap-speed.  Checkin stealth ai - inactive.
 * 
 * 54    6/16/99 10:21a Dave
 * Added send-message-list sexpression.
 * 
 * 53    6/15/99 9:25a Andsager
 * Make guard and dynamic chase (who hit you) work with stealth
 * 
 * 52    6/14/99 3:21p Andsager
 * Allow collisions between ship and its debris.  Fix up collision pairs
 * when large ship is warping out.
 * 
 * 51    6/14/99 10:45a Dave
 * Made beam weapons specify accuracy by skill level in the weapons.tbl
 * 
 * 50    6/03/99 8:11a Andsager
 * 
 * 49    6/02/99 5:41p Andsager
 * Reduce range of secondary weapons not fired from turrets in nebula.
 * Reduce range of beams fired from turrrets in nebula
 * 
 * 48    6/02/99 3:23p Andsager
 * Make AI aware of team visibility.  Allow player targeting with team
 * visibility info.  Make stealth ships not targetable by AI in nebula
 * unless tagged.
 * 
 * 47    6/02/99 12:52p Andsager
 * Added team-wide ship visibility.  Implemented for player.
 * 
 * 46    6/01/99 8:35p Dave
 * Finished lockarm weapons. Added proper supercap weapons/damage. Added
 * awacs-set-radius sexpression.
 * 
 * 45    5/28/99 5:35p Andsager
 * Make ai nebula aware
 * 
 * 44    5/24/99 9:55a Dave
 * Fixed stream weapon ai firing problem. ick.
 * 
 * 43    5/20/99 7:00p Dave
 * Added alternate type names for ships. Changed swarm missile table
 * entries.
 * 
 * 42    5/18/99 1:30p Dave
 * Added muzzle flash table stuff.
 * 
 * 41    5/12/99 2:55p Andsager
 * Implemented level 2 tag as priority in turret object selection
 * 
 * 40    5/12/99 10:42a Andsager
 * Fix turret bug allowing HUGE turrets to fire at fighters
 * 
 * 39    5/06/99 11:46a Andsager
 * Bug fixes.  Don't get into illegal strafe submode.  Don't choose turret
 * enemy objnum for beam protected.
 * 
 * 38    5/03/99 10:50p Andsager
 * Make Asteroid_obj_list.  Change get_nearest_turret_objnum() to use
 * Asteroid_obj_list, Ship_obj_list and Missile_obj_list vs.
 * obj_used_list.
 * 
 * 37    4/29/99 2:29p Dave
 * Made flak work much better in multiplayer.
 * 
 * 36    4/28/99 11:36p Dave
 * Tweaked up subspace missile strike a bit,
 * 
 * 35    4/28/99 3:11p Andsager
 * Stagger turret weapon fire times.  Make turrets smarter when target is
 * protected or beam protected.  Add weaopn range to weapon info struct.
 * 
 * 34    4/26/99 10:58a Andsager
 * Add OF_BEAM_PROTECTED flag to keep object from being targeted for zing.
 * 
 * 33    4/23/99 12:12p Andsager
 * Modify wing positions when player is wing leader to prevent some
 * collisions.
 * 
 * 32    4/23/99 12:01p Johnson
 * Added SIF_HUGE_SHIP
 * 
 * 31    4/22/99 11:06p Dave
 * Final pass at beam weapons. Solidified a lot of stuff. All that remains
 * now is to tweak and fix bugs as they come up. No new beam weapon
 * features.
 * 
 * 30    4/20/99 6:39p Dave
 * Almost done with artillery targeting. Added support for downloading
 * images on the PXO screen.
 * 
 * 29    4/20/99 3:40p Andsager
 * Changes to big ship ai.  Uses bounding box as limit where to fly to
 * when flying away.
 * 
 * 28    4/16/99 5:54p Dave
 * Support for on/off style "stream" weapons. Real early support for
 * target-painting lasers.
 * 
 * 27    4/02/99 9:55a Dave
 * Added a few more options in the weapons.tbl for beam weapons. Attempt
 * at putting "pain" packets into multiplayer.
 * 
 * 26    3/28/99 5:58p Dave
 * Added early demo code. Make objects move. Nice and framerate
 * independant, but not much else. Don't use yet unless you're me :)
 * 
 * 25    3/19/99 9:51a Dave
 * Checkin to repair massive source safe crash. Also added support for
 * pof-style nebulae, and some new weapons code.
 * 
 * 24    3/08/99 7:03p Dave
 * First run of new object update system. Looks very promising.
 * 
 * 23    3/05/99 3:55p Anoop
 * Handle some asserts properly.
 * 
 * 22    3/04/99 6:09p Dave
 * Added in sexpressions for firing beams and checking for if a ship is
 * tagged.
 * 
 * 21    3/02/99 9:25p Dave
 * Added a bunch of model rendering debug code. Started work on fixing
 * beam weapon wacky firing.
 * 
 * 20    2/25/99 2:32p Anoop
 * (Alan). Fixed ai path following code for AI_BAY_EMERGE. Put in sanity
 * check so that when the last point on the path is reached, it finishes.
 * 
 * 19    2/19/99 2:11p Anoop
 * Put in some nice handling code for wacky support ship problems (like no
 * docking paths)
 * 
 * 18    2/17/99 2:11p Dave
 * First full run of squad war. All freespace and tracker side stuff
 * works.
 * 
 * 17    2/11/99 5:22p Andsager
 * Fixed bugs, generalized block Sexp_variables
 * 
 * 16    1/29/99 5:07p Dave
 * Fixed multiplayer stuff. Put in multiplayer support for rapid fire
 * missiles.
 * 
 * 15    1/29/99 2:25p Andsager
 * Added turret_swarm_missiles
 * 
 * 14    1/27/99 9:56a Dave
 * Temporary checkin of beam weapons for Dan to make cool sounds.
 * 
 * 13    1/24/99 11:37p Dave
 * First full rev of beam weapons. Very customizable. Removed some bogus
 * Int3()'s in low level net code.
 * 
 * 12    1/21/99 10:44a Dave
 * More beam weapon stuff. Put in warmdown time.
 * 
 * 11    1/12/99 5:45p Dave
 * Moved weapon pipeline in multiplayer to almost exclusively client side.
 * Very good results. Bandwidth goes down, playability goes up for crappy
 * connections. Fixed object update problem for ship subsystems.
 * 
 * 10    1/08/99 2:08p Dave
 * Fixed software rendering for pofview. Super early support for AWACS and
 * beam weapons.
 * 
 * 9     12/23/98 2:53p Andsager
 * Added ship activation and gas collection subsystems, removed bridge
 * 
 * 8     11/12/98 12:13a Dave
 * Tidied code up for multiplayer test. Put in network support for flak
 * guns.
 * 
 * 7     11/05/98 5:55p Dave
 * Big pass at reducing #includes
 * 
 * 6     10/26/98 9:42a Dave
 * Early flak gun support.
 * 
 * 5     10/23/98 3:51p Dave
 * Full support for tstrings.tbl and foreign languages. All that remains
 * is to make it active in Fred.
 * 
 * 4     10/20/98 1:39p Andsager
 * Make so sparks follow animated ship submodels.  Modify
 * ship_weapon_do_hit_stuff() and ship_apply_local_damage() to add
 * submodel_num.  Add submodel_num to multiplayer hit packet.
 * 
 * 3     10/13/98 9:29a Dave
 * Started neatening up freespace.h. Many variables renamed and
 * reorganized. Added AlphaColors.[h,cpp]
 * 
 * 2     10/07/98 10:53a Dave
 * Initial checkin.
 * 
 * 1     10/07/98 10:51a Dave
 * 
 * 
 * $NoKeywords: $
 */

// This module contains the actual AI code that does interesting stuff
// to objects.   The code in Ai.cpp is just for bookeeping, allocating
// ai slots and linking them to ships.

#include "pstypes.h"
#include "fix.h"
#include "linklist.h"
#include "object.h"
#include "physics.h"
#include "vecmat.h"
#include "ship.h"
#include "model.h"
#include "2d.h"
#include "3d.h"
#include "ai.h"
#include "floating.h"
#include "player.h"
#include "freespace.h"
#include "weapon.h"
#include "missiongoals.h"
#include "missionlog.h"
#include "timer.h"
#include "sound.h"
#include "aigoals.h"
#include "gamesnd.h"
#include "hudmessage.h"
#include "missionmessage.h"
#include "cmeasure.h"
#include "staticrand.h"
#include "multimsgs.h"
#include "afterburner.h"
#include "hudets.h"
#include "shipfx.h"
#include "shiphit.h"
#include "aibig.h"
#include "multiutil.h"
#include "hud.h"
#include "objcollide.h"
#include "asteroid.h"
#include "hudlock.h"
#include "missiontraining.h"
#include "gamesequence.h"
#include "joy_ff.h"
#include "localize.h"
#include "flak.h"
#include "beam.h"
#include "multi.h"
#include "swarm.h"
#include "multi_team.h"
#include "awacs.h"
#include "fvi.h"

#ifndef PLAT_UNIX
#pragma optimize("", off)
#pragma auto_inline(off)
#endif

#define UNINITIALIZED_VALUE     -99999.9f

#define INSTRUCTOR_SHIP_NAME NOX("instructor")

#define AICODE_SMALL_MAGNITUDE  0.001f          // cosider a vector NULL if mag is less than this

#define NEXT_REARM_TIMESTAMP (60*1000)                  //      Ships will re-request rearm, typically, after this long.

#define BEAM_NEBULA_RANGE_REDUCE_FACTOR         0.8

// AIM_CHASE submode defines
// SM_STEALTH_FIND
#define SM_SF_AHEAD             0
#define SM_SF_BEHIND    1
#define SM_SF_BAIL              2

// SM_STEALTH_SWEEP
#define SM_SS_SET_GOAL  -1
#define SM_SS_BOX0              0
#define SM_SS_LR                        1
#define SM_SS_UL                        2
#define SM_SS_BOX1              3
#define SM_SS_UR                        4
#define SM_SS_LL                        5
#define SM_SS_BOX2              6
#define SM_SS_DONE              7

//XSTR:OFF

char *Mode_text[MAX_AI_BEHAVIORS] = {
        "CHASE",
        "EVADE",
        "GET_BEHIND",
        "CHASE_LONG",
        "SQUIGGLE",
        "GUARD",
        "AVOID",
        "WAYPOINTS",
        "DOCK",
        "NONE",
        "BIGSHIP",
        "PATH",
        "BE_REARMED",
        "SAFETY",
        "EV_WEAPON",
        "STRAFE",
        "PLAY_DEAD",
        "BAY_EMERGE",
        "BAY_DEPART",
        "SENTRYGUN",
        "WARP_OUT",
};

//      Submode text is only valid for CHASE mode.
char *Submode_text[] = {
"undefined",
"CONT_TURN",
"ATTACK   ",
"E_SQUIG  ",
"E_BRAKE  ",
"EVADE    ",
"SUP_ATTAK",
"AVOID    ",
"BEHIND   ",
"GET_AWAY ",
"E_WEAPON ",
"FLY_AWAY ",
"ATK_4EVER",
"STLTH_FND",
"STLTH_SWP",
"BIG_APPR",
"BIG_CIRC",
"BIG_PARL"
};

char *Strafe_submode_text[5] = {
"ATTACK",
"AVOID",
"RETREAT1",
"RETREAT2",
"POSITION"
};
//XSTR:ON

/*
//      Used for global ignore of objects.  If an object appears in the Ignore_objects array,
//      no one will attack it.
#define MAX_IGNORE_OBJECTS      16
typedef struct {
        int     objnum;
        int     signature;
} ignore_object;

ignore_object   Ignore_objects[MAX_IGNORE_OBJECTS];
*/

typedef struct eval_enemy_obj_struct {
        int                     turret_parent_objnum;                   // parent of turret
        float                   weapon_travel_dist;                             // max targeting range of turret weapon
        int                     enemy_team_mask;
        int                     weapon_system_ok;                                       // is the weapon subsystem of turret ship ok
        int                     big_only_flag;                                          // turret fires only at big and huge ships
        vector          *tpos;
        vector          *tvec;
        ship_subsys *turret_subsys;
        int                     current_enemy;


        float                   nearest_attacker_dist;                  // nearest ship 
        int                     nearest_attacker_objnum;

        float                   nearest_homing_bomb_dist;               // nearest homing bomb
        int                     nearest_homing_bomb_objnum;

        float                   nearest_bomb_dist;                              // nearest non-homing bomb
        int                     nearest_bomb_objnum;

        float                   nearest_dist;                                           // nearest ship attacking this turret
        int                     nearest_objnum;
}       eval_enemy_obj_struct;


control_info    AI_ci;

object *Pl_objp;
object *En_objp;

waypoint_list Waypoint_lists[MAX_WAYPOINT_LISTS];

// How close a turret has to be point at its target before it
// can fire.  If the dot of the gun normal and the vector from gun
// to target is greater than this, the turret fires.  The smaller
// the sloppier the shooting.
#define AICODE_TURRET_DUMBFIRE_ANGLE            (0.8f)  
#define AICODE_TURRET_HEATSEEK_ANGLE            (0.7f)  
#define AICODE_TURRET_MAX_TIME_IN_RANGE (5.0f)

#define REARM_SOUND_DELAY               (3*F1_0)                //      Amount of time to delay rearm/repair after mode start
#define REARM_BREAKOFF_DELAY    (3*F1_0)                //      Amount of time to wait after fully rearmed to breakoff.

#define MIN_DIST_TO_WAYPOINT_GOAL       5.0f
#define MAX_GUARD_DIST                                  250.0f
#define BIG_GUARD_RADIUS                                500.0f

#define MAX_EVADE_TIME                  (15 * 1000)     //      Max time to evade a weapon.

// defines for repair ship stuff.
#define MAX_REPAIR_SPEED                        25.0f
#define MAX_UNDOCK_ABORT_SPEED  2.0f

// defines for EMP effect stuff
#define MAX_EMP_INACCURACY              50.0f

// defines for stealth
#define MAX_STEALTH_INACCURACY  50.0f           // at max view dist
#define STEALTH_MAX_VIEW_DIST   400             // dist at which 1) stealth no longer visible 2) firing inaccuracy is greatest
#define STEALTH_VIEW_CONE_DOT   0.707           // (half angle of 45 degrees)


ai_class        Ai_classes[MAX_AI_CLASSES];
int     Ai_firing_enabled = 1;
int     Num_ai_classes;

int     AI_FrameCount = 0;
int     Ship_info_inited = 0;
int     AI_watch_object = 0; // Debugging, object to spew debug info for.
int     Num_waypoint_lists = 0;
int     Mission_all_attack = 0;                                 //      !0 means all teams attack all teams.

char *Skill_level_names(int level, int translate)
{
        char *str = NULL;

        #if NUM_SKILL_LEVELS != 5
        #error Number of skill levels is wrong!
        #endif

        if(translate){
                switch( level ) {
                case 0:
                        str = XSTR("Very Easy", 469);
                        break;
                case 1:
                        str = XSTR("Easy", 470);
                        break;
                case 2:
                        str = XSTR("Medium", 471);
                        break;
                case 3:
                        str = XSTR("Hard", 472);
                        break;
                case 4:
                        str = XSTR("Insane", 473);
                        break;
                default:        
                        Int3();
                }
        } else {
                switch( level ) {
                case 0:
                        str = NOX("Very Easy");
                        break;
                case 1:
                        str = NOX("Easy");
                        break;
                case 2:
                        str = NOX("Medium");
                        break;
                case 3:
                        str = NOX("Hard");
                        break;
                case 4:
                        str = NOX("Insane");
                        break;
                default:        
                        Int3();
                }
        }

        return str;
}

#define DELAY_TARGET_TIME       (12*1000)               //      time in milliseconds until a ship can target a new enemy after an order.

//      Make enemy ships turn more slowly at lower skill levels.
float   Turn_time_skill_level_scale[NUM_SKILL_LEVELS] = {3.0f, 2.2f, 1.6f, 1.3f, 1.0f};

//      Maximum number of simultaneous homing weapons on player based on skill level.
int     Max_allowed_player_homers[NUM_SKILL_LEVELS] = {2, 3, 4, 7, 99};

//      Number of ships that can attack another ship at a given skill level.
int     Skill_level_max_attackers[NUM_SKILL_LEVELS] = {2, 3, 4, 5, 99};

//      How long until next predict position.
fix Skill_level_delay[NUM_SKILL_LEVELS] = {2*F1_0, 3*F1_0/2, 4*F1_0/3, F1_0/2, 0};

//      AI ships link primary weapons if energy levels greater than the following amounts:
float   Link_energy_levels_always[NUM_SKILL_LEVELS] = {100.0f, 80.0f, 60.0f, 40.0f, 20.0f};     //      always link
float   Link_energy_levels_maybe[NUM_SKILL_LEVELS] = {90.0f, 60.0f, 40.0f, 20.0f, 10.0f};       //      link if hull strength low

//      Seconds to add to time it takes to get enemy in range.  Only for player's enemies.
float   In_range_time[NUM_SKILL_LEVELS] = {2.0f, 1.4f, 0.75f, 0.0f, -1.0f};

//      No matter what, a random unit vector gets scaled by this amount in firing at an enemy.
//      Note that for shorter in-range times, these values get scaled, so a value of 0.5f is meaningful.
float   Aiming_error[NUM_SKILL_LEVELS] = {3.0f, 2.2f, 1.3f, 0.7f, 0.2f};

//      Chance a countermeasure will be fired based on skill level.
float Cmeasure_fire_chance[NUM_SKILL_LEVELS] = {0.2f, 0.3f, 0.5f, 0.9f, 1.1f};  //      Note, this gets scaled by ai_class

float Shield_manage_delays[NUM_SKILL_LEVELS] = {5.0f, 4.0f, 2.5f, 1.2f, 0.1f};

// accuracy we feed into the beam weapons based upon skill system
// float Beam_accuracy[NUM_SKILL_LEVELS] = {2.0f, 1.5f, 1.0f, 0.7f, 0.4f};

extern float Ship_fire_delay_scale_hostile[NUM_SKILL_LEVELS];
extern float Ship_fire_delay_scale_friendly[NUM_SKILL_LEVELS];

pnode           Path_points[MAX_PATH_POINTS];
pnode           *Ppfp;                  //      Free pointer in path points.

float   AI_frametime;

char *Ai_class_names[MAX_AI_CLASSES];

// global for rearm status for teams
int Ai_friendly_rearm_timestamp, Ai_hostile_rearm_timestamp, Ai_neutral_rearm_timestamp, Ai_traitor_rearm_timestamp, Ai_unknown_rearm_timestamp;

// globals for dealing with when to fire huge secondary weapons
#define MAX_HUGE_SECONDARY_INFO 10

typedef struct {
        int team;
        int weapon_index;
        int max_fire_count;
        char    *shipname;
} huge_fire_info;

huge_fire_info Ai_huge_fire_info[MAX_HUGE_SECONDARY_INFO];

int Ai_last_arrive_path;        // index of ship_bay path used by last arrival from a fighter bay

// forward declarations
int     ai_return_path_num_from_dockbay(object *dockee_objp, int dockbay_index);
void    create_model_exit_path(object *pl_objp, object *mobjp, int path_num, int count=1);
void    copy_xlate_model_path_points(object *objp, model_path *mp, int dir, int count, int path_num, pnode *pnp, int randomize_pnt=-1);

// ai_set_rearm_status takes a team (friendly, hostile, neutral) and a time.  This function
// sets the timestamp used to tell is it is a good time for this team to rearm.  Once the timestamp
// is no longer valid, then rearming is not a "good time"
// not safe.  Called from sexpression code.
void ai_set_rearm_status( int team, int time )
{
        Assert( time >= 0 );

        switch (team) {
        case TEAM_FRIENDLY:
                Ai_friendly_rearm_timestamp = timestamp( time * 1000 );
                break;
        case TEAM_HOSTILE:
                Ai_hostile_rearm_timestamp = timestamp( time * 1000 );
                break;
        case TEAM_NEUTRAL:
                Ai_neutral_rearm_timestamp = timestamp( time * 1000 );
                break;
        case TEAM_TRAITOR:
                Ai_traitor_rearm_timestamp = timestamp( time * 1000 );
                break;
        case TEAM_UNKNOWN:
                Ai_traitor_rearm_timestamp = timestamp( time * 1000 );
                break;
        default:
                Int3();
                break;
        }
}

// int ai_good_time_to_rearm returns true(1) or false(0) if it is "safe" for the given
// object to rearm.  "safe" is currently defined by the mission designer using the good/bad
// time to rearm sexpressions.  This status is currently team based.  This function could
// be easily expended to further the definition of "safe"
int ai_good_time_to_rearm( object *objp )
{
        int team, status;

        Assert(objp->type == OBJ_SHIP);
        team = Ships[objp->instance].team;
        status = 0;

        switch(team) {
        case TEAM_FRIENDLY:
                status = timestamp_valid(Ai_friendly_rearm_timestamp);
                break;
        case TEAM_HOSTILE:
                status = timestamp_valid(Ai_hostile_rearm_timestamp);
                break;
        case TEAM_NEUTRAL:
                status = timestamp_valid(Ai_neutral_rearm_timestamp);
                break;
        case TEAM_TRAITOR:
                status = timestamp_valid(Ai_traitor_rearm_timestamp);
                break;
        case TEAM_UNKNOWN:
                status = timestamp_valid(Ai_unknown_rearm_timestamp);
                break;
        default:
                Int3();
                break;
        }

        return status;
}

// functions to deal with letting the ai know about good times to fire powerful secondary
// weapons.

// this function is entry point from sexpression code to set internal data for use by ai code.
void ai_good_secondary_time( int team, int weapon_index, int max_fire_count, char *shipname )
{
        int i, index;

        // find an open slot to put this data
        for ( i = 0; i < MAX_HUGE_SECONDARY_INFO; i++ ) {
                if ( Ai_huge_fire_info[i].weapon_index == -1 )
                        break;
        }

        Assert( i < MAX_HUGE_SECONDARY_INFO );                  // we've run out of room

        Ai_huge_fire_info[i].weapon_index = weapon_index;
        Ai_huge_fire_info[i].team = team;
        Ai_huge_fire_info[i].max_fire_count = max_fire_count;

        Ai_huge_fire_info[i].shipname = ai_get_goal_ship_name( shipname, &index );
}

// function called internally to the ai code to tell whether or not weapon_num can be fired
// from firer_objp at target_objp.  This function will resolve the team for the firer.
// returns:
//              -1  -- when conditions don't allow firer to fire weapon_num on target_objp
//              >=0 -- when conditions allow firer to fire.  Return value is max number of weapon_nums
//           which can be fired on target_objp
int is_preferred_weapon(int weapon_num, object *firer_objp, object *target_objp)
{
        int i, firer_team, target_signature;
        ship *firer_ship;
        huge_fire_info *hfi = NULL;

        Assert( firer_objp->type == OBJ_SHIP );
        firer_ship = &Ships[firer_objp->instance];
        firer_team = firer_ship->team;

        // get target object's signature and try to find it in the list.
        target_signature = target_objp->signature;
        for ( i = 0; i < MAX_HUGE_SECONDARY_INFO; i++ ) {
                int ship_index, signature;

                hfi = &Ai_huge_fire_info[i];
                if ( hfi->weapon_index == -1 )
                        continue;

                ship_index = ship_name_lookup( hfi->shipname );
                if ( ship_index == -1 )
                        continue;

                signature = Objects[Ships[ship_index].objnum].signature;

                // sigatures, weapon_index, and team must match
                if ( (signature == target_signature) && (hfi->weapon_index == weapon_num) && (hfi->team == firer_team) )
                        break;
        }

        // return -1 if not found
        if ( i == MAX_HUGE_SECONDARY_INFO )
                return -1;

        // otherwise, we can return the max number of weapons we can fire against target_objps

        return hfi->max_fire_count;
}

// function to clear out secondary firing infomration between levels
void ai_init_secondary_info()
{
        int i;

        // clear out the data for dealing with when ai ships can fire huge secondary weapons
        for (i = 0; i < MAX_HUGE_SECONDARY_INFO; i++ ) {
                Ai_huge_fire_info[i].weapon_index = -1;
                Ai_huge_fire_info[i].team = -1;
                Ai_huge_fire_info[i].max_fire_count = -1;
                Ai_huge_fire_info[i].shipname = NULL;
        }
}


//      Garbage collect the Path_points buffer.
//      Scans all objects, looking for used Path_points records.
//      Compresses Path_points buffer, updating aip->path_start and aip->path_cur indices.
//      Updates Ppfp to point to first free record.
//      This function is fairly fast.  Its worst-case running time is proportional to
//      3*MAX_PATH_POINTS + MAX_OBJECTS
//      Things to do to optimize this function:
//              1. if (t != 0) xlt++; can be replaced by xlt += t; assuming t can only be 0 or 1.
//              2. When pp_xlate is getting stuffed the first time, note highest index and use that 
//                      instead of MAX_PATH_POINTS in following two for loops.
void garbage_collect_path_points()
{
        int     i;
        int     pp_xlate[MAX_PATH_POINTS];
        object  *A;
        ship_obj        *so;

        //      Scan all objects and create Path_points xlate table.
        for (i=0; i<MAX_PATH_POINTS; i++)
                pp_xlate[i] = 0;

        //      in pp_xlate, mark all used Path_point records
        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                A = &Objects[so->objnum];
                ship    *shipp = &Ships[A->instance];
                if (shipp->ai_index != -1) {
                        ai_info *aip = &Ai_info[shipp->ai_index];

                        if ((aip->path_length > 0) && (aip->path_start > -1)) {

                                for (int i=aip->path_start; i<aip->path_start + aip->path_length; i++) {
                                        Assert(pp_xlate[i] == 0);       //      If this is not 0, then two paths use this point!
                                        pp_xlate[i] = 1;
                                }
                        }
                }
        }

        //      Now, stuff xlate index in pp_xlate.  This is the number to translate any path_start
        //      or path_cur index to.
        int     xlt = 0;
        for (i=0; i<MAX_PATH_POINTS; i++) {
                int     t = pp_xlate[i];

                pp_xlate[i] = xlt;
                if (t != 0)
                        xlt++;
        }
        
        //      Update global Path_points free pointer.
        Ppfp = &Path_points[xlt];

        //      Now, using pp_xlate, fixup all aip->path_cur and aip->path_start indices
        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                A = &Objects[so->objnum];
                ship    *shipp = &Ships[A->instance];
                if (shipp->ai_index != -1) {
                        ai_info *aip = &Ai_info[shipp->ai_index];

                        if ((aip->path_length > 0) && (aip->path_start > -1)) {
                                Assert(aip->path_start < MAX_PATH_POINTS);
                                aip->path_start = pp_xlate[aip->path_start];

                                Assert((aip->path_cur >= 0) && (aip->path_cur < MAX_PATH_POINTS));
                                aip->path_cur = pp_xlate[aip->path_cur];
                        }
                }
        }

        //      Now, compress the buffer.
        for (i=0; i<MAX_PATH_POINTS; i++)
                if (i != pp_xlate[i])
                        Path_points[pp_xlate[i]] = Path_points[i];

}

//      Hash two values together, return result.
//      Hash function: curval shifted right circular by one, newval xored in.
int hash(unsigned int curval, int newval)
{
        int     addval = curval & 1;

        curval >>= 1;
        if (addval)
                curval |= 0x80000000;
        curval ^= newval;

        return curval;
}

//      Hash some information in an object together.
//      On 2/20/97, the information is position and orientation.
int create_object_hash(object *objp)
{
        int     *ip;
        unsigned int    hashval = 0;
        int     i;

        ip = (int *) &objp->orient;

        for (i=0; i<9; i++) {
                hashval = hash(hashval, *ip);
                ip++;
        }

        ip = (int *) &objp->pos;

        for (i=0; i<3; i++) {
                hashval = hash(hashval, *ip);
                ip++;
        }

        return hashval;
}

//      Stuff a list of NUM_SKILL_LEVELS floats at *plist.
void parse_float_list(float *plist)
{
        int     i;

        for (i=0; i<NUM_SKILL_LEVELS; i++) {
                stuff_float(&plist[i]);
        }
}

void parse_ai_class()
{
        ai_class        *aicp = &Ai_classes[Num_ai_classes];

        required_string("$Name:");
        stuff_string(aicp->name, F_NAME, NULL);

        Ai_class_names[Num_ai_classes] = aicp->name;

        required_string("$accuracy:");
        parse_float_list(aicp->ai_accuracy);

        required_string("$evasion:");
        parse_float_list(aicp->ai_evasion);

        required_string("$courage:");
        parse_float_list(aicp->ai_courage);

        required_string("$patience:");
        parse_float_list(aicp->ai_patience);
}

void parse_aitbl()
{
        // open localization
        lcl_ext_open();

        read_file_text("ai.tbl");

        reset_parse();

        Num_ai_classes = 0;

        required_string("#AI Classes");

        while (required_string_either("#End", "$Name:")) {
                Assert( Num_ai_classes < MAX_AI_CLASSES);

                parse_ai_class();

                Num_ai_classes++;
        }

        // close localization
        lcl_ext_close();
}

LOCAL int ai_inited = 0;

//========================= BOOK-KEEPING FUNCTIONS =======================

// Called once at game start-up
void ai_init()
{
        if ( !ai_inited )       {
                // Do the first time initialization stuff here
                int     rval;

                if ((rval = setjmp(parse_abort)) != 0) {
                        Error(LOCATION, "Error parsing 'ai.tbl'\r\nError code = %i.\r\n", rval);
                } else {                        
                        parse_aitbl();                  
                }

                ai_inited = 1;
        }

        init_semirand();
        
        ai_level_init();
}

// this inits the ai.  You should be able to call this between
// levels to reset everything.
void ai_level_init()
{
        int i;
 
        // Do the stuff to reset all ai stuff here
        for (i=0; i<MAX_AI_INFO ; i++) {
                Ai_info[i].shipnum = -1;
        }
        Ai_goal_signature = 0;
        Ai_friendly_rearm_timestamp = timestamp(-1);
        Ai_hostile_rearm_timestamp = timestamp(-1);
        Ai_neutral_rearm_timestamp = timestamp(-1);
        Ai_traitor_rearm_timestamp = timestamp(-1);

        // clear out the stuff needed for AI firing powerful secondary weapons
        ai_init_secondary_info();

        Ai_last_arrive_path=0;
}

// BEGIN STEALTH
// -----------------------------------------------------------------------------
// Check if object is a stealth ship
int is_object_stealth_ship(object* objp)
{
        if (objp->type == OBJ_SHIP) {
                if (Ship_info[Ships[objp->instance].ship_info_index].flags & SIF_STEALTH) {
                        return 1;
                }
        }

        // not stealth ship
        return 0;
}

// -----------------------------------------------------------------------------
// Init necessary ai info for new stealth target
void init_ai_stealth_info(ai_info *aip, object *stealth_objp)
{
        Assert(is_object_stealth_ship(stealth_objp));

        // set necessary ai info for new stealth target
        aip->stealth_last_pos = stealth_objp->pos;
        aip->stealth_velocity = stealth_objp->phys_info.vel;
        aip->stealth_last_visible_stamp = timestamp();
}

// -----------------------------------------------------------------------------
// Check whether Pl_objp can see a stealth ship object
#define STEALTH_INVISIBLE                       0
#define STEALTH_VISIBLE                         1
#define STEALTH_FULLY_TARGETABLE        2

float get_skill_stealth_dist_scaler()
{
        // return dist scaler based on skill level
        switch (Game_skill_level) {
        case 0: // very easy
                return 0.65f;

        case 1: // easy
                return 0.9f;

        case 2: // medium
                return 1.0f;

        case 3: // hard
                return 1.1f;

        case 4: // insane
                return 1.3f;

        default:
                Int3();
        }

        return 1.0f;
}

float get_skill_stealth_dot_scaler()
{
        // return multiplier on dot based on skill level
        switch (Game_skill_level) {
        case 0: // very easy
                return 1.3f;

        case 1: // easy
                return 1.1f;

        case 2: // medium
                return 1.0f;

        case 3: // hard
                return 0.9f;

        case 4: // insane
                return 0.7f;

        default:
                Int3();
        }

        return 1.0f;
}

int ai_is_stealth_visible(object *viewer_objp, object *stealth_objp)
{
        ship *shipp;
        vector vec_to_stealth;
        float dot_to_stealth, dist_to_stealth, max_stealth_dist;

        Assert(stealth_objp->type == OBJ_SHIP);
        shipp = &Ships[stealth_objp->instance];
        Assert(viewer_objp->type == OBJ_SHIP);

        // check if stealth ship
        Assert(Ship_info[shipp->ship_info_index].flags & SIF_STEALTH);

        // check if in neb and below awac level for visible
        if ( !ship_is_visible_by_team(stealth_objp->instance, Ships[viewer_objp->instance].team) ) {
                vm_vec_sub(&vec_to_stealth, &stealth_objp->pos, &viewer_objp->pos);
                dist_to_stealth = vm_vec_mag_quick(&vec_to_stealth);
                dot_to_stealth = vm_vec_dotprod(&viewer_objp->orient.v.fvec, &vec_to_stealth) / dist_to_stealth;

                // get max dist at which stealth is visible
                max_stealth_dist = get_skill_stealth_dist_scaler() * STEALTH_MAX_VIEW_DIST;

                // now check if within view frustrum
                float needed_dot_to_stealth;
                if (dist_to_stealth < 100) {
                        needed_dot_to_stealth = 0.0f;
                } else {
                        needed_dot_to_stealth = get_skill_stealth_dot_scaler() * float(STEALTH_VIEW_CONE_DOT) * (dist_to_stealth / max_stealth_dist);
                }
                if (dot_to_stealth > needed_dot_to_stealth) {
                        if (dist_to_stealth < max_stealth_dist) {
                                return STEALTH_VISIBLE;
                        }
                }

                // not within frustrum
                return STEALTH_INVISIBLE;
        }

        // visible by awacs level
        return STEALTH_FULLY_TARGETABLE;
}

// END STEALTH

//      Compute dot product of direction vector and forward vector.
//      Direction vector is vector from one object to other object.
//      Forward vector is the forward vector of the ship.
//      If from_dot == NULL, don't fill it in.
float compute_dots(object *objp, object *other_objp, float *to_dot, float *from_dot)
{
        vector  v2o;
        float           dist;

        dist = vm_vec_normalized_dir(&v2o, &other_objp->pos, &objp->pos);

        *to_dot = vm_vec_dot(&objp->orient.v.fvec, &v2o);

        if (from_dot != NULL)
                *from_dot = - vm_vec_dot(&other_objp->orient.v.fvec, &v2o);

        return dist;
}

// -----------------------------------------------------------------------------
// update estimated stealth info
// this is a "cheat" update
// error increases with time not seen, true distance away, dot to enemey
// this is done only if we can not see the stealth target
// need to infer its position either by weapon fire pos or last know pos
void update_ai_stealth_info_with_error(ai_info *aip/*, int no_error*/)
{
        object *ship;
        object *stealth_objp;
        /*
        float error_time_mult, error_dist_mult, error_dot_mult, error_mult;
        float pos_error, vel_error;
        vector error_vec, vec_to_stealth;
        float dist_to_stealth, dot_to_stealth;
        float delta_time, delta_capped;
        */

        // make sure I am targeting a stealth ship
        Assert( is_object_stealth_ship(&Objects[aip->target_objnum]) );
        stealth_objp = &Objects[aip->target_objnum];

        // my_ship
        ship = &Objects[Ships[aip->shipnum].objnum];

        // if update is due to weapon fire, get exact stealth position
//      if (no_error) {
        aip->stealth_last_pos = stealth_objp->pos;
        aip->stealth_velocity = stealth_objp->phys_info.vel;
        aip->stealth_last_visible_stamp = timestamp();
//              return;
//      }
/*
        // get time since last seen
        delta_time = 0.001f * (timestamp() - aip->stealth_last_visible_stamp);

        // we don't want our "cheat" guess to more off than what we would get from extrapolating from last visible
        // only update if stealth info is "old"
        if ( (delta_time) < 0.5 ) {
                return;
        }

        // find vec_to_stealth and dist
        vm_vec_sub(&vec_to_stealth, &stealth_objp->pos, &ship->pos);
        dist_to_stealth = vm_vec_normalize_quick(&vec_to_stealth);
        dot_to_stealth = vm_vec_dotprod(&vec_to_stealth, &ship->orient.v.fvec);

        // put cap on time
        delta_capped = delta_time;
        if (delta_time > 5.0) {
                delta_capped = 5.0f;
        }

        // erorr_time_mult (for 0-5) -> (1-6)
        error_time_mult = (1.0f + delta_capped);

        // error_dot_mult (-1 to 1) -> (1-3)
        error_dot_mult = (2 - dot_to_stealth);

        // error_dist_mult (0-1000+) -> (1-4)
        error_dist_mult = dist_to_stealth * 4.0f * 0.001f;
        if (error_dist_mult < 1) {
                error_dist_mult = 1.0f;
        } else if (error_dist_mult > 4) {
                error_dist_mult = 4.0f;
        }

        // multiply error out
        error_mult = error_time_mult * error_dot_mult * error_dist_mult;

        float base_pos_error = 10;
        float base_vel_error = 2;

        // find the position and velocity error magnitude;
        pos_error = base_pos_error * error_mult;
        vel_error = base_vel_error * error_mult;

        // get an error that changes slowly over time
        static_randvec( ((int)aip ^ (Missiontime >> 18)) & 7, &error_vec);
        vm_vec_zero(&error_vec);

        // update pos and vel with error
        vm_vec_scale_add(&aip->stealth_velocity, &stealth_objp->phys_info.vel, &error_vec, vel_error);

        // revise last "known" position to arrive at last pos with given error
        vm_vec_scale_add(&aip->stealth_last_pos, &stealth_objp->pos, &error_vec, pos_error);
        vm_vec_scale_add2(&aip->stealth_last_pos, &aip->stealth_velocity, -(0.001f * delta_time));
        */
}

//      Update danger_weapon_objnum and signature in ai_info to say this weapon is to be avoided.
void ai_update_danger_weapon(int attacked_objnum, int weapon_objnum)
{
        object  *objp, *weapon_objp;
        ai_info *aip;
        float           old_dist, new_dist;
        float           old_dot, new_dot;
        object  *old_weapon_objp = NULL;

        if ((attacked_objnum == -1) || (weapon_objnum == -1)) {
                return;
        }

        objp = &Objects[attacked_objnum];

        // AL 2-24-98: If this isn't a ship, we don't need to worry about updating weapon_objnum (ie it would be
        //                                      an asteroid or bomb).
        if ( objp->type != OBJ_SHIP ) {
                return;
        }

        weapon_objp = &Objects[weapon_objnum];

        aip = &Ai_info[Ships[objp->instance].ai_index];

        // if my taraget is a stealth ship and is not visible
        if (aip->target_objnum >= 0) {
                if ( is_object_stealth_ship(&Objects[aip->target_objnum]) ) {
                        if ( ai_is_stealth_visible(objp, &Objects[aip->target_objnum]) == STEALTH_INVISIBLE ) {
                                // and the weapon is coming from that stealth ship
                                if (weapon_objp->parent == aip->target_objnum) {
                                        // update my position estimate for stealth ship
                                        update_ai_stealth_info_with_error(aip/*, 1*/);
                                }
                        }
                }
        }

        if (aip->danger_weapon_objnum != -1) {
                old_weapon_objp = &Objects[aip->danger_weapon_objnum];
                if ((old_weapon_objp->type == OBJ_WEAPON) && (old_weapon_objp->signature == aip->danger_weapon_signature)) {
                        ;
                } else {
                        aip->danger_weapon_objnum = -1;
                }
        }

        new_dist = compute_dots(weapon_objp, objp, &new_dot, NULL);

        if (aip->danger_weapon_objnum == -1) {
                if (new_dist < 1500.0f) {
                        if (new_dot > 0.5f) {
                                aip->danger_weapon_objnum = weapon_objnum;
                                aip->danger_weapon_signature = weapon_objp->signature;
                        }
                }
        } else {
                Assert(old_weapon_objp != NULL);
                old_dist = compute_dots(old_weapon_objp, objp, &old_dot, NULL);
        
                if (old_dot < 0.5f) {
                        aip->danger_weapon_objnum = -1;
                        old_dist = 9999.9f;
                }

                if ((new_dot > 0.5f) && (new_dot > old_dot-0.01f)) {
                        if (new_dist < old_dist) {
                                aip->danger_weapon_objnum = weapon_objnum;
                                aip->danger_weapon_signature = weapon_objp->signature;
                        }
                }
        }
}

//      If rvec != NULL, use it to match bank by calling vm_matrix_interpolate.
//      (rvec defaults to NULL)
void ai_turn_towards_vector(vector *dest, object *objp, 
                                                                         float frametime, float turn_time, vector *slide_vec, vector *rel_pos, float bank_override, int flags, vector *rvec)
{
        //matrix        goal_orient;
        matrix  curr_orient;
        vector  vel_in, vel_out, desired_fvec, src;
        float           delta_time;
        physics_info    *pip;
        vector  vel_limit, acc_limit;
        float           delta_bank;

        //      Don't allow a ship to turn if it has no engine strength.
        // AL 3-12-98: objp may not always be a ship!
        if ( objp->type == OBJ_SHIP ) {
                if (ship_get_subsystem_strength(&Ships[objp->instance], SUBSYSTEM_ENGINE) <= 0.0f)
                        return;
        }
                        
        //nprintf(("AI", "Ship %s turning towards point %7.3f %7.3f %7.3f\n", Ships[objp->instance].ship_name, dest->x, dest->y, dest->z));
        pip = &objp->phys_info;

        vel_in = pip->rotvel;
        curr_orient = objp->orient;
        delta_time = flFrametime;

        Assert(turn_time > 0.0f);
        
        //      Scale turn_time based on skill level and team.
        if (!(flags & AITTV_FAST)){
                if (objp->type == OBJ_SHIP){
                        if (Ships[objp->instance].team != Ships[Player_obj->instance].team){
                                turn_time *= Turn_time_skill_level_scale[Game_skill_level];
                        }
                }
        }

        //      Set max turn rate.
        vel_limit.xyz.x = 2*PI/turn_time;
        vel_limit.xyz.y = 2*PI/turn_time;
        vel_limit.xyz.z = 2*PI/turn_time;

        //      Set rate at which ship can accelerate to its rotational velocity.
        //      For now, weapons just go much faster.
        acc_limit = vel_limit;
        if (objp->type == OBJ_WEAPON)
                vm_vec_scale(&acc_limit, 8.0f);

        src = objp->pos;

        if (rel_pos != NULL) {
                vector  gun_point;
                vm_vec_unrotate(&gun_point, rel_pos, &objp->orient);
                vm_vec_add2(&src, &gun_point);
        }

        vm_vec_normalized_dir(&desired_fvec, dest, &src);

        //      Since ship isn't necessarily moving in the direction it's pointing, sometimes it's better
        //      to be moving towards goal rather than just pointing.  So, if slide_vec is !NULL, try to
        //      make ship move towards goal, not point at goal.
        if (slide_vec != NULL) {
                vm_vec_add2(&desired_fvec, slide_vec);
                vm_vec_normalize(&desired_fvec);
        }

        //      Should be more general case here.  Currently, anything that is not a weapon will bank when it turns.
        if (objp->type == OBJ_WEAPON)
                delta_bank = 0.0f;
        else if ((bank_override) && (Ships[objp->instance].team & opposing_team_mask(Player_ship->team))) {     //      Theoretically, this will only happen for Shivans.
                delta_bank = bank_override;
                //nprintf(("AI", "%i: %7.3f\n", Framecount, bank_override));
        } else {
                delta_bank = vm_vec_dot(&curr_orient.v.rvec, &objp->last_orient.v.rvec);
                delta_bank = 100.0f * (1.0f - delta_bank);
                if (vm_vec_dot(&objp->last_orient.v.fvec, &objp->orient.v.rvec) < 0.0f)
                        delta_bank = -delta_bank;

                //nprintf(("AI", "%s: Frame %i: delta bank = %7.3f\n", Ships[objp->instance].ship_name, Framecount, delta_bank));
        }

        //      Dave Andsager: The non-indented lines here are debug code to help you track down the problem in the physics
        //      that is causing ships to inexplicably rotate very far.  If you hit the Int3(), set the next statement to be
        //      the one marked "HERE".  (Do this clicking the cursor there, then right clicking.  Choose the right option.)
        //      This will allow you to rerun vm_forward_interpolate() with the values that caused the error.
        //      Note, you'll need to enable the Int3() about ten lines below.
#ifndef NDEBUG
vector tvec = objp->orient.v.fvec;
vector  vel_in_copy;
matrix  objp_orient_copy;

vel_in_copy = vel_in;
objp_orient_copy = objp->orient;

vel_in = vel_in_copy;   //      HERE
objp->orient = objp_orient_copy;
#endif
        if (rvec != NULL) {
                matrix  out_orient, goal_orient;

                vm_vector_2_matrix(&goal_orient, &desired_fvec, NULL, rvec);
                vm_matrix_interpolate(&goal_orient, &curr_orient, &vel_in, delta_time, &out_orient, &vel_out, &vel_limit, &acc_limit);
                objp->orient = out_orient;
        } else {
                vm_forward_interpolate(&desired_fvec, &curr_orient, &vel_in, delta_time, delta_bank, &objp->orient, &vel_out, &vel_limit, &acc_limit);
        }
#ifndef NDEBUG
if (!((objp->type == OBJ_WEAPON) && (Weapon_info[Weapons[objp->instance].weapon_info_index].subtype == WP_MISSILE))) {
        if (delta_time < 0.25f && vm_vec_dot(&objp->orient.v.fvec, &tvec) < 0.1f)
                Int3(); //      Get Andsager.  A ship has turned too far in one frame.
}
#endif

        pip->rotvel = vel_out;
}

void init_ship_info()
{
        int     i;

        if (Ship_info_inited)
                return;

        for (i=0; i<MAX_SHIP_TYPES; i++) {
                Ship_info[i].min_speed = - Ship_info[i].max_rear_vel;
                Ship_info[i].max_accel = Ship_info[i].max_vel.xyz.z;
        }

        Ship_info_inited = 1;

}

//      Set aip->target_objnum to objnum
//      Update aip->previous_target_objnum.
//      If new target (objnum) is different than old target, reset target_time.
int set_target_objnum(ai_info *aip, int objnum)
{
/*
        char    old_name[32], new_name[32];

        if (!timestamp_elapsed(aip->ok_to_target_timestamp))
                return aip->target_objnum;

        if (Player_ship && (Ships[aip->shipnum].team == Player_ship->team)) {
                if (aip->target_objnum == -1)
                        strcpy(old_name, "none");
                else
                        strcpy(old_name, Ships[Objects[aip->target_objnum].instance].ship_name);

                if (objnum == -1)
                        strcpy(new_name, "none");
                else
                        strcpy(new_name, Ships[Objects[objnum].instance].ship_name);

                nprintf(("AI", "Ship %s changing target from %s to %s\n", Ships[aip->shipnum].ship_name, old_name, new_name));
        }
*/

        // AL 2-25-97: Ensure that a protected ship isn't being set as a target (for non-players only)
        /*
        if ( objnum >= 0 ) {
                if ( !(Objects[Ships[aip->shipnum].objnum].flags & OF_PLAYER_SHIP) ) {
                        if ( Objects[objnum].flags & OF_PROTECTED ) {
                                // AL 2-26-97: removing Int3() until issue with setting OF_PROTECTED in ai_set_attack_subsystem()
                                //Int3();                                                               // this should not happen
                                return aip->target_objnum;              // don't change targets
                        }
                }
        }
        */

        if ((aip != Player_ai) && (!timestamp_elapsed(aip->ok_to_target_timestamp))) {
                return aip->target_objnum;
        }

        if (aip->target_objnum == objnum) {
                aip->previous_target_objnum = aip->target_objnum;
        } else {
                aip->previous_target_objnum = aip->target_objnum;

                // ignore this assert if a multiplayer observer
                if((Game_mode & GM_MULTIPLAYER) && (aip == Player_ai) && (Player_obj->type == OBJ_OBSERVER)){
                } else {
                        Assert(objnum != Ships[aip->shipnum].objnum);   //      make sure not targeting self
                }

                // if stealth target, init ai_info for stealth
                if ( (objnum > 0) && is_object_stealth_ship(&Objects[objnum]) ) {
                        init_ai_stealth_info(aip, &Objects[objnum]);
                }

                aip->target_objnum = objnum;
                aip->target_time = 0.0f;
                aip->target_signature = Objects[objnum].signature;
                // clear targeted subsystem
                set_targeted_subsys(aip, NULL, -1);
        }
        
        return aip->target_objnum;
}

int ai_select_primary_weapon(object *objp, object *other_objp, int flags);

//      Make new_subsys the targeted subsystem of ship *aip.
ship_subsys *set_targeted_subsys(ai_info *aip, ship_subsys *new_subsys, int parent_objnum)
{
        Assert(aip != NULL);

        aip->last_subsys_target = aip->targeted_subsys;
        aip->targeted_subsys = new_subsys;
        aip->targeted_subsys_parent = parent_objnum;

        if ( new_subsys ) {
                // Make new_subsys target
                if (new_subsys->system_info->type == SUBSYSTEM_ENGINE) {
                        if ( aip != Player_ai ) {
                                ai_select_primary_weapon(&Objects[Ships[aip->shipnum].objnum], &Objects[parent_objnum], WIF_PUNCTURE);
                                ship_primary_changed(&Ships[aip->shipnum]);     // AL: maybe send multiplayer information when AI ship changes primaries
                        }
                }

                if ( aip == Player_ai ) {
                        hud_lock_reset(0.5f);
                }

        } else {
                // Cleanup any subsys path information if it exists
                ai_big_subsys_path_cleanup(aip);
        }
        
        return aip->targeted_subsys;
}                                                                                         

// called to init the data for single ai object.  At this point,
// the ship and the object and the ai_info are are correctly
// linked together. Ai_info[ai_index].shipnum is the only valid field 
// in ai_info.
//      This is called right when the object is parsed, so you can't assume much
//      has been initialized.  For example, wings, waypoints, goals are probably
//      not yet loaded. --MK, 10/8/96
void ai_object_init(object * obj, int ai_index)
{
        ai_info *aip;
        Assert(ai_index >= 0 && ai_index < MAX_AI_INFO);

        aip = &Ai_info[ai_index];

        aip->type = 0;          //      0 means not in use.
        aip->wing = -1;         //      Member of what wing? -1 means none.
        aip->ai_class = Ship_info[Ships[obj->instance].ship_info_index].ai_class;
        aip->behavior = AIM_NONE;
}

//      If *aip is docked, set max acceleration to A->mass/(A->mass + B->mass) where A is *aip and B is dock object
void adjust_accel_for_docking(ai_info *aip)
{
        if (aip->dock_objnum != -1) {
                object  *obj2p = &Objects[aip->dock_objnum];
                object  *obj1p;

                obj1p = &Objects[Ships[aip->shipnum].objnum];

                if (obj2p->signature == aip->dock_signature) {
                        float   ratio;

                        ratio = obj1p->phys_info.mass / (obj1p->phys_info.mass + obj2p->phys_info.mass);

                        // put cap on how much ship can slow down
                        if (ratio < 0.8) {
                                ratio = 0.8f;
                        }

                        if (AI_ci.forward > ratio) {
                                AI_ci.forward = ratio;
                        }
                }
        }
}

// -------------------------------------------------------------------
void accelerate_ship(ai_info *aip, float accel)
{
        aip->prev_accel = accel;
        AI_ci.forward = accel;
        adjust_accel_for_docking(aip);
}

//      --------------------------------------------------------------------------
void change_acceleration(ai_info *aip, float delta_accel)
{
        float   new_accel;

        if (delta_accel < 0.0f) {
                if (aip->prev_accel > 0.0f)
                        aip->prev_accel = 0.0f;
        } else if (aip->prev_accel < 0.0f)
                aip->prev_accel = 0.0f;

        new_accel = aip->prev_accel + delta_accel * flFrametime;

        if (new_accel > 1.0f)
                new_accel = 1.0f;
        else if (new_accel < -1.0f)
                new_accel = -1.0f;
        
        aip->prev_accel = new_accel;

        AI_ci.forward = new_accel;
        adjust_accel_for_docking(aip);
}

void set_accel_for_target_speed(object *objp, float tspeed)
{
        float   max_speed;
        ai_info *aip;

        aip = &Ai_info[Ships[objp->instance].ai_index];

        max_speed = Ships[objp->instance].current_max_speed;

        AI_ci.forward = tspeed/max_speed;
        aip->prev_accel = AI_ci.forward;

        adjust_accel_for_docking(aip);
}

//      Stuff perim_point with a point on the perimeter of the sphere defined by object *objp
//      on the vector from the center of *objp through the point *vp.
void project_point_to_perimeter(vector *perim_point, vector *pos, float radius, vector *vp)
{
        vector  v1;
        float           mag;

        vm_vec_sub(&v1, vp, pos);
        mag = vm_vec_mag(&v1);

        if (mag == 0.0f) {
                Warning(LOCATION, "projectable point is at center of sphere.");
                vm_vec_make(&v1, 0.0f, radius, 0.0f);
        } else {
                vm_vec_normalize(&v1);
                vm_vec_scale(&v1, 1.1f * radius + 10.0f);
        }

        vm_vec_add2(&v1, pos);
        *perim_point = v1;
}

//      Stuff tan1 with tangent point on sphere.  tan1 is point nearer to *p1
//      *p0 is point through which tangents pass.
//      *centerp is center of sphere.
//      *p1 is another point in space to define the plane in which tan1, tan2 reside.
//      radius is the radius of the sphere.
//      Note, this is a very approximate function just for AI.
//      Note also: On 12/26/96, p1 is used to define the plane perpendicular to that which
//      contains the tangent point.
void get_tangent_point(vector *tan1, vector *p0, vector *centerp, vector *p1, float radius)
{
        vector  dest_vec, v2c, perp_vec, temp_vec, v2;
        float           dist, ratio;

        //      Detect condition of point inside sphere.
        if (vm_vec_dist(p0, centerp) < radius)
                project_point_to_perimeter(tan1, centerp, radius, p0);
        else {
                vm_vec_normalized_dir(&v2c, centerp, p0);

                //      Compute perpendicular vector using p0, centerp, p1
                vm_vec_normal(&temp_vec, p0, centerp, p1);
                vm_vec_sub(&v2, centerp, p0);
                vm_vec_cross(&perp_vec, &temp_vec, &v2);

                vm_vec_normalize(&perp_vec);

                dist = vm_vec_dist_quick(p0, centerp);
                ratio = dist / radius;

                if (ratio < 2.0f)
                        vm_vec_scale_add(&dest_vec, &perp_vec, &v2c, ratio-1.0f);
                else
                        vm_vec_scale_add(&dest_vec, &v2c, &perp_vec, (1.0f + 1.0f/ratio));

                vm_vec_scale_add(tan1, p0, &dest_vec, dist + radius);
        }
}

//      --------------------------------------------------------------------------
//      Given an object and a point, turn towards the point, resulting in
// approach behavior.
void turn_towards_point(object *objp, vector *point, vector *slide_vec, float bank_override)
{
        ai_info *aip;
        aip = &Ai_info[Ships[Pl_objp->instance].ai_index];
        
        // check if in formation and if not leader, don't change rotvel.xyz.z (bank to match leader elsewhere)
        if (aip->ai_flags & AIF_FORMATION) {
                if (&Objects[aip->goal_objnum] != objp) {
                        float rotvel_z = objp->phys_info.rotvel.xyz.z;
                        ai_turn_towards_vector(point, objp, flFrametime, Ship_info[Ships[objp->instance].ship_info_index].srotation_time, slide_vec, NULL, bank_override, 0);
                        objp->phys_info.rotvel.xyz.z = rotvel_z;
                }
        } else {
                // normal turn
                ai_turn_towards_vector(point, objp, flFrametime, Ship_info[Ships[objp->instance].ship_info_index].srotation_time, slide_vec, NULL, bank_override, 0);
        }
}

//      --------------------------------------------------------------------------
//      Given an object and a point, turn away from the point, resulting in avoidance behavior.
//      Note: Turn away at full speed, not scaled down by skill level.
void turn_away_from_point(object *objp, vector *point, float bank_override)
{
        vector  opposite_point;

        vm_vec_sub(&opposite_point, &objp->pos, point);
        vm_vec_add2(&opposite_point, &objp->pos);

        ai_turn_towards_vector(&opposite_point, objp, flFrametime, Ship_info[Ships[objp->instance].ship_info_index].srotation_time, NULL, NULL, bank_override, AITTV_FAST);
}


//      --------------------------------------------------------------------------
//      Given an object and a point, turn tangent to the point, resulting in
// a circling behavior.
//      Make object *objp turn around the point *point with a radius of radius.
//      Note that this isn't the same as following a circle of radius radius with
//      center *point, but it should be adequate.
//      Note that if you want to circle an object without hitting it, you should use
//      about twice that object's radius for radius, else you'll certainly bump into it.
//      Return dot product to goal point.
float turn_towards_tangent(object *objp, vector *point, float radius)
{
        vector  vec_to_point;
        vector  goal_point;
        vector  perp_point;                             //      point radius away from *point on vector to objp->pos
        vector  up_vec, perp_vec;

        vm_vec_normalized_dir(&vec_to_point, point, &objp->pos);
        vm_vec_crossprod(&up_vec, &vec_to_point, &objp->orient.v.fvec);
        vm_vec_crossprod(&perp_vec, &vec_to_point, &up_vec);

        vm_vec_scale_add(&perp_point, point, &vec_to_point, -radius);
        if (vm_vec_dot(&objp->orient.v.fvec, &perp_vec) > 0.0f) {
                vm_vec_scale_add(&goal_point, &perp_point, &perp_vec, radius);
        } else {
                vm_vec_scale_add(&goal_point, &perp_point, &perp_vec, -radius);
        }

//      Ai_info[Ships[objp->instance].ai_index].goal_point = goal_point;
        turn_towards_point(objp, &goal_point, NULL, 0.0f);

        vector  v2g;

        vm_vec_normalized_dir(&v2g, &goal_point, &objp->pos);
        return vm_vec_dot(&objp->orient.v.fvec, &v2g);
}

float turn_toward_tangent_with_axis(object *objp, object *center_objp, float radius)
{
        vector r_vec, theta_vec;
        vector center_vec, vec_on_cylinder, sph_r_vec;
        float center_obj_z;

        // find closest z of center objp
        vm_vec_sub(&sph_r_vec, &objp->pos, &center_objp->pos);
        center_obj_z = vm_vec_dotprod(&sph_r_vec, &center_objp->orient.v.fvec);

        // find pt on axis with closest z
        vm_vec_scale_add(&center_vec, &center_objp->pos, &center_objp->orient.v.fvec, center_obj_z);

        // get r_vec
        vm_vec_sub(&r_vec, &objp->pos, &center_vec);
//      float r_mag = vm_vec_normalize_quick(&r_vec);
//      mprintf(("cur_r: %.1f, desired_r: %.1f\n", r_mag, radius));
        Assert( (vm_vec_dotprod(&r_vec, &center_objp->orient.v.fvec) < 0.0001));

        // get theta vec - perp to r_vec and z_vec
        vm_vec_crossprod(&theta_vec, &center_objp->orient.v.fvec, &r_vec);

#ifndef NDEBUG
        float mag = vm_vec_normalize(&theta_vec);
        Assert(mag > 0.9999 && mag < 1.0001);
#endif

        vector temp;
        vm_vec_crossprod(&temp, &r_vec, &theta_vec);

#ifndef NDEBUG
        float dot = vm_vec_dotprod(&temp, &center_objp->orient.v.fvec);
        Assert( dot >0.9999 && dot < 1.0001);
#endif

        // find pt on clylinder with closest z
        vm_vec_scale_add(&vec_on_cylinder, &center_vec, &r_vec, radius);

        vector goal_pt, v2g;
        vm_vec_scale_add(&goal_pt, &vec_on_cylinder, &theta_vec, radius);

//      Ai_info[Ships[objp->instance].ai_index].goal_point = goal_pt;
        turn_towards_point(objp, &goal_pt, NULL, 0.0f);

        vm_vec_normalized_dir(&v2g, &goal_pt, &objp->pos);
        return vm_vec_dot(&objp->orient.v.fvec, &v2g);
}

//      Returns a point radius units away from *point that *objp should turn towards to orbit *point
void get_tangent_point(vector *goal_point, object *objp, vector *point, float radius)
{
        vector  vec_to_point;
        vector  perp_point;                             //      point radius away from *point on vector to objp->pos
        vector  up_vec, perp_vec;

        vm_vec_normalized_dir(&vec_to_point, point, &objp->pos);
        vm_vec_crossprod(&up_vec, &vec_to_point, &objp->orient.v.fvec);
        vm_vec_crossprod(&perp_vec, &vec_to_point, &up_vec);
        vm_vec_normalize(&perp_vec);

        vm_vec_scale_add(&perp_point, point, &vec_to_point, -radius);

        if (vm_vec_dot(&objp->orient.v.fvec, &perp_vec) > 0.0f) {
                vm_vec_scale_add(goal_point, &perp_point, &perp_vec, radius);
        } else {
                vm_vec_scale_add(goal_point, &perp_point, &perp_vec, -radius);
        }
}

int     Player_attacking_enabled = 1;

// -----------------------------------------------------------------------------
// Determine whether an object is targetable within a nebula
int object_is_targetable(object *target, ship *viewer)
{
        int stealth_ship = 0;

        // if target is ship, check if visible by team
        if (target->type == OBJ_SHIP) {
                stealth_ship = (Ship_info[Ships[target->instance].ship_info_index].flags & SIF_STEALTH);
                if ( ship_is_visible_by_team(target->instance, viewer->team) == 1) {
                        return 1;
                }
        }

        // for AI partially targetable works as fully targetable, except for stealth ship
        if (stealth_ship) {
                // if not team targetable, check if within frustrum
                if ( ai_is_stealth_visible(&Objects[viewer->objnum], target) == STEALTH_VISIBLE ) {
                        return 1;
                } else {
                        return 0;
                }
        }

        // if not fully targetable by team, check awacs level with viewer
        // allow targeting even if only only partially targetable to player
        float radar_return = awacs_get_level(target, viewer);
        if ( radar_return > 0.4 ) {
                return 1;
        } else {
                return 0;
        }
}

//      Return number of enemies attacking object objnum
//
// AL 10.26.97: Also include turrets on large ships when couting enemies attacking
int num_enemies_attacking(int objnum)
{
        object          *objp;
        ship                    *sp;
        ship_subsys     *ssp;
        ship_obj                *so;
        int                     count;

        count = 0;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                objp = &Objects[so->objnum];
                Assert(objp->instance != -1);
                sp = &Ships[objp->instance];

                if (Ai_info[sp->ai_index].target_objnum == objnum)
                        count++;

                // consider turrets that may be attacking objnum (but only turrets on SIF_BIG_SHIP ships)
                if ( Ship_info[sp->ship_info_index].flags & SIF_BIG_SHIP ) {

                        // loop through all the subsystems, check if turret has objnum as a target
                        ssp = GET_FIRST(&sp->subsys_list);
                        while ( ssp != END_OF_LIST( &sp->subsys_list ) ) {

                                if ( ssp->system_info->type == SUBSYSTEM_TURRET ) {
                                        if ( (ssp->turret_enemy_objnum == objnum) && (ssp->current_hits > 0) ) {
                                                count++;
                                        }
                                }
                                ssp = GET_NEXT( ssp );
                        } // end while
                }
        }

        return count;
}

//      Get the team to fire on given an object.
int get_enemy_team_mask(int objnum)
{
        int     my_team, enemy_team_mask;

        my_team = Ships[Objects[objnum].instance].team;

        if (Mission_all_attack) {
                //      All teams attack all teams.
                switch (my_team) {
                case TEAM_FRIENDLY:
                        enemy_team_mask = TEAM_HOSTILE | TEAM_NEUTRAL | TEAM_TRAITOR;
                        break;
                case TEAM_HOSTILE:
                        enemy_team_mask = TEAM_FRIENDLY | TEAM_NEUTRAL | TEAM_TRAITOR;
                        break;
                case TEAM_NEUTRAL:
                        enemy_team_mask = TEAM_FRIENDLY | TEAM_HOSTILE | TEAM_TRAITOR;
                        break;
                case TEAM_UNKNOWN:
                        enemy_team_mask = TEAM_HOSTILE;
                        break;
                case TEAM_TRAITOR:
                        enemy_team_mask = TEAM_FRIENDLY | TEAM_NEUTRAL | TEAM_HOSTILE | TEAM_TRAITOR;
                        break;
                default:
                        enemy_team_mask = TEAM_HOSTILE;
                        Int3();                 //      Illegal value for team!
                        break;
                }
        } else {
                switch (my_team) {
                case TEAM_FRIENDLY:
                        enemy_team_mask = TEAM_HOSTILE | TEAM_NEUTRAL | TEAM_TRAITOR;
                        break;
                case TEAM_HOSTILE:
                        enemy_team_mask = TEAM_FRIENDLY | TEAM_NEUTRAL | TEAM_TRAITOR;
                        break;
                case TEAM_NEUTRAL:
                        enemy_team_mask = TEAM_FRIENDLY | TEAM_TRAITOR;
                        break;
                case TEAM_UNKNOWN:
                        enemy_team_mask = TEAM_HOSTILE;
                        break;
                case TEAM_TRAITOR:
                        enemy_team_mask = TEAM_FRIENDLY | TEAM_NEUTRAL | TEAM_HOSTILE | TEAM_TRAITOR;
                        break;
                default:
                        enemy_team_mask = TEAM_HOSTILE;
                        Int3();                 //      Illegal value for team!
                        break;
                }
        }

        return enemy_team_mask;
}

//      Scan all the ships in *objp's wing.
//      Return the lowest maximum speed of a ship in the wing.
//      Current maximum speed (based on energy settings) is shipp->current_max_speed
float get_wing_lowest_max_speed(object *objp)
{
        ship            *shipp;
        ai_info *aip;
        float           lowest_max_speed;
        int             wingnum;
        object  *o;
        ship_obj        *so;

        Assert(objp->type == OBJ_SHIP);
        Assert((objp->instance >= 0) && (objp->instance < MAX_OBJECTS));
        shipp = &Ships[objp->instance];
        Assert((shipp->ai_index >= 0) && (shipp->ai_index < MAX_AI_INFO));
        aip = &Ai_info[shipp->ai_index];

        wingnum = aip->wing;

        lowest_max_speed = shipp->current_max_speed;

        if ( wingnum == -1 )
                return lowest_max_speed;

        Assert(wingnum >= 0);

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                o = &Objects[so->objnum];
                ship    *oshipp = &Ships[o->instance];
                ai_info *oaip = &Ai_info[oshipp->ai_index];

                if ((oaip->mode == AIM_WAYPOINTS) && (oaip->wing == wingnum)) {
                        //      Note: If a ship in the wing has a super low max speed, probably its engines are disabled.  So, fly along and
                        //      ignore the poor guy.
                        float   cur_max = oshipp->current_max_speed;

                        if (oaip->ai_flags & AIF_DOCKED) {
                                if (oaip->dock_objnum > -1)
                                        if (Objects[oaip->dock_objnum].type == OBJ_SHIP) 
                                                cur_max *= o->phys_info.mass/(o->phys_info.mass + Objects[oaip->dock_objnum].phys_info.mass);
                        }
                                                        
                        if ((oshipp->current_max_speed > 5.0f) && (cur_max < lowest_max_speed)) {
                                lowest_max_speed = cur_max;
                        }
                }
        }

        return lowest_max_speed;
}

/*
//      Tell everyone to ignore object objnum.
void set_global_ignore_object(int objnum)
{
        int     i;

        Assert(Objects[objnum].type == OBJ_SHIP);

        nprintf(("AI", "Telling everyone to ignore object %s\n", Ships[Objects[objnum].instance].ship_name));

        for (i=0; i<MAX_IGNORE_OBJECTS; i++) {
                if (Ignore_objects[i].objnum == -1) {
                        Ignore_objects[i].objnum = objnum;
                        Ignore_objects[i].signature = Objects[objnum].signature;
                        break;
                }
        }

        if (i == MAX_IGNORE_OBJECTS) {
                //      Couldn't find a free slot, but maybe one of these objects has died.
                for (i=0; i<MAX_IGNORE_OBJECTS; i++) {
                        int     o = Ignore_objects[i].objnum;
                        if (Objects[o].type != OBJ_SHIP)
                                break;          //      Not a ship, so use this slot.
                        if (Objects[o].signature != Ignore_objects[i].signature)
                                break;          //      Signatures don't match, so use this slot.
                }

                if (i != MAX_IGNORE_OBJECTS) {
                        Ignore_objects[i].objnum = objnum;
                        Ignore_objects[i].signature = Objects[objnum].signature;
                } else {
                        nprintf(("Warning", "Ignore_objects buffer full.  Stealing a slot to ignore object #%i\n"));
                        Int3();

                        int     r;

                        r = objnum % MAX_IGNORE_OBJECTS;

                        Ignore_objects[r].objnum = objnum;
                        Ignore_objects[r].signature = Objects[objnum].signature;
                }
        }
}

*/

//      Determine if object objnum is supposed to be ignored by object with ai_info *aip.
//      Return:
//              TRUE    if objnum is aip->ignore_objnum (and signatures match)
//                              or objnum is in ignore wing
//              FALSE   otherwise
int is_ignore_object(ai_info *aip, int objnum)
{

/*      //      First, scan all objects in global array of objects to be ignored.
        for (int i=0; i<MAX_IGNORE_OBJECTS; i++)
                if (Ignore_objects[i].objnum != -1)
                        if (objnum == Ignore_objects[i].objnum)
                                if (Objects[Ignore_objects[i].objnum].signature == Ignore_objects[i].signature)
                                        return 1;
*/

        //      Didn't find in global list.  Now check 
        if (aip->ignore_objnum == UNUSED_OBJNUM)
                return 0;                                                                       //      Not ignoring anything.
        else if (aip->ignore_objnum >= 0) {             //      This means it's ignoring an object, not a wing.
                if (aip->ignore_objnum == objnum) {
                        if (Objects[aip->ignore_objnum].signature == aip->ignore_signature) {
                                return 1;
                        } else {
                                aip->ignore_objnum = UNUSED_OBJNUM;
                                return 0;
                        }
                } else {
                        return 0;
                }
        } else {                                                                                        //      Ignoring a wing.
                Int3(); // Should never happen.  I thought I removed this behavior! -- MK, 5/17/98
                return 0;
/*              int     ignore_wingnum = -(aip->ignore_objnum + 1);

                Assert(ignore_wingnum < MAX_WINGS);
                Assert(aip->shipnum >= 0);
                return (Ships[Objects[objnum].instance].wingnum == ignore_wingnum);
*/      }
}

// -----------------------------------------------------------------------------

// given a ship with bounding box and a point, find the closest point on the bbox
int get_nearest_bbox_point(object *ship_obj, vector *start, vector *box_pt)
{
        vector temp, rf_start;
        polymodel *pm;
        pm = model_get(Ship_info[Ships[ship_obj->instance].ship_info_index].modelnum);

        // get start in ship rf
        vm_vec_sub(&temp, start, &ship_obj->pos);
        vm_vec_rotate(&rf_start, &temp, &ship_obj->orient);

        // find box_pt
        int inside = project_point_onto_bbox(&pm->mins, &pm->maxs, &rf_start, &temp);

        // get box_pt in world rf
        vm_vec_unrotate(box_pt, &temp, &ship_obj->orient);
        vm_vec_add2(box_pt, &ship_obj->pos);

        return inside;
}


typedef struct eval_nearest_objnum {
        int     objnum;
        object *trial_objp;
        int     enemy_team_mask;
        int     enemy_wing;
        float   range;
        int     max_attackers;
        int     nearest_objnum;
        float   nearest_dist;
        int     check_danger_weapon_objnum;
} eval_nearest_objnum;


void evaluate_object_as_nearest_objnum(eval_nearest_objnum *eno)
{
        ai_info *aip;
        ship_subsys     *attacking_subsystem;

        aip = &Ai_info[Ships[Objects[eno->objnum].instance].ai_index];

        attacking_subsystem = aip->targeted_subsys;

        if ((attacking_subsystem != NULL) || !(eno->trial_objp->flags & OF_PROTECTED)) {
                if ( OBJ_INDEX(eno->trial_objp) != eno->objnum ) {
#ifndef NDEBUG
                        if (!Player_attacking_enabled && (eno->trial_objp == Player_obj))
                                return;
#endif
                        //      If only supposed to attack ship in a specific wing, don't attack other ships.
                        if ((eno->enemy_wing != -1) && (Ships[eno->trial_objp->instance].wingnum != eno->enemy_wing))
                                return;

                        //      Don't keep firing at a ship that is in its death throes.
                        if (Ships[eno->trial_objp->instance].flags & SF_DYING)
                                return;

                        if (is_ignore_object(aip, ((eno->trial_objp)-Objects)))
                                return;

                        if (eno->trial_objp->flags & OF_PROTECTED)
                                return;

                        if (Ships[eno->trial_objp->instance].flags & SF_ARRIVING)
                                return;

                        ship_info *sip = &Ship_info[Ships[eno->trial_objp->instance].ship_info_index];

                        if (sip->flags & (SIF_NO_SHIP_TYPE | SIF_NAVBUOY))
                                return;

                        if (Ships[eno->trial_objp->instance].team & eno->enemy_team_mask) {
                                float   dist;
                                int     num_attacking;

                                // Allow targeting of stealth in nebula by his firing at me
                                // This is done for a specific ship, not generally.
                                if ( !eno->check_danger_weapon_objnum ) {
                                        // check if can be targeted if inside nebula
                                        if ( !object_is_targetable(eno->trial_objp, &Ships[Objects[eno->objnum].instance]) ) {
                                                // check if stealth ship is visible, but not "targetable"
                                                if ( !((sip->flags & SIF_STEALTH) && ai_is_stealth_visible(&Objects[eno->objnum], eno->trial_objp)) ) {
                                                        return;
                                                }
                                        }
                                }

                                // if objnum is BIG or HUGE, find distance to bbox
                                if (sip->flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP)) {
                                        vector box_pt;
                                        // check if inside bbox
                                        int inside = get_nearest_bbox_point(eno->trial_objp, &Objects[eno->objnum].pos, &box_pt);
                                        if (inside) {
                                                dist = 10.0f;
                                                // on the box
                                        } else {
                                                dist = vm_vec_dist_quick(&Objects[eno->objnum].pos, &box_pt);
                                        }
                                } else {
                                        dist = vm_vec_dist_quick(&Objects[eno->objnum].pos, &eno->trial_objp->pos);
                                }
                                
                                //      Make it more likely that fighters (or bombers) will be picked as an enemy by scaling up distance for other types.
                                if ((Ship_info[Ships[eno->trial_objp->instance].ship_info_index].flags & (SIF_FIGHTER | SIF_BOMBER))) {
                                        dist = dist * 0.5f;
                                }

                                num_attacking = num_enemies_attacking(eno->trial_objp-Objects);
                                if ((sip->flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP)) || (num_attacking < eno->max_attackers)) {
                                        if (!(sip->flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP))){
                                                dist *= (float) (num_attacking+2)/2.0f;                         //      prevents lots of ships from attacking same target
                                        }

                                        if (eno->trial_objp->flags & OF_PLAYER_SHIP){
                                                dist *= 1.0f + (NUM_SKILL_LEVELS - Game_skill_level - 1)/NUM_SKILL_LEVELS;      //      Favor attacking non-players based on skill level.
                                        }

                                        if (dist < eno->nearest_dist) {
                                                eno->nearest_dist = dist;
                                                eno->nearest_objnum = eno->trial_objp-Objects;
                                        }
                                }
                        }
                }
        }

}


//      Given an object and an enemy team, return the index of the nearest enemy object.
//      Unless aip->targeted_subsys != NULL, don't allow to attack objects
//      with OF_PROTECTED bit set.
//      Ship must be within range "range".
//      Don't attack a ship that already has at least max_attackers attacking it.
int get_nearest_objnum(int objnum, int enemy_team_mask, int enemy_wing, float range, int max_attackers)
{
        object  *danger_weapon_objp;
        ai_info *aip;
        ship_obj        *so;

        // initialize eno struct
        eval_nearest_objnum eno;
        eno.enemy_team_mask = enemy_team_mask;
        eno.enemy_wing = enemy_wing;
        eno.max_attackers = max_attackers;
        eno.objnum = objnum;
        eno.range = range;
        eno.nearest_dist = range;
        eno.nearest_objnum = -1;
        eno.check_danger_weapon_objnum = 0;

        // go through the list of all ships and evaluate as potential targets
        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                eno.trial_objp = &Objects[so->objnum];
                evaluate_object_as_nearest_objnum(&eno);

        }

        // check if danger_weapon_objnum has will show a stealth ship
        aip = &Ai_info[Ships[Objects[objnum].instance].ai_index];
        if (aip->danger_weapon_objnum >= 0) {
                danger_weapon_objp = &Objects[aip->danger_weapon_objnum];
                // validate weapon
                if (danger_weapon_objp->signature == aip->danger_weapon_signature) {
                        Assert(danger_weapon_objp->type == OBJ_WEAPON);
                        // check if parent is a ship
                        if (danger_weapon_objp->parent >= 0) {
                                if ( is_object_stealth_ship(&Objects[danger_weapon_objp->parent]) ) {
                                        // check if stealthy
                                        if ( ai_is_stealth_visible(&Objects[objnum], &Objects[danger_weapon_objp->parent]) != STEALTH_FULLY_TARGETABLE ) {
                                                // check if weapon is laser
                                                if (Weapon_info[Weapons[danger_weapon_objp->instance].weapon_info_index].subtype == WP_LASER) {
                                                        // check stealth ship by its laser fire
                                                        eno.check_danger_weapon_objnum = 1;
                                                        eno.trial_objp = &Objects[danger_weapon_objp->parent];
                                                        evaluate_object_as_nearest_objnum(&eno);
                                                }
                                        }
                                }
                        }
                }
        }

        //      If only looking for target in certain wing and couldn't find anything in
        //      that wing, look for any object.
        if ((eno.nearest_objnum == -1) && (enemy_wing != -1)) {
                return get_nearest_objnum(objnum, enemy_team_mask, -1, range, max_attackers);
        }

        return eno.nearest_objnum;
}

//      Given an object and an enemy team, return the index of the nearest enemy object.
//      Unlike find_enemy or find_nearest_objnum, this doesn't care about things like the protected flag or number
//      of enemies attacking.
//      It is used to find the nearest enemy to determine things like whether to rearm.
int find_nearby_hostile(int objnum, int enemy_team_mask, float range, int *count)
{
        int             nearest_objnum;
        float           nearest_dist;
        object  *objp;
        ai_info *aip;
        ship_obj        *so;

        nearest_objnum = -1;
        nearest_dist = range;

        aip = &Ai_info[Ships[Objects[objnum].instance].ai_index];

        *count = 0;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                objp = &Objects[so->objnum];

                if ( OBJ_INDEX(objp) != objnum ) {
                        if (Ships[objp->instance].flags & SF_DYING)
                                continue;

                        if (Ship_info[Ships[objp->instance].ship_info_index].flags & (SIF_NO_SHIP_TYPE | SIF_NAVBUOY))
                                continue;

                        if (Ships[objp->instance].team & enemy_team_mask) {
                                float   dist;

                                dist = vm_vec_dist_quick(&Objects[objnum].pos, &objp->pos) - objp->radius*0.75f;
                                
                                if (dist < range) {
                                        (*count)++;

                                        if (dist < nearest_dist) {
                                                nearest_dist = dist;
                                                nearest_objnum = objp-Objects;
                                        }
                                }
                        }
                }
        }

        return nearest_objnum;
}

// return !0 if objp can be considered for a turret target, 0 otherwise
// input:       objp                            =>      object that turret is considering as an enemy
//                              turret_parent   =>      object index for ship that turret sits on
int valid_turret_enemy(object *objp, object *turret_parent)
{
        if ( objp == turret_parent ) {
                return 0;
        }

        if ( objp->type == OBJ_ASTEROID ) {
                return 1;
        }

        if ( (objp->type == OBJ_SHIP) ) {
                ship *shipp;
                shipp = &Ships[objp->instance];

                // don't fire at ships with protected bit set!!!
                if ( objp->flags & OF_PROTECTED ) {
                        return 0;
                }

                if ( !(Ship_info[shipp->ship_info_index].flags & SIF_DO_COLLISION_CHECK)) {
                        return 0;
                }

                if (shipp->flags & SF_ARRIVING) {
                        return 0;
                }

                return 1;
        }

        if ( objp->type == OBJ_WEAPON ) {
                if ( Weapon_info[Weapons[objp->instance].weapon_info_index].wi_flags & WIF_BOMB ) {
                        if ( obj_team(turret_parent) != Weapons[objp->instance].team ) {
                                return 1;
                        }
                }
        }

        return 0;
}

// return 1 if objp is in fov of the specified turret, tp.  Otherwise return 0.
//      dist = distance from turret to center point of object
int object_in_turret_fov(object *objp, model_subsystem *tp, vector *tvec, vector *tpos, float dist)
{
        vector  v2e;
        float           dot;
        vm_vec_normalized_dir(&v2e, &objp->pos, tpos);
        dot = vm_vec_dot(&v2e, tvec);

        dot += objp->radius / (dist + objp->radius);

        if ( dot >= tp->turret_fov ) {
                return 1;
        }

        return 0;
}

// return 1 if bomb_objp is headed towards ship_objp
int bomb_headed_towards_ship(object *bomb_objp, object *ship_objp)
{
        float           dot;
        vector  bomb_to_ship_vector;

        vm_vec_normalized_dir(&bomb_to_ship_vector, &ship_objp->pos, &bomb_objp->pos);
        dot = vm_vec_dot(&bomb_objp->orient.v.fvec, &bomb_to_ship_vector);

        if ( dot > 0 ) {
                return 1;
        }

        return 0;
}

// nubmer of live turrets with target_objnum 
int num_turrets_attacking(object *turret_parent, int target_objnum) 
{
        ship_subsys *ss;
        ship *shipp;
        int count = 0;
        shipp = &Ships[turret_parent->instance];

        Assert(turret_parent->type == OBJ_SHIP);
        Assert(Objects[target_objnum].type == OBJ_SHIP);

        for (ss=GET_FIRST(&shipp->subsys_list); ss!=END_OF_LIST(&shipp->subsys_list); ss=GET_NEXT(ss)) {
                // check if subsys is alive
                if (ss->current_hits <= 0.0f) {
                        continue;
                }

                // check if it's a turret
                if (ss->system_info->type != SUBSYSTEM_TURRET) {
                        continue;
                }

                // if the turret is locked
                if(ss->weapons.flags & SW_FLAG_TURRET_LOCK){
                        continue;
                }               

                // check if turret is targeting target_objnum
                if (ss->turret_enemy_objnum == target_objnum) {
                        count++;
                }
        }

        return count;
}

float Lethality_range_const = 2.0f;
DCF(lethality_range, "N for modifying range: 1 / (1+N) at 100")
{
        dc_get_arg(ARG_FLOAT);
        Lethality_range_const = Dc_arg_float;
}

float Player_lethality_bump[NUM_SKILL_LEVELS] = {
        // 0.0f, 5.0f, 10.0f, 25.0f, 40.0f
        0.0f, 0.0f, 0.0f, 0.0f, 0.0f
};

// evaluate obj as posssible target for turret
void evaluate_obj_as_target(object *objp, eval_enemy_obj_struct *eeo)
{
        object  *turret_parent_obj = &Objects[eeo->turret_parent_objnum];
        ship            *shipp;
        model_subsystem *tp = eeo->turret_subsys->system_info;
        float dist;

        // Don't look for bombs when weapon system is not ok
        if (objp->type == OBJ_WEAPON && !eeo->weapon_system_ok) {
                return;
        }

        if ( !valid_turret_enemy(objp, turret_parent_obj) ) {
                return;
        }

#ifndef NDEBUG
        if (!Player_attacking_enabled && (objp == Player_obj)) {
                return;
        }
#endif

        if ( objp->type == OBJ_SHIP ) {
                shipp = &Ships[objp->instance];

                // check on enemy team
                if ( !(shipp->team & eeo->enemy_team_mask) ) {
                        return;
                }

                // check if protected
                if (objp->flags & OF_PROTECTED) {
                        return;
                }

                // check if beam protected
                if (Weapon_info[tp->turret_weapon_type].wi_flags & WIF_BEAM) {
                        if (objp->flags & OF_BEAM_PROTECTED) {
                                return;
                        }
                }

                if (eeo->big_only_flag) {
                        if (!(Ship_info[shipp->ship_info_index].flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP))) {
                                return;
                        }
                }

                // check if     turret flagged to only target tagged ships
                if ( (eeo->turret_subsys->weapons.flags & SW_FLAG_TAGGED_ONLY) && !ship_is_tagged(objp) ) {
                        return;
                }

                // check if valid target in nebula
                if ( !object_is_targetable(objp, &Ships[Objects[eeo->turret_parent_objnum].instance]) ) {
                        // BYPASS ocassionally for stealth
                        int try_anyway = FALSE;
                        if ( is_object_stealth_ship(objp) ) {
                                float turret_stealth_find_chance = 0.5f;
                                float speed_mod = -0.1f + vm_vec_mag_quick(&objp->phys_info.vel) / 70.0f;
                                if (frand() > (turret_stealth_find_chance + speed_mod)) {
                                        try_anyway = TRUE;
                                }
                        }

                        if (!try_anyway) {
                                return;
                        }
                }

        } else {
                shipp = NULL;
        }

        // modify dist for BIG|HUGE, getting closest point on bbox, if not inside
        dist = vm_vec_dist_quick(eeo->tpos, &objp->pos) - objp->radius;
        if (dist < 0.0f) {
                dist = 0.0f;
        }

        // check if object is a bomb attacking the turret parent
        // check if bomb is homing on the turret parent ship
        if (objp->type == OBJ_WEAPON) {
                if ( Weapons[objp->instance].homing_object == &Objects[eeo->turret_parent_objnum] ) {
                        if ( dist < eeo->nearest_homing_bomb_dist ) {
                                if ( (eeo->current_enemy == -1) || object_in_turret_fov(objp, tp, eeo->tvec, eeo->tpos, dist + objp->radius) ) {
                                        eeo->nearest_homing_bomb_dist = dist;
                                        eeo->nearest_homing_bomb_objnum = OBJ_INDEX(objp);
                                }
                        }
                // if not homing, check if bomb is flying towards ship
                } else if ( bomb_headed_towards_ship(objp, &Objects[eeo->turret_parent_objnum]) ) {
                        if ( dist < eeo->nearest_bomb_dist ) {
                                if ( (eeo->current_enemy == -1) || object_in_turret_fov(objp, tp, eeo->tvec, eeo->tpos, dist + objp->radius) ) {
                                        eeo->nearest_bomb_dist = dist;
                                        eeo->nearest_bomb_objnum = OBJ_INDEX(objp);
                                }
                        }
                }
        } // end weapon section

        // maybe recalculate dist for big or huge ship
//      if (shipp && (Ship_info[shipp->ship_info_index].flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP))) {
//              fvi_ray_boundingbox(min, max, start, direction, hit);
//              dist = vm_vec_dist_quick(hit, tvec);
//      }

        // check for nearest attcker
        if ( (shipp) && (dist < eeo->weapon_travel_dist) ) {
                ai_info *aip = &Ai_info[shipp->ai_index];

                // modify distance based on number of turrets from my ship attacking enemy (add 10% per turret)
                // dist *= (num_enemies_attacking(OBJ_INDEX(objp))+2)/2;        //      prevents lots of ships from attacking same target
                int num_att_turrets = num_turrets_attacking(turret_parent_obj, OBJ_INDEX(objp));
                dist *= (1.0f + 0.1f*num_att_turrets);

                // return if we're over the cap
                int max_turrets = 3 + Game_skill_level * Game_skill_level;
                if (num_att_turrets > max_turrets) {
                        return;
                }

                // modify distance based on lethality of objp to my ship
                float active_lethality = aip->lethality;
                if (objp->flags & OF_PLAYER_SHIP) {
                        active_lethality += Player_lethality_bump[Game_skill_level];
                }

                dist /= (1.0f + 0.01f*Lethality_range_const*active_lethality);

                // Make level 2 tagged ships more likely to be targeted
                if (shipp->level2_tag_left > 0.0f) {
                        dist *= 0.3f;
                }

                // check if objp is targeting the turret's ship, or if objp has just hit the turret's ship
                if ( aip->target_objnum == eeo->turret_parent_objnum || aip->last_objsig_hit == Objects[eeo->turret_parent_objnum].signature ) {
                        // A turret will always target a ship that is attacking itself... self-preservation!
                        if ( aip->targeted_subsys == eeo->turret_subsys ) {
                                dist *= 0.5f;   // highest priority
                        }
                }

                // maybe update nearest attacker
                if ( dist < eeo->nearest_attacker_dist ) {
                        if ( (eeo->current_enemy == -1) || object_in_turret_fov(objp, tp, eeo->tvec, eeo->tpos, dist + objp->radius) ) {
                                // nprintf(("AI", "Nearest enemy = %s, dist = %7.3f, dot = %6.3f, fov = %6.3f\n", Ships[objp->instance].ship_name, dist, vm_vec_dot(&v2e, tvec), tp->turret_fov));
                                eeo->nearest_attacker_dist = dist;
                                eeo->nearest_attacker_objnum = OBJ_INDEX(objp);
                        }
                }
        } // end ship section
}

// return 0 only if objnum is beam protected and turret is beam turret
int is_target_beam_valid(ship_subsys *turret_subsys, int objnum)
{
        // check if turret has beam weapon
        model_subsystem *tp = turret_subsys->system_info;

        if (Weapon_info[tp->turret_weapon_type].wi_flags & WIF_BEAM) {
                if (Objects[objnum].flags & OF_BEAM_PROTECTED) {
                        return 0;
                }

                if (Weapon_info[tp->turret_weapon_type].wi_flags & WIF_HUGE) {
                        if (Objects[objnum].type == OBJ_SHIP && !(Ship_info[Ships[Objects[objnum].instance].ship_info_index].flags & (SIF_BIG_SHIP|SIF_HUGE_SHIP)) ) {
                                return 0;
                        }
                }
        }

        return 1;
}


//      Given an object and an enemy team, return the index of the nearest enemy object.
//
// input:
//                              turret_parent_objnum    => parent objnum for the turret
//                              turret_subsys                   => pointer to system_info for the turret subsystem
//                              enemy_team_mask         => OR'ed TEAM_ flags for the enemy of the turret parent ship
//                              tpos                                            => position of turret (world coords)
//                              tvec                                            => forward vector of turret (world coords)
//                              current_enemy                   =>      objnum of current turret target
int get_nearest_turret_objnum(int turret_parent_objnum, ship_subsys *turret_subsys, int enemy_team_mask, vector *tpos, vector *tvec, int current_enemy, int big_only_flag)
{
        float                                   weapon_travel_dist;
        int                                     weapon_system_ok;
        object                          *objp;
        model_subsystem *tp;
        eval_enemy_obj_struct eeo;

        // list of stuff to go thru
        ship_obj                *so;
        missile_obj *mo;

        tp = turret_subsys->system_info;
        weapon_travel_dist = min(Weapon_info[tp->turret_weapon_type].lifetime * Weapon_info[tp->turret_weapon_type].max_speed, Weapon_info[tp->turret_weapon_type].weapon_range);

        // Set flag based on strength of weapons subsystem.  If weapons subsystem is destroyed, don't let turrets fire at bombs
        weapon_system_ok = 0;
        if ( ship_get_subsystem_strength( &Ships[Objects[turret_parent_objnum].instance], SUBSYSTEM_WEAPONS ) > 0 ) {
                weapon_system_ok = 1;
        }

        // Initialize eeo struct.
        eeo.turret_parent_objnum = turret_parent_objnum;
        eeo.weapon_system_ok = weapon_system_ok;
        eeo.weapon_travel_dist = weapon_travel_dist;
        eeo.big_only_flag = big_only_flag;
        eeo.enemy_team_mask = enemy_team_mask;
        eeo.current_enemy = current_enemy;
        eeo.tpos = tpos;
        eeo.tvec = tvec;
        eeo.turret_subsys = turret_subsys;

        eeo.nearest_attacker_dist = 99999.0f;
        eeo.nearest_attacker_objnum = -1;

        eeo.nearest_homing_bomb_dist = 99999.0f;
        eeo.nearest_homing_bomb_objnum = -1;

        eeo.nearest_bomb_dist = 99999.0f;
        eeo.nearest_bomb_objnum = -1;

        eeo.nearest_dist = 99999.0f;
        eeo.nearest_objnum = -1;


        // Missile_obj_list
        for( mo = GET_FIRST(&Missile_obj_list); mo != END_OF_LIST(&Missile_obj_list); mo = GET_NEXT(mo) ) {
                objp = &Objects[mo->objnum];
                evaluate_obj_as_target(objp, &eeo);
        }
        // highest priority
        if ( eeo.nearest_homing_bomb_objnum != -1 ) {                                   // highest priority is an incoming homing bomb
                return eeo.nearest_homing_bomb_objnum;
        } else if ( eeo.nearest_bomb_objnum != -1 ) {                                   // next highest priority is an incoming dumbfire bomb
                return eeo.nearest_bomb_objnum;
        }


        // Ship_used_list
        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                objp = &Objects[so->objnum];
                evaluate_obj_as_target(objp, &eeo);
        }

        Assert(eeo.nearest_attacker_objnum < 0 || is_target_beam_valid(turret_subsys, eeo.nearest_attacker_objnum));
                // next highest priority is attacking ship
        if ( eeo.nearest_attacker_objnum != -1 ) {                      // next highest priority is an attacking ship
                return eeo.nearest_attacker_objnum;
         }


#ifndef FS2_DEMO
                asteroid_obj *ao;
        // Asteroid_obj_list
        for( ao = GET_FIRST(&Asteroid_obj_list); ao != END_OF_LIST(&Asteroid_obj_list); ao = GET_NEXT(ao) ) {
                objp = &Objects[ao->objnum];
                evaluate_obj_as_target(objp, &eeo);
        }
#endif

        return eeo.nearest_objnum;                                                                              // lowest priority is the closest enemy objnum
}

//      Return timestamp until a ship can find an enemy.
//      Yes, no parameters.  Based solely on skill level.
int get_enemy_timestamp()
{
        return (NUM_SKILL_LEVELS - Game_skill_level) * ( (myrand() % 500) + 500);
}

// -------------------------------------------------------------------
//      Return objnum if enemy found, else return -1;
//      Don't attack a ship that already has at least max_attackers attacking it.
int find_enemy(int objnum, float range, int max_attackers)
{
        int     enemy_team_mask;

        enemy_team_mask = get_enemy_team_mask(objnum);

        //      if target_objnum != -1, use that as goal.
        ai_info *aip = &Ai_info[Ships[Objects[objnum].instance].ai_index];
        if (timestamp_elapsed(aip->choose_enemy_timestamp)) {
                aip->choose_enemy_timestamp = timestamp(get_enemy_timestamp());
                if (aip->target_objnum != -1) {
                        int     target_objnum = aip->target_objnum;

                        // DKA don't undo object as target in nebula missions.
                        // This could cause attack on ship on fringe on nebula to stop if attackee moves our of nebula range.  (BAD)
                        if ( (Objects[target_objnum].signature == aip->target_signature) ) {
                                if (Ships[Objects[target_objnum].instance].team & enemy_team_mask) {
                                        if (!(Objects[target_objnum].flags & OF_PROTECTED)) {
                                                // nprintf(("AI", "Frame %i: Object %i resuming goal of object %i\n", AI_FrameCount, objnum, target_objnum));
                                                return target_objnum;
                                        }
                                }
                        } else {
                                aip->target_objnum = -1;
                                aip->target_signature = -1;
                        }
                }
                return get_nearest_objnum(objnum, enemy_team_mask, aip->enemy_wing, range, max_attackers);
        } else {
                aip->target_objnum = -1;
                aip->target_signature = -1;
                return -1;
        }

}

int Use_parent_target = 0;
DCF_BOOL(use_parent_target, Use_parent_target)

// -------------------------------------------------------------------
//      Return objnum if enemy found, else return -1;
//
// input:
//                              turret_subsys   => pointer to turret subsystem
//                              objnum                  => parent objnum for the turret
//                              tpos                            => position of turret (world coords)
//                              tvec                            => forward vector of turret (world coords)
//                              current_enemy   =>      objnum of current turret target
int find_turret_enemy(ship_subsys *turret_subsys, int objnum, vector *tpos, vector *tvec, int current_enemy, float fov, int big_only_flag = 0)
{
        int                                     enemy_team_mask, enemy_objnum;
        model_subsystem *tp;
        ship_info                       *sip;

        tp = turret_subsys->system_info;
        enemy_team_mask = get_enemy_team_mask(objnum);

        //      If a small ship and target_objnum != -1, use that as goal.
        ai_info *aip = &Ai_info[Ships[Objects[objnum].instance].ai_index];
        sip = &Ship_info[Ships[Objects[objnum].instance].ship_info_index];

        if ((sip->flags & SIF_SMALL_SHIP) && (aip->target_objnum != -1)) {
                int target_objnum = aip->target_objnum;

                if (Objects[target_objnum].signature == aip->target_signature) {
                        if (Ships[Objects[target_objnum].instance].team & enemy_team_mask) {
                                if ( !(Objects[target_objnum].flags & OF_PROTECTED) ) {         // check this flag as well.
                                        // nprintf(("AI", "Frame %i: Object %i resuming goal of object %i\n", AI_FrameCount, objnum, target_objnum));
                                        return target_objnum;
                                }
                        }
                } else {
                        aip->target_objnum = -1;
                        aip->target_signature = -1;
                }
        // Not small or small with target objnum
        } else {
                // maybe use aip->target_objnum as next target
                if ((frand() < 0.8f) && (aip->target_objnum != -1) && Use_parent_target) {

                        //check if aip->target_objnum is valid target
                        int target_flags = Objects[aip->target_objnum].flags;
                        if ( target_flags & OF_PROTECTED ) {
                                // AL 2-27-98: why is a protected ship being targeted?
                                set_target_objnum(aip, -1);
                                return -1;
                        }

                        // maybe use ship target_objnum if valid for turret
                        // check for beam weapon and beam protected
                        if ( !((target_flags & OF_BEAM_PROTECTED) && (Weapon_info[tp->turret_weapon_type].wi_flags & WIF_BEAM)) ) {
                                if ( Objects[aip->target_objnum].type == OBJ_SHIP ) {
                                        // check for huge weapon and huge ship
                                        if ( !big_only_flag || (Ship_info[Ships[Objects[aip->target_objnum].instance].ship_info_index].flags & (SIF_BIG_SHIP|SIF_HUGE_SHIP)) ) {
                                                // check for tagged only and tagged ship
                                                if ( (turret_subsys->weapons.flags & SW_FLAG_TAGGED_ONLY) && ship_is_tagged(&Objects[aip->target_objnum]) ) {
                                                        // select new target if aip->target_objnum is out of field of view
                                                        vector v2e;
                                                        float dot, dist;
                                                        dist = vm_vec_normalized_dir(&v2e, &Objects[aip->target_objnum].pos, tpos);
                                                        dot = vm_vec_dot(&v2e, tvec);
                                                        //      MODIFY FOR ATTACKING BIG SHIP
                                                        // dot += (0.5f * Objects[aip->target_objnum].radius / dist);
                                                        if (dot > fov) {
                                                                return aip->target_objnum;
                                                        }
                                                }
                                        }
                                }
                        }
                }
        }

        enemy_objnum = get_nearest_turret_objnum(objnum, turret_subsys, enemy_team_mask, tpos, tvec, current_enemy, big_only_flag);
        if ( enemy_objnum >= 0 ) {
                Assert( !((Objects[enemy_objnum].flags & OF_BEAM_PROTECTED) && (Weapon_info[tp->turret_weapon_type].wi_flags & WIF_BEAM)) );
                if ( Objects[enemy_objnum].flags & OF_PROTECTED ) {
                        Int3();
                        enemy_objnum = aip->target_objnum;
                }
        }

        return enemy_objnum;
}

//      If issued an order to a ship that's awaiting repair, abort that process.
//      However, do not abort process for an object that is currently being repaired -- let it finish.
void ai_set_goal_maybe_abort_dock(object *objp, ai_info *aip)
{
        if (aip->ai_flags & AIF_AWAITING_REPAIR) {
                object  *repair_obj;

                if (aip->dock_objnum == -1) {
                        repair_obj = NULL;
                } else {
                        repair_obj = &Objects[aip->dock_objnum];
                }
                ai_do_objects_repairing_stuff( objp, repair_obj, REPAIR_INFO_ABORT );
        }
        aip->next_rearm_request_timestamp = timestamp(NEXT_REARM_TIMESTAMP);    //      Might request again after 30 seconds.
}

void force_avoid_player_check(object *objp, ai_info *aip)
{
        if (Ships[objp->instance].team == Player_ship->team){
                aip->avoid_check_timestamp = timestamp(0);              //      Force a check for collision next frame.
        }
}

//      --------------------------------------------------------------------------
//      Set *attacked as object to attack for object *attacker
//      If attacked == NULL, then attack any enemy object.
//      Attack point *rel_pos on object.  This is for supporting attacking subsystems.
void ai_attack_object(object *attacker, object *attacked, int priority, ship_subsys *ssp)
{
        ai_info *aip;

        Assert(attacker != NULL);
        Assert(attacker->instance != -1);
        Assert(Ships[attacker->instance].ai_index != -1);

        aip = &Ai_info[Ships[attacker->instance].ai_index];
        force_avoid_player_check(attacker, aip);

        aip->ok_to_target_timestamp = timestamp(0);             //      Guarantee we can target.

//      if (!strnicmp(Ships[attacker->instance].ship_name, NOX("Kami"), 4)) {
//              aip->ai_flags |= AIF_KAMIKAZE;
//              aip->ai_flags |= AIF_NO_DYNAMIC;
//      }

        if (attacker == attacked) {
                Int3();         //      Bogus!  Who tried to get me to attack myself!  Trace out and fix!
                return;
        }

        //      Only set to chase if a fighter or bomber, otherwise just return.
        if (!(Ship_info[Ships[attacker->instance].ship_info_index].flags & SIF_SMALL_SHIP)) {
//              nprintf(("AI","Note: AI ship %s refusing to set AI mode to AIM_CHASE\n", Ships[attacker->instance].ship_name));
//              return;
                nprintf(("AI", "AI ship %s is large ship ordered to attack %s\n", Ships[attacker->instance].ship_name, Ships[attacked->instance].ship_name));
        }

        //      This is how "engage enemy" gets processed
        if (attacked == NULL) {
                aip->choose_enemy_timestamp = timestamp(0);
                // nebula safe
                set_target_objnum(aip, find_enemy(attacker-Objects, 99999.9f, 4));
        } else {
                // check if we can see atacked in nebula
                if (aip->target_objnum != attacked - Objects) {
                        aip->aspect_locked_time = 0.0f;
                }
                set_target_objnum(aip, attacked - Objects);
        }

        ai_set_goal_maybe_abort_dock(attacker, aip);
        aip->ok_to_target_timestamp = timestamp(DELAY_TARGET_TIME);     //      No dynamic targeting for 7 seconds.

        if (is_ignore_object(aip, aip->target_objnum)) {
                aip->ignore_objnum = UNUSED_OBJNUM;
        }

        aip->mode = AIM_CHASE;
        aip->submode = SM_ATTACK;       // AL 12-15-97: need to set submode?  I got an assert() where submode was bogus
                                                                                //                                       for AIM_CHASE... it may have been not set correctly here
        if (ssp == NULL) {
                set_targeted_subsys(aip, NULL, -1);
                if (aip->target_objnum != -1) {
                        //nprintf(("AI", "Unprotecting ship %s\n", Ships[Objects[aip->target_objnum].instance].ship_name));
                        Objects[aip->target_objnum].flags &= ~OF_PROTECTED;     //      If ship had been protected, unprotect it.
                }
        } else {
                Int3(); //      Not supported yet!
        }
}

//      --------------------------------------------------------------------------
//      Set *attacked as object to attack for object *attacker
//      Attack point *rel_pos on object.  This is for supporting attacking subsystems.
void ai_attack_wing(object *attacker, int wingnum, int priority)
{
        ai_info *aip;

        Assert(attacker != NULL);
        Assert(attacker->instance != -1);
        Assert(Ships[attacker->instance].ai_index != -1);

        aip = &Ai_info[Ships[attacker->instance].ai_index];

        aip->enemy_wing = wingnum;
        aip->mode = AIM_CHASE;
        aip->submode = SM_ATTACK;       // AL 12-15-97: need to set submode?  I got an assert() where submode was bogus
                                                                                //                                       for AIM_CHASE... it may have been not set correctly here

        aip->ok_to_target_timestamp = timestamp(0);             //      Guarantee we can target.

        int count = Wings[wingnum].current_count;
        if (count > 0) {
                int     index;

                index = (int) (frand() * count);

                if (index >= count)
                        index = 0;

                set_target_objnum(aip, Ships[Wings[wingnum].ship_index[index]].objnum);

                ai_set_goal_maybe_abort_dock(attacker, aip);
                aip->ok_to_target_timestamp = timestamp(DELAY_TARGET_TIME);     //      No dynamic targeting for 7 seconds.
        }
}

//      --------------------------------------------------------------------------
//      Set *evaded as object for *evader to evade.
void ai_evade_object(object *evader, object *evaded, int priority)
{
        ai_info *aip;

        Assert(evader != NULL);
        Assert(evaded != NULL);
        Assert(evader->instance != -1);
        Assert(Ships[evader->instance].ai_index != -1);

        if (evaded == evader) {
                Int3(); //      Bogus!  Who tried to get me to evade myself!  Trace out and fix!
                return;
        }

        aip = &Ai_info[Ships[evader->instance].ai_index];

        set_target_objnum(aip, evaded - Objects);
        aip->mode = AIM_EVADE;

}

//      Ignore some object without changing mode.
void ai_ignore_object(object *ignorer, object *ignored, int priority)
{
        ai_info *aip;

        Assert(ignorer != NULL);
        Assert(ignored != NULL);
        Assert(ignorer->instance != -1);
        Assert(Ships[ignorer->instance].ai_index != -1);
        Assert(ignorer != ignored);

        aip = &Ai_info[Ships[ignorer->instance].ai_index];

        //      MK, 5/17/98, removing ignoring of wings.
        //      It's too confusing.  It often causes mysterious behavior in which fighters unexpectedly refuse to attack anything.
/*      if (Ships[ignored->instance].wingnum > -1) {
                int wingnum, i;

                wingnum = Ships[ignored->instance].wingnum;
                aip->ignore_objnum = -(wingnum+1);
                // set protected bit for each ship in a wing
                //      MK, 4/23/98: Only set for fighters if they are the original "ignored" object
                for (i = 0; i < Wings[wingnum].current_count; i++ ) {
                        object  *objp;

                        objp = &Objects[Ships[Wings[wingnum].ship_index[i]].objnum];
                        if (objp != ignored) {
                                if (Ship_info[Ships[objp->instance].ship_info_index].flags & (SIF_FIGHTER | SIF_BOMBER))
                                        continue;
                        }

                        Objects[Ships[Wings[wingnum].ship_index[i]].objnum].flags |= OF_PROTECTED;
                }

        } else {
        */ {
                aip->ignore_objnum = ignored - Objects;
                aip->ignore_signature = ignored->signature;
                aip->ai_flags &= ~AIF_TEMPORARY_IGNORE;
                ignored->flags |= OF_PROTECTED;                                 // set protected bit of ignored ship.
        }

}

//      Ignore some object without changing mode.
void ai_ignore_wing(object *ignorer, int wingnum, int priority)
{
        ai_info *aip;

        Assert(ignorer != NULL);
        Assert(ignorer->instance != -1);
        Assert(Ships[ignorer->instance].ai_index != -1);
        Assert((wingnum >= 0) && (wingnum < MAX_WINGS));

        aip = &Ai_info[Ships[ignorer->instance].ai_index];

        aip->ignore_objnum = -(wingnum +1);
        aip->ai_flags &= ~AIF_TEMPORARY_IGNORE;
}


//      Add a path point in the global buffer Path_points.
//      modify_index = index in Path_points at which to store path point.
//      If modify_index == -1, then create a new point.
//      If a new point is created (ie, modify_index == -1), then Ppfp is updated.
void add_path_point(vector *pos, int path_num, int path_index, int modify_index)
{
        pnode   *pnp;

        if (modify_index == -1) {
                Assert(Ppfp-Path_points < MAX_PATH_POINTS-1);
                pnp = Ppfp;
                Ppfp++;
        } else {
                Assert((modify_index >= 0) && (modify_index < MAX_PATH_POINTS-1));
                pnp = &Path_points[modify_index];
        }

        pnp->pos = *pos;
        pnp->path_num = path_num;
        pnp->path_index = path_index;
}

//      Given two points on a sphere, the center of the sphere and the radius, return a
//      point on the vector through the midpoint of the chord on the sphere.
void bisect_chord(vector *p0, vector *p1, vector *centerp, float radius)
{
        vector  tvec;
        vector  new_pnt;

        vm_vec_add(&tvec, p0, p1);
        vm_vec_sub2(&tvec, centerp);
        vm_vec_sub2(&tvec, centerp);
        if (vm_vec_mag_quick(&tvec) < 0.1f) {
                vm_vec_sub(&tvec, p0, p1);
                if (fl_abs(tvec.xyz.x) <= fl_abs(tvec.xyz.z)){
                        tvec.xyz.x = -tvec.xyz.z;
                } else {
                        tvec.xyz.y = -tvec.xyz.x;
                }
        }

        vm_vec_normalize(&tvec);
        vm_vec_scale(&tvec, radius);
        vm_vec_add(&new_pnt, centerp, &tvec);

        add_path_point(&new_pnt, -1, -1, -1);
}
                        
//      Create a path from the current position to a goal position.
//      The current position is in the current object and the goal position is
//      in the goal object.
//      It is ok to intersect the current object, but not the goal object.
//      This function is useful for creating a path to an initial point near a large
//      object.
//
// input:       subsys_path:    optional param (default 0), indicates this is a path to a subsystem
void create_path_to_point(vector *curpos, vector *goalpos, object *curobjp, object *goalobjp, int subsys_path)
{
        //      If can't cast vector to goalpos, then create an intermediate point.
        if (pp_collide(curpos, goalpos, goalobjp, curobjp->radius)) {
                vector  tan1;
                float           radius;

                // If this is a path to a subsystem, use SUBSYS_PATH_DIST as the radius for the object you are
                // trying to avoid.  This is needed since subsystem paths extend out to SUBSYS_PATH_DIST, and we
                // want ships to reach their path destination without flying to points that sit on the radius of
                // a small ship
                radius = goalobjp->radius;
                if (subsys_path) {
                        if ( SUBSYS_PATH_DIST > goalobjp->radius ) {
                                radius = SUBSYS_PATH_DIST;
                        }
                }

                //      The intermediate point is at the intersection of:
                //              tangent to *goalobjp sphere at point *goalpos
                //              tangent to *goalobjp sphere through point *curpos in plane defined by *curpos, *goalpos, goalobjp->pos
                //      Note, there are two tangents through *curpos, unless *curpos is on the
                //      sphere.  The tangent that causes the nearer intersection (to *goalpos) is chosen.
                get_tangent_point(&tan1, curpos, &goalobjp->pos, goalpos, radius);

                //      If we can't reach tan1 from curpos, insert a new point.
                if (pp_collide(&tan1, curpos, goalobjp, curobjp->radius))
                        bisect_chord(curpos, &tan1, &goalobjp->pos, radius);

                add_path_point(&tan1, -1, -1, -1);

                //      If we can't reach goalpos from tan1, insert a new point.
                if (pp_collide(goalpos, &tan1, goalobjp, curobjp->radius))
                        bisect_chord(goalpos, &tan1, &goalobjp->pos, radius);
        }

}

//      Given an object and a model path, globalize the points on the model
//      and copy into the global path list.
//      If pnp != NULL, then modify, in place, the path points.  This is used to create new
//      globalized points when the base object has moved.
// input:       randomize_pnt   => optional parameter (default value -1), add random vector in sphere to this path point
void copy_xlate_model_path_points(object *objp, model_path *mp, int dir, int count, int path_num, pnode *pnp, int randomize_pnt)
{
        matrix  m;
        int             i;
        vector  v1;
        int             pp_index;               //      index in Path_points at which to store point, if this is a modify-in-place (pnp ! NULL)
        int             start_index, finish_index;
        
        // nprintf(("AI", "Creating path for object %s in frame #%i\n", Ships[objp->instance].ship_name, AI_FrameCount));
        
        //      Initialize pp_index.
        //      If pnp == NULL, that means we're creating new points.  If not NULL, then modify in place.
        if (pnp == NULL)
                pp_index = -1;                  //      This tells add_path_point to create a new point.
        else
                pp_index = 0;                   //      pp_index will get assigned to index in Path_points to reuse.

        vm_copy_transpose_matrix(&m, &objp->orient);

        if (dir == 1) {
                start_index = 0;
                finish_index = min(count, mp->nverts);
        } else {
                Assert(dir == -1);      //      direction must be up by 1 or down by 1 and it's neither!
                start_index = mp->nverts-1;
                finish_index = max(-1, mp->nverts-1-count);
        }

        int offset = 0;
        for (i=start_index; i != finish_index; i += dir) {
                //      Globalize the point.
                vm_vec_rotate(&v1, &mp->verts[i].pos, &m);
                vm_vec_add2(&v1, &objp->pos);

                if ( randomize_pnt == i ) {
                        vector v_rand;
                        static_randvec(OBJ_INDEX(objp), &v_rand);
                        vm_vec_scale(&v_rand, 30.0f);
                        vm_vec_add2(&v1, &v_rand);
                }

                if (pp_index != -1)
                        pp_index = pnp-Path_points + offset;

                add_path_point(&v1, path_num, i, pp_index);
                offset++;
        }
}


//      For pl_objp, create a path along path path_num into mobjp.
//      The tricky part of this problem is creating the entry to the first point on the
//      predefined path.  The points on this entry path are based on the location of Pl_objp
//      relative to the start of the path.
//
// input:
//                              subsys_path:    optional param (default 0), indicating this is a path to a subsystem
void create_model_path(object *pl_objp, object *mobjp, int path_num, int subsys_path)
{       
        ship                    *shipp = &Ships[pl_objp->instance];
        ai_info         *aip = &Ai_info[shipp->ai_index];

        ship_info       *osip = &Ship_info[Ships[mobjp->instance].ship_info_index];
        polymodel       *pm = model_get(osip->modelnum);
        int                     num_points;
        model_path      *mp;
        pnode                   *ppfp_start = Ppfp;
        matrix          m;
        vector          gp0;

        Assert(path_num >= 0);

        //      Do garbage collection if necessary.
        if (Ppfp-Path_points + 64 > MAX_PATH_POINTS) {
                garbage_collect_path_points();
                ppfp_start = Ppfp;
        }

        aip->path_start = Ppfp - Path_points;
        Assert(path_num < pm->n_paths);
        
        mp = &pm->paths[path_num];
        num_points = mp->nverts;

        Assert(Ppfp-Path_points + num_points + 4 < MAX_PATH_POINTS);

        vm_copy_transpose_matrix(&m, &mobjp->orient);
        vm_vec_rotate(&gp0, &mp->verts[0].pos, &m);
        vm_vec_add2(&gp0, &mobjp->pos);

        if (pp_collide(&pl_objp->pos, &gp0, mobjp, pl_objp->radius)) {
                vector  perim_point1;
                vector  perim_point2;

                perim_point2 = pl_objp->pos;
                
                //      If object that wants to dock is inside bounding sphere of object it wants to dock with, make it fly out.
                //      Assume it can fly "straight" out to the bounding sphere.
                if (vm_vec_dist_quick(&pl_objp->pos, &mobjp->pos) < mobjp->radius) {
                        project_point_to_perimeter(&perim_point2, &mobjp->pos, mobjp->radius, &pl_objp->pos);
                        add_path_point(&perim_point2, path_num, -1, -1);
                }

                //      If last point on pre-defined path is inside bounding sphere, create a new point on the surface of the sphere.
                if (vm_vec_dist_quick(&mobjp->pos, &gp0) < mobjp->radius) {
                        project_point_to_perimeter(&perim_point1, &mobjp->pos, mobjp->radius, &gp0);
                        create_path_to_point(&perim_point2, &perim_point1, pl_objp, mobjp, subsys_path);
                        add_path_point(&perim_point1, path_num, -1, -1);
                } else {                //      The predefined path extends outside the sphere.  Create path to that point.
                        create_path_to_point(&perim_point2, &gp0, pl_objp, mobjp, subsys_path);
                }
        }

        // AL 12-31-97: If following a subsystem path, add random vector to second last path point
        if ( subsys_path ) {
                copy_xlate_model_path_points(mobjp, mp, 1, mp->nverts, path_num, NULL, mp->nverts-2);
        } else {
                copy_xlate_model_path_points(mobjp, mp, 1, mp->nverts, path_num, NULL);
        }

        aip->path_cur = aip->path_start;
        aip->path_dir = PD_FORWARD;
        aip->path_objnum = mobjp-Objects;
        aip->mp_index = path_num;
        aip->path_length = Ppfp - ppfp_start;
        aip->path_next_check_time = timestamp(1);

        aip->path_goal_obj_hash = create_object_hash(&Objects[aip->path_objnum]);

        aip->path_next_create_time = timestamp(1000);   //      OK to try to create one second later
        aip->path_create_pos = pl_objp->pos;
        aip->path_create_orient = pl_objp->orient;

        aip->ai_flags &= ~AIF_USE_EXIT_PATH;                    // ensure this flag is cleared
}

//      For pl_objp, create a path along path path_num into mobjp.
//      The tricky part of this problem is creating the entry to the first point on the
//      predefined path.  The points on this entry path are based on the location of pl_objp
//      relative to the start of the path.
void create_model_exit_path(object *pl_objp, object *mobjp, int path_num, int count)
{       
        ship                    *shipp = &Ships[pl_objp->instance];
        ai_info         *aip = &Ai_info[shipp->ai_index];

        ship_info       *osip = &Ship_info[Ships[mobjp->instance].ship_info_index];
        polymodel       *pm = model_get(osip->modelnum);
        int                     num_points;
        model_path      *mp;
        pnode                   *ppfp_start = Ppfp;

        aip->path_start = Ppfp - Path_points;
        Assert(path_num < pm->n_paths);
        
        mp = &pm->paths[path_num];
        num_points = mp->nverts;

        Assert(Ppfp-Path_points + num_points + 4 < MAX_PATH_POINTS);

        copy_xlate_model_path_points(mobjp, mp, -1, count, path_num, NULL);

        aip->path_cur = aip->path_start;
        aip->path_dir = PD_FORWARD;
        aip->path_objnum = mobjp-Objects;
        aip->mp_index = path_num;
        aip->path_length = Ppfp - ppfp_start;
        aip->path_next_check_time = timestamp(1);

        aip->ai_flags |= AIF_USE_EXIT_PATH;             // mark as exit path, referenced in maybe
}

//      Return true if the vector from curpos to goalpos intersects with any ship other than the ignore objects.
//      Calls pp_collide
int pp_collide_any(vector *curpos, vector *goalpos, float radius, object *ignore_objp1, object *ignore_objp2, int big_only_flag)
{
        ship_obj        *so;    

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                object *objp = &Objects[so->objnum];

                if (big_only_flag) {
                        if (!(Ship_info[Ships[objp->instance].ship_info_index].flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP)))
                                continue;
                }

                if ((objp != ignore_objp1) && (objp != ignore_objp2)) {
                        if (pp_collide(curpos, goalpos, objp, radius))
                                return OBJ_INDEX(objp);
                }
        }

        return -1;
}

//      Used to create docking paths and other pre-defined paths through ships.
//      Creates a path in absolute space.
//      Create a path into the object objnum.
//
// input:
//      pl_objp:                        object that will use the path
//      objnum:                 Object to find path to.
//      path_num:               model path index to use
//      exit_flag:              true means this is an exit path in the model
// subsys_path: optional param (default 0) that indicates this is a path to a subsystem
//      Exit:
//      ai_info struct in Pl_objp gets stuffed with information to enable Pl_objp to fly the path.
void ai_find_path(object *pl_objp, int objnum, int path_num, int exit_flag, int subsys_path)
{
        ai_info *aip = &Ai_info[Ships[pl_objp->instance].ai_index];

        Assert(path_num >= 0);

        //      This is test code, find an object with paths.
        if (objnum != -1) {
                object  *objp = &Objects[objnum];

                if (objp->type == OBJ_SHIP) {
                        polymodel *pm;

                        ship    *shipp = &Ships[objp->instance];
                        pm = model_get( shipp->modelnum );
                        Assert(pm->n_paths > path_num);
                        aip->goal_objnum = objp-Objects;
                        aip->goal_signature = objp->signature;
                        if (exit_flag)
                                create_model_exit_path(pl_objp, objp, path_num);
                        else
                                create_model_path(pl_objp, objp, path_num, subsys_path);
                        return;
                }

        }
}

extern int vector_object_collision(vector *start_pos, vector *end_pos, object *objp, float radius_scale);

//      Maybe make *objp avoid a player object.
//      For now, 4/6/98, only check Player_obj.
//      If player collision would occur, set AIF_AVOIDING_SMALL_SHIP bit in ai_flags.
//      Set aip->avoid_goal_point
int maybe_avoid_player(object *objp, vector *goal_pos)
{
        ai_info *aip;
        vector  cur_pos, new_goal_pos;
        object  *player_objp;
        vector  n_vec_to_goal, n_vec_to_player;

        aip = &Ai_info[Ships[objp->instance].ai_index];

        if (!timestamp_elapsed(aip->avoid_check_timestamp))
                return 0;

        player_objp = Player_obj;

        float   speed_time;

        //      How far two ships could be apart and still collide within one second.
        speed_time = player_objp->phys_info.speed + objp->phys_info.speed;

        float   obj_obj_dist;

        obj_obj_dist = vm_vec_dist_quick(&player_objp->pos, &objp->pos);

        if (obj_obj_dist > speed_time*2.0f)
                return 0;

        cur_pos = objp->pos;

        new_goal_pos = *goal_pos;

        float dist = vm_vec_normalized_dir(&n_vec_to_goal, goal_pos, &objp->pos);
        vm_vec_normalized_dir(&n_vec_to_player, &player_objp->pos, &objp->pos);

        if (dist > speed_time*2.0f) {
                vm_vec_scale_add(&new_goal_pos, &objp->pos, &n_vec_to_goal, 200.0f);
        }

        if (vector_object_collision(&objp->pos, &new_goal_pos, player_objp, 1.5f)) {
                aip->ai_flags |= AIF_AVOIDING_SMALL_SHIP;

                vector  avoid_vec;

                vm_vec_sub(&avoid_vec, &n_vec_to_goal, &n_vec_to_player);
                if (vm_vec_mag_quick(&avoid_vec) < 0.01f) {
                        vm_vec_copy_scale(&avoid_vec, &objp->orient.v.rvec, frand()-0.5f);
                        vm_vec_scale_add2(&avoid_vec, &objp->orient.v.uvec, frand()-0.5f);
                        vm_vec_normalize(&avoid_vec);
                } else {
                        vector  tvec1;
                        vm_vec_normalize(&avoid_vec);
                        vm_vec_crossprod(&tvec1, &n_vec_to_goal, &avoid_vec);
                        vm_vec_crossprod(&avoid_vec, &tvec1, &n_vec_to_player);
                }

                //      Now, avoid_vec is a vector perpendicular to the vector to the player and the direction *objp
                //      should fly in to avoid the player while still approaching its goal.
                vm_vec_scale_add(&aip->avoid_goal_point, &player_objp->pos, &avoid_vec, 400.0f);

                aip->avoid_check_timestamp = timestamp(1000);

                return 1;
        } else {
                aip->ai_flags &= ~AIF_AVOIDING_SMALL_SHIP;
                aip->avoid_check_timestamp = timestamp((int) (obj_obj_dist/200.0f) + 500);

                return 0;
        }
}

//      Make object *still_objp enter AIM_STILL mode.
//      Make it point at view_pos.
void ai_stay_still(object *still_objp, vector *view_pos)
{
        ship    *shipp;
        ai_info *aip;

        Assert(still_objp->type == OBJ_SHIP);
        Assert((still_objp->instance >= 0) && (still_objp->instance < MAX_OBJECTS));

        shipp = &Ships[still_objp->instance];
        Assert((shipp->ai_index >= 0) && (shipp->ai_index < MAX_AI_INFO));

        aip = &Ai_info[shipp->ai_index];

        aip->mode = AIM_STILL;

        //      If view_pos not NULL, point at that point.  Else, point at a point directly in front of ship.  Ie, don't turn.
        if (view_pos != NULL)
                aip->goal_point = *view_pos;
        else
                vm_vec_scale_add(&aip->goal_point, &still_objp->pos, &still_objp->orient.v.fvec, 100.0f);
}

// code which is called from ai_dock_with_object and ai_dock to set flags and apprioriate variable
// when two objects have completed docking.  used because we can dock object initially at misison load
// time (meaning that ai_dock() might never get called).  docker has docked with dockee (i.e. docker
// would be a freighter and dockee would be a cargo).
void ai_do_objects_docked_stuff(object *docker, object *dockee)
{
        ai_info *aip, *other_aip;

        aip = &Ai_info[Ships[docker->instance].ai_index];
        other_aip = &Ai_info[Ships[dockee->instance].ai_index];

        // set the flags and dock_objnum for both objects
        aip->ai_flags |= AIF_DOCKED;
        aip->dock_objnum = OBJ_INDEX(dockee);
        other_aip->ai_flags |= AIF_DOCKED;
        other_aip->dock_objnum = OBJ_INDEX(docker);
        aip->dock_signature = dockee->signature;
        other_aip->dock_signature = docker->signature;

        // add multiplayer hook here to deal with docked objects.  We need to only send information
        // about the object that is docking.  Both flags will get updated.
        if ( MULTIPLAYER_MASTER )
                send_ai_info_update_packet( docker, AI_UPDATE_DOCK );

}

// code which is called when objects become undocked. Equivalent of above function.
// dockee might not be valid since this code can get called to cleanup after a ship
// has blown up!
void ai_do_objects_undocked_stuff( object *docker, object *dockee )
{
        ai_info *aip, *other_aip;

        // add multiplayer hook here to deal with undocked objects.  Do it before we
        // do anything else.  We don't need to send info for both objects, since we can find
        // it be dock_objnum
        if ( MULTIPLAYER_MASTER )
                send_ai_info_update_packet( docker, AI_UPDATE_UNDOCK );

        aip = &Ai_info[Ships[docker->instance].ai_index];

        // set the flags and dock_objnum for both objects
        aip->ai_flags &= ~(AIF_DOCKED | AIF_BEING_REPAIRED);
        aip->dock_objnum = -1;
        
        if ( dockee != NULL ) {
                other_aip = &Ai_info[Ships[dockee->instance].ai_index];
                other_aip->ai_flags &= ~(AIF_DOCKED | AIF_BEING_REPAIRED);
                other_aip->dock_objnum = -1;
        }

}


//      --------------------------------------------------------------------------
//      Interface from goals code to AI.
//      Cause *docker to dock with *dockee.
//      priority is priority of goal from goals code.
//      dock_type is:
//              AIDO_DOCK               set goal of docking
//              AIDO_DOCK_NOW   immediately dock, used for ships that need to be docked at mission start
//              AIDO_UNDOCK             set goal of undocking
void ai_dock_with_object(object *docker, object *dockee, int priority, int dock_type, int docker_index, int dockee_index)
{
        ai_info         *aip;
        polymodel       *pm;
        ai_info         *dockee_aip;

        Assert(docker != NULL);
        Assert(dockee != NULL);
        Assert(docker->instance != -1);
        Assert(Ships[docker->instance].ai_index != -1);
        Assert(Ships[dockee->instance].ai_index != -1);
        Assert( docker_index != -1 );
        Assert( dockee_index != -1 );

        aip = &Ai_info[Ships[docker->instance].ai_index];

        if ((aip->ai_flags & AIF_DOCKED) && (dock_type == AIDO_DOCK)) {
                object  *dockee2;
                int             docker_index2, dockee_index2;

                Assert(aip->dock_objnum > -1);
                dockee2 = &Objects[aip->dock_objnum];
                docker_index2 = aip->dock_index;
                dockee_index2 = aip->dockee_index;
                // MWA -- 2/9/98.  use the goal code to undock the ships since goals might need to get removed
                // and that code will do it properly.  I'd actually be surprised if we got into this code anymore
                // since the outer layer goal code should deal with this issue....but who knows...
                ai_add_goal_ship_internal( aip, AI_GOAL_UNDOCK, NULL, -1, -1, 0 );

                // old code below
                //ai_dock_with_object(docker, dockee2, priority, AIDO_UNDOCK, docker_index2, dockee_index2);
                nprintf(("AI", "Ship %s told to dock with %s, but it was already docked with %s.\n", Ships[docker->instance].ship_name, Ships[dockee->instance].ship_name, Ships[Objects[aip->dock_objnum].instance].ship_name));
                nprintf(("AI", "...so ship %s will now undock.\n", Ships[docker->instance].ship_name));
                return;
        }

        dockee_aip = &Ai_info[Ships[dockee->instance].ai_index];

        aip->goal_objnum = dockee - Objects;
        aip->goal_signature = dockee->signature;

        aip->mode = AIM_DOCK;

        switch (dock_type) {
        case AIDO_DOCK:
                aip->submode = AIS_DOCK_0;
                break;
        case AIDO_DOCK_NOW:
                aip->submode = AIS_DOCK_3A;
                break;
        case AIDO_UNDOCK:
                aip->submode = AIS_UNDOCK_0;
                break;
        default:
                Int3();         //      Bogus dock_type.
        }

        aip->submode_start_time = Missiontime;
        aip->dock_index = docker_index;
        aip->dockee_index = dockee_index;

        dockee_aip->dock_index = dockee_index;
        dockee_aip->dockee_index = docker_index;

        // get the path number to the docking point on the dockee.  Each docking point contains a list
        // of paths that the point can be reached by.  Pick the first path in the path list for now.
        // We only want to do this stuff if we are docking!!!  Be sure to set the path index
        if ((dock_type == AIDO_DOCK) || (dock_type == AIDO_DOCK_NOW)) {
                pm = model_get( Ships[dockee->instance].modelnum );
                Assert( pm->docking_bays[dockee_index].num_spline_paths > 0 );

                // only set the dock path index if we are docking.  undocking will assume that dock_path_index
                // already set from some other docking command
                aip->dock_path_index = dockee_index;
                dockee_aip->dock_path_index = docker_index;
        }

        if (dock_type != AIDO_DOCK_NOW) {
                int path_num;
                //      Note: Second parameter is dock path index.  This should be specified as an
                //      _input_ to this function and passed through.  The path index should be already
                // set for the undock function
                path_num = ai_return_path_num_from_dockbay(dockee, dockee_index);
                ai_find_path(docker, dockee-Objects, path_num, 0);
//              ai_find_path(dockee-Objects, dockee_index, 0);
        } else {
                dock_orient_and_approach(docker, dockee, DOA_DOCK_STAY);
                //aip->dock_objnum = OBJ_INDEX(dockee);
                ai_do_objects_docked_stuff( docker, dockee );
        }

}

//      Cause a ship to fly its waypoints.
//      flags tells:
//              WPF_REPEAT      Set -> repeat waypoints.
void ai_start_waypoints(object *objp, int waypoint_list_index, int wp_flags)
{
        ai_info *aip;

        Assert(waypoint_list_index < Num_waypoint_lists);

        //nprintf(("AI", "Frame %i: Ship %s instructed to fly waypoint list #%i\n", AI_FrameCount, Ships[objp->instance].ship_name, waypoint_list_index));
        aip = &Ai_info[Ships[objp->instance].ai_index];

        if ( (aip->mode == AIM_WAYPOINTS) && (aip->wp_index == waypoint_list_index) )
                return;

        aip->ai_flags |= AIF_FORMATION_WING;
        aip->ai_flags &= ~AIF_FORMATION_OBJECT;
        aip->wp_list = waypoint_list_index;
        aip->wp_index = 0;
        aip->wp_flags = wp_flags;
        aip->mode = AIM_WAYPOINTS;

        Assert(aip->active_goal != AI_ACTIVE_GOAL_DYNAMIC);
}

//      Make *objp stay within dist units of *other_objp
void ai_do_stay_near(object *objp, object *other_objp, float dist)
{
        ai_info *aip;

        Assert(objp != other_objp);             //      Bogus!  Told to stay near self.
        Assert(objp->type == OBJ_SHIP);
        Assert((objp->instance >= 0) && (objp->instance < MAX_SHIPS));

        aip = &Ai_info[Ships[objp->instance].ai_index];

        aip->mode = AIM_STAY_NEAR;
        aip->submode = -1;
        aip->stay_near_distance = dist;
        aip->goal_objnum = other_objp-Objects;
        aip->goal_signature = other_objp->signature;

}

//      Make object *objp form on wing of object *goal_objp
void ai_form_on_wing(object *objp, object *goal_objp)
{
        ai_info *aip;
        ship                    *shipp;
        ship_info       *sip;

        // objp == goal_objp sometimes in multiplayer when someone leaves a game -- make a simple
        // out for this case.
        if ( Game_mode & GM_MULTIPLAYER ) {
                if ( objp == goal_objp ) {
                        return;
                }
        }

        Assert(objp != goal_objp);              //      Bogus!  Told to form on own's wing!

        shipp = &Ships[objp->instance];
        sip = &Ship_info[shipp->ship_info_index];

        //      Only fighters or bombers allowed to form on wing.
        if (!(sip->flags & (SIF_FIGHTER | SIF_BOMBER))) {
                nprintf(("AI", "Warning: Ship %s tried to form on player's wing, but not fighter or bomber.\n", shipp->ship_name));
                return;
        }

        aip = &Ai_info[Ships[objp->instance].ai_index];

        aip->ai_flags &= ~AIF_FORMATION_WING;
        aip->ai_flags |= AIF_FORMATION_OBJECT;

        aip->goal_objnum = goal_objp-Objects;
        ai_set_goal_maybe_abort_dock(objp, aip);
        aip->ok_to_target_timestamp = timestamp(DELAY_TARGET_TIME*4);           //      Super extra long time until can target another ship.

}

//      Given an object and an object on whose wing to form, return slot to use.
//      Optimize:
//              This function is called per object in formation per frame.  Should store slot in ai_info struct.
int ai_formation_object_get_slotnum(int objnum, object *objp)
{
        int     slotnum = 1;                    //      Note: Slot #0 means leader, which isn't someone who was told to form-on-wing.
        object *o;

        for ( o = GET_FIRST(&obj_used_list); o != END_OF_LIST(&obj_used_list); o = GET_NEXT(o) ) {
                if (objp == o)
                        break;
                else if (o->type == OBJ_SHIP)
                        if (Ai_info[Ships[o->instance].ai_index].ai_flags & AIF_FORMATION_OBJECT)
                                if (Ai_info[Ships[o->instance].ai_index].goal_objnum == objnum)
                                        slotnum++;
        }

        Assert(o != END_OF_LIST(&obj_used_list));       //      Didn't find objp in list of used ships.  Impossible!

        return slotnum;
}

#define BIGNUM  100000.0f

int Debug_k = 0;

//      Given an attacker's position and a target's position and velocity, compute the time of
//      intersection of a weapon fired by the attacker with speed weapon_speed.
//      Return this value.  Return value of 0.0f means no collision is possible.
float compute_collision_time(vector *targpos, vector *targvel, vector *attackpos, float weapon_speed)
{
        vector  vec_to_target;
        float           pos_dot_vel;
        float           vel_sqr;
        float           discrim;

        vm_vec_sub(&vec_to_target, targpos, attackpos);
        pos_dot_vel = vm_vec_dot(&vec_to_target, targvel);
        vel_sqr = vm_vec_dot(targvel, targvel) - weapon_speed*weapon_speed;
        discrim = pos_dot_vel*pos_dot_vel - vel_sqr*vm_vec_dot(&vec_to_target, &vec_to_target);

        if (discrim > 0.0f) {
                float   t1, t2, t_solve;

                t1 = (-pos_dot_vel + fl_sqrt(discrim)) / vel_sqr;
                t2 = (-pos_dot_vel - fl_sqrt(discrim)) / vel_sqr;

                t_solve = BIGNUM;

                if (t1 > 0.0f)
                        t_solve = t1;
                if ((t2 > 0.0f) && (t2 < t_solve))
                        t_solve = t2;

                if (t_solve < BIGNUM-1.0f) {
                        return t_solve + Debug_k * flFrametime;
                }
        }

        return 0.0f;
}


//      --------------------------------------------------------------------------
//      If far away, use player's speed.
//      If in between, lerp between player and laser speed
//      If close, use laser speed.
// Want to know how much time it will take to get to the enemy.
// This function doesn't account for the fact that by the time the player
// (or his laser) gets to the current enemy position, the enemy will have moved.
// This is dealt with in polish_predicted_enemy_pos.
float compute_time_to_enemy(float dist_to_enemy, object *pobjp, object *eobjp)
{
        float   time_to_enemy;
        float   pl_speed = pobjp->phys_info.speed;
        float   max_laser_distance, max_laser_speed;
        int     bank_num, weapon_num;
        ship    *shipp = &Ships[pobjp->instance];

        bank_num = shipp->weapons.current_primary_bank;
        weapon_num = shipp->weapons.primary_bank_weapons[bank_num];
        max_laser_speed = Weapon_info[weapon_num].max_speed;
        max_laser_distance = max_laser_speed * Weapon_info[weapon_num].lifetime;

        //      If pretty far away, use player's speed to predict position, else
        //      use laser's speed because when close, we care more about hitting
        //      with a laser than about causing ship:ship rendezvous.
        if (dist_to_enemy > 1.5 * max_laser_distance) {
                if (pl_speed > 0.0f)
                        time_to_enemy = dist_to_enemy/pl_speed;
                else
                        time_to_enemy = 1.0f;
        } else if (dist_to_enemy > 1.1*max_laser_distance) {
                if (pl_speed > 0.1f) {
                        float   scale;

                        scale = (float) ((dist_to_enemy - max_laser_distance) / max_laser_distance);
                
                        time_to_enemy = (float) (dist_to_enemy/(pl_speed * scale + max_laser_speed * (1.0f - scale)));
                } else
                        time_to_enemy = 2.0f;
        } else
                time_to_enemy = (float) (dist_to_enemy/max_laser_speed);

        // return time_to_enemy * (1.0f + Ai_info[Ships[pobjp->instance].ai_index].lead_scale);
        return time_to_enemy + flFrametime;
}

//      Stuff *dot and *tts.
//      *dot is always computed.  If dot is less than zero, the magnitude is
//      incorrect, not having been divided by distance.
//      If *dot is > 0.0f, then tts is computed.  This is the time it will take object
//      *objp to get to *pos, assuming it moves right at it.
void fds_aux(float *dot, float *tts, vector *pos, float dtime, object *objp)
{
        vector  v2s;

        vm_vec_sub(&v2s, pos, &objp->pos);
        *dot = vm_vec_dot(&v2s, &objp->orient.v.fvec);

        if (*dot > 0.0f) {
                float   dist;

                dist = vm_vec_dist(&objp->pos, pos);

                if (dist > 0.1f)
                        *dot /= dist;
                else
                        *dot = 1.0f;

                if (objp->phys_info.speed > 0.1f)
                        *tts = dist / objp->phys_info.speed;
                else
                        *tts = dist * 100.0f;
        }
}

/*
//      Return index of weapon that could hit object *sobjp within dtime seconds.
//      Actual time until impact returned in *atime.
int find_danger_weapon(object *sobjp, float dtime, float *atime, float dot_threshhold)
{
        object  *objp, *best_objp = NULL;
        float           best_tts = 1000.0f;

        for ( objp = GET_FIRST(&obj_used_list); objp !=END_OF_LIST(&obj_used_list); objp = GET_NEXT(objp) ) {
                if ((objp->type == OBJ_WEAPON) && (sobjp-Objects != objp->parent)) {
                        float           dot, tts;
                        // vector       psp;            //      Predicted ship position.

                        //      Get dot and time to current ship position.
                        fds_aux(&dot, &tts, &sobjp->pos, dtime, objp);

                        //      If dot and tts are in plausible range, do more expensive stuff.
                        if (dot > 0.98f) {
//                              float   dot_from_sobjp;
                                vector  v2e;

                                vm_vec_normalized_dir(&v2e, &objp->pos, &sobjp->pos);
//                              dot_from_sobjp = vm_vec_dot(&sobjp->orient.v.fvec, &v2e);
//                              if (dot_from_sobjp >= dot_threshhold)
                                        if (tts < dtime) {
                                                if (tts < best_tts) {
                                                        best_tts = tts;
                                                        best_objp = objp;
                                                }
                                        }
                        }
                }
        }

        *atime = best_tts;

        if (best_objp != NULL)
                return best_objp-Objects;
        else
                return -1;
}
*/

//      --------------------------------------------------------------------------
void ai_set_positions(object *pl_objp, object *en_objp, ai_info *aip, vector *player_pos, vector *enemy_pos)
{
        *player_pos = pl_objp->pos;

        if (aip->next_predict_pos_time > Missiontime) {
                *enemy_pos = aip->last_predicted_enemy_pos;
        } else {
                *enemy_pos = en_objp->pos;

                aip->next_predict_pos_time = Missiontime + Skill_level_delay[Game_skill_level];
                aip->last_predicted_enemy_pos = *enemy_pos;
        }


}

//      --------------------------------------------------------------------------
int find_nearest_waypoint(object *objp)
{
        int     i;
        float   dist, min_dist, dot;
        int     min_ind;
        ship    *shipp;
        int     wp_listnum;
        waypoint_list   *wpl;

        shipp = &Ships[objp->instance];
        wp_listnum = Ai_info[Ships[objp->instance].ai_index].wp_list;
        Assert(wp_listnum > 0);
        wpl = &Waypoint_lists[wp_listnum];

        min_dist = 999999.0f;
        min_ind = -1;

        for (i=0; i<wpl->count; i++) {
                dist = vm_vec_dist_quick(&objp->pos, &wpl->waypoints[i]);
                dot = vm_vec_dot_to_point(&objp->orient.v.fvec, &objp->pos, &wpl->waypoints[i]);
                dist = (float) (dist * (1.25 - dot));
                if (dist < min_dist) {
                        min_dist = dist;
                        min_ind = i;
                }
        }

        Assert(min_ind != -1);

        return min_ind;
}

//      Given an ai_info struct, by reading current goal and path information,
//      extract base path information and return in pmp and pmpv.
//      Return true if found, else return false.
//      false means the current point is not on the original path.
int get_base_path_info(int path_cur, int goal_objnum, model_path **pmp, mp_vert **pmpv)
{
        pnode                   *pn = &Path_points[path_cur];
        ship_info       *sip = &Ship_info[Ships[Objects[goal_objnum].instance].ship_info_index];
        polymodel       *pm = model_get(sip->modelnum);
        static          int     debug_last_index = -1;
        *pmpv = NULL;
        *pmp = NULL;

        if (pn->path_num != -1) {
                *pmp = &pm->paths[pn->path_num];
                if (pn->path_index != -1)
                        *pmpv = &(*pmp)->verts[pn->path_index];
                else
                        return 0;
        } else
                return 0;

/*      if (debug_last_index != *pmpv-(*pmp)->verts) {
                debug_last_index = *pmpv-(*pmp)->verts;
                nprintf(("AI", "Point %i has %i turrets: ", *pmpv-(*pmp)->verts, (*pmpv)->nturrets));
                for (int i=0; i<(*pmpv)->nturrets; i++) {
                        nprintf(("AI", "%i ", (*pmpv)->turret_ids[i]));
                }
                nprintf(("AI", "\n"));
        }
*/
        return 1;
}

//      Modify, in place, the points in a global model path.
//      Only modify those points that are defined in the model path.  Don't modify the
//      leadin points, such as those that are necessary to get the model on the path.
void modify_model_path_points(object *objp)
{       
        ai_info         *aip = &Ai_info[Ships[objp->instance].ai_index];
        object          *mobjp = &Objects[aip->path_objnum];
        ship_info       *osip = &Ship_info[Ships[mobjp->instance].ship_info_index];
        polymodel       *pm = model_get(osip->modelnum);
        pnode                   *pnp;
        int                     path_num, dir;

        Assert((aip->path_start >= 0) && (aip->path_start < MAX_PATH_POINTS));

        pnp = &Path_points[aip->path_start];
        while ((pnp->path_index == -1) && (pnp-Path_points - aip->path_start < aip->path_length))
                pnp++;

        path_num = pnp->path_num;
        Assert((path_num >= 0) && (path_num < pm->n_paths));
        
        Assert(pnp->path_index != -1);  //      If this is -1, that means we never found the model path points

        dir = 1;
        if ( aip->ai_flags & AIF_USE_EXIT_PATH ) {
                dir = -1;
        }

        copy_xlate_model_path_points(mobjp, &pm->paths[path_num], dir, pm->paths[path_num].nverts, path_num, pnp);
}

//      Return an indication of the distance between two matrices.
//      This is the sum of the distances of their dot products from 1.0f.
float ai_matrix_dist(matrix *mat1, matrix *mat2)
{
        float   t;

        t =  1.0f - vm_vec_dot(&mat1->v.fvec, &mat2->v.fvec);
        t += 1.0f - vm_vec_dot(&mat1->v.uvec, &mat2->v.uvec);
        t += 1.0f - vm_vec_dot(&mat1->v.rvec, &mat2->v.rvec);

        return t;
}


//      Paths are created in absolute space, so a moving object needs to have model paths within it recreated.
//      This uses the hash functions which means the slightest movement will cause a recreate, though the timestamp
//      prevents this from happening too often.
//      force_recreate_flag TRUE means to recreate regardless of timestamp.
//      Returns TRUE if path recreated.
float maybe_recreate_path(object *objp, ai_info *aip, int force_recreate_flag)
{
        int     hashval;

        Assert(&Ai_info[Ships[objp->instance].ai_index] == aip);

        if ((aip->mode == AIM_BAY_EMERGE) || (aip->mode == AIM_BAY_DEPART))
                if ((OBJ_INDEX(objp) % 4) == (Framecount % 4))
                        force_recreate_flag = 1;

        //      If no path, that means we don't need one.
        if (aip->path_start == -1)
                return 0.0f;

        // AL 11-12-97: If AIF_USE_STATIC_PATH is set, don't try to recreate.  This is needed when ships
        //                                  emerge from fighter bays.  We don't need to recreate the path.. and in case the 
        //              parent ship dies, we still want to be able to continue on the path
        if ( aip->ai_flags & AIF_USE_STATIC_PATH ) 
                return 0.0f;

        if (force_recreate_flag || timestamp_elapsed(aip->path_next_create_time)) {
                object  *path_objp;

                path_objp = &Objects[aip->path_objnum];

                if ((hashval = create_object_hash(path_objp)) != aip->path_goal_obj_hash) {
                        float dist;
                        
                        dist = vm_vec_dist_quick(&path_objp->pos, &aip->path_create_pos);
                        dist += ai_matrix_dist(&path_objp->orient, &aip->path_create_orient) * 25.0f;

                        if (force_recreate_flag || (dist > 2.0f)) {
                                aip->path_next_create_time = timestamp(1000);   //      Update again in as little as 1000 milliseconds, ie 1 second.
                                aip->path_goal_obj_hash = hashval;
                                modify_model_path_points(objp);

                                aip->path_create_pos = path_objp->pos;
                                aip->path_create_orient = path_objp->orient;
                                
                                return dist;
                        }
                }
        }

        return 0.0f;
}

//      Set acceleration for ai_dock().
void set_accel_for_docking(object *objp, ai_info *aip, float dot, float dot_to_next, float dist_to_next, float dist_to_goal, ship_info *sip)
{
        float prev_dot_to_goal = aip->prev_dot_to_goal;
        
        aip->prev_dot_to_goal = dot;

        if (objp->phys_info.speed < 0.0f) {
                accelerate_ship(aip, 1.0f/32.0f);
        } else if ((prev_dot_to_goal-dot) > 0.01) {
                if (prev_dot_to_goal > dot + 0.05f) {
                        accelerate_ship(aip, 0.0f);
                } else {
                        change_acceleration(aip, -1.0f);        //      -1.0f means subtract off flFrametime from acceleration value in 0.0..1.0
                }
        } else {
                if ((aip->mode == AIM_DOCK) && (dist_to_next < 150.0f) && (aip->path_start + aip->path_length - 2 == aip->path_cur)) {
                        set_accel_for_target_speed(objp, sip->max_speed * max(dist_to_next/500.0f, 1.0f));
                        //mprintf(("dist = %7.3f, speed = %7.3f\n", dist_to_next, objp->phys_info.speed));
                } else if ((dot_to_next >= dot * .9) || (dist_to_next > 100.0f)) {
                        if (dist_to_goal > 200.0f)
                                set_accel_for_target_speed(objp, sip->max_speed * (dot + 1.0f) / 2.0f);
                        else {
                                float   xdot;

                                xdot = (dot_to_next + dot)/2.0f;
                                if (xdot < 0.0f)
                                        xdot = 0.0f;

                                // AL: if following a path not in dock mode, move full speed
                                if (( aip->mode != AIM_DOCK ) && (dot > 0.9f)) {
                                        set_accel_for_target_speed(objp, sip->max_speed*dot*dot*dot);
                                } else {
                                        if ((aip->path_cur - aip->path_start < aip->path_length-2) && (dist_to_goal < 2*objp->radius)) {
                                                //nprintf(("AI", "Target speed = %7.3f\n", dist_to_goal/8.0f));
                                                set_accel_for_target_speed(objp, dist_to_goal/8.0f + 2.0f);
                                        } else {
                                                set_accel_for_target_speed(objp, sip->max_speed * (2*xdot + 0.25f)/4.0f);
                                        }
                                }
                        }
                } else {
                        float   xdot;

                        xdot = max(dot_to_next, 0.1f);
                        if ( aip->mode != AIM_DOCK ) {
                                set_accel_for_target_speed(objp, sip->max_speed);
                        } else {
                                float   speed;
                                if ((aip->path_cur - aip->path_start < aip->path_length-2) && (dist_to_goal < 2*objp->radius)) {
                                        speed = dist_to_goal/8.0f + 2.0f;
                                } else if (dist_to_goal < 4*objp->radius + 50.0f) {
                                        speed = dist_to_goal/4.0f + 4.0f;
                                } else {
                                        speed = sip->max_speed * (3*xdot + 1.0f)/4.0f;
                                }
                                if (aip->mode == AIM_DOCK) {
                                        speed = speed * 2.0f + 1.0f;
                                        if (aip->goal_objnum != -1) {
                                                speed += Objects[aip->goal_objnum].phys_info.speed;
                                        }
                                }

                                set_accel_for_target_speed(objp, speed);
                        }
                }
        }
}

//      --------------------------------------------------------------------------
//      Follow a path associated with a large object, such as a capital ship.
//      The points defined on the path are in the object's reference frame.
//      The object of interest is goal_objnum.
//      The paths are defined in the model.  The path of interest is wp_list.
//      The next goal point in the path is wp_index.
//      wp_flags contain special information specific to the path.

// The path vertices are defined by model_path structs:
//              typedef struct model_path {
//                      char            name[MAX_NAME_LEN];                                     // name of the subsystem.  Probably displayed on HUD
//                      int             nverts;
//                      vector  *verts;
//              } model_path;

//      The polymodel struct for the object contains the following:
//              int                     n_paths;
//              model_path      *paths;

//      Returns distance to goal point.
float ai_path()
{
        polymodel       *pm;
        int             num_paths, num_points;
        float           dot, dist_to_goal, dist_to_next, speed, dot_to_next;
        ship            *shipp = &Ships[Pl_objp->instance];
        ship_info       *sip = &Ship_info[shipp->ship_info_index];
        ai_info *aip;
        vector  nvel_vec;
        float           mag, prev_dot_to_goal;
        vector  temp_vec, *slop_vec;
        object  *gobjp;
        ship            *gshipp;
        vector  *cvp, *nvp, next_vec, gcvp, gnvp;               //      current and next vertices in global coordinates.

        aip = &Ai_info[Ships[Pl_objp->instance].ai_index];

        Assert(aip->goal_objnum != -1);
        Assert(Objects[aip->goal_objnum].type == OBJ_SHIP);

        gobjp = &Objects[aip->goal_objnum];
        gshipp = &Ships[gobjp->instance];

        pm = model_get( gshipp->modelnum );
        num_paths = pm->n_paths;
        Assert(num_paths > 0);

        if (aip->path_start == -1) {
                int path_num;
                path_num = ai_return_path_num_from_dockbay(&Objects[aip->goal_objnum], aip->dockee_index);
                Assert(aip->goal_objnum >= 0 && aip->goal_objnum < MAX_OBJECTS);
                ai_find_path(Pl_objp, aip->goal_objnum, path_num, 0);
        }

        // nprintf(("AI", "Frame: %i, Path index = %i/%i\n", AI_FrameCount, aip->path_cur-aip->path_start, aip->path_length));

        maybe_recreate_path(Pl_objp, aip, 0);

        num_points = aip->path_length;

        //      Set cvp and nvp as pointers to current and next vertices of interest on path.
        cvp = &Path_points[aip->path_cur].pos;
        if ((aip->path_cur + aip->path_dir - aip->path_start < num_points) || (aip->path_cur + aip->path_dir < aip->path_start))
                nvp = &Path_points[aip->path_cur + aip->path_dir].pos;
        else {
                //      If this is 0, then path length must be 1 which means we have no direction!
                Assert((aip->path_cur - aip->path_dir >= aip->path_start) && (aip->path_cur - aip->path_dir - aip->path_start < num_points));
                //      Cleanup for above Assert() which we hit too near release. -- MK, 5/24/98.
                if (aip->path_cur - aip->path_dir - aip->path_start >= num_points) {
                        if (aip->path_dir == 1)
                                aip->path_cur = aip->path_start;
                        else
                                aip->path_cur = aip->path_start + num_points - 1;
                }

                vector  delvec;
                vm_vec_sub(&delvec, cvp, &Path_points[aip->path_cur - aip->path_dir].pos);
                vm_vec_normalize(&delvec);
                vm_vec_scale_add(&next_vec, cvp, &delvec, 10.0f);
                nvp = &next_vec;
        }

        //      Interrupt if can't get to current goal point.  Debug only.
/*      if (pp_collide(&Pl_objp->pos, cvp, gobjp, Pl_objp->radius)) {
                Int3();
        }
*/
        //      See if can reach next point (as opposed to current point)
        //      However, don't do this if docking and next point is last point.
        //      That is, we don't want to pursue the last point under control of the
        //      path code.  In docking, this is a special hack.
        if ((aip->mode != AIM_DOCK) || ((aip->path_cur-aip->path_start) < num_points - 2)) {
                if ((aip->path_cur + aip->path_dir > aip->path_start) && (aip->path_cur + aip->path_dir < aip->path_start + num_points-2)) {
                        if ( timestamp_elapsed(aip->path_next_check_time)) {
                                aip->path_next_check_time = timestamp( 3000 );
                                if (!pp_collide(&Pl_objp->pos, nvp, gobjp, 1.1f * Pl_objp->radius)) {
                                        cvp = nvp;
                                        aip->path_cur += aip->path_dir;
                                        nvp = &Path_points[aip->path_cur].pos;
                                        //nprintf(("AI", "Reach: Advancing from point %i to %i of %i points.\n", aip->path_cur-aip->path_dir, aip->path_cur, num_points));
                                }
                        }
                }
        }

        gcvp = *cvp;
        gnvp = *nvp;

        speed = Pl_objp->phys_info.speed;

        dist_to_goal = vm_vec_dist_quick(&Pl_objp->pos, &gcvp);
        dist_to_next = vm_vec_dist_quick(&Pl_objp->pos, &gnvp);
        //      Can't use fvec, need to use velocity vector because we aren't necessarily
        //      moving in the direction we're facing.

//      if (IS_VEC_NULL(&Pl_objp->phys_info.vel)) {
        if ( vm_vec_mag_quick(&Pl_objp->phys_info.vel) < AICODE_SMALL_MAGNITUDE ) {
                mag = 0.0f;
                vm_vec_zero(&nvel_vec);
        } else
                mag = vm_vec_copy_normalize(&nvel_vec, &Pl_objp->phys_info.vel);

        //      If moving not-very-slowly and sliding, then try to slide at goal, rather than
        //      point at goal.
        slop_vec = NULL;
        if (mag < 1.0f)
                nvel_vec = Pl_objp->orient.v.fvec;
        else if (mag > 5.0f) {
                float   nv_dot;
                nv_dot = vm_vec_dot(&Pl_objp->orient.v.fvec, &nvel_vec);
                if ((nv_dot > 0.5f) && (nv_dot < 0.97f)) {
                        slop_vec = &temp_vec;
                        vm_vec_sub(slop_vec, &nvel_vec, &Pl_objp->orient.v.fvec);
                }
        }

        if (dist_to_goal > 0.1f)
                ai_turn_towards_vector(&gcvp, Pl_objp, flFrametime, sip->srotation_time, slop_vec, NULL, 0.0f, 0);

        //      Code to control speed is MUCH less forgiving in path following than in waypoint
        //      following.  Must be very close to path or might hit objects.
        prev_dot_to_goal = aip->prev_dot_to_goal;
        dot = vm_vec_dot_to_point(&nvel_vec, &Pl_objp->pos, &gcvp);
        dot_to_next = vm_vec_dot_to_point(&nvel_vec, &Pl_objp->pos, &gnvp);

        set_accel_for_docking(Pl_objp, aip, dot, dot_to_next, dist_to_next, dist_to_goal, sip);
        aip->prev_dot_to_goal = dot;

//mprintf(("Goal index = %i, dist = %7.3f, dot = %7.3f\n", wp_index, dist_to_goal, dot));

        //      If moving at a non-tiny velocity, detect attaining path point by its being close to
        //      line between previous and current object location.
        if ((dist_to_goal < MIN_DIST_TO_WAYPOINT_GOAL) || (vm_vec_dist_quick(&Pl_objp->last_pos, &Pl_objp->pos) > 0.1f)) {
                vector  nearest_point;
                float           r, min_dist_to_goal;

                r = find_nearest_point_on_line(&nearest_point, &Pl_objp->last_pos, &Pl_objp->pos, &gcvp);

                //      Set min_dist_to_goal = how close must be to waypoint to pick next one.
                //      If docking and this is the second last waypoint, must be very close.
                if ((aip->mode == AIM_DOCK) && (aip->path_cur >= aip->path_length-2))
                        min_dist_to_goal = MIN_DIST_TO_WAYPOINT_GOAL;
                else
                        min_dist_to_goal = MIN_DIST_TO_WAYPOINT_GOAL + Pl_objp->radius;

                if ( (vm_vec_dist_quick(&Pl_objp->pos, &gcvp) < min_dist_to_goal) ||
                        ((r >= 0.0f) && (r <= 1.0f)) && (vm_vec_dist_quick(&nearest_point, &gcvp) < (MIN_DIST_TO_WAYPOINT_GOAL + Pl_objp->radius))) {
                        aip->path_cur += aip->path_dir;
                        //nprintf(("AI", " Near: Advancing from point %i to %i of %i points.\n", aip->path_cur-aip->path_dir, aip->path_cur, num_points));
                        if (((aip->path_cur - aip->path_start) > (num_points+1)) || (aip->path_cur < aip->path_start)) {
                                Assert(aip->mode != AIM_DOCK);          //      If docking, should never get this far, getting to last point handled outside ai_path()
                                aip->path_dir = -aip->path_dir;
//                              aip->path_cur += aip->path_dir;
                        }
                }
        }

        return dist_to_goal;
}

void update_min_max(float val, float *min, float *max)
{
        if (val < *min)
                *min = val;
        else if (val > *max)
                *max = val;
}

//      Stuff bounding box of all enemy objects within "range" units of object *my_objp.
//      Stuff ni min_vec and max_vec.
//      Return value: Number of enemy objects in bounding box.
int get_enemy_team_range(object *my_objp, float range, int enemy_team_mask, vector *min_vec, vector *max_vec)
{
        object  *objp;
        ship_obj        *so;
        int             count = 0;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                objp = &Objects[so->objnum];
                if (Ships[objp->instance].team & enemy_team_mask) {
                        if (Ship_info[Ships[objp->instance].ship_info_index].flags & (SIF_FIGHTER | SIF_BOMBER | SIF_CRUISER | SIF_CAPITAL | SIF_SUPERCAP | SIF_DRYDOCK | SIF_CORVETTE | SIF_AWACS | SIF_GAS_MINER))
                                if (vm_vec_dist_quick(&my_objp->pos, &objp->pos) < range) {
                                        if (count == 0) {
                                                *min_vec = objp->pos;
                                                *max_vec = objp->pos;
                                                count++;
                                        } else {
                                                update_min_max(objp->pos.xyz.x, &min_vec->xyz.x, &max_vec->xyz.x);
                                                update_min_max(objp->pos.xyz.y, &min_vec->xyz.y, &max_vec->xyz.y);
                                                update_min_max(objp->pos.xyz.z, &min_vec->xyz.z, &max_vec->xyz.z);
                                        }
                                }

                }
        }

        return count;
}

//      Pick a relatively safe spot for objp to fly to.
//      Problem:
//              Finds a spot away from any enemy within a bounding box.
//              Doesn't verify that "safe spot" is not near some other enemy.
void ai_safety_pick_spot(object *objp)
{
        int             objnum;
        int             enemy_team_mask;
        vector  min_vec, max_vec;
        vector  vec_to_center, center;
        vector  goal_pos;

        objnum = OBJ_INDEX(objp);

        enemy_team_mask = get_enemy_team_mask(objnum);

        if (get_enemy_team_range(objp, 1000.0f, enemy_team_mask, &min_vec, &max_vec)) {
                vm_vec_avg(&center, &min_vec, &max_vec);
                vm_vec_normalized_dir(&vec_to_center, &center, &objp->pos);

                vm_vec_scale_add(&goal_pos, &center, &vec_to_center, 2000.0f);
        } else
                vm_vec_scale_add(&goal_pos, &objp->pos, &objp->orient.v.fvec, 100.0f);

        Ai_info[Ships[objp->instance].ai_index].goal_point = goal_pos;
}

//      Fly to desired safe point.
// Returns distance to that point.
float ai_safety_goto_spot(object *objp)
{
        float   dot, dist;
        ai_info *aip;
        vector  vec_to_goal;
        ship_info       *sip;
        float   dot_val;

        sip = &Ship_info[Ships[objp->instance].ship_info_index];

        aip = &Ai_info[Ships[objp->instance].ai_index];
        dist = vm_vec_normalized_dir(&vec_to_goal, &aip->goal_point, &objp->pos);
        dot = vm_vec_dot(&vec_to_goal, &objp->orient.v.fvec);

        dot_val = (1.1f + dot) / 2.0f;
        if (dist > 200.0f) {
                set_accel_for_target_speed(objp, sip->max_speed * dot_val);
        } else
                set_accel_for_target_speed(objp, sip->max_speed * dot_val * (dist/200.0f + 0.2f));

        return dist;
}

void ai_safety_circle_spot(object *objp)
{
        vector  goal_point;
        ship_info       *sip;
        float           dot;

        sip = &Ship_info[Ships[objp->instance].ship_info_index];

        goal_point = Ai_info[Ships[objp->instance].ai_index].goal_point;
        dot = turn_towards_tangent(objp, &goal_point, 250.0f);  //      Increased from 50 to 250 to make circling not look so wacky.

        set_accel_for_target_speed(objp, 0.5f * (1.0f + dot) * sip->max_speed/4.0f);

//      float dist = vm_vec_dist_quick(&goal_point, &Pl_objp->pos);
//      nprintf(("AI", "Ship %s circling %7.3f %7.3f %7.3f.  Distance = %7.3f\n", Ships[Pl_objp->instance].ship_name, goal_point.xyz.x, goal_point.xyz.y, goal_point.xyz.z, dist));

}

//      --------------------------------------------------------------------------
void ai_safety()
{
        ai_info *aip;

        aip = &Ai_info[Ships[Pl_objp->instance].ai_index];

        switch (aip->submode) {
        case AISS_1:
                ai_safety_pick_spot(Pl_objp);
                aip->submode = AISS_2;
                aip->submode_start_time = Missiontime;
                break;
        case AISS_1a:   //      Pick a safe point because we just got whacked!
                Int3();
                break;
        case AISS_2:
                if (ai_safety_goto_spot(Pl_objp) < 25.0f) {
                        aip->submode = AISS_3;
                        aip->submode_start_time = Missiontime;
                }
                break;
        case AISS_3:
                ai_safety_circle_spot(Pl_objp);
                break;
        default:
                Int3();         //      Illegal submode for ai_safety();
                break;
        }
}

//      --------------------------------------------------------------------------
//      make Pl_objp fly waypoints.
void ai_waypoints()
{
        int             wp_index;
        vector  *wp_cur, *wp_next;
        float           dot, dist_to_goal, dist_to_next, speed, dot_to_next;
        ship            *shipp = &Ships[Pl_objp->instance];
        ship_info       *sip = &Ship_info[shipp->ship_info_index];
        waypoint_list   *wpl;
        ai_info *aip;
        vector  nvel_vec;
        float           mag;
        float           prev_dot_to_goal;
        vector  temp_vec;
        vector  *slop_vec;

        aip = &Ai_info[Ships[Pl_objp->instance].ai_index];

        wp_index = aip->wp_index;

        if (wp_index == -1) {
                ai_start_waypoints(Pl_objp, 0, WPF_REPEAT);
                wp_index = aip->wp_index;
                aip->wp_dir = 1;
        }

        wpl = &Waypoint_lists[Ai_info[Ships[Pl_objp->instance].ai_index].wp_list];

        Assert(wpl->count);     // What? Is this zero? Probably wp_index never got initialized!

        wp_cur = &wpl->waypoints[wp_index];
        wp_next = &wpl->waypoints[(wp_index+1) % wpl->count];
        speed = Pl_objp->phys_info.speed;

        dist_to_goal = vm_vec_dist_quick(&Pl_objp->pos, wp_cur);
        dist_to_next = vm_vec_dist_quick(&Pl_objp->pos, wp_next);

        //      Can't use fvec, need to use velocity vector because we aren't necessarily
        //      moving in the direction we're facing.
        // AL 23-3-98: Account for very small velocities by checking result of vm_vec_mag().
        //                                      If we don't vm_vec_copy_normalize() will think it is normalizing a null vector.
//      if (IS_VEC_NULL(&Pl_objp->phys_info.vel)) {
        if ( vm_vec_mag_quick(&Pl_objp->phys_info.vel) < AICODE_SMALL_MAGNITUDE ) {
                mag = 0.0f;
                vm_vec_zero(&nvel_vec);
        } else {
                mag = vm_vec_copy_normalize(&nvel_vec, &Pl_objp->phys_info.vel);
        }

        //      If moving not-very-slowly and sliding, then try to slide at goal, rather than
        //      point at goal.
        slop_vec = NULL;
        if (mag < 1.0f) {
                nvel_vec = Pl_objp->orient.v.fvec;
        } else if (mag > 5.0f) {
                float   nv_dot;
                nv_dot = vm_vec_dot(&Pl_objp->orient.v.fvec, &nvel_vec);
                if ((nv_dot > 0.5f) && (nv_dot < 0.97f)) {
                        slop_vec = &temp_vec;
                        vm_vec_sub(slop_vec, &nvel_vec, &Pl_objp->orient.v.fvec);
                }
        }

        //      If a wing leader, take turns more slowly, based on size of wing.
        int     scale;

        if (Ai_info[Ships[Pl_objp->instance].ai_index].wing >= 0) {
                scale = Wings[Ai_info[Ships[Pl_objp->instance].ai_index].wing].current_count;
                scale = (int) ((scale+1)/2);
        } else {
                scale = 1;
        }

        if (dist_to_goal > 0.1f) {
                ai_turn_towards_vector(wp_cur, Pl_objp, flFrametime, sip->srotation_time*3.0f*scale, slop_vec, NULL, 0.0f, 0);
        }

        prev_dot_to_goal = aip->prev_dot_to_goal;
        dot = vm_vec_dot_to_point(&nvel_vec, &Pl_objp->pos, wp_cur);
        dot_to_next = vm_vec_dot_to_point(&nvel_vec, &Pl_objp->pos, wp_next);
        aip->prev_dot_to_goal = dot;

        //      If there is no next point on the path, don't care about dot to next.
        if (wp_index + 1 >= wpl->count) {
                dot_to_next = dot;
        }

        // nprintf(("AI", "Wp #%i, dot = %6.3f, next dot = %6.3f, dist = %7.2f\n", wp_index, dot, dot_to_next, dist_to_goal));

        if (Pl_objp->phys_info.speed < 0.0f) {
                accelerate_ship(aip, 1.0f/32);
        } else if (prev_dot_to_goal > dot+0.01f) {
                //      We are further from pointing at our goal this frame than last frame, so slow down.
                set_accel_for_target_speed(Pl_objp, Pl_objp->phys_info.speed * 0.95f);
        } else if (dist_to_goal < 100.0f) {
                float slew_dot = vm_vec_dot(&Pl_objp->orient.v.fvec, &nvel_vec);
                if (fl_abs(slew_dot) < 0.9f) {
                        accelerate_ship(aip, 0.0f);
                } else if (dot < 0.88f + 0.1f*(100.0f - dist_to_goal)/100.0f) {
                        accelerate_ship(aip, 0.0f);
                } else {
                        accelerate_ship(aip, 0.5f * dot * dot);
                }
        } else {
                float   dot1;
                if (dist_to_goal < 250.0f) {
                        dot1 = dot*dot*dot;                             //      Very important to be pointing towards goal when nearby.  Note, cubing preserves sign.
                } else {
                        if (dot > 0.0f) {
                                dot1 = dot*dot;
                        } else {
                                dot1 = dot;
                        }
                }

                if (dist_to_goal > 100.0f + Pl_objp->radius * 2) {
                        if (dot < 0.2f) {
                                dot1 = 0.2f;
                        }
                }

                if (sip->flags & SIF_SMALL_SHIP) {
                        set_accel_for_target_speed(Pl_objp, dot1 * dist_to_goal/5.0f);
                } else {
                        set_accel_for_target_speed(Pl_objp, dot1 * dist_to_goal/10.0f);
                }
        }

        //      Make sure not travelling too fast for someone to keep up.
        float   max_allowed_speed = 9999.9f;

        if (shipp->wingnum != -1) {
                max_allowed_speed = 0.9f * get_wing_lowest_max_speed(Pl_objp);
        }

        // check if waypoint speed cap is set and adjust max speed
        if (aip->waypoint_speed_cap > 0) {
                max_allowed_speed = (float) aip->waypoint_speed_cap;
        }

        if (aip->prev_accel * shipp->current_max_speed > max_allowed_speed) {
                accelerate_ship(aip, max_allowed_speed / shipp->current_max_speed);
        }

        if (vm_vec_dist_quick(&Pl_objp->last_pos, &Pl_objp->pos) > 0.1f) {
                vector  nearest_point;
                float           r;

                r = find_nearest_point_on_line(&nearest_point, &Pl_objp->last_pos, &Pl_objp->pos, wp_cur);

                if ( (vm_vec_dist_quick(&Pl_objp->pos, wp_cur) < (MIN_DIST_TO_WAYPOINT_GOAL + fl_sqrt(Pl_objp->radius) + vm_vec_dist_quick(&Pl_objp->pos, &Pl_objp->last_pos))) ||
                        ((r >= 0.0f) && (r <= 1.0f)) && (vm_vec_dist_quick(&nearest_point, wp_cur) < (MIN_DIST_TO_WAYPOINT_GOAL + fl_sqrt(Pl_objp->radius)))) {
                        wp_index++;
                        if (wp_index >= wpl->count)
                                if (aip->wp_flags & WPF_REPEAT) {
                                        wp_index = 0;
                                } else {
                                        int treat_as_ship;

                                        // when not repeating waypoints -- mark the goal as done and put and entry into the mission log
                                        // we must be careful when dealing with wings.  A ship in a wing might be completing
                                        // a waypoint for for the entire wing, or it might be completing a goal for itself.  If
                                        // for itself and in a wing, treat the completion as we would a ship
                                        treat_as_ship = 1;
                                        if ( Ships[Pl_objp->instance].wingnum != -1 ) {
                                                int type;

                                                // I don't think that you can fly waypoints as dynamic goals!!!
                                                // -- This is legal, just stupid. -- Assert( (aip->active_goal != AI_GOAL_NONE) && (aip->active_goal != AI_ACTIVE_GOAL_DYNAMIC) );
                                                
                                                //      Clean up from above Assert, just in case we ship without fixing it.  (Encountered by JimB on 2/9/98)
                                                if ( (aip->active_goal == AI_GOAL_NONE) || (aip->active_goal == AI_ACTIVE_GOAL_DYNAMIC) ) {
                                                        aip->mode = AIM_NONE;
                                                        Int3(); //      Look at the ship, find out of it's supposed to be flying waypoints. -- MK.
                                                }

                                                type = aip->goals[aip->active_goal].type;
                                                if ( (type == AIG_TYPE_EVENT_WING) || (type == AIG_TYPE_PLAYER_WING) ) {
                                                        treat_as_ship = 0;
                                                } else {
                                                        treat_as_ship = 1;
                                                }
                                        }

                                        // if the ship is not in a wing, remove the goal and continue on
                                        if ( treat_as_ship ) {
                                                ai_mission_goal_complete( aip );                                        // this call should reset the AI mode
                                                mission_log_add_entry(LOG_WAYPOINTS_DONE, Ships[Pl_objp->instance].ship_name, wpl->name, -1 );
                                        } else {
                                                // this ship is in a wing.  We must mark the goal as being completed for all ships
                                                // in the wing.  We will also mark an entry in the log that the wing completed the goal
                                                // not the individual ship.
                                                ai_mission_wing_goal_complete( Ships[Pl_objp->instance].wingnum, &(aip->goals[aip->active_goal]) );
                                                mission_log_add_entry( LOG_WAYPOINTS_DONE, Wings[Ships[Pl_objp->instance].wingnum].name, wpl->name, -1 );
                                        }
                                        //wp_index = wpl->count-1;
                                }

                        aip->wp_index = wp_index;
                }
        }
}

//      Make Pl_objp avoid En_objp
//      Not like evading.  This is for avoiding a collision!
//      Note, use sliding if available.
void avoid_ship()
{
        //      To avoid an object, turn towards right or left vector until facing away from object.
        //      To choose right vs. left, pick one that is further from center of avoid object.
        //      Keep turning away from until pointing away from ship.
        //      Stay in avoid mode until at least 3 enemy ship radii away.

        //      Speed setting:
        //      If inside sphere, zero speed and turn towards outside.
        //      If outside sphere, inside 2x sphere, set speed percent of max to:
        //              max(away_dot, (dist-rad)/rad)
        //      where away_dot is dot(Pl_objp->v.fvec, vec_En_objp_to_Pl_objp)

        vector  vec_to_enemy;
        float           away_dot;
        float           dist;
        ship            *shipp = &Ships[Pl_objp->instance];
        ship_info       *sip = &Ship_info[shipp->ship_info_index];
        ai_info *aip = &Ai_info[shipp->ai_index];
        vector  player_pos, enemy_pos;

        // if we're avoiding a stealth ship, then we know where he is, update with no error
        if ( is_object_stealth_ship(En_objp) ) {
                update_ai_stealth_info_with_error(aip/*, 1*/);
        }

        ai_set_positions(Pl_objp, En_objp, aip, &player_pos, &enemy_pos);
        vm_vec_sub(&vec_to_enemy, &enemy_pos, &Pl_objp->pos);

        dist = vm_vec_normalize(&vec_to_enemy);
        away_dot = -vm_vec_dot(&Pl_objp->orient.v.fvec, &vec_to_enemy);
        
        if ((sip->max_vel.xyz.x > 0.0f) || (sip->max_vel.xyz.y > 0.0f)) {
                if (vm_vec_dot(&Pl_objp->orient.v.rvec, &vec_to_enemy) > 0.0f) {
                        AI_ci.sideways = -1.0f;
                } else {
                        AI_ci.sideways = 1.0f;
                }
                if (vm_vec_dot(&Pl_objp->orient.v.uvec, &vec_to_enemy) > 0.0f) {
                        AI_ci.vertical = -1.0f;
                } else {
                        AI_ci.vertical = 1.0f;
                }
        }               

        //nprintf(("AI", "Frame %i: Sliding: %s %s\n", Framecount, AI_ci.sideways < 0 ? "left" : "right", AI_ci.vertical < 0 ? "down" : "up" ));
        // nprintf(("AI", "away_dot = %6.3f, dist = %7.2f, dist/radsum = %6.3f\n", away_dot, dist, dist/(Pl_objp->radius + En_objp->radius)));

        //      If in front of enemy, turn away from it.
        //      If behind enemy, try to get fully behind it.
        if (away_dot < 0.0f) {
                turn_away_from_point(Pl_objp, &enemy_pos, Pl_objp->phys_info.speed);
        } else {
                vector  goal_pos;

                vm_vec_scale_add(&goal_pos, &En_objp->pos, &En_objp->orient.v.fvec, -100.0f);
                turn_towards_point(Pl_objp, &goal_pos, NULL, Pl_objp->phys_info.speed);
        }

        //      Set speed.
        float   radsum = Pl_objp->radius + En_objp->radius;

        if (dist < radsum)
                accelerate_ship(aip, max(away_dot, 0.2f));
        else if (dist < 2*radsum)
                accelerate_ship(aip, max(away_dot, (dist - radsum) / radsum)+0.2f);
        else
                accelerate_ship(aip, 1.0f);

}

//      Maybe it's time to resume the previous AI mode in aip->previous_mode.
//      Each type of previous_mode has its own criteria on when to resume.
//      Return true if previous mode was resumed.
int maybe_resume_previous_mode(object *objp, ai_info *aip)
{
        //      Only (maybe) resume previous goal if current goal is dynamic.
        if (aip->active_goal != AI_ACTIVE_GOAL_DYNAMIC)
                return 0;

        if (aip->mode == AIM_EVADE_WEAPON) {
                if (timestamp_elapsed(aip->mode_time) || (((aip->nearest_locked_object == -1) || (Objects[aip->nearest_locked_object].type != OBJ_WEAPON)) && (aip->danger_weapon_objnum == -1))) {
                        Assert(aip->previous_mode != AIM_EVADE_WEAPON);
                        aip->mode = aip->previous_mode;
                        aip->submode = aip->previous_submode;
                        aip->submode_start_time = Missiontime;
                        aip->active_goal = AI_GOAL_NONE;
                        aip->mode_time = -1;                    //      Means do forever.
                        return 1;
                }
        } else if ( aip->previous_mode == AIM_GUARD) {
                if ((aip->guard_objnum != -1) && (aip->guard_signature == Objects[aip->guard_objnum].signature)) {
                        object  *guard_objp;
                        float   dist;

                        guard_objp = &Objects[aip->guard_objnum];
                        dist = vm_vec_dist_quick(&guard_objp->pos, &objp->pos);

                        //      If guarding ship is far away from guardee and enemy is far away from guardee,
                        //      then stop chasing and resume guarding.
                        if (dist > (MAX_GUARD_DIST + guard_objp->radius) * 6) {
                                if ((En_objp != NULL) && (En_objp->type == OBJ_SHIP)) {
                                        if (vm_vec_dist_quick(&guard_objp->pos, &En_objp->pos) > (MAX_GUARD_DIST + guard_objp->radius) * 6) {
                                                Assert(aip->previous_mode == AIM_GUARD);
                                                aip->mode = aip->previous_mode;
                                                aip->submode = AIS_GUARD_PATROL;
                                                aip->active_goal = AI_GOAL_NONE;
                                                return 1;
                                        }
                                }
                        }
                }
        }

        return 0;

}

//      Call this function if you want something to happen on average every N quarters of a second.
//      The truth value returned by this function will be the same for any given quarter second interval.
//      The value "num" is only passed in to get asynchronous behavior for different objects.
//      modulus == 1 will always return true.
//      modulus == 2 will return true half the time.
//      modulus == 16 will return true for one quarter second interval every four seconds.
int static_rand_timed(int num, int modulus)
{
        if (modulus < 2)
                return 1;
        else {
                int     t;

                t = Missiontime >> 18;          //      Get time in quarters of a second
                t += num;

                return !(t % modulus);
        }
}

//      Maybe fire afterburner based on AI class
int ai_maybe_fire_afterburner(object *objp, ai_info *aip)
{
        if (aip->ai_class == 0)
                return 0;               //      Lowest level never aburners away
        else  {
                //      Maybe don't afterburner because of a potential collision with the player.
                //      If not multiplayer, near player and player in front, probably don't afterburner.
                if (!(Game_mode & GM_MULTIPLAYER)) {
                        if (Ships[objp->instance].team == Player_ship->team) {
                                float   dist;

                                dist = vm_vec_dist_quick(&objp->pos, &Player_obj->pos) - Player_obj->radius - objp->radius;
                                if (dist < 150.0f) {
                                        vector  v2p;
                                        float           dot;

                                        vm_vec_normalized_dir(&v2p, &Player_obj->pos, &objp->pos);
                                        dot = vm_vec_dot(&v2p, &objp->orient.v.fvec);

                                        if (dot > 0.0f) {
                                                if (dot * dist > 50.0f)
                                                        return 0;
                                        }
                                }
                        }
                }

                if (aip->ai_class >= Num_ai_classes-2)
                        return 1;               //      Highest two levels always aburner away.
                else {
                        return static_rand_timed(objp-Objects, Num_ai_classes - aip->ai_class);
                }
        }
}

//      Maybe engage afterburner after being hit by an object.
void maybe_afterburner_after_ship_hit(object *objp, ai_info *aip, object *en_objp)
{
        //      Only do if facing a little away.
        if (en_objp != NULL) {
                vector  v2e;

                vm_vec_normalized_dir(&v2e, &en_objp->pos, &objp->pos);
                if (vm_vec_dot(&v2e, &objp->orient.v.fvec) > -0.5f)
                        return;
        }

        if (!( objp->phys_info.flags & PF_AFTERBURNER_ON )) {
                if (ai_maybe_fire_afterburner(objp, aip)) {
                        afterburners_start(objp);
                        aip->afterburner_stop_time = Missiontime + F1_0/2;
                }
        }
}

//      Return true if object *objp is an instructor.
//      Is an instructor if name begins INSTRUCTOR_SHIP_NAME else not.
int is_instructor(object *objp)
{
        return !strnicmp(Ships[objp->instance].ship_name, INSTRUCTOR_SHIP_NAME, strlen(INSTRUCTOR_SHIP_NAME));
}

//      Evade the weapon aip->danger_weapon_objnum
//      If it's not valid, do a quick out.
//      Evade by accelerating hard.
//      If necessary, turn hard left or hard right.
void evade_weapon()
{
        object  *weapon_objp = NULL;
        object  *unlocked_weapon_objp = NULL, *locked_weapon_objp = NULL;
        vector  weapon_pos, player_pos, goal_point;
        vector  vec_from_enemy;
        float           dot_from_enemy, dot_to_enemy;
        float           dist;
        ship            *shipp = &Ships[Pl_objp->instance];
        ai_info *aip = &Ai_info[shipp->ai_index];

        if (is_instructor(Pl_objp))
                return;

        //      Make sure we're actually being attacked.
        //      Favor locked objects.
        if (aip->nearest_locked_object != -1) {
                if (Objects[aip->nearest_locked_object].type == OBJ_WEAPON)
                        locked_weapon_objp = &Objects[aip->nearest_locked_object];
        }
        
        if (aip->danger_weapon_objnum != -1)
                if (Objects[aip->danger_weapon_objnum].signature == aip->danger_weapon_signature)
                        unlocked_weapon_objp = &Objects[aip->danger_weapon_objnum];
                else
                        aip->danger_weapon_objnum = -1;         //      Signatures don't match, so no longer endangered.

        if (locked_weapon_objp != NULL) {
                if (unlocked_weapon_objp != NULL) {
                        if (vm_vec_dist_quick(&locked_weapon_objp->pos, &Pl_objp->pos) < 1.5f * vm_vec_dist_quick(&unlocked_weapon_objp->pos, &Pl_objp->pos))
                                weapon_objp = locked_weapon_objp;
                        else
                                weapon_objp = unlocked_weapon_objp;
                } else
                        weapon_objp = locked_weapon_objp;
        } else if (unlocked_weapon_objp != NULL)
                weapon_objp = unlocked_weapon_objp;
        else {
                if (aip->mode == AIM_EVADE_WEAPON)
                        maybe_resume_previous_mode(Pl_objp, aip);
                return;
        }

        Assert(weapon_objp != NULL);

        if (weapon_objp->type != OBJ_WEAPON) {
                if (aip->mode == AIM_EVADE_WEAPON)
                        maybe_resume_previous_mode(Pl_objp, aip);
                return;
        }
        
        weapon_pos = weapon_objp->pos;
        player_pos = Pl_objp->pos;

        //      Make speed based on skill level, varying at highest skill level, which is harder to hit.
        accelerate_ship(aip, 1.0f);

        dist = vm_vec_normalized_dir(&vec_from_enemy, &player_pos, &weapon_pos);

        dot_to_enemy = -vm_vec_dot(&Pl_objp->orient.v.fvec, &vec_from_enemy);
        dot_from_enemy = vm_vec_dot(&weapon_objp->orient.v.fvec, &vec_from_enemy);
        //nprintf(("AI", "dot from enemy = %7.3f\n", dot_from_enemy));

        //      If shot is incoming...
        if (dot_from_enemy < 0.3f) {
                if (weapon_objp == unlocked_weapon_objp)
                        aip->danger_weapon_objnum = -1;
                return;
        } else if (dot_from_enemy > 0.7f) {
                if (dist < 200.0f) {
                        if (!( Pl_objp->phys_info.flags & PF_AFTERBURNER_ON )) {
                                if (ai_maybe_fire_afterburner(Pl_objp, aip)) {
                                        //nprintf(("AI", "Frame %i, turning on afterburner.\n", AI_FrameCount));
                                        afterburners_start(Pl_objp);
                                        aip->afterburner_stop_time = Missiontime + F1_0/2;
                                }
                        }
                }

                //      If we're sort of pointing towards it...
                if ((dot_to_enemy < -0.5f) || (dot_to_enemy > 0.5f)) {
                        float   rdot;

                        //      Turn hard left or right, depending on which gets out of way quicker.
                        rdot = vm_vec_dot(&Pl_objp->orient.v.rvec, &vec_from_enemy);

                        if ((rdot < -0.5f) || (rdot > 0.5f))
                                vm_vec_scale_add(&goal_point, &Pl_objp->pos, &Pl_objp->orient.v.rvec, -200.0f);
                        else
                                vm_vec_scale_add(&goal_point, &Pl_objp->pos, &Pl_objp->orient.v.rvec, 200.0f);

                        turn_towards_point(Pl_objp, &goal_point, NULL, 0.0f);
                }
        }

}

//      Use sliding and backwards moving to face enemy.
//      (Coded 2/20/98.  Works fine, but it's hard to see how to integrate it into the AI system.
//       Typically ships are moving so fast that a little sliding isn't enough to gain an advantage.
//       It's currently used to avoid collisions and could be used to evade weapon fire, but the latter
//       would be frustrating, I think.
//       This function is currently not called.)
void slide_face_ship()
{
        ship_info       *sip;

        sip = &Ship_info[Ships[Pl_objp->instance].ship_info_index];

        //      If can't slide, return.
        if ((sip->max_vel.xyz.x == 0.0f) && (sip->max_vel.xyz.y == 0.0f))
                return;

        vector  goal_pos;
        float           dot_from_enemy, dot_to_enemy;
        vector  vec_from_enemy, vec_to_goal;
        float           dist;
        float           up, right;
        ai_info         *aip;

        aip = &Ai_info[Ships[Pl_objp->instance].ai_index];

        dist = vm_vec_normalized_dir(&vec_from_enemy, &Pl_objp->pos, &En_objp->pos);

        ai_turn_towards_vector(&En_objp->pos, Pl_objp, flFrametime, sip->srotation_time, NULL, NULL, 0.0f, 0);

        dot_from_enemy = vm_vec_dot(&vec_from_enemy, &En_objp->orient.v.fvec);
        dot_to_enemy = -vm_vec_dot(&vec_from_enemy, &Pl_objp->orient.v.fvec);

        if (vm_vec_dot(&vec_from_enemy, &En_objp->orient.v.rvec) > 0.0f)
                right = 1.0f;
        else
                right = -1.0f;

        if (vm_vec_dot(&vec_from_enemy, &En_objp->orient.v.uvec) > 0.0f)
                up = 1.0f;
        else
                up = -1.0f;

        vm_vec_scale_add(&goal_pos, &En_objp->pos, &En_objp->orient.v.rvec, right * 200.0f);
        vm_vec_scale_add(&goal_pos, &En_objp->pos, &En_objp->orient.v.uvec, up * 200.0f);

        vm_vec_normalized_dir(&vec_to_goal, &goal_pos, &Pl_objp->pos);

        if (vm_vec_dot(&vec_to_goal, &Pl_objp->orient.v.rvec) > 0.0f)
                AI_ci.sideways = 1.0f;
        else
                AI_ci.sideways = -1.0f;

        if (vm_vec_dot(&vec_to_goal, &Pl_objp->orient.v.uvec) > 0.0f)
                AI_ci.vertical = 1.0f;
        else
                AI_ci.vertical = -1.0f;

        if (dist < 200.0f) {
                if (dot_from_enemy < 0.7f)
                        accelerate_ship(aip, -1.0f);
                else
                        accelerate_ship(aip, dot_from_enemy + 0.5f);
        } else {
                if (dot_from_enemy < 0.7f) {
                        accelerate_ship(aip, 0.2f);
                } else {
                        accelerate_ship(aip, 1.0f);
                }
        }
}

//      General code for handling one ship evading another.
//      Problem: This code is also used for avoiding an impending collision.
//      In such a case, it is not good to go to max speed, which is often good
//      for a certain kind of evasion.
void evade_ship()
{
        vector  player_pos, enemy_pos, goal_point;
        vector  vec_from_enemy;
        float           dot_from_enemy;
        float           dist;
        ship            *shipp = &Ships[Pl_objp->instance];
        ship_info       *sip = &Ship_info[shipp->ship_info_index];
        ai_info *aip = &Ai_info[shipp->ai_index];
        float           bank_override = 0.0f;

        ai_set_positions(Pl_objp, En_objp, aip, &player_pos, &enemy_pos);

        //      Make speed based on skill level, varying at highest skill level, which is harder to hit.
        if (Game_skill_level == NUM_SKILL_LEVELS-1) {
                int     rand_int;
                float   accel_val;

                rand_int = static_rand(Pl_objp-Objects);
                accel_val = (float) (((Missiontime^rand_int) >> 14) & 0x0f)/32.0f + 0.5f;
                accelerate_ship(aip, accel_val);
                //nprintf(("AI", "Accel value = %7.3f\n", accel_val));
        } else
                accelerate_ship(aip, (float) (Game_skill_level+2) / (NUM_SKILL_LEVELS+1));

        if ((Missiontime - aip->submode_start_time > F1_0/2) && (sip->afterburner_fuel_capacity > 0.0f)) {
                float percent_left = 100.0f * shipp->afterburner_fuel / sip->afterburner_fuel_capacity;
                if (percent_left > 30.0f + ((Pl_objp-Objects) & 0x0f)) {
                        afterburners_start(Pl_objp);
                        aip->afterburner_stop_time = Missiontime + F1_0 + static_rand(Pl_objp-Objects)/4;
                }
        }

        vm_vec_sub(&vec_from_enemy, &player_pos, &enemy_pos);

        dist = vm_vec_normalize(&vec_from_enemy);
        dot_from_enemy = vm_vec_dot(&En_objp->orient.v.fvec, &vec_from_enemy);

        if (dist > 250.0f) {
                vector  gp1, gp2;
                //      If far away from enemy, circle, going to nearer of point far off left or right wing
                vm_vec_scale_add(&gp1, &enemy_pos, &En_objp->orient.v.rvec, 250.0f);
                vm_vec_scale_add(&gp2, &enemy_pos, &En_objp->orient.v.rvec, -250.0f);
                if (vm_vec_dist_quick(&gp1, &Pl_objp->pos) < vm_vec_dist_quick(&gp2, &Pl_objp->pos))
                        goal_point = gp1;
                else
                        goal_point = gp2;
        } else if (dot_from_enemy < 0.1f) {
                //      If already close to behind, goal is to get completely behind.
                vm_vec_scale_add(&goal_point, &enemy_pos, &En_objp->orient.v.fvec, -1000.0f);
        } else if (dot_from_enemy > 0.9f) {
                //      If enemy pointing almost right at self, and self pointing close to enemy, turn away from
                vector  vec_to_enemy;
                float           dot_to_enemy;

                vm_vec_sub(&vec_to_enemy, &enemy_pos, &player_pos);

                vm_vec_normalize(&vec_to_enemy);
                dot_to_enemy = vm_vec_dot(&Pl_objp->orient.v.fvec, &vec_to_enemy);
                if (dot_to_enemy > 0.75f) {
                        //      Used to go to En_objp's right vector, but due to banking while turning, that
                        //      caused flying in an odd spiral.
                        vm_vec_scale_add(&goal_point, &enemy_pos, &Pl_objp->orient.v.rvec, 1000.0f);
                        if (dist < 100.0f)
                                bank_override = Pl_objp->phys_info.speed; 
                } else {
                        bank_override = Pl_objp->phys_info.speed;                       //      In enemy's sights, not pointing at him, twirl away.
                        // nprintf(("Mike", " Do sumpin' else."));
                        goto evade_ship_l1;
                }
        } else {
evade_ship_l1: ;
                if (aip->ai_evasion > myrand()*100.0f/32767.0f) {
                        int     temp;
                        float   scale;
                        float   psrandval;      //      some value close to zero to choose whether to turn right or left.

                        psrandval = (float) (((Missiontime >> 14) & 0x0f) - 8); //      Value between -8 and 7
                        psrandval = psrandval/16.0f;                                                    //      Value between -1/2 and 1/2 (approx)

                        //      If not close to behind, turn towards his right or left vector, whichever won't cross his path.
                        if (vm_vec_dot(&vec_from_enemy, &En_objp->orient.v.rvec) > psrandval) {
                                scale = 1000.0f;
                        } else {
                                scale = -1000.0f;
                        }

                        vm_vec_scale_add(&goal_point, &enemy_pos, &En_objp->orient.v.rvec, scale);

                        temp = ((Missiontime >> 16) & 0x07);
                        temp = ((temp * (temp+1)) % 16)/2 - 4;
                        if ((psrandval == 0) && (temp == 0))
                                temp = 3;

                        scale = 200.0f * temp;

                        vm_vec_scale_add2(&goal_point, &En_objp->orient.v.uvec, scale);
                } else {
                        //      No evasion this frame, but continue with previous turn.
                        //      Reason: If you don't, you lose rotational momentum.  Turning every other frame,
                        //      and not in between results in a very slow turn because of loss of momentum.
                        if ((aip->prev_goal_point.xyz.x != 0.0f) || (aip->prev_goal_point.xyz.y != 0.0f) || (aip->prev_goal_point.xyz.z != 0.0f))
                                goal_point = aip->prev_goal_point;
                        else
                                vm_vec_scale_add(&goal_point, &enemy_pos, &En_objp->orient.v.rvec, 100.0f);
                }
        }

        // nprintf(("Mike", "Goal point = %7.1f %7.1f %7.1f\n", goal_point.xyz.x, goal_point.xyz.y, goal_point.xyz.z));
        turn_towards_point(Pl_objp, &goal_point, NULL, bank_override);

        aip->prev_goal_point = goal_point;
}

//      --------------------------------------------------------------------------
//      Fly in a manner making it difficult for opponent to attack.
void ai_evade()
{
        evade_ship();
}

/*
// -------------------------------------------------------------------
//      Refine predicted enemy position because enemy will move while we move
//      towards predicted enemy position.
//      last_delta_vec is stuffed with size of polishing in last step.  This small amount
//      can be used to perturb the predicted position to make firing not be exact.
//      This function will almost always undershoot actual position, assuming both ships
//      are moving at constant speed.  But with even one polishing step, the error should
//      be under 1%. The number of polishing steps is specified in the parameter num_polish_steps.
void polish_predicted_enemy_pos(vector *predicted_enemy_pos, object *pobjp, object *eobjp, float dist_to_enemy, vector *last_delta_vec, int num_polish_steps) // Not used:, float time_to_enemy)
{
        int     iteration;
        vector  player_pos = pobjp->pos;
        vector  enemy_pos = *predicted_enemy_pos;
        physics_info    *en_physp = &eobjp->phys_info;
        float           time_to_enemy;
        vector  last_predicted_enemy_pos = *predicted_enemy_pos;
        
        vm_vec_zero(last_delta_vec);

        for (iteration=0; iteration < num_polish_steps; iteration++) {
                dist_to_enemy = vm_vec_dist_quick(predicted_enemy_pos, &player_pos);
                time_to_enemy = compute_time_to_enemy(dist_to_enemy, pobjp, eobjp);
                vm_vec_scale_add(predicted_enemy_pos, &eobjp->pos, &eobjp->phys_info.vel, time_to_enemy);
                vm_vec_sub(last_delta_vec, predicted_enemy_pos, &last_predicted_enemy_pos);
                last_predicted_enemy_pos= *predicted_enemy_pos;
        }
}
*/

/*
Relevant variables are:
        best_dot_to_enemy               best dot product to enemy in last BEST_DOT_TIME seconds
        best_dot_to_time                time at which best dot occurred
        best_dot_from_enemy     best dot product for enemy to player in last BEST_DOT_TIME seconds
        best_dot_from_time      time at which best dot occurred
        submode_start_time      time at which we entered the current submode
        previous_submode                previous submode, get it?
Legal submodes are:
        CONTINUOUS_TURN vector_id {0..3 = right, -right, up, -up}
        ATTACK
        EVADE_SQUIGGLE
        EVADE_BRAKE
*/

float   G_collision_time;
vector  G_predicted_pos, G_fire_pos;

/*
void show_firing_diag()
{
        float           dot;
        vector  v2t;
        vector  pos1, pos2;
        float           dist;

        if (G_collision_time == 0.0f)
                return;

        mprintf(("Fired from %5.1f, %5.1f %5.1f at time = %5.1f, predict collision in %5.2f seconds at %5.1f %5.1f %5.1f\n",
                Pl_objp->pos.xyz.x, Pl_objp->pos.xyz.y, Pl_objp->pos.xyz.z, (float) Missiontime/1000.0f, G_collision_time, G_predicted_pos.xyz.x, G_predicted_pos.xyz.y, G_predicted_pos.xyz.z));
        vm_vec_normalized_dir(&v2t, &G_predicted_pos, &G_fire_pos);
        dot = vm_vec_dot(&v2t, &Pl_objp->orient.v.fvec);
        mprintf(("Dot of v.fvec and vector to predicted position = %10.7f (%7.3f degrees)\n", dot, acos(dot)*180.0f/3.141592654f));

        vm_vec_scale_add(&pos1, &En_objp->pos, &En_objp->phys_info.vel, G_collision_time);
        vm_vec_scale_add(&pos2, &G_fire_pos, &Pl_objp->orient.v.fvec, G_collision_time*300.0f);
        dist = vm_vec_dist(&pos1, &pos2);

        mprintf(("Enemy, laser pos, distance: [%5.1f %5.1f %5.1f]  [%5.1f %5.1f %5.1f]  %6.2f\n", pos1.xyz.x, pos1.xyz.y, pos1.xyz.z, pos2.xyz.x, pos2.xyz.y, pos2.xyz.z, dist));
}
*/

//      If:
//              flags & WIF_PUNCTURE
//      Then Select a Puncture weapon.
//      Else
//              Select Any ol' weapon.
//      Returns primary_bank index.
int ai_select_primary_weapon(object *objp, object *other_objp, int flags)
{
        ship    *shipp = &Ships[objp->instance];
        ship_weapon *swp = &shipp->weapons;
        ship_info *sip;

        //Assert( other_objp != NULL );
        Assert( shipp->ship_info_index >= 0 && shipp->ship_info_index < MAX_SHIP_TYPES);

        sip = &Ship_info[shipp->ship_info_index];

        if (flags & WIF_PUNCTURE) {
                if (swp->current_primary_bank >= 0) {
                        int     bank_index;

                        bank_index = swp->current_primary_bank;

                        if (Weapon_info[swp->primary_bank_weapons[bank_index]].wi_flags & WIF_PUNCTURE) {
                                //nprintf(("AI", "%i: Ship %s selecting weapon %s\n", Framecount, Ships[objp->instance].ship_name, Weapon_info[swp->primary_bank_weapons[bank_index]].name));
                                return swp->current_primary_bank;
                        }
                }
                for (int i=0; i<swp->num_primary_banks; i++) {
                        int     weapon_info_index;

                        weapon_info_index = swp->primary_bank_weapons[i];

                        if (weapon_info_index > -1){
                                if (Weapon_info[weapon_info_index].wi_flags & WIF_PUNCTURE) {
                                        swp->current_primary_bank = i;
                                        //nprintf(("AI", "%i: Ship %s selecting weapon %s\n", Framecount, Ships[objp->instance].ship_name, Weapon_info[swp->primary_bank_weapons[i]].name));
                                        return i;
                                }
                        }
                }
                
                // AL 26-3-98: If we couldn't find a puncture weapon, pick first available weapon if one isn't active
                if ( swp->current_primary_bank < 0 ) {
                        if ( swp->num_primary_banks > 0 ) {
                                swp->current_primary_bank = 0;
                        }
                }

        } else {                //      Don't need to be using a puncture weapon.
                if (swp->current_primary_bank >= 0) {
                        if (!(Weapon_info[swp->primary_bank_weapons[swp->current_primary_bank]].wi_flags & WIF_PUNCTURE)){
                                return swp->current_primary_bank;
                        }
                }
                for (int i=0; i<swp->num_primary_banks; i++) {
                        if (swp->primary_bank_weapons[i] > -1) {
                                if (!(Weapon_info[swp->primary_bank_weapons[i]].wi_flags & WIF_PUNCTURE)) {
                                        swp->current_primary_bank = i;
                                        nprintf(("AI", "%i: Ship %s selecting weapon %s\n", Framecount, Ships[objp->instance].ship_name, Weapon_info[swp->primary_bank_weapons[i]].name));
                                        return i;
                                }
                        }
                }
                //      Wasn't able to find a non-puncture weapon.  Stick with what we have.
        }

        Assert( swp->current_primary_bank != -1 );              // get Alan or Allender

        return swp->current_primary_bank;
}

//      --------------------------------------------------------------------------
//      Maybe link primary weapons.
void set_primary_weapon_linkage(object *objp)
{
        ship            *shipp;
        ai_info *aip;

        shipp = &Ships[objp->instance];
        aip     = &Ai_info[shipp->ai_index];

        shipp->flags &= ~SF_PRIMARY_LINKED;

        if (Num_weapons > (int) (MAX_WEAPONS * 0.75f)) {
                if (shipp->flags & SF_PRIMARY_LINKED)
                        nprintf(("AI", "Frame %i, ship %s: Unlinking primaries.\n", Framecount, shipp->ship_name));
                shipp->flags &= ~SF_PRIMARY_LINKED;
                return;         //      If low on slots, don't link.
        }

        shipp->flags &= ~SF_PRIMARY_LINKED;

        // AL: ensure target is a ship!
        if ( Objects[aip->target_objnum].type == OBJ_SHIP ) {
                // If trying to destroy a big ship (i.e., not disable/disarm), always unleash all weapons
                if ( ship_get_SIF(&Ships[Objects[aip->target_objnum].instance]) & SIF_BIG_SHIP) {
                        if ( aip->targeted_subsys == NULL ) {
                                shipp->flags |= SF_PRIMARY_LINKED;
                                shipp->flags |= SF_SECONDARY_DUAL_FIRE;
                                return;
                        }
                }
        }

        // AL 2-11-98: If ship has a disarm or disable goal, don't link unless both weapons are
        //                                      puncture weapons
        if ( (aip->active_goal != AI_GOAL_NONE) && (aip->active_goal != AI_ACTIVE_GOAL_DYNAMIC) ) {
                if ( aip->goals[aip->active_goal].ai_mode & (AI_GOAL_DISABLE_SHIP|AI_GOAL_DISARM_SHIP) ) {
                        ship_weapon     *swp;
                        swp = &shipp->weapons;
                        // only continue if both primaries are puncture weapons
                        if ( swp->num_primary_banks == 2 ) {
                                if ( !(Weapon_info[swp->primary_bank_weapons[0]].wi_flags & WIF_PUNCTURE) ) 
                                        return;
                                if ( !(Weapon_info[swp->primary_bank_weapons[1]].wi_flags & WIF_PUNCTURE) ) 
                                        return;
                        }
                }
        }

        //      Don't want all ships always linking weapons at start, so asynchronize.
        if (Missiontime < i2f(30))
                return;
        else if (Missiontime < i2f(120)) {
                int r = static_rand((Missiontime >> 17) ^ OBJ_INDEX(objp));
                if ( (r&3) != 0)
                        return;
        }

        if (shipp->weapon_energy > Link_energy_levels_always[Game_skill_level]) {
                shipp->flags |= SF_PRIMARY_LINKED;
        } else if (shipp->weapon_energy > Link_energy_levels_maybe[Game_skill_level]) {
                if (objp->hull_strength < Ship_info[shipp->ship_info_index].initial_hull_strength/3.0f)
                        shipp->flags |= SF_PRIMARY_LINKED;
        }
}

//      --------------------------------------------------------------------------
//      Fire the current primary weapon.
//      *objp is the object to fire from.
void ai_fire_primary_weapon(object *objp)
{
        ship                    *shipp = &Ships[objp->instance];
        ship_weapon     *swp = &shipp->weapons;
        ship_info       *sip;
        ai_info         *aip;
        object          *enemy_objp;

        Assert( shipp->ship_info_index >= 0 && shipp->ship_info_index < MAX_SHIP_TYPES);
        sip = &Ship_info[shipp->ship_info_index];

        aip = &Ai_info[shipp->ai_index];

        //      If low on slots, fire a little less often.
        if (Num_weapons > (int) (0.9f * MAX_WEAPONS)) {
                if (frand() > 0.5f) {
                        nprintf(("AI", "Frame %i, %s not fire.\n", Framecount, shipp->ship_name));
                        return;
                }
        }

        if (!Ai_firing_enabled){
                return;
        }

        if (aip->target_objnum != -1){
                enemy_objp = &Objects[aip->target_objnum];
        } else {
                enemy_objp = NULL;
        }

        if ( (swp->current_primary_bank < 0) || (swp->current_primary_bank >= swp->num_primary_banks) || timestamp_elapsed(aip->primary_select_timestamp)) {
                int     flags = 0;
                // AL 2-11-98: If attacking any subsystem (not just engines), use disrupter weapon
//              if ((aip->targeted_subsys != NULL) && (aip->targeted_subsys->system_info->type == SUBSYSTEM_ENGINE)) {
                if ( aip->targeted_subsys != NULL ) {
                        flags = WIF_PUNCTURE;
                }
                ai_select_primary_weapon(objp, enemy_objp, flags);
                ship_primary_changed(shipp);    // AL: maybe send multiplayer information when AI ship changes primaries
                aip->primary_select_timestamp = timestamp(5 * 1000);    //      Maybe change primary weapon five seconds from now.
        }

        //      If pointing nearly at predicted collision point of target, bash orientation to be perfectly pointing.
        float   dot;
        vector  v2t;

//      if (!IS_VEC_NULL(&G_predicted_pos)) {
        if (!( vm_vec_mag_quick(&G_predicted_pos) < AICODE_SMALL_MAGNITUDE )) {
                if ( !vm_vec_cmp(&G_predicted_pos, &G_fire_pos) ) {
                        nprintf(("Warning", "Avoid NULL vector assert.. why are G_predicted_pos and G_fire_pos the same?\n"));
                } else {
                        vm_vec_normalized_dir(&v2t, &G_predicted_pos, &G_fire_pos);
                        dot = vm_vec_dot(&v2t, &objp->orient.v.fvec);
                        if (dot > .998629534f){ //      if within 3.0 degrees of desired heading, bash
                                vm_vector_2_matrix(&objp->orient, &v2t, &objp->orient.v.uvec, NULL);
                        }
                }
        }

        //      Make sure not firing at a protected ship unless firing at a live subsystem.
        //      Note: This happens every time the ship tries to fire, perhaps every frame.
        //      Should be wrapped in a timestamp, same one that enables it to fire, but that is complicated
        //      by multiple banks it can fire from.
        if (aip->target_objnum != -1) {
                object  *tobjp = &Objects[aip->target_objnum];
                if (tobjp->flags & OF_PROTECTED) {
                        if (aip->targeted_subsys != NULL) {
                                int     type;

                                type = aip->targeted_subsys->system_info->type;
                                if (ship_get_subsystem_strength(&Ships[tobjp->instance], type) == 0.0f) {
                                        aip->target_objnum = -1;
                                        return;
                                }
                        } else {
                                aip->target_objnum = -1;
                                return;
                        }
                }
        }

        //      If enemy is protected, not firing a puncture weapon and enemy's hull is low, don't fire.
        if ((enemy_objp != NULL) && (enemy_objp->flags & OF_PROTECTED)) {
                // AL: 3-6-98: Check if current_primary_bank is valid
                if ((enemy_objp->hull_strength < 750.0f) && 
                        ((aip->targeted_subsys == NULL) || (enemy_objp->hull_strength < aip->targeted_subsys->current_hits + 50.0f)) &&
                        (swp->current_primary_bank >= 0) ) {
                        if (!(Weapon_info[swp->primary_bank_weapons[swp->current_primary_bank]].wi_flags & WIF_PUNCTURE)) {
                                //nprintf(("AI", "Ship %s not firing at protected ship %s because not using disruptor.\n", Ships[objp->instance].ship_name, Ships[enemy_objp->instance].ship_name));
                                swp->next_primary_fire_stamp[swp->current_primary_bank] = timestamp(1000);
                                return;
                        }

                        /*
                        int     num_attacking;
                        num_attacking = num_enemies_attacking(enemy_objp-Objects);
                        if (enemy_objp->hull_strength / num_attacking < 200.0f) {
                                if (frand() < 0.75f) {
                                        nprintf(("AI", "Ship %s not firing at protected ship %s because too many attacking.\n", Ships[objp->instance].ship_name, Ships[enemy_objp->instance].ship_name));
                                        swp->next_primary_fire_stamp[swp->current_primary_bank] = timestamp(500);
                                        return;
                                }
                        }
                        */
                }
        }

        set_primary_weapon_linkage(objp);
        
        // I think this will properly solve the problem
        // fire non-streaming weapons
        ship_fire_primary(objp, 0);
        
        // fire streaming weapons
        shipp->flags |= SF_TRIGGER_DOWN;
        ship_fire_primary(objp, 1);
        shipp->flags &= ~SF_TRIGGER_DOWN;
}

//      --------------------------------------------------------------------------
//      Return number of nearby enemy fighters.
//      threshold is the distance within which a ship is considered near.
//
// input:       enemy_team_mask =>      teams that are considered as an enemy
//                              pos                                     =>      world position to measure ship distances from
//                              threshold                       =>      max distance from pos to be considered "near"
//
// exit:                number of ships within threshold units of pos
int num_nearby_fighters(int enemy_team_mask, vector *pos, float threshold)
{
        ship_obj        *so;
        object  *ship_objp;
        int             count = 0;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {

                ship_objp = &Objects[so->objnum];

                if (Ships[ship_objp->instance].team & enemy_team_mask) {
                        if (Ship_info[Ships[ship_objp->instance].ship_info_index].flags & (SIF_FIGHTER | SIF_BOMBER)) {
                                if (vm_vec_dist_quick(pos, &ship_objp->pos) < threshold)
                                        count++;
                        }
                }
        }

        return count;
}

//      --------------------------------------------------------------------------
//      Select secondary weapon to fire.
//      Currently, 1/16/98:
//              If 0 secondary weapons available, return -1
//              If 1 available, use it.
//              If 2 or more, if the current weapon is one of them, stick with it, otherwise choose a random one.
//      priority1 and priority2 are Weapon_info[] bitmasks such as WIF_HOMING_ASPECT.  If any weapon has any bit in priority1
//      set, that weapon will be selected.  If not, apply to priority2.  If neither, return -1, meaning no weapon selected.
//      Note, priorityX have default values of -1, meaning if not set, they will match any weapon.
//      Return value:
//              bank index
//      Should do this:
//              Favor aspect seekers when attacking small ships faraway.
//              Favor rapid fire dumbfire when attacking a large ship.
//              Ignore heat seekers because we're not sure how they'll work.
void ai_select_secondary_weapon(object *objp, ship_weapon *swp, int priority1 = -1, int priority2 = -1)
{
        int     num_weapon_types;
        int     weapon_id_list[MAX_WEAPON_TYPES], weapon_bank_list[MAX_WEAPON_TYPES];
        int     i;
        int     ignore_mask;
        int     initial_bank;

        initial_bank = swp->current_secondary_bank;

        //      Ignore bombs unless one of the priorities asks for them to be selected.
        if (WIF_HUGE & (priority1 | priority2))
                ignore_mask = 0;
        else
                ignore_mask = WIF_HUGE;

        if (!(WIF_BOMBER_PLUS & (priority1 | priority2)))
                ignore_mask |= WIF_BOMBER_PLUS;

#ifndef NDEBUG
        for (i=0; i<MAX_WEAPON_TYPES; i++) {
                weapon_id_list[i] = -1;
                weapon_bank_list[i] = -1;
        }
#endif

        //      Stuff weapon_bank_list with bank index of available weapons.
        num_weapon_types = get_available_secondary_weapons(objp, weapon_id_list, weapon_bank_list);

        int     priority2_index = -1;

        for (i=0; i<num_weapon_types; i++) {
                int     wi_flags;

                wi_flags = Weapon_info[swp->secondary_bank_weapons[weapon_bank_list[i]]].wi_flags;
                if (!(wi_flags & ignore_mask)) {                                        //      Maybe bombs are illegal.
                        if (wi_flags & priority1) {
                                swp->current_secondary_bank = weapon_bank_list[i];                              //      Found first priority, return it.
                                break;
                        } else if (wi_flags & priority2)
                                priority2_index = weapon_bank_list[i];  //      Found second priority, but might still find first priority.
                }
        }

        //      If didn't find anything above, then pick any secondary weapon.
        if (i == num_weapon_types) {
                swp->current_secondary_bank = priority2_index;  //      Assume we won't find anything.
                if (priority2_index == -1) {
                        for (i=0; i<num_weapon_types; i++) {
                                int     wi_flags;

                                wi_flags = Weapon_info[swp->secondary_bank_weapons[weapon_bank_list[i]]].wi_flags;
                                if (!(wi_flags & ignore_mask)) {                                        //      Maybe bombs are illegal.
                                        if (swp->secondary_bank_ammo[i] > 0) {
                                                swp->current_secondary_bank = i;
                                                break;
                                        }
                                }
                        }
                }
        }

        //      If switched banks, force reacquisition of aspect lock.
        if (swp->current_secondary_bank != initial_bank) {
                ai_info *aip = &Ai_info[Ships[objp->instance].ai_index];
                
                aip->aspect_locked_time = 0.0f;
                aip->current_target_is_locked = 0;
        }


        ship_secondary_changed(&Ships[objp->instance]); // AL: let multiplayer know if secondary bank has changed
        // nprintf(("AI", "Ship %s selected weapon %s\n", Ships[objp->instance].ship_name, Weapon_info[swp->secondary_bank_weapons[swp->current_secondary_bank]].name));
}

//      Return number of objects homing on object *target_objp
int compute_num_homing_objects(object *target_objp)
{
        object  *objp;
        int             count = 0;

        for ( objp = GET_FIRST(&obj_used_list); objp !=END_OF_LIST(&obj_used_list); objp = GET_NEXT(objp) ) {
                if (objp->type == OBJ_WEAPON) {
                        if (Weapon_info[Weapons[objp->instance].weapon_info_index].wi_flags & WIF_HOMING) {
                                if (Weapons[objp->instance].homing_object == target_objp) {
                                        count++;
                                }
                        }
                }
        }

        return count;
}

//      Object *firing_objp just fired weapon weapon_index (index in Weapon_info).
//      If it's a shockwave weapon, tell your team about it!
void ai_maybe_announce_shockwave_weapon(object *firing_objp, int weapon_index)
{
        if ((firing_objp->type == OBJ_SHIP) && (Weapon_info[weapon_index].shockwave_speed > 0.0f)) {
                ship_obj        *so;
                int             firing_ship_team;

                firing_ship_team = Ships[firing_objp->instance].team;

                for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                        object  *A = &Objects[so->objnum];
                        Assert(A->type == OBJ_SHIP);

                        if (Ships[A->instance].team == firing_ship_team) {
                                ai_info *aip = &Ai_info[Ships[A->instance].ai_index];
                                // AL 1-5-98: only avoid shockwave if not docked or repairing
                                if ( !(aip->ai_flags & (AIF_DOCKED|AIF_BEING_REPAIRED)) ) {
                                        aip->ai_flags |= AIF_AVOID_SHOCKWAVE_WEAPON;
                                }
                        }
                }
        }
}

//      Return total payload of all incoming missiles.
float compute_incoming_payload(object *target_objp)
{
        missile_obj     *mo;
        float                   payload = 0.0f;

        for ( mo = GET_NEXT(&Missile_obj_list); mo != END_OF_LIST(&Missile_obj_list); mo = GET_NEXT(mo) ) {
                object  *objp;

                objp = &Objects[mo->objnum];
                Assert(objp->type == OBJ_WEAPON);
                if (Weapons[objp->instance].homing_object == target_objp) {
                        payload += Weapon_info[Weapons[objp->instance].weapon_info_index].damage;
                }
        }

        return payload;
}

//      --------------------------------------------------------------------------
//      Return true if OK for *aip to fire its current weapon at its current target.
//      Only reason this function returns false is:
//              weapon is a homer
//              targeted at player
//                      OR:     player has too many homers targeted at him
//                                      Missiontime in that dead zone in which can't fire at this player
//      Note: If player is attacking a ship, that ship is allowed to fire at player.  Otherwise, we get in a situation in which
//      player is attacking a large ship, but that large ship is not defending itself with missiles.
int check_ok_to_fire(int objnum, int target_objnum, weapon_info *wip)
{
        int     num_homers = 0;
        object  *tobjp = &Objects[target_objnum];

        if (target_objnum > -1) {
                // AL 3-4-98: Ensure objp target is a ship first 
                if ( tobjp->type == OBJ_SHIP ) {

                        // should not get this far. check if ship is protected from beam and weapon is type beam
                        if ( (wip->wi_flags & WIF_BEAM) && (tobjp->flags & OF_BEAM_PROTECTED) ) {
                                Int3();
                                return 0;
                        }
                        if (Ship_info[Ships[tobjp->instance].ship_info_index].flags & SIF_SMALL_SHIP) {
                                num_homers = compute_num_homing_objects(&Objects[target_objnum]);
                        }
                }

                //      If player, maybe fire based on Skill_level and number of incoming weapons.
                //      If non-player, maybe fire based on payload of incoming weapons.
                if (wip->wi_flags & WIF_HOMING) {
                        if ((target_objnum > -1) && (tobjp->flags & OF_PLAYER_SHIP)) {
                                if (Ai_info[Ships[tobjp->instance].ai_index].target_objnum != objnum) {
                                        //      Don't allow AI ships to fire at player for fixed periods of time based on skill level.
                                        //      With 5 skill levels, at Very Easy, they fire in 1/7 of every 10 second interval.
                                        //      At Easy, 2/7...at Expert, 5/7
                                        int t = ((Missiontime /(65536*10)) ^ target_objnum ^ 0x01) % (NUM_SKILL_LEVELS+2);
                                        if (t > Game_skill_level) {
                                                //nprintf(("AI", "Not OK to fire homer at time thing %i\n", t));
                                                return 0;
                                        }
                                }
                                //nprintf(("AI", " IS OK to fire homer at time thing %i ***\n", t));
                                int     swarmers = 0;
                                if (wip->wi_flags & WIF_SWARM)
                                        swarmers = 2;   //      Note, always want to be able to fire swarmers if no currently incident homers.
                                if (Max_allowed_player_homers[Game_skill_level] < num_homers + swarmers) {
                                        return 0;
                                }
                        } else if (num_homers > 3) {
                                float   incoming_payload;

                                incoming_payload = compute_incoming_payload(&Objects[target_objnum]);

                                if (incoming_payload > tobjp->hull_strength) {
                                        return 0;
                                }
                        }
                }
        }

        return 1;
}

//      --------------------------------------------------------------------------
//      Fire a secondary weapon.
//      Maybe choose to fire a different one.
//      priority1 and priority2 are optional parameters with defaults = -1
int ai_fire_secondary_weapon(object *objp, int priority1, int priority2)
{
        ship_weapon *swp;
        ship    *shipp;
        ship_info *sip;
        int             current_bank;
        int             rval = 0;

#ifndef NDEBUG
        if (!Ai_firing_enabled)
                return rval;
#endif

        Assert( objp != NULL );
        Assert(objp->type == OBJ_SHIP);
        shipp = &Ships[objp->instance];
        swp = &shipp->weapons;

        Assert( shipp->ship_info_index >= 0 && shipp->ship_info_index < MAX_SHIP_TYPES);
        sip = &Ship_info[shipp->ship_info_index];

        //      Select secondary weapon.
        current_bank = swp->current_secondary_bank; //ai_select_secondary_weapon(objp, swp, priority1, priority2);

        //nprintf(("AI", "Frame %i: Current bank = %i, ammo remaining = %i\n", Framecount, current_bank, swp->secondary_bank_ammo[current_bank]));
        if (current_bank == -1) {
                swp->next_secondary_fire_stamp[current_bank] = timestamp(500);
                return rval;
        }

        Assert(current_bank < shipp->weapons.num_secondary_banks);

        weapon_info     *wip = &Weapon_info[shipp->weapons.secondary_bank_weapons[current_bank]];

        if ((wip->wi_flags & WIF_HOMING_ASPECT) && (!Ai_info[shipp->ai_index].current_target_is_locked)) {
                //nprintf(("AI", "Not firing secondary weapon because not aspect locked.\n"));
                swp->next_secondary_fire_stamp[current_bank] = timestamp(250);
        } else if ((wip->wi_flags & WIF_BOMB) || (vm_vec_dist_quick(&objp->pos, &En_objp->pos) > 50.0f)) {
                //      This might look dumb, firing a bomb even if closer than 50 meters, but the reason is, if you're carrying
                //      bombs, delivering them is probably more important than surviving.
                ai_info *aip;

                aip = &Ai_info[shipp->ai_index];
                
                //      Note, maybe don't fire if firing at player and any homers yet fired.
                //      Decreasing chance to fire the more homers are incoming on player.
                if (check_ok_to_fire(OBJ_INDEX(objp), aip->target_objnum, wip)) {
                        if (ship_fire_secondary(objp)) {
                                rval = 1;
                                swp->next_secondary_fire_stamp[current_bank] = timestamp(500);
                                //nprintf(("AI", "Frane %i: Ship %s fired secondary %s\n", Framecount, Ships[objp->instance].ship_name, Weapon_info[swp->secondary_bank_weapons[current_bank]].name));
                        }

                } else {
                        swp->next_secondary_fire_stamp[current_bank] = timestamp(500);
                }
        }

        return rval;
}

//      Return true if it looks like obj1, if continuing to move along current vector, will
//      collide with obj2.
int might_collide_with_ship(object *obj1, object *obj2, float dot_to_enemy, float dist_to_enemy, float duration)
{
        if (obj1->phys_info.speed * duration + 2*(obj1->radius + obj2->radius) > dist_to_enemy)
                if (dot_to_enemy > 0.8f - 2*(obj1->radius + obj2->radius)/dist_to_enemy)
                        return objects_will_collide(obj1, obj2, duration, 2.0f);

//              BABY - 
//              CONDITION 1, dist_to_enemy < o1_rad + o2_rad + (obj1.speed + obj2.speed) * time + 50
        
        return 0;

}

//      --------------------------------------------------------------------------
//      Return true if ship *objp firing a laser believes it will hit a teammate.
int might_hit_teammate(object *firing_objp)
{
        int             team;
        object  *objp;
        ship_obj        *so;

        team = Ships[firing_objp->instance].team;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                objp = &Objects[so->objnum];
                if (Ships[objp->instance].team == team) {
                        float           dist, dot;
                        vector  vec_to_objp;

                        vm_vec_sub(&vec_to_objp, &firing_objp->pos, &objp->pos);
                        dist = vm_vec_mag_quick(&vec_to_objp);
                        dot = vm_vec_dot(&firing_objp->orient.v.fvec, &vec_to_objp)/dist;
                        if (might_collide_with_ship(firing_objp, objp, dot, dist, 2.0f))
                                return 1;
                }
        }

        return 0;

}

//int   Team_not_fire_count=0, Team_hit_count = 0;

void render_all_ship_bay_paths(object *objp)
{
        int             i,j,color;
        ship            *sp = &Ships[objp->instance];
        polymodel       *pm;
        model_path      *mp;

        pm = model_get(sp->modelnum);
        vector  global_path_point;
        vertex  v, prev_vertex;

        if ( pm->ship_bay == NULL )
                return;

        for ( i = 0; i < pm->ship_bay->num_paths; i++ ) {
                mp = &pm->paths[pm->ship_bay->paths[i]];

                for ( j = 0; j < mp->nverts; j++ ) {
                        vm_vec_unrotate(&global_path_point, &mp->verts[j].pos, &objp->orient);
                        vm_vec_add2(&global_path_point, &objp->pos);
                        g3_rotate_vertex(&v, &global_path_point);
                        color = 255 - j*50;
                        if ( color < 50 ) 
                                color = 100;
                        gr_set_color(0, color, 0);

                        if ( j == mp->nverts-1 ) {
                                gr_set_color(255, 0, 0);
                        }

                        g3_draw_sphere( &v, 1.5f);

                        if ( j > 0 )
                                g3_draw_line(&v, &prev_vertex);

                        prev_vertex = v;
        
                }
        }
}

// debug function to show all path points associated with an object
void render_all_subsys_paths(object *objp)
{
        int             i,j,color;
        ship            *sp = &Ships[objp->instance];
        polymodel       *pm;
        model_path      *mp;

        pm = model_get(sp->modelnum);
        vector  global_path_point;
        vertex  v, prev_vertex;

        if ( pm->ship_bay == NULL )
                return;

        for ( i = 0; i < pm->n_paths; i++ ) {
                mp = &pm->paths[i];
                for ( j = 0; j < mp->nverts; j++ ) {
                        vm_vec_unrotate(&global_path_point, &mp->verts[j].pos, &objp->orient);
                        vm_vec_add2(&global_path_point, &objp->pos);
                        g3_rotate_vertex(&v, &global_path_point);
                        color = 255 - j*50;
                        if ( color < 50 ) 
                                color = 100;
                        gr_set_color(0, color, 0);

                        if ( j == mp->nverts-1 ) {
                                gr_set_color(255, 0, 0);
                        }

                        g3_draw_sphere( &v, 1.5f);

                        if ( j > 0 )
                                g3_draw_line(&v, &prev_vertex);

                        prev_vertex = v;
                }
        }
}

void render_path_points(object *objp)
{
        ship            *shipp = &Ships[objp->instance];
        ai_info *aip = &Ai_info[shipp->ai_index];
        object  *dobjp;
        polymodel       *pm;

        render_all_subsys_paths(objp);
        render_all_ship_bay_paths(objp);

        if (aip->goal_objnum < 0)
                return;

        dobjp = &Objects[aip->goal_objnum];
        pm = model_get(Ships[dobjp->instance].modelnum);
        vector  dock_point, global_dock_point;
        vertex  v;

        ship_model_start(&Objects[aip->goal_objnum]);
        if (pm->n_docks) {
                dock_point = pm->docking_bays[0].pnt[0];
                model_find_world_point(&global_dock_point, &dock_point, Ships[dobjp->instance].modelnum, 0, &dobjp->orient, &dobjp->pos );
                g3_rotate_vertex(&v, &global_dock_point);
                gr_set_color(255, 255, 255);
                g3_draw_sphere( &v, 1.5f);
        }

        if (aip->path_start != -1) {
                vertex          prev_vertex;
                pnode                   *pp = &Path_points[aip->path_start];
                int                     num_points = aip->path_length;
                int                     i;

                for (i=0; i<num_points; i++) {
                        vertex  v0;

                        g3_rotate_vertex( &v0, &pp->pos );

                        gr_set_color(0, 128, 96);
                        if (i != 0)
                                g3_draw_line(&v0, &prev_vertex);

                        if (pp-Path_points == aip->path_cur)
                                gr_set_color(255,255,0);
                        
                        g3_draw_sphere( &v0, 4.5f);

                        //      Connect all the turrets that can fire upon this point to this point.
/*                      if (0) { //pp->path_index != -1) {
                                model_path      *pmp;
                                mp_vert         *pmpv;

                                get_base_path_info(pp->path_index, aip->goal_objnum, &pmp, &pmpv);

                                if (pmpv->nturrets) {
                                        for (int j = 0; j<pmpv->nturrets; j++) {
                                                vertex  v1;
                                                vector  turret_pos;
                                                ship_subsys     *ssp;

                                                ssp = ship_get_indexed_subsys(&Ships[Objects[aip->goal_objnum].instance], pmpv->turret_ids[j]);

model_find_world_point(&turret_pos, &ssp->system_info->pnt, Ships[dobjp->instance].modelnum, 0, &dobjp->orient, &dobjp->pos );
        
                                                g3_rotate_vertex(&v1, &turret_pos);
                                                gr_set_color(255, 255, 0);
                                                g3_draw_line(&v0, &v1);
                                                g3_draw_sphere( &v1, 1.5f);
                                        }
                                }
                        } */

                        prev_vertex = v0;

                        pp++;
                }
        }

        ship_model_stop(&Objects[aip->goal_objnum]);
}

// Return the distance that the current AI weapon will travel
float ai_get_weapon_dist(ship_weapon *swp)
{
        int     bank_num, weapon_num;

        bank_num = swp->current_primary_bank;
        weapon_num = swp->primary_bank_weapons[bank_num];

        //      If weapon_num is illegal, return a reasonable value.  A valid weapon
        //      will get selected when this ship tries to fire.
        if (weapon_num == -1) {
                // Int3();
                return 1000.0f;
        }

        return Weapon_info[weapon_num].max_speed * Weapon_info[weapon_num].lifetime;
}

float ai_get_weapon_speed(ship_weapon *swp)
{
        int     bank_num, weapon_num;

        bank_num = swp->current_primary_bank;
        if (bank_num < 0)
                return 100.0f;

        weapon_num = swp->primary_bank_weapons[bank_num];

        if (weapon_num == -1) {
                //Int3();
                return 100.0f;
        }

        return Weapon_info[weapon_num].max_speed;
}

//      Compute the predicted position of a ship to be fired upon from a turret.
//      This is based on position of firing gun, enemy object, weapon speed and skill level constraints.
//      Return value in *predicted_enemy_pos.
//      Also, stuff globals G_predicted_pos, G_collision_time and G_fire_pos.
//      *pobjp          object firing the weapon
//      *eobjp          object being fired upon
void set_predicted_enemy_pos_turret(vector *predicted_enemy_pos, vector *gun_pos, object *pobjp, vector *enemy_pos, vector *enemy_vel, float weapon_speed, float time_enemy_in_range)
{
        ship    *shipp = &Ships[pobjp->instance];
        float   range_time;

        //weapon_speed = ai_get_weapon_speed(&shipp->weapons);

        if (weapon_speed < 1.0f)
                weapon_speed = 1.0f;

        range_time = 2.0f;

        //      Make it take longer for enemies to get player's allies in range based on skill level.
        if (Ships[pobjp->instance].team != Ships[Player_obj->instance].team)
                range_time += In_range_time[Game_skill_level];

        //nprintf(("AI", "time enemy in range = %7.3f\n", aip->time_enemy_in_range));

        if (time_enemy_in_range < range_time) {
                float   dist;

                dist = vm_vec_dist_quick(&pobjp->pos, enemy_pos);
                vm_vec_scale_add(predicted_enemy_pos, enemy_pos, enemy_vel, time_enemy_in_range * dist/weapon_speed);
        } else {
                float   collision_time, scale;
                vector  rand_vec;
                ai_info *aip = &Ai_info[shipp->ai_index];

                collision_time = compute_collision_time(enemy_pos, enemy_vel, gun_pos, weapon_speed);

                if (collision_time == 0.0f){
                        collision_time = 100.0f;
                }

                vm_vec_scale_add(predicted_enemy_pos, enemy_pos, enemy_vel, collision_time);
                if (time_enemy_in_range > 2*range_time){
                        scale = (1.0f - aip->ai_accuracy) * 4.0f;
                } else {
                        scale = (1.0f - aip->ai_accuracy) * 4.0f * (1.0f + 4.0f * (1.0f - time_enemy_in_range/(2*range_time)));
                }               

                static_randvec(((pobjp-Objects) ^ (Missiontime >> 16)) & 7, &rand_vec);

                vm_vec_scale_add2(predicted_enemy_pos, &rand_vec, scale);
                G_collision_time = collision_time;
                G_fire_pos = *gun_pos;
        }

        G_predicted_pos = *predicted_enemy_pos;
}

//      Compute the predicted position of a ship to be fired upon.
//      This is based on current position of firing object, enemy object, relative position of gun on firing object,
//      weapon speed and skill level constraints.
//      Return value in *predicted_enemy_pos.
//      Also, stuff globals G_predicted_pos, G_collision_time and G_fire_pos.
void set_predicted_enemy_pos(vector *predicted_enemy_pos, object *pobjp, object *eobjp, ai_info *aip)
{
        float   weapon_speed, range_time;
        ship    *shipp = &Ships[pobjp->instance];

        weapon_speed = ai_get_weapon_speed(&shipp->weapons);
        weapon_speed = max(weapon_speed, 1.0f);         // set not less than 1

        range_time = 2.0f;

        //      Make it take longer for enemies to get player's allies in range based on skill level.
        // but don't bias team v. team missions
        if ( !((Game_mode & GM_MULTIPLAYER) && (Netgame.type_flags & NG_TYPE_TEAM)) ) {
                if (Ships[pobjp->instance].team != Ships[Player_obj->instance].team) {
                        range_time += In_range_time[Game_skill_level];
                }
        }
        //nprintf(("AI", "time enemy in range = %7.3f\n", aip->time_enemy_in_range));

        if (aip->time_enemy_in_range < range_time) {
                float   dist;

                dist = vm_vec_dist_quick(&pobjp->pos, &eobjp->pos);
                vm_vec_scale_add(predicted_enemy_pos, &eobjp->pos, &eobjp->phys_info.vel, aip->time_enemy_in_range * dist/weapon_speed);
        } else {
                float   collision_time;
                vector  gun_pos, pnt;
                polymodel *po = model_get( Ship_info[shipp->ship_info_index].modelnum );

                //      Compute position of gun in absolute space and use that as fire position.
                if(po->gun_banks != NULL){
                        pnt = po->gun_banks[0].pnt[0];
                } else {
                        pnt = Objects[shipp->objnum].pos;
                }
                vm_vec_unrotate(&gun_pos, &pnt, &pobjp->orient);
                vm_vec_add2(&gun_pos, &pobjp->pos);

                collision_time = compute_collision_time(&eobjp->pos, &eobjp->phys_info.vel, &gun_pos, weapon_speed);

                if (collision_time == 0.0f) {
                        collision_time = 100.0f;
                }

                vm_vec_scale_add(predicted_enemy_pos, &eobjp->pos, &eobjp->phys_info.vel, collision_time);

                // set globals
                G_collision_time = collision_time;
                G_fire_pos = gun_pos;
        }

        // Now add error terms (1) regular aim (2) EMP (3) stealth
        float scale = 0.0f;
        vector rand_vec;

        // regular skill level error in aim
        if (aip->time_enemy_in_range > 2*range_time) {
                scale = (1.0f - aip->ai_accuracy) * 4.0f;
        } else {
                scale = (1.0f - aip->ai_accuracy) * 4.0f * (1.0f + 4.0f * (1.0f - aip->time_enemy_in_range/(2*range_time)));
        }

        // if this ship is under the effect of an EMP blast, throw his aim off a bit
        if (shipp->emp_intensity > 0.0f) {
                // never go lower than 1/2 of the EMP effect max, otherwise things aren't noticeable
                scale += (MAX_EMP_INACCURACY * (shipp->emp_intensity < 0.5f ? 0.5f : shipp->emp_intensity));
                mprintf(("AI miss scale factor (EMP) %f\n",scale));
        }

        // if stealthy ship, throw his aim off, more when farther away and when dot is small
        if ( aip->ai_flags & AIF_STEALTH_PURSIUT ) {
                float dist = vm_vec_dist_quick(&pobjp->pos, &eobjp->pos);
                vector temp;
                vm_vec_sub(&temp, &eobjp->pos, &pobjp->pos);
                vm_vec_normalize_quick(&temp);
                float dot = vm_vec_dotprod(&temp, &pobjp->orient.v.fvec);
                float st_err = 3.0f * (1.4f - dot) * (1.0f + dist / (get_skill_stealth_dist_scaler() * STEALTH_MAX_VIEW_DIST)) * (1 - aip->ai_accuracy);
                scale += st_err;
                // mprintf(("error term: %.1f, total %.1f, dot %.3f\n", st_err, scale, dot));
        }

        // get a random vector that changes slowly over time (1x / sec)
        static_randvec(((pobjp-Objects) ^ (Missiontime >> 16)) & 7, &rand_vec);

        vm_vec_scale_add2(predicted_enemy_pos, &rand_vec, scale);

        // set global
        G_predicted_pos = *predicted_enemy_pos;
}

//      Handler of submode for Chase.  Go into a continuous turn for awhile.
void ai_chase_ct()
{
        vector          tvec;
        ship_info       *sip;
        ai_info         *aip;

        Assert(Ships[Pl_objp->instance].ship_info_index >= 0);
        sip = &Ship_info[Ships[Pl_objp->instance].ship_info_index];
        Assert(Ships[Pl_objp->instance].ai_index >= 0);
        aip = &Ai_info[Ships[Pl_objp->instance].ai_index];

        //      Make a continuous turn towards any combination of possibly negated
        // up and right vectors.
        tvec = Pl_objp->pos;

        if (aip->submode_parm0 & 0x01)
                vm_vec_add2(&tvec, &Pl_objp->orient.v.rvec);
        if (aip->submode_parm0 & 0x02)
                vm_vec_sub2(&tvec, &Pl_objp->orient.v.rvec);
        if (aip->submode_parm0 & 0x04)
                vm_vec_add2(&tvec, &Pl_objp->orient.v.uvec);
        if (aip->submode_parm0 & 0x08)
                vm_vec_sub2(&tvec, &Pl_objp->orient.v.uvec);

        //      Detect degenerate cases that cause tvec to be same as player pos.
        if (vm_vec_dist_quick(&tvec, &Pl_objp->pos) < 0.1f) {
                aip->submode_parm0 &= 0x05;
                if (aip->submode_parm0 == 0)
                        aip->submode_parm0 = 1;
                vm_vec_add2(&tvec, &Pl_objp->orient.v.rvec);
        }

        ai_turn_towards_vector(&tvec, Pl_objp, flFrametime, sip->srotation_time, NULL, NULL, 0.0f, 0);
        accelerate_ship(aip, 1.0f);
}

//      ATTACK submode handler for chase mode.
void ai_chase_eb(ai_info *aip, ship_info *sip, vector *predicted_enemy_pos, float dist_to_enemy)
{
        vector  _pep;
        float           dot_to_enemy, dot_from_enemy;

        compute_dots(Pl_objp, En_objp, &dot_to_enemy, &dot_from_enemy);

        //      If we're trying to slow down to get behind, then point to turn towards is different.
        _pep = *predicted_enemy_pos;
        if ((dot_to_enemy > dot_from_enemy + 0.1f) || (dot_to_enemy > 0.9f))
                vm_vec_scale_add(&_pep, &Pl_objp->pos, &En_objp->orient.v.fvec, 100.0f);

        ai_turn_towards_vector(&_pep, Pl_objp, flFrametime, sip->srotation_time, NULL, NULL, 0.0f, 0);

        accelerate_ship(aip, 0.0f);
}

//      Return time until weapon_objp might hit ship_objp.
//      Assumes ship_objp is not moving.
//      Returns negative time if not going to hit.
//      This is a very approximate function, but is pretty fast.
float ai_endangered_time(object *ship_objp, object *weapon_objp)
{
        float           to_dot, from_dot, dist;

        dist = compute_dots(ship_objp, weapon_objp, &to_dot, &from_dot);

        //      Note, this is bogus.  It assumes only the weapon is moving.
        //      Only proceed if weapon sort of pointing at object and object pointing towards or away from weapon
        //      (Ie, if object moving at right angle to weapon, just continue for now...)
        if (weapon_objp->phys_info.speed < 1.0f)
                return dist + 1.0f;
        else if ((from_dot > 0.1f) && (dist/(from_dot*from_dot) < 48*ship_objp->radius)) //: don't require them to see it, they have instruments!: && (fl_abs(to_dot) > 0.5f))
                return dist / weapon_objp->phys_info.speed;
        else
                return -1.0f;
}

//      Return time until danger weapon could hit this ai object.
//      Return negative time if not endangered.
float ai_endangered_by_weapon(ai_info *aip)
{
        object  *weapon_objp;

        if (aip->danger_weapon_objnum == -1) {
                return -1.0f;
        }

        weapon_objp = &Objects[aip->danger_weapon_objnum];

        if (weapon_objp->signature != aip->danger_weapon_signature) {
                aip->danger_weapon_objnum = -1;
                return -1.0f;
        }

        return ai_endangered_time(&Objects[Ships[aip->shipnum].objnum], weapon_objp);
}

//      Return true if this ship is near full strength.
int ai_near_full_strength(object *objp, ship_info *sip)
{
        return (objp->hull_strength/sip->initial_hull_strength > 0.9f) || (get_shield_strength(objp)/sip->shields > 0.8f);
}
                                
//      Set acceleration while in attack mode.
void attack_set_accel(ai_info *aip, float dist_to_enemy, float dot_to_enemy, float dot_from_enemy)
{
        float   speed_ratio;

        if (En_objp->phys_info.speed > 1.0f)
                speed_ratio = Pl_objp->phys_info.speed/En_objp->phys_info.speed;
        else
                speed_ratio = 5.0f;

        //      Sometimes, told to attack slowly.  Allows to get in more hits.
        if (aip->ai_flags & AIF_ATTACK_SLOWLY) {
                if ((dist_to_enemy > 200.0f) && (dist_to_enemy < 800.0f)) {
                        if ((dot_from_enemy < 0.9f) || ai_near_full_strength(Pl_objp, &Ship_info[Ships[Pl_objp->instance].ship_info_index])) {
                                //nprintf(("AI", " slowly "));
                                accelerate_ship(aip, max(1.0f - (dist_to_enemy-200.0f)/600.0f, 0.1f));
                                return;
                        }
                } else
                        aip->ai_flags &= ~AIF_ATTACK_SLOWLY;
        }

        if (dist_to_enemy > 200.0f + vm_vec_mag_quick(&En_objp->phys_info.vel) * dot_from_enemy + Pl_objp->phys_info.speed * speed_ratio) {
                //nprintf(("AI", "1"));
                if (ai_maybe_fire_afterburner(Pl_objp, aip)) {
                        if (dist_to_enemy > 800.0f) {
                                if (!( Pl_objp->phys_info.flags & PF_AFTERBURNER_ON )) {
                                        float percent_left;
                                        ship    *shipp;
                                        ship_info *sip;

                                        shipp = &Ships[Pl_objp->instance];
                                        sip = &Ship_info[shipp->ship_info_index];

                                        if (sip->afterburner_fuel_capacity > 0.0f) {
                                                percent_left = 100.0f * shipp->afterburner_fuel / sip->afterburner_fuel_capacity;
                                                if (percent_left > 30.0f + ((Pl_objp-Objects) & 0x0f)) {
                                                        afterburners_start(Pl_objp);
                                                        aip->afterburner_stop_time = Missiontime + F1_0 + static_rand(Pl_objp-Objects)/4;
                                                }
                                        }
                                }
                        }
                }

                accelerate_ship(aip, 1.0f);
        } else if ((Missiontime - aip->last_hit_time > F1_0*7)
                && (En_objp->phys_info.speed < 10.0f) 
                && (dist_to_enemy > 25.0f) 
                && (dot_to_enemy > 0.8f)
                && (dot_from_enemy < 0.8f)) {
                accelerate_ship(aip, 0.0f);             //      No one attacking us, so don't need to move.
        } else if ((dot_from_enemy < 0.25f) && (dot_to_enemy > 0.5f)) {
                set_accel_for_target_speed(Pl_objp, En_objp->phys_info.speed);
        } else if (Pl_objp->phys_info.speed < 15.0f) {
                accelerate_ship(aip, 1.0f);
        } else if (Pl_objp->phys_info.speed > En_objp->phys_info.speed - 1.0f) {
                if (dot_from_enemy > 0.75f)
                        accelerate_ship(aip, 1.0f);
                else
                        set_accel_for_target_speed(Pl_objp, En_objp->phys_info.speed*0.75f + 3.0f);
        } else {
                change_acceleration(aip, 0.5f);
        }
}

//      Pl_objp (aip) tries to get behind En_objp.
//      New on 2/21/98: If this ship can move backwards and slide, maybe do that to get behind.
void get_behind_ship(ai_info *aip, ship_info *sip, float dist_to_enemy)
{
        vector  new_pos;
        float           dot;
        vector  vec_from_enemy;
        float           dist;

        dist = vm_vec_normalized_dir(&vec_from_enemy, &Pl_objp->pos, &En_objp->pos);

        vm_vec_scale_add(&new_pos, &En_objp->pos, &En_objp->orient.v.fvec, -100.0f);            //      Pick point 100 units behind.
        ai_turn_towards_vector(&new_pos, Pl_objp, flFrametime, sip->srotation_time, NULL, NULL, 0.0f, 0);

        dot = vm_vec_dot(&vec_from_enemy, &En_objp->orient.v.fvec);

        if (dot > 0.25f) {
                accelerate_ship(aip, 1.0f);
        } else {
                accelerate_ship(aip, (dot + 1.0f)/2.0f);
        }
}

int avoid_player(object *objp, vector *goal_pos)
{
        maybe_avoid_player(Pl_objp, goal_pos);
        ai_info *aip = &Ai_info[Ships[objp->instance].ai_index];

        if (aip->ai_flags & AIF_AVOIDING_SMALL_SHIP) {
                ship_info *sip = &Ship_info[Ships[objp->instance].ship_info_index];

                if (aip->ai_flags & AIF_AVOIDING_SMALL_SHIP) {
                        ai_turn_towards_vector(&aip->avoid_goal_point, objp, flFrametime, sip->srotation_time, NULL, NULL, 0.0f, 0);
                        accelerate_ship(aip, 0.5f);
                        return 1;
                }
        }

        return 0;
}

//      Determine if a cylinder of width radius from p0 to p1 will collide with big_objp.
//      If so, stuff *collision_point.
int will_collide_pp(vector *p0, vector *p1, float radius, object *big_objp, vector *collision_point)
{
        mc_info mc;

        mc.model_num = Ships[big_objp->instance].modelnum;              // Fill in the model to check
        mc.orient = &big_objp->orient;                  // The object's orient
        mc.pos = &big_objp->pos;                                        // The object's position
        mc.p0 = p0;                                                                             // Point 1 of ray to check
        mc.p1 = p1;
        mc.flags = MC_CHECK_MODEL | MC_CHECK_SPHERELINE | MC_SUBMODEL;                                  // flags

        mc.radius = radius;

        // Only check the 2nd lowest hull object
        polymodel *pm = model_get(Ships[big_objp->instance].modelnum);
        mc.submodel_num = pm->detail[0]; //pm->submodel->num_details-2];
        model_collide(&mc);

        if (mc.num_hits)
                *collision_point = mc.hit_point_world;

        return mc.num_hits;
}

//      Return true/false if *objp will collide with *big_objp
//      Stuff distance in *distance to collision point if *objp will collide with *big_objp within delta_time seconds.
//      Global collision point stuffed in *collision_point
int will_collide_with_big_ship(object *objp, vector *goal_point, object *big_objp, vector *collision_point, float delta_time)
{
        float           radius;
        vector  end_pos;

        radius = big_objp->radius + delta_time * objp->phys_info.speed;

        if (vm_vec_dist_quick(&big_objp->pos, &objp->pos) > radius) {
                return 0;
        }

        if (goal_point == NULL) {
                vm_vec_scale_add(&end_pos, &objp->pos, &objp->phys_info.vel, delta_time);                                       // Point 2 of ray to check
        } else {
                end_pos = *goal_point;
        }

        return will_collide_pp(&objp->pos, &end_pos, objp->radius, big_objp, collision_point);
}

//      Return true if *objp is expected to collide with a large ship.
//      Stuff global collision point in *collision_point.
//      If *goal_point is not NULL, use that as the point towards which *objp will be flying.  Don't use *objp velocity
//      *ignore_objp will typically be the target this ship is pursuing, either to attack or guard.  We don't want to avoid it.
int will_collide_with_big_ship_all(object *objp, object *ignore_objp, vector *goal_point, vector *collision_point, float *distance, float delta_time)
{
        ship_obj        *so;
        object  *big_objp;
        int             collision_obj_index = -1;
        float           min_dist = 999999.9f;
        float           collision_time = -1.0f;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                float   time = 0.0f;
                big_objp = &Objects[so->objnum];

                if (big_objp == ignore_objp)
                        continue;

                if (Ship_info[Ships[big_objp->instance].ship_info_index].flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP)) {
                        vector  cur_collision_point;
                        float           cur_dist;

                        if (will_collide_with_big_ship(objp, goal_point, big_objp, &cur_collision_point, delta_time)) {

                                cur_dist = vm_vec_dist(&cur_collision_point, &objp->pos);

                                if (cur_dist < min_dist) {
                                        min_dist = cur_dist;
                                        *collision_point = cur_collision_point;
                                        collision_time = time;
                                        collision_obj_index = OBJ_INDEX(big_objp);
                                }
                        }
                }
        }

        *distance = min_dist;
        return collision_obj_index;

}

typedef struct {
        float           dist;
        int             collide;
        vector  pos;
} sgoal;

//int will_collide_pp(vector *p0, vector *p1, float radius, object *big_objp, vector *collision_point)
//      Pick a point for *objp to fly towards to avoid a collision with *big_objp at *collision_point
//      Return result in *avoid_pos
void mabs_pick_goal_point(object *objp, object *big_objp, vector *collision_point, vector *avoid_pos)
{
        matrix  mat1;
        sgoal           goals[4];
        vector  v2b;

        vm_vec_normalized_dir(&v2b, collision_point, &objp->pos);
        vm_vector_2_matrix(&mat1, &v2b, NULL, NULL);

        int     found = 0;

        //      Try various scales, in 0.5f, 0.75f, 1.0f, 1.25f.
        //      First try 0.5f to see if we can find a point that near the center of the target ship, which presumably
        //      means less of a turn.
        //      Try going as far as 1.25f * radius.
        float   s;
        for (s=0.5f; s<1.3f; s += 0.25f) {
                int     i;
                for (i=0; i<4; i++) {
                        vector p = big_objp->pos;
                        float ku = big_objp->radius*s + objp->radius * (OBJ_INDEX(objp) % 4)/4;         //      This objp->radius stuff to prevent ships from glomming together at one point
                        float kr = big_objp->radius*s + objp->radius * ((OBJ_INDEX(objp) % 4) ^ 2)/4;
                        if (i&1)
                                ku = -ku;
                        if (i&2)
                                kr = -kr;
                        vm_vec_scale_add2(&p, &mat1.v.uvec, ku);
                        vm_vec_scale_add2(&p, &mat1.v.rvec, kr);
                        goals[i].pos = p;
                        goals[i].dist = vm_vec_dist_quick(&objp->pos, &p);
                        goals[i].collide = will_collide_pp(&objp->pos, &p, objp->radius, big_objp, collision_point);
                        if (!goals[i].collide)
                                found = 1;
                }

                //      If we found a point that doesn't collide, find the nearest one and make that the *avoid_pos.
                if (found) {
                        float   min_dist = 9999999.9f;
                        int     min_index = -1;

                        for (i=0; i<4; i++) {
                                if (!goals[i].collide && (goals[i].dist < min_dist)) {
                                        min_dist = goals[i].dist;
                                        min_index = i;
                                }
                        }

                        Assert(i != -1);
                        if (i != -1) {
                                *avoid_pos = goals[min_index].pos;
                                return;
                        }
                }
        }

        //      Drat.  We tried and tried and could not find a point that did not cause a collision.
        //      Get this dump pilot far away from the problem ship.
        vector  away_vec;
        vm_vec_normalized_dir(&away_vec, &objp->pos, collision_point);
        vm_vec_scale_add(avoid_pos, &objp->pos, &away_vec, big_objp->radius*1.5f);

}

//      Return true if a large ship is being ignored.
int maybe_avoid_big_ship(object *objp, object *ignore_objp, ai_info *aip, vector *goal_point, float delta_time)
{
        if (timestamp_elapsed(aip->avoid_check_timestamp)) {
                float           distance;
                vector  collision_point;
                int             ship_num;
                if ((ship_num = will_collide_with_big_ship_all(Pl_objp, ignore_objp, goal_point, &collision_point, &distance, delta_time)) != -1) {
                        aip->ai_flags |= AIF_AVOIDING_BIG_SHIP;
                        mabs_pick_goal_point(objp, &Objects[ship_num], &collision_point, &aip->avoid_goal_point);
                        float dist = vm_vec_dist_quick(&aip->avoid_goal_point, &objp->pos);
                        aip->avoid_check_timestamp = timestamp(2000 + min(1000, (int) (dist * 2.0f)));  //      Delay until check again is based on distance to avoid point.
                        aip->avoid_ship_num = ship_num;
                } else {
                        aip->ai_flags &= ~AIF_AVOIDING_BIG_SHIP;
                        aip->ai_flags &= ~AIF_AVOIDING_SMALL_SHIP;
                        aip->avoid_ship_num = -1;
                        aip->avoid_check_timestamp = timestamp(1500);
                }
        }
        
        if (aip->ai_flags & AIF_AVOIDING_BIG_SHIP) {
                ship_info *sip = &Ship_info[Ships[Pl_objp->instance].ship_info_index];

                vector  v2g;

                ai_turn_towards_vector(&aip->avoid_goal_point, Pl_objp, flFrametime, sip->srotation_time, NULL, NULL, 0.0f, 0);
                vm_vec_normalized_dir(&v2g, &aip->avoid_goal_point, &Pl_objp->pos);
                float dot = vm_vec_dot(&objp->orient.v.fvec, &v2g);
                float d2 = (1.0f + dot) * (1.0f + dot);
                accelerate_ship(aip, d2/4.0f);
                return 1;
        }

        return 0;
}

//      Set desired right vector for ships flying towards another ship.
//      Since this is governed only by vector to target, it causes ships to align bank and look less chaotic.
void compute_desired_rvec(vector *rvec, vector *goal_pos, vector *cur_pos)
{
        vector  v2e;

        vm_vec_normalized_dir(&v2e, goal_pos, cur_pos);
        rvec->xyz.x = v2e.xyz.z;
        rvec->xyz.y = 0.0f;
        rvec->xyz.z = -v2e.xyz.x;
        if (vm_vec_mag_squared(rvec) < 0.001f)
                rvec->xyz.y = 1.0f;
}

// Handler for stealth find submode of Chase.
void ai_stealth_find()
{
        ai_info         *aip;
        ship_info       *sip;

        vector new_pos, vec_to_enemy;
        float dist_to_enemy, dot_to_enemy, dot_from_enemy;

        Assert(Ships[Pl_objp->instance].ship_info_index >= 0);
        sip = &Ship_info[Ships[Pl_objp->instance].ship_info_index];
        Assert(Ships[Pl_objp->instance].ai_index >= 0);
        aip = &Ai_info[Ships[Pl_objp->instance].ai_index];

        // get time since last seen
        int delta_time = (timestamp() - aip->stealth_last_visible_stamp);

        // if delta_time is really big, i'm real confused, start sweep
        if (delta_time > 10000) {
                aip->submode_parm0 = SM_SF_BAIL;
        }

        // guestimate new position
        vm_vec_scale_add(&new_pos, &aip->stealth_last_pos, &aip->stealth_velocity, (delta_time * 0.001f));

        // if I think he's behind me, go to the goal point
        if ( aip->submode_parm0 == SM_SF_BEHIND ) {
                new_pos = aip->goal_point;
        }

        // check for collision with big ships
        if (maybe_avoid_big_ship(Pl_objp, En_objp, aip, &new_pos, 10.0f)) {
                // reset ai submode to chase
                return;
        }

        // if dist is near max and dot is close to 1, accel, afterburn
        vm_vec_sub(&vec_to_enemy, &new_pos, &Pl_objp->pos);
        dist_to_enemy = vm_vec_normalize_quick(&vec_to_enemy);
        dot_to_enemy = vm_vec_dotprod(&vec_to_enemy, &Pl_objp->orient.v.fvec);

        // if i think i should see him ahead and i don't, set goal pos and turn around, but only if I haven't seen him for a while
        if ( (delta_time > 800) && (aip->submode_parm0 == SM_SF_AHEAD) && (dot_to_enemy > .94) && (dist_to_enemy < get_skill_stealth_dist_scaler()*STEALTH_MAX_VIEW_DIST + 50) ) {
                // do turn around)
                vm_vec_scale_add(&aip->goal_point, &Pl_objp->pos, &Pl_objp->orient.v.fvec, -300.0f);
                aip->submode_parm0 = SM_SF_BEHIND;
                vm_vec_sub(&vec_to_enemy, &new_pos, &Pl_objp->pos);
                dist_to_enemy = vm_vec_normalize_quick(&vec_to_enemy);
                dot_to_enemy = vm_vec_dotprod(&vec_to_enemy, &Pl_objp->orient.v.fvec);
        }

        if ( (dist_to_enemy > get_skill_stealth_dist_scaler()*STEALTH_MAX_VIEW_DIST) && (dot_to_enemy > 0.94f) ) {              // 20 degree half angle
                // accelerate ship
                accelerate_ship(aip, 1.0f);

                // engage afterburner
                if (!( Pl_objp->phys_info.flags & PF_AFTERBURNER_ON )) {
                        if (ai_maybe_fire_afterburner(Pl_objp, aip)) {
                                afterburners_start(Pl_objp);
                                aip->afterburner_stop_time = Missiontime + 3*F1_0/2;
                        }
                }

                ai_turn_towards_vector(&new_pos, Pl_objp, flFrametime, sip->srotation_time, NULL, NULL, 0.0f, 0);
                return;
        }

        //      If enemy more than 500 meters away, all ships flying there will tend to match bank.
        //      They do this by using their vector to their target to compute their right vector and causing ai_turn_towards_vector
        //      to interpolate a matrix rather than just a vector.
        if (dist_to_enemy > 500.0f) {
                vector  rvec;
                compute_desired_rvec(&rvec, &new_pos, &Pl_objp->pos);
                ai_turn_towards_vector(&new_pos, Pl_objp, flFrametime, sip->srotation_time, NULL, NULL, 0.0f, 0, &rvec);
        } else {
                ai_turn_towards_vector(&new_pos, Pl_objp, flFrametime, sip->srotation_time, NULL, NULL, 0.0f, 0);
        }

        dot_from_enemy = -vm_vec_dotprod(&vec_to_enemy, &En_objp->orient.v.fvec);

        attack_set_accel(aip, dist_to_enemy, dot_to_enemy, dot_from_enemy);
}

// -----------------------------------------------------------------------------
// try to find stealth ship by sweeping an area
void ai_stealth_sweep()
{
        ai_info         *aip;
        ship_info       *sip;

        Assert(Ships[Pl_objp->instance].ship_info_index >= 0);
        sip = &Ship_info[Ships[Pl_objp->instance].ship_info_index];
        Assert(Ships[Pl_objp->instance].ai_index >= 0);
        aip = &Ai_info[Ships[Pl_objp->instance].ai_index];

        vector goal_pt;
        vector forward, right, up;
        int lost_time;

        // time since stealth last seen
        lost_time = (timestamp() - aip->stealth_last_visible_stamp);

        // determine which pt to fly to in sweep by keeping track of parm0
        if (aip->submode_parm0 == SM_SS_SET_GOAL) {

                // don't make goal pt more than 2k from current pos
                vm_vec_scale_add(&goal_pt, &aip->stealth_last_pos, &aip->stealth_velocity, (0.001f * lost_time));

                // make box size based on speed of stealth and expected time to intercept (keep box in range 200-500)
                float box_size = vm_vec_mag_quick(&aip->stealth_velocity) * (0.001f * lost_time);
                box_size = min(200.0f, box_size);
                box_size = max(500.0f, box_size);
                aip->stealth_sweep_box_size = box_size;

                aip->goal_point = goal_pt;
                aip->submode_parm0 = SM_SS_BOX0;
        }

        // GET UP, RIGHT, FORWARD FOR BOX based on stealth ship's velocity
        // if velocity changes in stealth mode, then ship is *seen*, and falls out of sweep mode
        // if stealth has no velocity make a velocity
        if ( vm_vec_mag_quick(&aip->stealth_velocity) < 1 ) {
                vm_vec_rand_vec_quick(&aip->stealth_velocity);
        }

        // get "right" vector for box
        vm_vec_crossprod(&right, &aip->stealth_velocity, &vmd_y_vector);

        if ( vm_vec_mag_quick(&right) < 0.01 ) {
                vm_vec_crossprod(&right, &aip->stealth_velocity, &vmd_z_vector);
        }

        vm_vec_normalize_quick(&right);

        // get forward for box
        vm_vec_copy_normalize_quick(&forward, &aip->stealth_velocity);

        // get "up" for box
        vm_vec_crossprod(&up, &forward, &right);
        
        // lost far away ahead (do box)
        switch(aip->submode_parm0) {
        case SM_SS_BOX0:
                goal_pt = aip->goal_point;
                break;

        // pt1 -U +R
        case SM_SS_LR:
                vm_vec_scale_add(&goal_pt, &aip->goal_point, &up, -aip->stealth_sweep_box_size);
                vm_vec_scale_add2(&goal_pt, &right, aip->stealth_sweep_box_size);
                vm_vec_scale_add2(&goal_pt, &forward, 0.5f*aip->stealth_sweep_box_size);
                break;

        // pt2 +U -R
        case SM_SS_UL:
                vm_vec_scale_add(&goal_pt, &aip->goal_point, &up, aip->stealth_sweep_box_size);
                vm_vec_scale_add2(&goal_pt, &right, -aip->stealth_sweep_box_size);
                vm_vec_scale_add2(&goal_pt, &forward, 0.5f*aip->stealth_sweep_box_size);
                break;

        // pt3 back
        case SM_SS_BOX1:
                goal_pt = aip->goal_point;
                break;

        // pt4 +U +R
        case SM_SS_UR:
                vm_vec_scale_add(&goal_pt, &aip->goal_point, &up, aip->stealth_sweep_box_size);
                vm_vec_scale_add2(&goal_pt, &right, aip->stealth_sweep_box_size);
                vm_vec_scale_add2(&goal_pt, &forward, 0.5f*aip->stealth_sweep_box_size);
                break;

        // pt5 -U -R
        case SM_SS_LL:
                vm_vec_scale_add(&goal_pt, &aip->goal_point, &up, -aip->stealth_sweep_box_size);
                vm_vec_scale_add2(&goal_pt, &right, -aip->stealth_sweep_box_size);
                vm_vec_scale_add2(&goal_pt, &forward, 0.5f*aip->stealth_sweep_box_size);
                break;

        // pt6 back
        case SM_SS_BOX2:
                goal_pt = aip->goal_point;
                break;

        default:
                Int3();

        }

        // when close to goal_pt, update next goal pt
        float dist_to_goal = vm_vec_dist(&goal_pt, &Pl_objp->pos);
        if (dist_to_goal < 15) {
                aip->submode_parm0++;
        }

        // check for collision with big ship
        if (maybe_avoid_big_ship(Pl_objp, En_objp, aip, &goal_pt, 10.0f)) {
                // skip to the next pt on box
                aip->submode_parm0++;
                return;
        }

        ai_turn_towards_vector(&goal_pt, Pl_objp, flFrametime, sip->srotation_time, NULL, NULL, 0.0f, 0);

        float dot = 1.0f;
        if (dist_to_goal < 100) {
                vector vec_to_goal;
                vm_vec_normalized_dir(&vec_to_goal, &goal_pt, &Pl_objp->pos);
                dot = vm_vec_dotprod(&vec_to_goal, &Pl_objp->orient.v.fvec);
        }

        accelerate_ship(aip, 0.8f*dot);
}

//      ATTACK submode handler for chase mode.
void ai_chase_attack(ai_info *aip, ship_info *sip, vector *predicted_enemy_pos, float dist_to_enemy)
{
        int             start_bank;
        float           dot_to_enemy, dot_from_enemy; //, time_to_hit;
        float           bank_override = 0.0f;

        if (avoid_player(Pl_objp, predicted_enemy_pos))
                return;

        compute_dots(Pl_objp, En_objp, &dot_to_enemy, &dot_from_enemy);

        polymodel *po = model_get( sip->modelnum );

        vector  *rel_pos;
        float           scale;
        vector  randvec;
        vector  new_pos;

        start_bank = Ships[aip->shipnum].weapons.current_primary_bank;
        if (po->n_guns && start_bank != -1 ) {
                rel_pos = &po->gun_banks[start_bank].pnt[0];
        } else
                rel_pos = NULL;

        //      If ship moving slowly relative to its size, then don't attack its center point.
        //      How far from center we attack is based on speed, size and distance to enemy
        if (En_objp->radius > En_objp->phys_info.speed) {
                static_randvec(Pl_objp-Objects, &randvec);
                scale = dist_to_enemy/(dist_to_enemy + En_objp->radius) * En_objp->radius;
                scale *= 0.5f * En_objp->radius/(En_objp->phys_info.speed + En_objp->radius);   // scale downward by 1/2 to 1/4
                vm_vec_scale_add(&new_pos, predicted_enemy_pos, &randvec, scale);
        } else
                new_pos = *predicted_enemy_pos;

        if (dist_to_enemy < 250.0f) {
                if (dot_from_enemy > 0.7f) {
                        bank_override = Pl_objp->phys_info.speed;
                }
        }

        //      If enemy more than 500 meters away, all ships flying there will tend to match bank.
        //      They do this by using their vector to their target to compute their right vector and causing ai_turn_towards_vector
        //      to interpolate a matrix rather than just a vector.
        if (dist_to_enemy > 500.0f) {
                vector  rvec;
                compute_desired_rvec(&rvec, predicted_enemy_pos, &Pl_objp->pos);
                ai_turn_towards_vector(&new_pos, Pl_objp, flFrametime, sip->srotation_time, NULL, rel_pos, bank_override, 0, &rvec);
        } else {
                ai_turn_towards_vector(&new_pos, Pl_objp, flFrametime, sip->srotation_time, NULL, rel_pos, bank_override, 0);
        }

        attack_set_accel(aip, dist_to_enemy, dot_to_enemy, dot_from_enemy);
}

//      EVADE_SQUIGGLE submode handler for chase mode.
//      Changed by MK on 5/5/97.
//      Used to evade towards a point off the right or up vector.
//      Now, evade straight away to try to get far away.
//      The squiggling should protect against laser fire.
void ai_chase_es(ai_info *aip, ship_info *sip)
{
        vector  tvec;
        fix             timeslice;
        fix             scale;
        float           bank_override = 0.0f;

        tvec = Pl_objp->pos;

        timeslice = (Missiontime >> 16) & 0x0f;
        scale = ((Missiontime >> 16) & 0x0f) << 14;

        if (timeslice & 0x01)
                vm_vec_scale_add2(&tvec, &Pl_objp->orient.v.rvec, f2fl(scale ^ 0x10000));
        if (timeslice & 0x02)
                vm_vec_scale_sub2(&tvec, &Pl_objp->orient.v.rvec, f2fl(scale));
        if (timeslice & 0x04)
                vm_vec_scale_add2(&tvec, &Pl_objp->orient.v.uvec, f2fl(scale ^ 0x10000));
        if (timeslice & 0x08)
                vm_vec_scale_sub2(&tvec, &Pl_objp->orient.v.uvec, f2fl(scale));

        while (vm_vec_dist_quick(&tvec, &Pl_objp->pos) < 0.1f) {
                tvec.xyz.x += frand();
                tvec.xyz.y += frand();
        }

        bank_override = Pl_objp->phys_info.speed;

        ai_turn_towards_vector(&tvec, Pl_objp, flFrametime/2, sip->srotation_time, NULL, NULL, bank_override, 0);
        accelerate_ship(aip, 1.0f);
}

//      Trying to get away from opponent.
void ai_chase_ga(ai_info *aip, ship_info *sip)
{
        //      If not near end of this submode, evade squiggly.  If near end, just fly straight for a bit
        vector  tvec;
        float           bank_override;
        vector  vec_from_enemy;

        if (En_objp != NULL) {
                vm_vec_normalized_dir(&vec_from_enemy, &Pl_objp->pos, &En_objp->pos);
        } else
                vec_from_enemy = Pl_objp->orient.v.fvec;

        static_randvec(Missiontime >> 15, &tvec);
        vm_vec_scale(&tvec, 100.0f);
        vm_vec_scale_add2(&tvec, &vec_from_enemy, 300.0f);
        vm_vec_add2(&tvec, &Pl_objp->pos);

        bank_override = Pl_objp->phys_info.speed;

        ai_turn_towards_vector(&tvec, Pl_objp, flFrametime/2, sip->srotation_time, NULL, NULL, bank_override, 0);

        accelerate_ship(aip, 2.0f);

        if (ai_maybe_fire_afterburner(Pl_objp, aip)) {
                if (!(Pl_objp->phys_info.flags & PF_AFTERBURNER_ON )) {
                        float percent_left = 100.0f * Ships[Pl_objp->instance].afterburner_fuel / sip->afterburner_fuel_capacity;
                        if (percent_left > 30.0f + ((Pl_objp-Objects) & 0x0f)) {
                                afterburners_start(Pl_objp);
                                aip->afterburner_stop_time = Missiontime + 3*F1_0/2;
                        }
                        afterburners_start(Pl_objp);
                        aip->afterburner_stop_time = Missiontime + 3*F1_0/2;
                }
        }

}

//      Make object *objp attack subsystem with ID = subnum.
//      Return true if found a subsystem to attack, else return false.
//      Note, can fail if subsystem exists, but has no hits.
int ai_set_attack_subsystem(object *objp, int subnum)
{
        ship                    *shipp, *attacker_shipp;
        ai_info         *aip;
        ship_subsys     *ssp;
        object          *attacked_objp;

        Assert(objp->type == OBJ_SHIP);
        Assert(objp->instance >= 0);

        attacker_shipp = &Ships[objp->instance];
        Assert(attacker_shipp->ai_index >= 0);

        aip = &Ai_info[attacker_shipp->ai_index];

        // MWA -- 2/27/98.  Due to AL's changes, target_objnum is now not always valid (at least sometimes
        // in terms of goals).  So, bail if we don't have a valid target.
        if ( aip->target_objnum == -1 )
                return 0;

        attacked_objp = &Objects[aip->target_objnum];
        shipp = &Ships[attacked_objp->instance];                //  need to get our target's ship pointer!!!

        ssp = ship_get_indexed_subsys(shipp, subnum, &objp->pos);
        if (ssp == NULL)
                return 0;

        set_targeted_subsys(aip, ssp, aip->target_objnum);
        
        if (aip->ignore_objnum == aip->target_objnum)
                aip->ignore_objnum = UNUSED_OBJNUM;

        // -- Done at caller in ai_process_mission_orders -- attacked_objp->flags |= OF_PROTECTED;

        ai_set_goal_maybe_abort_dock(objp, aip);
        aip->ok_to_target_timestamp = timestamp(DELAY_TARGET_TIME);

        return 1;
}

void ai_set_guard_vec(object *objp, object *guard_objp)
{
        ai_info *aip;
        float   radius;

        aip = &Ai_info[Ships[objp->instance].ai_index];

        //      Handle case of bogus call in which ship is told to guard self.
        Assert(objp != guard_objp);
        if (objp == guard_objp) {
                vm_vec_rand_vec_quick(&aip->guard_vec);
                vm_vec_scale(&aip->guard_vec, 100.0f);
                return;
        }

        // check if guard_objp is BIG
        radius = 5.0f * (objp->radius + guard_objp->radius) + 50.0f;
        if (radius > 300.0f) {
                radius = guard_objp->radius * 1.25f;
        }

        vm_vec_sub(&aip->guard_vec, &objp->pos, &guard_objp->pos);

        if (vm_vec_mag(&aip->guard_vec) > 3.0f*radius) {
                //      Far away, don't just use vector to object, causes clustering of guard ships.
                vector  tvec, rvec;
                float   mag;
                mag = vm_vec_copy_normalize(&tvec, &aip->guard_vec);
                vm_vec_rand_vec_quick(&rvec);                   
                vm_vec_scale_add2(&tvec, &rvec, 0.5f);
                vm_vec_copy_scale(&aip->guard_vec, &tvec, mag);
        }

        vm_vec_normalize_quick(&aip->guard_vec);
        vm_vec_scale(&aip->guard_vec, radius);
}

//      Make object *objp guard object *other_objp.
//      To be called from the goals code.
void ai_set_guard_wing(object *objp, int wingnum)
{
        ship            *shipp;
        ai_info *aip;
        int             leader_objnum, leader_shipnum;

        Assert(wingnum >= 0);

        Assert(objp->type == OBJ_SHIP);
        Assert(objp->instance >= 0);

        // shouldn't set the ai mode for the player
        if ( objp == Player_obj ) {
                return;
        }

        shipp = &Ships[objp->instance];

        Assert(shipp->ai_index >= 0);

        aip = &Ai_info[shipp->ai_index];
        force_avoid_player_check(objp, aip);

        ai_set_goal_maybe_abort_dock(objp, aip);
        aip->ok_to_target_timestamp = timestamp(DELAY_TARGET_TIME);

        //      This function is called whenever a guarded ship is destroyed, so this code
        //      prevents a ship from trying to guard a non-existent wing.
        if (Wings[wingnum].current_count < 1) {
                aip->guard_objnum = -1;
                aip->guard_wingnum = -1;
                aip->mode = AIM_NONE;
        } else {
                leader_shipnum = Wings[wingnum].ship_index[0];
                leader_objnum = Ships[leader_shipnum].objnum;

                Assert((leader_objnum >= 0) && (leader_objnum < MAX_OBJECTS));
                //Assert(leader_objnum != objp-Objects);        //      Don't allow ships to guard themselves.
                if (leader_objnum == OBJ_INDEX(objp)) {
                        //Int3();       //      Seems illegal, but let's clean up.  Get MikeK.
                        return;
                }

                aip->guard_wingnum = wingnum;
                aip->guard_objnum = leader_objnum;
                aip->guard_signature = Objects[leader_objnum].signature;
                aip->mode = AIM_GUARD;
                aip->submode = AIS_GUARD_STATIC;

                ai_set_guard_vec(objp, &Objects[leader_objnum]);
        }
}

//      Make object *objp guard object *other_objp.
//      To be called from the goals code.
void ai_set_evade_object(object *objp, object *other_objp)
{
        ship            *shipp;
        ai_info *aip;
        int             other_objnum;

        Assert(objp->type == OBJ_SHIP);
        Assert(objp->instance >= 0);

        shipp = &Ships[objp->instance];

        Assert(shipp->ai_index >= 0);

        aip = &Ai_info[shipp->ai_index];

        other_objnum = OBJ_INDEX(other_objp);
        Assert(other_objnum >= 0);

        Assert(other_objnum != Ships[aip->shipnum].objnum);     //      make sure not targeting self
        aip->target_objnum = other_objnum;

        aip->mode = AIM_EVADE;
}

//      Make objp guard other_objp
//      If other_objp is a member of a wing, objp will guard that whole wing
//      UNLESS objp is also a member of the wing!
void ai_set_guard_object(object *objp, object *other_objp)
{
        ship            *shipp;
        ai_info *aip;
        int             other_objnum;

        Assert(objp->type == OBJ_SHIP);
        Assert(objp->instance >= 0);
        Assert(objp != other_objp);

        shipp = &Ships[objp->instance];

        Assert(shipp->ai_index >= 0);

        aip = &Ai_info[shipp->ai_index];
        aip->avoid_check_timestamp = timestamp(1);

        //      If ship to guard is in a wing, guard that whole wing.
        ai_info *other_aip = &Ai_info[Ships[other_objp->instance].ai_index];
        if ((other_aip->wing != -1) && (other_aip->wing != aip->wing)) {
                ai_set_guard_wing(objp, Ai_info[Ships[other_objp->instance].ai_index].wing);
        } else {

                other_objnum = other_objp-Objects;

                aip->guard_objnum = other_objnum;
                aip->guard_signature = other_objp->signature;
                aip->guard_wingnum = -1;

                aip->mode = AIM_GUARD;
                aip->submode = AIS_GUARD_STATIC;

                Assert(other_objnum >= 0);      //      Hmm, bogus object and we need its position for guard_vec.

                // vm_vec_sub(&aip->guard_vec, &objp->pos, &Objects[other_objnum].pos);
                ai_set_guard_vec(objp, &Objects[other_objnum]);

                ai_set_goal_maybe_abort_dock(objp, aip);
                aip->ok_to_target_timestamp = timestamp(DELAY_TARGET_TIME);
        }
}

//      Update the aspect_locked_time field based on whether enemy is in view cone.
//      Also set/clear AIF_SEEK_LOCK.
void update_aspect_lock_information(ai_info *aip, vector *vec_to_enemy, float dist_to_enemy, float enemy_radius)
{
        float   dot_to_enemy;
        int     num_weapon_types;
        int     weapon_id_list[MAX_WEAPON_TYPES], weapon_bank_list[MAX_WEAPON_TYPES];
        ship    *shipp;
        ship_weapon     *swp;
        weapon_info     *wip;

        shipp = &Ships[aip->shipnum];
        swp = &shipp->weapons;

        // AL 3-7-98: This probably should never happen, but check to ensure that current_secondary_bank is valid
        if ( (swp->current_secondary_bank < 0) || (swp->current_secondary_bank > swp->num_secondary_banks) ) {
                return;
        }

        num_weapon_types = get_available_secondary_weapons(Pl_objp, weapon_id_list, weapon_bank_list);

        wip = &Weapon_info[swp->secondary_bank_weapons[swp->current_secondary_bank]];

        if (num_weapon_types && (wip->wi_flags & WIF_HOMING_ASPECT)) {
                if (dist_to_enemy > 300.0f - min(enemy_radius, 100.0f))
                        aip->ai_flags |= AIF_SEEK_LOCK;
                else
                        aip->ai_flags &= ~AIF_SEEK_LOCK;

                //      Update locking information for aspect seeking missiles.
                aip->current_target_is_locked = 0;
                dot_to_enemy = vm_vec_dot(vec_to_enemy, &Pl_objp->orient.v.fvec);

                float   needed_dot = 0.9f - 0.5f * enemy_radius/(dist_to_enemy + enemy_radius); //      Replaced MIN_TRACKABLE_DOT with 0.9f
                if (dot_to_enemy > needed_dot) {
                        aip->aspect_locked_time += flFrametime;
                        // nprintf(("AI", "+ Lock time = %7.3f\n", aip->aspect_locked_time));
                        if (aip->aspect_locked_time >= wip->min_lock_time) {
                                aip->aspect_locked_time = wip->min_lock_time;
                                aip->current_target_is_locked = 1;
                        }
                } else {
                        aip->aspect_locked_time -= flFrametime*2;
                        // nprintf(("AI", "- Lock time = %7.3f\n", aip->aspect_locked_time));
                        if (aip->aspect_locked_time < 0.0f)
                                aip->aspect_locked_time = 0.0f;
                }
                //nprintf(("AI", "dot = %7.3f, time = %7.3f\n", dot_to_enemy, aip->aspect_locked_time));
        
        } else {
                aip->current_target_is_locked = 0;
                aip->aspect_locked_time = 0.0f; // Used to be this, why?: wip->min_lock_time;
                aip->ai_flags &= ~AIF_SEEK_LOCK;
        }

}

//      We're in chase mode and we've recently collided with our target.
//      Fly away from it!
void ai_chase_fly_away(object *objp, ai_info *aip)
{
        int     abort_flag = 0;

        if (aip->ai_flags & AIF_TARGET_COLLISION) {
                aip->ai_flags &= ~AIF_TARGET_COLLISION; //      Don't process this hit again next frame.
                aip->submode = SM_FLY_AWAY;                                     //      Focus on avoiding target
                aip->submode_start_time = Missiontime;
        }

        if ((aip->target_objnum == -1) || (Objects[aip->target_objnum].signature != aip->target_signature)) {
                abort_flag = 1;
        }

        if (abort_flag || (Missiontime > aip->submode_start_time + F1_0)) {
                aip->last_attack_time = Missiontime;
                aip->submode = SM_ATTACK;
                aip->submode_start_time = Missiontime;
        } else {
                vector  v2e;
                float           dot;

                vm_vec_normalized_dir(&v2e, &Objects[aip->target_objnum].pos, &objp->pos);

                dot = vm_vec_dot(&objp->orient.v.fvec, &v2e);
                if (dot < 0.0f)
                        accelerate_ship(aip, 1.0f);
                else
                        accelerate_ship(aip, 1.0f - dot);
                turn_away_from_point(objp, &Objects[aip->target_objnum].pos, 0.0f);
        }
}

//      Return bank index of favored secondary weapon.
//      Return -1 if nothing favored.
//      "favored" means SEXPs have specified the weapon as being good to fire at en_objp.
int has_preferred_secondary(object *objp, object *en_objp, ship_weapon *swp)
{
// int is_preferred_weapon(int weapon_num, object *firer_objp, object *target_objp)
        int     i;

        for (i=0; i<swp->num_secondary_banks; i++) {
                if (swp->secondary_bank_capacity[i] > 0) {
                        if (swp->secondary_bank_ammo[i] > 0) {
                                if (is_preferred_weapon(swp->secondary_bank_weapons[i], objp, en_objp) != -1){
                                        return i;
                                }
                        }
                }
        }

        return -1;
}

//      Choose which secondary weapon to fire.
//      Note, this is not like ai_select_secondary_weapon().  "choose" means make a choice.
//      "select" means execute an order.  Get it?
//      This function calls ai_select_secondary_weapon() with the characteristics it should search for.
void ai_choose_secondary_weapon(object *objp, ai_info *aip, object *en_objp)
{
        float                   subsystem_strength = 0.0f;
        int                     is_big_ship, priority1, priority2;
        ship_weapon     *swp;
        ship_info       *esip;

        if ( en_objp->type == OBJ_SHIP ) {
                esip = &Ship_info[Ships[en_objp->instance].ship_info_index];
        } else {
                esip = NULL;
        }

        swp = &Ships[objp->instance].weapons;

        // AL 3-5-98: do a quick out if the ship has no secondaries
        if ( swp->num_secondary_banks <= 0 ) {
                swp->current_secondary_bank = -1;
                return;
        }

        int preferred_secondary = has_preferred_secondary(objp, en_objp, swp);

        if (preferred_secondary != -1) {
                if (swp->current_secondary_bank != preferred_secondary) {
                        aip->current_target_is_locked = 0;
                        aip->aspect_locked_time = 0.0f;
                        swp->current_secondary_bank = preferred_secondary;
                }
                //nprintf(("AI", "Favored secondary = %s\n", Weapon_info[swp->secondary_bank_weapons[swp->current_secondary_bank]].name));
                aip->ai_flags |= AIF_UNLOAD_SECONDARIES;
        } else {
                aip->ai_flags &= ~AIF_UNLOAD_SECONDARIES;
                if (aip->targeted_subsys) {
                        subsystem_strength = aip->targeted_subsys->current_hits;
                }

                if ( esip ) {
                        is_big_ship = esip->flags & (SIF_HUGE_SHIP | SIF_BIG_SHIP);
                } else {
                        is_big_ship=0;
                }

                if (is_big_ship) {
                        priority1 = WIF_HUGE;
                        priority2 = WIF_HOMING;
                } else if ( (esip != NULL) && (esip->flags & SIF_BOMBER) ) {
                        priority1 = WIF_BOMBER_PLUS;
                        priority2 = WIF_HOMING;
                } else if (subsystem_strength > 100.0f) {
                        priority1 = WIF_PUNCTURE;
                        priority2 = WIF_HOMING;
                } else {
                        priority1 = WIF_HOMING;
                        priority2 = 0;
                }
                
                ai_select_secondary_weapon(objp, swp, priority1, priority2);
        }

        // nprintf(("AI", "Frame %i: Chose secondary %s\n", Framecount, Weapon_info[swp->secondary_bank_weapons[swp->current_secondary_bank]].name));
}

//      Return time, in seconds, at which this ship can next fire its current secondary weapon.
float set_secondary_fire_delay(ai_info *aip, ship *shipp, weapon_info *swip)
{
        float t = swip->fire_wait;              //      Base delay for this weapon.
        if (shipp->team == Player_ship->team) {
                //      On player's team, _lower_ skill level = faster firing
                t = t * (Game_skill_level+2) / (NUM_SKILL_LEVELS);
        } else {                //      Not on player's team, higher skill level = faster firing
                t = t * (NUM_SKILL_LEVELS - Game_skill_level+2) / (NUM_SKILL_LEVELS);
        }

        t += (Num_ai_classes - aip->ai_class + 1) * 0.5f;
        t *= frand_range(0.8f, 1.2f);

        //      For the missiles that fire fairly quickly, occasionally add an additional substantial delay.
        if (t < 5.0f)
                if (frand() < 0.5f)
                        t = t * 2.0f + 2.0f;

        return t;
}


void ai_chase_big_approach_set_goal(vector *goal_pos, object *attack_objp, object *target_objp, float *accel)
{
        float dist_to_goal;

        // head straight toward him and maybe circle later
        vm_vec_avg(goal_pos, &attack_objp->pos, &target_objp->pos);

        // get distance to goal
        dist_to_goal = vm_vec_dist(goal_pos, &attack_objp->pos);
        
        // set accel
        if (dist_to_goal > 400.0f) {
                *accel = 1.0f;
        } else {
                *accel = dist_to_goal/400.0f;
        }
}

void ai_chase_big_circle_set_goal(vector *goal_pos, object *attack_objp, object *target_objp, float *accel)
{
        get_tangent_point(goal_pos, attack_objp, &target_objp->pos, attack_objp->radius + target_objp->radius + 100.0f);

        *accel = 1.0f;
}

// get the current and desired horizontal separations between target
void ai_chase_big_get_separations(object *attack_objp, object *target_objp, vector *horz_vec_to_target, float *desired_separation, float *cur_separation)
{
        float temp, r_target, r_attacker, h_attacker, h_target;
        float perp_dist;
        vector vec_to_target;
        polymodel *pm;

        // get parameters of ships (as cylinders - radius and height)
        // get radius of attacker (for rotations about forward)
        pm = model_get(Ships[attack_objp->instance].modelnum);
        temp = max(pm->maxs.xyz.x, pm->maxs.xyz.y);
        r_attacker = max(-pm->mins.xyz.x, -pm->mins.xyz.y);
        r_attacker = max(temp, r_attacker);
        h_attacker = max(-pm->mins.xyz.z, pm->maxs.xyz.z);

        // get radius of target (for rotations about forward)
        pm = model_get(Ships[attack_objp->instance].modelnum);
        temp = max(pm->maxs.xyz.x, pm->maxs.xyz.y);
        r_target = max(-pm->mins.xyz.x, -pm->mins.xyz.y);
        r_target = max(temp, r_target);
        h_target = max(-pm->mins.xyz.z, pm->maxs.xyz.z);

        // find separation between cylinders [if parallel]
        vm_vec_sub(&vec_to_target, &attack_objp->pos, &target_objp->pos);

        // find the distance between centers along forward direction of ships
        perp_dist = vm_vec_dotprod(&vec_to_target, &target_objp->orient.v.fvec);

        // subtract off perp component to get "horizontal" separation vector between cylinders [ASSUMING parallel]
        vm_vec_scale_add(horz_vec_to_target, &vec_to_target, &target_objp->orient.v.fvec, -perp_dist);
        *cur_separation = vm_vec_mag_quick(horz_vec_to_target);

        // choose "optimal" separation of 1000 + r_target + r_attacker
        *desired_separation = 1000 + r_target + r_attacker;
}

void ai_chase_big_parallel_set_goal(vector *goal_pos, object *attack_objp, object *target_objp, float *accel)
{
        int opposing;
        float temp, r_target, r_attacker, h_attacker, h_target;
        float separation, optimal_separation;
        vector  horz_vec_to_target;
        polymodel *pm;

        // get parameters of ships (as cylinders - radius and height)
        // get radius of attacker (for rotations about forward)
        pm = model_get(Ships[attack_objp->instance].modelnum);
        temp = max(pm->maxs.xyz.x, pm->maxs.xyz.y);
        r_attacker = max(-pm->mins.xyz.x, -pm->mins.xyz.y);
        r_attacker = max(temp, r_attacker);
        h_attacker = max(-pm->mins.xyz.z, pm->maxs.xyz.z);

        // get radius of target (for rotations about forward)
        pm = model_get(Ships[attack_objp->instance].modelnum);
        temp = max(pm->maxs.xyz.x, pm->maxs.xyz.y);
        r_target = max(-pm->mins.xyz.x, -pm->mins.xyz.y);
        r_target = max(temp, r_target);
        h_target = max(-pm->mins.xyz.z, pm->maxs.xyz.z);

        // are we opposing (only when other ship is not moving)
        opposing = ( vm_vec_dotprod(&attack_objp->orient.v.fvec, &target_objp->orient.v.fvec) < 0 );

        ai_chase_big_get_separations(attack_objp, target_objp, &horz_vec_to_target, &optimal_separation, &separation);

        // choose dist (2000) so that we don't bash
        float dist = 2000;
        if (opposing) {
                dist = - dist;
        }

        // set the goal pos as dist forward from target along target forward
        vm_vec_scale_add(goal_pos, &target_objp->pos, &target_objp->orient.v.fvec, dist);
        // then add horizontal separation
        vm_vec_scale_add2(goal_pos, &horz_vec_to_target, optimal_separation/separation);

        // find the distance between centers along forward direction of ships
        vector vec_to_target;
        vm_vec_sub(&vec_to_target, &target_objp->pos, &attack_objp->pos);
        float perp_dist = vm_vec_dotprod(&vec_to_target, &target_objp->orient.v.fvec);

        float match_accel = target_objp->phys_info.vel.xyz.z / Ship_info[Ships[attack_objp->instance].ship_info_index].max_vel.xyz.z;
        float length_scale = attack_objp->radius;

        // if we're heading toward enemy ship, we want to keep going if we're ahead
        if (opposing) {
                perp_dist = -perp_dist;
        }

        if (perp_dist > 0) {
                // falling behind, so speed up
                *accel = match_accel + (1.0f - match_accel) / length_scale * (perp_dist);
        } else {
                // up in front, so slow down
                *accel = match_accel  - match_accel / length_scale * -perp_dist;
                *accel = max(0.0f, *accel);
        }

}


//      Return *goal_pos for one cruiser to attack another (big ship).
//      Choose point fairly nearby that is not occupied by another cruiser.
void ai_cruiser_chase_set_goal_pos(vector *goal_pos, object *pl_objp, object *en_objp)
{
        ai_info *aip;

        aip = &Ai_info[Ships[pl_objp->instance].ai_index];
        float accel;

        switch (aip->submode) {
        case SM_BIG_APPROACH:
                // do approach stuff;
                ai_chase_big_approach_set_goal(goal_pos, pl_objp, en_objp, &accel);
                break;

        case SM_BIG_CIRCLE:
                // do circle stuff
                ai_chase_big_circle_set_goal(goal_pos, pl_objp, en_objp, &accel);
                break;

        case SM_BIG_PARALLEL:
                // do parallel stuff
                ai_chase_big_parallel_set_goal(goal_pos, pl_objp, en_objp, &accel);
                break;
        }
}

int maybe_hack_cruiser_chase_abort()
{
        ship                    *shipp = &Ships[Pl_objp->instance];     
        ship                    *eshipp = &Ships[En_objp->instance];
        ai_info         *aip = &Ai_info[shipp->ai_index];

        // mission sm3-08, sathanos chasing collosus
        if ( stricmp(Mission_filename, "sm3-08.fs2") == 0 ) {
                if (( stricmp(eshipp->ship_name, "colossus") == 0 ) || ( stricmp(shipp->ship_name, "colossus") == 0 )) {
                        // Changed so all big ships attacking the Colossus will not do the chase code.
                        // Did this so Beast wouldn't swerve away from Colossus. -- MK, 9/14/99
                        //if ( stricmp(shipp->ship_name, "Sathanas") == 0 ) {
                                // do cool hack stuff here
                                ai_clear_ship_goals( aip );
                                aip->mode = AIM_NONE;
                                return 1;
                        //}
                }
        }

        return 0;
}

//      Make a big ship pursue another big ship.
//      (Note, called "ai_cruiser_chase" because we already have ai_chase_big() which means fighter chases big ship.
void ai_cruiser_chase()
{
        ship_info       *sip = &Ship_info[Ships[Pl_objp->instance].ship_info_index];
        ship                    *shipp = &Ships[Pl_objp->instance];     
        ai_info         *aip = &Ai_info[shipp->ai_index];

        if (!(sip->flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP))) {
                Int3(); //      Hmm, not a very big ship, how did we get in this function?
                aip->mode = AIM_NONE;
                return;
        }

        if (En_objp->type != OBJ_SHIP) {
                Int3();
                return;
        }

        if (En_objp->instance < 0) {
                Int3();
                return;
        }

        ship                    *eshipp;
        ship_info       *esip;

        eshipp = &Ships[En_objp->instance];
        esip = &Ship_info[eshipp->ship_info_index];

        if (!(esip->flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP))) {
                // Int3();      //      Hmm, we're big and we're pursuing something other than a big ship?
                aip->mode = AIM_NONE;
                return;
        }

        vector  goal_pos;
        float turn_time = Ship_info[Ships[Pl_objp->instance].ship_info_index].srotation_time;

        // kamikaze - ram and explode
        if (aip->ai_flags & AIF_KAMIKAZE) {
                ai_turn_towards_vector(&En_objp->pos, Pl_objp, flFrametime, turn_time, NULL, NULL, 0.0f, 0);
                accelerate_ship(aip, 1.0f);
        } 
        
        // really track down and chase
        else {
                // check valid submode
                Assert( (aip->submode == SM_ATTACK) || (aip->submode == SM_BIG_APPROACH) || (aip->submode == SM_BIG_CIRCLE) || (aip->submode == SM_BIG_PARALLEL) );

                // just entering, approach enemy ship
                if (aip->submode == SM_ATTACK) {
                        aip->submode = SM_BIG_APPROACH;
                }

                // desired accel
                float accel = 0.0f;
                vector *rvecp = NULL;

                switch (aip->submode) {
                case SM_BIG_APPROACH:
                        // do approach stuff;
                        ai_chase_big_approach_set_goal(&goal_pos, Pl_objp, En_objp, &accel);
                        // maybe set rvec
                        break;

                case SM_BIG_CIRCLE:
                        // do circle stuff
                        ai_chase_big_circle_set_goal(&goal_pos, Pl_objp, En_objp, &accel);
                        // maybe set rvec
                        break;

                case SM_BIG_PARALLEL:
                        // do parallel stuff
                        ai_chase_big_parallel_set_goal(&goal_pos, Pl_objp, En_objp, &accel);
                        //maybe set rvec
                        break;
                }


                // now move as desired
                ai_turn_towards_vector(&goal_pos, Pl_objp, flFrametime, turn_time, NULL, NULL, 0.0f, 0, rvecp);
                accelerate_ship(aip, accel);


                // maybe switch to new mode
                vector vec_to_enemy;
                float dist_to_enemy;
                int moving = (En_objp->phys_info.vel.xyz.z > 0.5f);
                vm_vec_sub(&vec_to_enemy, &En_objp->pos, &Pl_objp->pos);
                dist_to_enemy = vm_vec_mag_quick(&vec_to_enemy);

                switch (aip->submode) {
                case SM_BIG_APPROACH:
                        if ( dist_to_enemy < (Pl_objp->radius + En_objp->radius)*1.25f + 200.0f ) {
                                // moving
                                if (moving) {
                                        // if within 90 degrees of en forward, go into parallel, otherwise circle
                                        if ( vm_vec_dotprod(&En_objp->orient.v.fvec, &Pl_objp->orient.v.fvec) > 0 ) {
                                                aip->submode = SM_BIG_PARALLEL;
                                        }
                                }

                                // otherwise cirle
                                if ( !maybe_hack_cruiser_chase_abort() ) {
                                        aip->submode = SM_BIG_CIRCLE;
                                }
                        }
                        break;

                case SM_BIG_CIRCLE:
                        // moving
                        if (moving) {
                                vector temp;
                                float desired_sep, cur_sep;
                                // we're behind the enemy ship
                                if (vm_vec_dotprod(&vec_to_enemy, &En_objp->orient.v.fvec) > 0) {
                                        // and we're turning toward the enemy
                                        if (vm_vec_dotprod(&En_objp->orient.v.fvec, &Pl_objp->orient.v.fvec) > 0) {
                                                // get separation
                                                ai_chase_big_get_separations(Pl_objp, En_objp, &temp, &desired_sep, &cur_sep);
                                                // and the separation is > 0.9 desired
                                                if (cur_sep > 0.9 * desired_sep) {
                                                        aip->submode = SM_BIG_PARALLEL;
                                                }
                                        }
                                }
                        } else {
                                // still
                                vector temp;
                                float desired_sep, cur_sep;
                                // we're behind the enemy ship
                                if (vm_vec_dotprod(&vec_to_enemy, &En_objp->orient.v.fvec) > 0) {
                                        // and we're turning toward the enemy
                                        if (vm_vec_dotprod(&En_objp->orient.v.fvec, &Pl_objp->orient.v.fvec) > 0) {
                                                // get separation
                                                ai_chase_big_get_separations(Pl_objp, En_objp, &temp, &desired_sep, &cur_sep);
                                                //and the separation is [0.9 to 1.1] desired
                                                if ( (cur_sep > 0.9f * desired_sep) ) {
                                                        aip->submode = SM_BIG_PARALLEL;
                                                }
                                        }
                                }
                                // in front of ship
                                else {
                                        // and we're turning toward the enemy
                                        if (vm_vec_dotprod(&En_objp->orient.v.fvec, &Pl_objp->orient.v.fvec) < 0) {
                                                // get separation
                                                ai_chase_big_get_separations(Pl_objp, En_objp, &temp, &desired_sep, &cur_sep);
                                                //and the separation is [0.9 to 1.1] desired
                                                if ( (cur_sep > 0.9f * desired_sep) ) {
                                                        aip->submode = SM_BIG_PARALLEL;
                                                }
                                        }
                                }
                        }
                        break;

                case SM_BIG_PARALLEL:
                        // we're opposing
                        if ( vm_vec_dotprod(&Pl_objp->orient.v.fvec, &En_objp->orient.v.fvec) < 0 ) {
                                // and the other ship is moving
                                if (moving) {
                                        // and we no longer overlap
                                        if ( dist_to_enemy > (0.75 * (En_objp->radius + Pl_objp->radius)) ) {
                                                aip->submode = SM_BIG_APPROACH;
                                        }
                                }
                        }
                        break;
                }
        }
}

// --------------------------------------------------------------------------
// Make object Pl_objp chase object En_objp
void ai_chase()
{
        float                   dist_to_enemy, time_to_enemy;
        float                   dot_to_enemy, dot_from_enemy, real_dot_to_enemy;
        vector          player_pos, enemy_pos, predicted_enemy_pos, real_vec_to_enemy, predicted_vec_to_enemy;
        ship_info       *sip = &Ship_info[Ships[Pl_objp->instance].ship_info_index];
        ship                    *shipp = &Ships[Pl_objp->instance];
        ship_weapon     *swp = &shipp->weapons;
        ai_info         *aip = &Ai_info[shipp->ai_index];
        int                     enemy_sip_flags;

        if (aip->mode != AIM_CHASE) {
                Int3();
        }

        if (sip->flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP)) {
                ai_cruiser_chase();
                return;
        }

        if (!(sip->flags & (SIF_FIGHTER | SIF_BOMBER | SIF_ESCAPEPOD))) {
                Warning(LOCATION, "Ship %s is not 'small', but is in chase mode.\nSwitching to AI=none.\n", shipp->ship_name);
                aip->mode = AIM_NONE;
                return;
        }

        //nprintf(("AI", "%7s ", Submode_text[aip->submode]));

        if ( En_objp->type == OBJ_SHIP ) {
                enemy_sip_flags = Ship_info[Ships[En_objp->instance].ship_info_index].flags;
        } else {
                enemy_sip_flags = 0;
        }

        if ( enemy_sip_flags > 0 ) {
                if (enemy_sip_flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP)) {
                        ai_big_chase();
                        return;
                }
        }

        //      If collided with target_objnum last frame, avoid that ship.
        //      This should prevent the embarrassing behavior of ships getting stuck on each other
        //      as if they were magnetically attracted. -- MK, 11/13/97.
        if ((aip->ai_flags & AIF_TARGET_COLLISION) || (aip->submode == SM_FLY_AWAY)) {
                ai_chase_fly_away(Pl_objp, aip);
                return;
        }

        ai_set_positions(Pl_objp, En_objp, aip, &player_pos, &enemy_pos);
        dist_to_enemy = vm_vec_dist_quick(&player_pos, &enemy_pos);
        time_to_enemy = compute_time_to_enemy(dist_to_enemy, Pl_objp, En_objp);
        vm_vec_sub(&real_vec_to_enemy, &enemy_pos, &player_pos);

        vm_vec_normalize(&real_vec_to_enemy);

        real_dot_to_enemy = vm_vec_dot(&real_vec_to_enemy, &Pl_objp->orient.v.fvec);

        int is_stealthy_ship = 0;
        if ( (enemy_sip_flags > 0) && (enemy_sip_flags & SIF_STEALTH) ) {
                if ( ai_is_stealth_visible(Pl_objp, En_objp) != STEALTH_FULLY_TARGETABLE ) {
                        is_stealthy_ship = 1;
                }
        }

        // Can only acquire lock on a target that isn't hidden from sensors
        if ( !(Ships[En_objp->instance].flags & SF_HIDDEN_FROM_SENSORS) && !is_stealthy_ship ) {
                update_aspect_lock_information(aip, &real_vec_to_enemy, dist_to_enemy, En_objp->radius);
        } else {
                aip->current_target_is_locked = 0;
                aip->ai_flags &= ~AIF_SEEK_LOCK;
        }

        //      If seeking lock, try to point directly at ship, else predict position so lasers can hit it.
        //      If just acquired target, or target is not in reasonable cone, don't refine believed enemy position.
        if ((real_dot_to_enemy < 0.25f) || (aip->target_time < 1.0f) || (aip->ai_flags & AIF_SEEK_LOCK)) {
                predicted_enemy_pos = enemy_pos;
        } else {
                //      Set predicted_enemy_pos.
                //      See if attacking a subsystem.
                if (aip->targeted_subsys != NULL) {
                        Assert(En_objp->type == OBJ_SHIP);
                        ship_info       *esip = &Ship_info[Ships[En_objp->instance].ship_info_index];
                        if (get_shield_strength(En_objp)/esip->shields < HULL_DAMAGE_THRESHOLD_PERCENT) {
                                //int   rval;

                                if (aip->targeted_subsys != NULL) {
                                        get_subsystem_pos(&enemy_pos, En_objp, aip->targeted_subsys);
                                        predicted_enemy_pos = enemy_pos;
                                        predicted_vec_to_enemy = real_vec_to_enemy;
                                } else {
                                        set_predicted_enemy_pos(&predicted_enemy_pos, Pl_objp, En_objp, aip);
                                        set_target_objnum(aip, -1);
                                }
                                // nprintf(("AI", "Attacking subsystem: rval = %i, pos = %7.3f %7.3f %7.3f\n", rval, predicted_enemy_pos.xyz.x, predicted_enemy_pos.xyz.y, predicted_enemy_pos.xyz.z));

                        } else {
                                set_predicted_enemy_pos(&predicted_enemy_pos, Pl_objp, En_objp, aip);
                                // nprintf(("AI", "Attacking subsystem: pos = %7.3f %7.3f %7.3f\n", predicted_enemy_pos.xyz.x, predicted_enemy_pos.xyz.y, predicted_enemy_pos.xyz.z));
                        }
                } else {
                        set_predicted_enemy_pos(&predicted_enemy_pos, Pl_objp, En_objp, aip);
                }
        }

        vm_vec_sub(&predicted_vec_to_enemy, &predicted_enemy_pos, &player_pos);

        vm_vec_normalize(&predicted_vec_to_enemy);

        dot_to_enemy = vm_vec_dot(&Pl_objp->orient.v.fvec, &predicted_vec_to_enemy);
        dot_from_enemy= - vm_vec_dot(&En_objp->orient.v.fvec, &real_vec_to_enemy);

        //
        //      Set turn and acceleration based on submode.
        //
        switch (aip->submode) {
        case SM_CONTINUOUS_TURN:
                ai_chase_ct();
                break;

        case SM_STEALTH_FIND:
                ai_stealth_find();
                break;

        case SM_STEALTH_SWEEP:
                ai_stealth_sweep();
                break;

        case SM_ATTACK:
        case SM_SUPER_ATTACK:
        case SM_ATTACK_FOREVER:
                if (vm_vec_dist_quick(&Pl_objp->pos, &predicted_enemy_pos) > 100.0f + En_objp->radius * 2.0f) {
                        if (maybe_avoid_big_ship(Pl_objp, En_objp, aip, &predicted_enemy_pos, 10.0f))
                                return;
                }

                ai_chase_attack(aip, sip, &predicted_enemy_pos, dist_to_enemy);
                break;

        case SM_EVADE_SQUIGGLE:
                ai_chase_es(aip, sip);
                break;

        case SM_EVADE_BRAKE:
                ai_chase_eb(aip, sip, &predicted_enemy_pos, dist_to_enemy);
                break;

        case SM_EVADE:
                evade_ship();
                break;

        case SM_AVOID:
                avoid_ship();
                break;

        case SM_GET_BEHIND:
                get_behind_ship(aip, sip, dist_to_enemy);
                break;

        case SM_GET_AWAY:               //      Used to get away from opponent to prevent endless circling.
                ai_chase_ga(aip, sip);
                break;

        case SM_EVADE_WEAPON:
                evade_weapon();
                break;

        default:
                // Int3();
                aip->last_attack_time = Missiontime;
                aip->submode = SM_ATTACK;
                aip->submode_start_time = Missiontime;
        }

        //
        //      Maybe choose a new submode.
        //
        if ( (aip->submode != SM_AVOID) && (aip->submode != SM_ATTACK_FOREVER) ) {
                //      If a very long time since attacked, attack no matter what!
                if ( (aip->submode != SM_SUPER_ATTACK) && (aip->submode != SM_GET_AWAY) && !(aip->ai_flags & AIF_STEALTH_PURSIUT) ) {
                        if (Missiontime - aip->last_attack_time > i2f(6)) {
                                aip->submode = SM_SUPER_ATTACK;
                                aip->submode_start_time = Missiontime;
                                aip->last_attack_time = Missiontime;
                        }
                }

                //      If a collision is expected, pull out!
                //      If enemy is pointing away and moving a bit, don't worry about collision detection.
                if ((dot_from_enemy > 0.5f) || (En_objp->phys_info.speed < 10.0f)) {
                        if (might_collide_with_ship(Pl_objp, En_objp, dot_to_enemy, dist_to_enemy, 4.0f)) {
                                if ((Missiontime - aip->last_hit_time > F1_0*4) && (dist_to_enemy < Pl_objp->radius*2 + En_objp->radius*2)) {
                                        accelerate_ship(aip, -1.0f);
                                } else {
                                        aip->submode = SM_AVOID;
                                        aip->submode_start_time = Missiontime;
                                }
                        }
                }
        }

        switch (aip->submode) {
        case SM_CONTINUOUS_TURN:
                if (Missiontime - aip->submode_start_time > i2f(3)) {
                        aip->last_attack_time = Missiontime;
                        aip->submode = SM_ATTACK;
                        aip->submode_start_time = Missiontime;
                }
                break;

        case SM_ATTACK:
                // if taraget is stealth and stealth not visible, then enter stealth find mode
                if ( (aip->ai_flags & AIF_STEALTH_PURSIUT) && (ai_is_stealth_visible(Pl_objp, En_objp) == STEALTH_INVISIBLE) ) {
                        aip->submode = SM_STEALTH_FIND;
                        aip->submode_start_time = Missiontime;
                        aip->submode_parm0 = SM_SF_AHEAD;
                } else if (ai_near_full_strength(Pl_objp, sip) && (Missiontime - aip->last_hit_target_time > i2f(3)) && (dist_to_enemy < 500.0f) && (dot_to_enemy < 0.5f)) {
                        aip->submode = SM_SUPER_ATTACK;
                        aip->submode_start_time = Missiontime;
                        aip->last_attack_time = Missiontime;
                } else if ((Missiontime - aip->last_hit_target_time > i2f(6)) &&
                        (dist_to_enemy < 500.0f) && (dot_to_enemy < 0.2f) &&
                        (frand() < (float) Game_skill_level/NUM_SKILL_LEVELS)) {
                        aip->submode = SM_GET_AWAY;
                        aip->submode_start_time = Missiontime;
                        aip->last_hit_target_time = Missiontime;
                } else if ((enemy_sip_flags & SIF_SMALL_SHIP)
                        && (dot_to_enemy < dot_from_enemy)
                        && (En_objp->phys_info.speed > 15.0f) 
                        && (dist_to_enemy < 200.0f) 
                        && (dist_to_enemy > 50.0f)
                        && (dot_to_enemy < 0.1f)
                        && (Missiontime - aip->submode_start_time > i2f(2))) {
                        aip->submode = SM_EVADE_BRAKE;
                        aip->submode_start_time = Missiontime;
                } else if ((dot_to_enemy > 0.2f) && (dot_from_enemy > -0.2f) && (dot_from_enemy < 0.1f)) {
                        aip->submode = SM_GET_BEHIND;
                        aip->submode_start_time = Missiontime;
                } else if ((enemy_sip_flags & SIF_SMALL_SHIP) && (dist_to_enemy < 150.0f) && (dot_from_enemy > dot_to_enemy + 0.5f + aip->ai_courage*.002)) {
                        if ((Missiontime - aip->last_hit_target_time > i2f(5)) && (frand() < (float) (aip->ai_class + Game_skill_level)/(Num_ai_classes + NUM_SKILL_LEVELS))) {                         aip->submode = SM_GET_AWAY;
                                aip->submode_start_time = Missiontime;
                                aip->last_hit_target_time = Missiontime;
                        } else {
                                aip->submode = SM_EVADE_SQUIGGLE;
                                aip->submode_start_time = Missiontime;
                        }
                } else if ((enemy_sip_flags & SIF_SMALL_SHIP) && (Missiontime - aip->submode_start_time > F1_0*2)) {
                        if ((dot_to_enemy < 0.8f) && (dot_from_enemy > dot_to_enemy)) {
                                if (frand() > 0.5f) {
                                        aip->submode = SM_CONTINUOUS_TURN;
                                        aip->submode_parm0 = myrand() & 0x0f;
                                        aip->submode_start_time = Missiontime;
                                } else {
                                        aip->submode = SM_EVADE;
                                        aip->submode_start_time = Missiontime;
                                }
                        } else {
                                aip->submode_start_time = Missiontime;
                        }
                }

                aip->last_attack_time = Missiontime;

                break;
                
        case SM_EVADE_SQUIGGLE:
                if ((Missiontime - aip->submode_start_time > i2f(5)) || (dist_to_enemy > 300.0f)) {
                        if ((dist_to_enemy < 100.0f) && (dot_to_enemy < 0.0f) && (dot_from_enemy > 0.5f)) {
                                aip->submode = SM_EVADE_BRAKE;
                                aip->submode_start_time = Missiontime;
                        } else {
                                aip->last_attack_time = Missiontime;
                                aip->submode = SM_ATTACK;
                                aip->submode_start_time = Missiontime;
                        }
                }
                break;
        
        case SM_EVADE_BRAKE:
                if ((dist_to_enemy < 15.0f) || (En_objp->phys_info.speed < 10.0f)) {
                        aip->submode = SM_AVOID;
                        aip->submode_start_time = Missiontime;
                } else if ((dot_to_enemy > 0.9f) || ((dot_from_enemy > 0.9f) && (Missiontime - aip->submode_start_time > i2f(1)))) {
                        aip->last_attack_time = Missiontime;
                        aip->submode = SM_ATTACK;
                        aip->submode_start_time = Missiontime;
                } else if (Missiontime - aip->submode_start_time > i2f(4)) {
                        aip->last_attack_time = Missiontime;
                        aip->submode = SM_ATTACK;
                        aip->submode_start_time = Missiontime;
                }
                break;

        case SM_EVADE:
                //      Modified by MK on 5/5/97 to keep trying to regain attack mode.  It's what a human would do.
                if ((dot_to_enemy < 0.2f) && (dot_from_enemy < 0.8f) && (dist_to_enemy < 100.0f) && (En_objp->phys_info.speed > 15.0f)) {
                        aip->last_attack_time = Missiontime;
                        aip->submode = SM_EVADE_BRAKE;
                        aip->submode_start_time = Missiontime;
                } else if (((dot_to_enemy > dot_from_enemy - 0.1f)
                        && (Missiontime > aip->submode_start_time + i2f(1)))
                        || (dist_to_enemy > 150.0f + 2*(Pl_objp->radius + En_objp->radius))) {
                        aip->last_attack_time = Missiontime;
                        aip->submode = SM_ATTACK;
                        aip->submode_start_time = Missiontime;
                } else if (Missiontime - aip->submode_start_time > i2f(2))
                        if (dot_from_enemy > 0.8f) {
                                aip->submode = SM_EVADE_SQUIGGLE;
                                aip->submode_start_time = Missiontime;
                        }

                break;

        case SM_SUPER_ATTACK:
                // if stealth and invisible, enter stealth find mode
                if ( (aip->ai_flags & AIF_STEALTH_PURSIUT) && (ai_is_stealth_visible(Pl_objp, En_objp) == STEALTH_INVISIBLE) ) {
                        aip->submode = SM_STEALTH_FIND;
                        aip->submode_start_time = Missiontime;
                        aip->submode_parm0 = SM_SF_AHEAD;
                } else if ((dist_to_enemy < 100.0f) && (dot_to_enemy < 0.8f) && (enemy_sip_flags & SIF_SMALL_SHIP) && (Missiontime - aip->submode_start_time > i2f(5) )) {
                        aip->ai_flags &= ~AIF_ATTACK_SLOWLY;    //      Just in case, clear here.

                        switch (myrand() % 5) {
                        case 0:
                                aip->submode = SM_CONTINUOUS_TURN;
                                aip->submode_start_time = Missiontime;
                                break;
                        case 1:
                                aip->submode_start_time = Missiontime;  //      Stay in super attack mode
                                break;
                        case 2:
                        case 3:
                                if (frand() < (float) 0.5f * (aip->ai_class + Game_skill_level)/(Num_ai_classes + NUM_SKILL_LEVELS)) {
                                        aip->submode = SM_GET_AWAY;
                                        aip->submode_start_time = Missiontime;
                                } else {
                                        aip->submode = SM_EVADE;
                                        aip->submode_start_time = Missiontime;
                                }
                                break;
                        case 4:
                                if (dot_from_enemy + (NUM_SKILL_LEVELS - Game_skill_level) * 0.1f > dot_to_enemy) {     //      Less likely to GET_AWAY at lower skill levels.
                                        aip->submode = SM_EVADE;
                                        aip->submode_start_time = Missiontime;
                                } else {
                                        aip->submode = SM_GET_AWAY;
                                        aip->submode_start_time = Missiontime;
                                }
                                break;
                        default:
                                Int3(); //      Impossible!
                        }
                }

                aip->last_attack_time = Missiontime;

                break;

        case SM_AVOID:
                if ((dot_to_enemy > -0.2f) && (dist_to_enemy / (dot_to_enemy + 0.3f) < 100.0f)) {
                        aip->submode_start_time = Missiontime;
                } else if (Missiontime - aip->submode_start_time > i2f(1)/2)
                        if (might_collide_with_ship(Pl_objp, En_objp, dot_to_enemy, dist_to_enemy, 3.0f)) {
                                aip->submode_start_time = Missiontime;
                        } else {
                                aip->submode = SM_GET_BEHIND;
                                aip->submode_start_time = Missiontime;
                        }

                break;

        case SM_GET_BEHIND:
                if ((dot_from_enemy < -0.7f) || (Missiontime - aip->submode_start_time > i2f(2))) {
                        aip->submode = SM_ATTACK;
                        aip->submode_start_time = Missiontime;
                        aip->last_attack_time = Missiontime;
                }
                break;

        case SM_GET_AWAY:
                if (Missiontime - aip->submode_start_time > i2f(2)) {
                        float   rand_dist;

                        rand_dist = ((Missiontime >> 17) & 0x03) * 100.0f + 200.0f;     //      Some value in 200..500
                        if ((Missiontime - aip->submode_start_time > i2f(5)) || (dist_to_enemy > rand_dist) || (dot_from_enemy < 0.4f)) {
                                aip->ai_flags |= AIF_ATTACK_SLOWLY;
                                aip->submode = SM_ATTACK;
                                aip->time_enemy_in_range = 2.0f;                //      Cheat.  Presumably if they were running away from you, they were monitoring you!
                                aip->submode_start_time = Missiontime;
                                aip->last_attack_time = Missiontime;
                        }
                }
                break;

        case SM_EVADE_WEAPON:
                if (aip->danger_weapon_objnum == -1) {
                        aip->submode = SM_ATTACK;
                        aip->submode_start_time = Missiontime;
                        aip->last_attack_time = Missiontime;
                }
                break;

        // Either change to SM_ATTACK or AIM_FIND_STEALTH
        case SM_STEALTH_FIND:
                // if time > 5 sec change mode to sweep
                if ( !(aip->ai_flags & AIF_STEALTH_PURSIUT) || (ai_is_stealth_visible(Pl_objp, En_objp) == STEALTH_VISIBLE) ) {
                        aip->submode = SM_ATTACK;
                        aip->submode_start_time = Missiontime;
                        aip->last_attack_time = Missiontime;
                        // sweep if I can't find in 5 sec or bail from find
                } else if ( ((Missiontime - aip->submode_start_time) > i2f(5)) || (aip->submode_parm0 == SM_SF_BAIL) ) {
                        // begin sweep mode
                        aip->submode = SM_STEALTH_SWEEP;
                        aip->submode_start_time = Missiontime;
                        aip->last_attack_time = Missiontime;
                        aip->submode_parm0 = SM_SS_SET_GOAL;
                }
                break;

        case SM_STEALTH_SWEEP:
                if ( !(aip->ai_flags & AIF_STEALTH_PURSIUT) || (ai_is_stealth_visible(Pl_objp, En_objp) == STEALTH_VISIBLE) ) {
                        aip->submode = SM_ATTACK;
                        aip->submode_start_time = Missiontime;
                        aip->last_attack_time = Missiontime;
                } else if ( (timestamp() - aip->stealth_last_visible_stamp) < 5000 ) {
                        // go back to find mode
                        aip->submode = SM_STEALTH_FIND;
                        aip->submode_start_time = Missiontime;
                        aip->submode_parm0 = SM_SF_AHEAD;
                } else if ( /*(Missiontime - aip->submode_start_time) > i2f(30) || */(aip->submode_parm0 == SM_SS_DONE) ) {
                        // set target objnum = -1
                        set_target_objnum(aip, -1);

                        // set submode to attack
                        aip->submode = SM_ATTACK;
                        aip->submode_start_time = Missiontime;
                        aip->last_attack_time = Missiontime;
                }
                break;

        case SM_ATTACK_FOREVER: //      Engines blown, just attack.
                break;

        default:
                //Int3();
                aip->submode = SM_ATTACK;
                aip->last_attack_time = Missiontime;

                aip->submode_start_time = Missiontime;
        }

        //
        //      Maybe fire primary weapon and update time_enemy_in_range
        //
        //nprintf(("AI", "time_enemy_in_range = %7.3f, dot = %7.3f\n", aip->time_enemy_in_range, dot_to_enemy));

        if (aip->mode != AIM_EVADE) {
                if (dot_to_enemy > 0.95f - 0.5f * En_objp->radius/max(1.0f, En_objp->radius + dist_to_enemy)) {
                        aip->time_enemy_in_range += flFrametime;
                        
                        //      Chance of hitting ship is based on dot product of firing ship's forward vector with vector to ship
                        //      and also the size of the target relative to distance to target.
                        if (dot_to_enemy > max(0.5f, 0.90f + aip->ai_accuracy/10.0f - En_objp->radius/max(1.0f,dist_to_enemy))) {

                                ship *temp_shipp;
                                ship_weapon *tswp;

                                temp_shipp = &Ships[Pl_objp->instance];
                                tswp = &temp_shipp->weapons;
                                if ( tswp->num_primary_banks > 0 ) {
                                        float   scale;
                                        Assert(tswp->current_primary_bank < tswp->num_primary_banks);
                                        weapon_info     *pwip = &Weapon_info[tswp->primary_bank_weapons[tswp->current_primary_bank]];

                                        //      Less likely to fire if far away and moving.
                                        scale = pwip->max_speed/(En_objp->phys_info.speed + pwip->max_speed);
                                        if (scale > 0.6f)
                                                scale = (scale - 0.6f) * 1.5f;
                                        else
                                                scale = 0.0f;
                                        if (dist_to_enemy < pwip->max_speed * (1.0f + scale)) {
                                                ai_fire_primary_weapon(Pl_objp);
                                        }

                                        //      Don't fire secondaries at a protected ship.
                                        if (!(En_objp->flags & OF_PROTECTED)) {
                                                ai_choose_secondary_weapon(Pl_objp, aip, En_objp);
                                                int current_bank = tswp->current_secondary_bank;
                                                weapon_info     *swip = &Weapon_info[tswp->secondary_bank_weapons[tswp->current_secondary_bank]];

                                                if (current_bank > -1) {
                                                        if (aip->ai_flags & AIF_UNLOAD_SECONDARIES) {
                                                                if (timestamp_until(swp->next_secondary_fire_stamp[current_bank]) > swip->fire_wait*1000.0f) {
                                                                        swp->next_secondary_fire_stamp[current_bank] = timestamp((int) (swip->fire_wait*1000.0f));
                                                                }
                                                        }

                                                        if (timestamp_elapsed(swp->next_secondary_fire_stamp[current_bank])) {
                                                                if (tswp->current_secondary_bank >= 0) {
                                                                        weapon_info     *swip = &Weapon_info[tswp->secondary_bank_weapons[tswp->current_secondary_bank]];
                                                                        float firing_range;
                                                                        
                                                                        if (swip->wi_flags & WIF_BOMB)
                                                                                firing_range = swip->max_speed * swip->lifetime * 0.75f;
                                                                        else
                                                                                firing_range = swip->max_speed * swip->lifetime * (Game_skill_level + 1 + aip->ai_class/2)/NUM_SKILL_LEVELS;

                                                                        // reduce firing range in nebula
                                                                        extern int Nebula_sec_range;
                                                                        if ((The_mission.flags & MISSION_FLAG_FULLNEB) && Nebula_sec_range) {
                                                                                firing_range *= 0.8f;
                                                                        }

                                                                        //      If firing a spawn weapon, distance doesn't matter.
                                                                        int     spawn_fire = 0;

                                                                        if (swip->wi_flags & WIF_SPAWN) {
                                                                                int     count;

                                                                                count = num_nearby_fighters(get_enemy_team_mask(OBJ_INDEX(Pl_objp)), &Pl_objp->pos, 1000.0f);

                                                                                if (count > 3)
                                                                                        spawn_fire = 1;
                                                                                else if (count >= 1) {
                                                                                        float hull_percent = Pl_objp->hull_strength/sip->initial_hull_strength;

                                                                                        if (hull_percent < 0.01f)
                                                                                                hull_percent = 0.01f;

                                                                                        if (frand() < 0.25f/(30.0f*hull_percent) * count)       //      With timestamp below, this means could fire in 30 seconds if one enemy.
                                                                                                spawn_fire = 1;
                                                                                }
                                                                        }

                                                                        if (spawn_fire || (dist_to_enemy < firing_range)) {
                                                                                if (ai_fire_secondary_weapon(Pl_objp)) {
                                                                                        //      Only if weapon was fired do we specify time until next fire.  If not fired, done in ai_fire_secondary...
                                                                                        float t;
                                                                                        
                                                                                        if (aip->ai_flags & AIF_UNLOAD_SECONDARIES) {
                                                                                                t = swip->fire_wait;
                                                                                        } else {
                                                                                                t = set_secondary_fire_delay(aip, temp_shipp, swip);
                                                                                        }
                                                                                        //nprintf(("AI", "Next secondary to be fired in %7.3f seconds.\n", t));
                                                                                        swp->next_secondary_fire_stamp[current_bank] = timestamp((int) (t*1000.0f));
                                                                                }
                                                                        } else {
                                                                                swp->next_secondary_fire_stamp[current_bank] = timestamp(250);
                                                                        }
                                                                }
                                                        }
                                                }
                                        }
                                }
                        }
                } else {
                        aip->time_enemy_in_range *= (1.0f - flFrametime);
                }
        } else
                aip->time_enemy_in_range *= (1.0f - flFrametime);

}

//      Make the object *objp move so that the point *dp on the object moves towards the point *vp
//      Return distance.
void dock_move_towards_point(object *objp, vector *dp, vector *vp, float speed_scale, float other_obj_speed = 0.0f)
{
        physics_info    *pi = &objp->phys_info;
        float                           dist;                   //      dist to goal
        vector                  v2g;                    //      vector to goal
        vector                  abs_pnt;                //      location of dock point, ie objp->pos + db

        if (dp == NULL)
                abs_pnt = objp->pos;
        else
                vm_vec_add(&abs_pnt, &objp->pos, dp);

        dist = vm_vec_dist_quick(vp, &abs_pnt);
        if (dist > 0.0f) {
                float   speed;

                dist = vm_vec_normalized_dir(&v2g, vp, &abs_pnt);
                speed = fl_sqrt(dist) * speed_scale;
                if (other_obj_speed < MAX_REPAIR_SPEED*0.75f)
                        speed += other_obj_speed;
                else
                        speed += MAX_REPAIR_SPEED*0.75f;

                vm_vec_copy_scale(&pi->desired_vel, &v2g, speed);
        } else
                vm_vec_zero(&pi->desired_vel);
}

//      Set the orientation in the global reference frame for an object to attain
//      to dock with another object.
//      *dom            resultant global matrix
//      *db_dest        pointer to destination docking bay information
//      *db_src pointer to source docking bay information
//      *dorient        pointer to global orientation of docking bay (ie, the dockee object's orient)
//      *sorient        pointer to global orientation of docker
void set_goal_dock_orient(matrix *dom, dock_bay *db_dest, dock_bay *db_src, matrix *dorient, matrix *sorient)
{
        vector  fvec, uvec;
        matrix  m1, m2, m3;

        //      Compute the global orientation of the docker's (dest) docking bay.
        fvec = db_dest->norm[0];
        vm_vec_negate(&fvec);

        vm_vec_normalized_dir(&uvec, &db_dest->pnt[1], &db_dest->pnt[0]);
        vm_vector_2_matrix(&m1, &fvec, &uvec, NULL);

        vm_matrix_x_matrix(&m3, dorient, &m1);

        //      Compute the matrix given by the source docking bay.
        //      Pre-multiply the orientation of the source object (sorient) by the transpose
        //      of the docking bay's orientation, ie unrotate the source object's matrix.
        fvec = db_src->norm[0];
        vm_vec_normalized_dir(&uvec, &db_src->pnt[1], &db_src->pnt[0]);
        vm_vector_2_matrix(&m2, &fvec, &uvec, NULL);
        vm_transpose(&m2);

        vm_matrix_x_matrix(dom, &m3, &m2);
}

#define DOCK_BACKUP_RETURN_VAL  99999.9f

//      Make objp dock with dobjp
//      Returns distance to goal, defined as distance between corresponding dock points, plus 10.0f * rotational velocity vector (DOA_DOCK only)
//      DOA_APPROACH    means   approach point aip->path_cur
//      DOA_DOCK                        means dock
//      DOA_UNDOCK_1    means undock, moving to point nearest dock bay
//      DOA_UNDOCK_2    means undock, moving to point nearest dock bay and facing away from ship
//      DOA_DOCK_STAY   means rigidly maintain position in dock bay.
float dock_orient_and_approach(object *objp, object *dobjp, int dock_mode)
{
        ship_info       *sip0, *sip1;
        polymodel       *pm0, *pm1;
        ai_info         *aip;
        matrix          dom, nm;
        vector          goal_point, docker_point;
        float                   fdist = UNINITIALIZED_VALUE;
        int                     docker_index, dockee_index;             // index into docking_bays[] array for objects docking
                                                                                                                                // docker is Pl_objp -- dockee is dobjp
        aip = &Ai_info[Ships[objp->instance].ai_index];

        //      If dockee has moved much, then path will be recreated.
        //      Might need to change state if moved too far.
        if ((dock_mode != DOA_DOCK_STAY) && (dock_mode != DOA_DOCK)) {
                if (maybe_recreate_path(objp, &Ai_info[Ships[objp->instance].ai_index], 0) > 5.0f) {
/*                      if (dock_mode == DOA_APPROACH) {
                                return DOCK_BACKUP_RETURN_VAL;
                        } else if (dock_mode == DOA_DOCK) {
                                return DOCK_BACKUP_RETURN_VAL;          
                        }
*/              }
        }

        objp->phys_info.forward_thrust = 0.0f;          //      Kill thrust so we don't have a sputtering thruster.

        sip0 = &Ship_info[Ships[objp->instance].ship_info_index];
        sip1 = &Ship_info[Ships[dobjp->instance].ship_info_index];
        pm0 = model_get( sip0->modelnum );
        pm1 = model_get( sip1->modelnum );

        docker_index = aip->dock_index;
        dockee_index = aip->dockee_index;

        Assert( docker_index >= 0 );
        Assert( dockee_index >= 0 );

        Assert(pm0->docking_bays[docker_index].num_slots == 2);
        Assert(pm1->docking_bays[dockee_index].num_slots == 2);

        float speed_scale = 1.0f;
        if (sip0->flags & SIF_SUPPORT) {
                speed_scale = 3.0f;
        }

        switch (dock_mode) {
        case DOA_APPROACH:
                {
                if (ship_get_subsystem_strength(&Ships[objp->instance], SUBSYSTEM_ENGINE) <= 0.0f) {
                        return 9999.9f;
                }
                
                //      Compute the desired global orientation matrix for the docker's station.
                //      That is, the normal vector of the docking station must be the same as the
                //      forward vector and the vector between its two points must be the uvec.
                set_goal_dock_orient(&dom, &pm1->docking_bays[dockee_index], &pm0->docking_bays[docker_index], &dobjp->orient, &objp->orient);

                //      Compute new orientation matrix and update rotational velocity.
                vector  w_in, w_out, vel_limit, acc_limit;
                float           tdist, mdist, ss1;

                w_in = objp->phys_info.rotvel;
                vel_limit = objp->phys_info.max_rotvel;
                vm_vec_copy_scale(&acc_limit, &vel_limit, 0.3f);
                
                if (sip0->flags & SIF_SUPPORT)
                        vm_vec_scale(&acc_limit, 2.0f);

                // 1 at end of line prevent overshoot
                vm_matrix_interpolate(&dom, &objp->orient, &w_in, flFrametime, &nm, &w_out, &vel_limit, &acc_limit, 1);
                objp->phys_info.rotvel = w_out;
                objp->orient = nm;

                //      Translate towards goal and note distance to goal.
                goal_point = Path_points[aip->path_cur].pos;
                mdist = ai_matrix_dist(&objp->orient, &dom);
                tdist = vm_vec_dist_quick(&objp->pos, &goal_point);

                //      If translation is badly lagging rotation, speed up translation.
                if (mdist > 0.1f) {
                        ss1 = tdist/(10.0f * mdist);
                        if (ss1 > 2.0f)
                                ss1 = 2.0f;
                } else
                        ss1 = 2.0f;

                // nprintf(("AI", "speed scale = %7.3f\n", ss1));
                speed_scale *= 1.0f + ss1;

                dock_move_towards_point(objp, NULL, &goal_point, speed_scale, dobjp->phys_info.speed);

                fdist = vm_vec_dist_quick(&objp->pos, &goal_point);

                //      Note, we're interested in distance from goal, so if we're still turning, bash that into return value.
                // nprintf(("AI", "matrix dist = %7.3f, threshold = %7.3f\n", mdist, 2*flFrametime));
                fdist += 2.0f * mdist;

                break;
        }
        case DOA_DOCK:
                if (ship_get_subsystem_strength(&Ships[objp->instance], SUBSYSTEM_ENGINE) <= 0.0f) {
                        return 9999.9f;
                }
        case DOA_DOCK_STAY:
                //      Compute the desired global orientation matrix for the docker's station.
                //      That is, the normal vector of the docking station must be the same as the
                //      forward vector and the vector between its two points must be the uvec.
                set_goal_dock_orient(&dom, &pm1->docking_bays[dockee_index], &pm0->docking_bays[docker_index], &dobjp->orient, &objp->orient);

                //      Compute distance between dock bay points.
                vector  db0, db1, db2, db3;

                vm_vec_unrotate(&db0, &pm0->docking_bays[docker_index].pnt[0], &objp->orient);
                vm_vec_add2(&db0, &objp->pos);

                vm_vec_unrotate(&db1, &pm0->docking_bays[docker_index].pnt[1], &objp->orient);
                vm_vec_add2(&db1, &objp->pos);

                vm_vec_unrotate(&db2, &pm1->docking_bays[dockee_index].pnt[0], &dobjp->orient);
                vm_vec_add2(&db2, &dobjp->pos);

                vm_vec_unrotate(&db3, &pm1->docking_bays[dockee_index].pnt[1], &dobjp->orient);
                vm_vec_add2(&db3, &dobjp->pos);

                vm_vec_avg(&goal_point, &db2, &db3);

                vm_vec_avg(&docker_point, &db0, &db1);
                vm_vec_sub2(&docker_point, &objp->pos);

                if (dock_mode == DOA_DOCK) {
                        vector  t1, t2;
                        vector  w_in, w_out, vel_limit, acc_limit;

                        fdist = vm_vec_dist_quick(vm_vec_avg(&t1, &db0, &db1), vm_vec_avg(&t2, &db2, &db3));

                        //      Compute new orientation matrix and update rotational velocity.
                        w_in = objp->phys_info.rotvel;
                        vel_limit = objp->phys_info.max_rotvel;
                        vm_vec_copy_scale(&acc_limit, &vel_limit, 0.3f);

                        if (sip0->flags & SIF_SUPPORT)
                                vm_vec_scale(&acc_limit, 2.0f);

                        vm_matrix_interpolate(&dom, &objp->orient, &w_in, flFrametime, &nm, &w_out, &vel_limit, &acc_limit);
                        objp->phys_info.rotvel = w_out;
                        objp->orient = nm;

                        //      Note, we're interested in distance from goal, so if we're still turning, bash that into return value.
                        fdist += 10.0f * vm_vec_mag_quick(&w_out);

                        dock_move_towards_point(objp, &docker_point, &goal_point, speed_scale, dobjp->phys_info.speed);
                } else {
                        Assert(dock_mode == DOA_DOCK_STAY);
                        objp->orient = dom;
                        vector  temp;
                        vm_vec_sub(&temp, &goal_point, &docker_point);
                        vm_vec_sub(&objp->pos, &goal_point, &docker_point);
                }

                break;
        case DOA_UNDOCK_1: {
                if (ship_get_subsystem_strength(&Ships[objp->instance], SUBSYSTEM_ENGINE) <= 0.0f) {
                        return 9999.9f;
                }

                //      Undocking.
                //      Move to point on dock path nearest to dock station.
                Assert(aip->path_length >= 2);
                goal_point = Path_points[aip->path_start + aip->path_length-2].pos;

                vm_vec_zero(&docker_point);
                fdist = vm_vec_dist_quick(&objp->pos, &goal_point);

                dock_move_towards_point(objp, &docker_point, &goal_point, speed_scale);

                break;
                          }

        case DOA_UNDOCK_2: {
                //      Undocking.
                //      Move to point on dock path nearest to dock station and orient away from big ship.
                int             desired_index;

                if (ship_get_subsystem_strength(&Ships[objp->instance], SUBSYSTEM_ENGINE) <= 0.0f) {
                        return 9999.9f;
                }

                Assert(aip->path_length >= 2);
//              if (aip->path_length >= 3)
//                      desired_index = aip->path_length-3;
//              else
                        desired_index = aip->path_length-2;

                goal_point = Path_points[aip->path_start + desired_index].pos;

                dock_move_towards_point(objp, NULL, &goal_point, speed_scale);

                fdist = vm_vec_dist_quick(&objp->pos, &goal_point);
                break;
                          }
        case DOA_UNDOCK_3: {
                float           dist, goal_dist;
                vector  away_vec;

                goal_dist = objp->radius + dobjp->radius + 25.0f;

                dist = vm_vec_normalized_dir(&away_vec, &objp->pos, &dobjp->pos);
                vm_vec_scale_add(&goal_point, &dobjp->pos, &away_vec, goal_dist);
                if (vm_vec_dist_quick(&goal_point, &dobjp->pos) < vm_vec_dist_quick(&objp->pos, &dobjp->pos))
                        fdist = 0.0f;
                else {
                        float   dot, accel;
                        float turn_time = Ship_info[Ships[objp->instance].ship_info_index].srotation_time;
                        ai_turn_towards_vector(&goal_point, objp, flFrametime, turn_time, NULL, NULL, 0.0f, 0);

                        dot = vm_vec_dot(&objp->orient.v.fvec, &away_vec);
                        accel = 0.1f;
                        if (dot > accel)
                                accel = dot;
                        if (dist > goal_dist/2)
                                accel *= 1.2f - 0.5f*goal_dist/dist;

                        accelerate_ship(aip, accel);
                        fdist = vm_vec_dist_quick(&objp->pos, &goal_point);
                }

                break;
                                                         }
        }

#ifndef NDEBUG
        //      For debug purposes, compute global orientation of both dock vectors and show
        //      how close they are.
        vector  d0, d1;

        vm_vec_unrotate(&d0, &pm0->docking_bays[docker_index].norm[0], &objp->orient);
        vm_vec_unrotate(&d1, &pm1->docking_bays[dockee_index].norm[0], &dobjp->orient);

        //nprintf(("AI", "or/app: dist = %7.3f/%7.3f, dot = %7.3f, global dot = %7.3f\n", 
        //      vm_vec_dist_quick(&goal_point, &objp->pos), fdist,
        //      vm_vec_dot(&objp->orient.v.fvec, &dom.v.fvec), 
        //      vm_vec_dot(&d0, &d1)));
#endif

        // -- Note, A lot of callers don't care about fdist, so OK to return ERROR value: Assert(fdist != UNINITIALIZED_VALUE);
        return fdist;

}

void debug_find_guard_object()
{
        ship                    *shipp = &Ships[Pl_objp->instance];     
        object          *objp;

        for ( objp = GET_FIRST(&obj_used_list); objp !=END_OF_LIST(&obj_used_list); objp = GET_NEXT(objp) ) {
                if ((Pl_objp != objp) && (objp->type == OBJ_SHIP)) {
                        if (objp->instance != -1) {
                                if (Ships[objp->instance].team == shipp->team)  {
                                        // nprintf(("AI", "Setting guard object for %s to %s\n", shipp->ship_name, Ships[objp->instance].ship_name));
                                        ai_set_guard_object(Pl_objp, objp);
                                }
                        }
                }
        }

}

//      Given an object number, return the number of ships attacking it.
int num_ships_attacking(int objnum)
{
        object  *objp;
        ship_obj        *so;
        int             count = 0;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                objp = &Objects[so->objnum];
                if (objp->instance != -1) {
                        ai_info *aip;
                        aip = &Ai_info[Ships[objp->instance].ai_index];

                        if ((aip->mode == AIM_CHASE) && (aip->target_objnum == objnum))
                                if (Ships[objp->instance].team != Ships[Objects[objnum].instance].team)
                                        count++;
                }
        }

        return count;
}

//      For all objects attacking object #objnum, remove the one that is farthest away.
//      Do this by resuming previous behavior, if any.  If not, set target_objnum to -1.
void remove_farthest_attacker(int objnum)
{
        object  *objp, *objp2, *farthest_objp;
        ship_obj        *so;
        float           farthest_dist;

        objp2 = &Objects[objnum];

        farthest_dist = 9999999.9f;
        farthest_objp = NULL;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                objp = &Objects[so->objnum];
                if ( !(objp->flags & OF_PLAYER_SHIP)) {
                        if (objp->instance != -1) {
                                ai_info *aip2;

                                aip2 = &Ai_info[Ships[objp->instance].ai_index];

                                if ((aip2->mode == AIM_CHASE) && (aip2->target_objnum == objnum)) {
                                        if (Ships[objp->instance].team != Ships[Objects[objnum].instance].team) {
                                                float   dist;

                                                dist = vm_vec_dist_quick(&objp->pos, &objp2->pos);
                                                if (dist < farthest_dist) {
                                                        farthest_dist = dist;
                                                        farthest_objp = objp;
                                                }
                                        }
                                }
                        }
                }
        }

        if (farthest_objp != NULL) {
                ai_info *aip;
                Assert(farthest_objp->type == OBJ_SHIP);
                Assert((farthest_objp->instance > -1) && (farthest_objp->instance < MAX_SHIPS));
                Assert(Ships[farthest_objp->instance].ai_index > -1);

                aip = &Ai_info[Ships[farthest_objp->instance].ai_index];

                if (!maybe_resume_previous_mode(Pl_objp, aip)) {
                        //      If already ignoring something under player's orders, don't ignore current target.
                        if ((aip->ignore_objnum == UNUSED_OBJNUM) || (aip->ai_flags & AIF_TEMPORARY_IGNORE)) {
                                aip->ignore_objnum = aip->target_objnum;
                                aip->ignore_signature = Objects[aip->target_objnum].signature;
                                aip->ai_flags |= AIF_TEMPORARY_IGNORE;
                                aip->ignore_expire_timestamp = timestamp(((myrand() % 10) + 20) * 1000);        //      OK to attack again in 20 to 24 seconds.
                        }
                        aip->target_objnum = -1;
                        ai_do_default_behavior(farthest_objp);
                }
        }
}

// Maybe limit the number of attackers on attack_objnum.  For now, only limit attackers
// in attacked_objnum is the player
// input:       attacked_objnum =>              object index for ship we want to limit attacks on
//
//      exit:                   1       =>      num attackers exceeds maximum, abort
//                                      0       =>      removed the farthest attacker
//                                      -1      =>      nothing was done
int ai_maybe_limit_attackers(int attacked_objnum)
{
        int rval=-1;

        // limit the number of ships attacking the _player_ only
//      if ( attacked_objnum == OBJ_INDEX(Player_obj) ) {
        if ( Objects[attacked_objnum].flags & OF_PLAYER_SHIP) {
                int num_attacking;
                num_attacking = num_ships_attacking(attacked_objnum);

                if (num_attacking == Skill_level_max_attackers[Game_skill_level]) {
                        remove_farthest_attacker(attacked_objnum);
                        rval=0;
                } else if (num_attacking > Skill_level_max_attackers[Game_skill_level]) {
                        rval=1;
                }
                //nprintf(("AI", "Num attacking player = %i\n", num_attacking));
        }

        return rval;
}

//      Object being guarded by object *guard_objp was hit by object *hitter_objp
void guard_object_was_hit(object *guard_objp, object *hitter_objp)
{
        int             hitter_objnum;
        ai_info *aip;

        aip = &Ai_info[Ships[guard_objp->instance].ai_index];

        if (guard_objp == hitter_objp) {
                // Int3();      //      Bogus!  Who tried to get me to attack myself!  Trace out and fix!
                return;
        }

        if (guard_objp->type == OBJ_GHOST || hitter_objp->type == OBJ_GHOST)
                return;

        if (aip->ai_flags & AIF_NO_DYNAMIC)     //      Not allowed to pursue dynamic goals.  So, why are we guarding?
                return;

        Assert( (hitter_objp->type == OBJ_SHIP) || (hitter_objp->type == OBJ_ASTEROID) || (hitter_objp->type == OBJ_WEAPON) );

        hitter_objnum = OBJ_INDEX(hitter_objp);

        if ( hitter_objp->type == OBJ_SHIP ) {
                //      If the hitter object is the ignore object, don't attack it.
                if (is_ignore_object(aip, hitter_objp-Objects))
                        return;

                //      If hitter is on same team as me, don't attack him.
                if (Ships[guard_objp->instance].team == Ships[hitter_objp->instance].team)
                        return;

                // limit the number of ships attacking hitter_objnum (for now, only if hitter_objnum is player)
                if ( ai_maybe_limit_attackers(hitter_objnum) == 1 ) {
                        return;
                }

                // dont attack if you can't see him
                if ( awacs_get_level(hitter_objp, &Ships[aip->shipnum], 1) < 1 ) {
                        // if he's a stealth and visible, but not targetable, ok to attack.
                        if ( is_object_stealth_ship(hitter_objp) ) {
                                if ( ai_is_stealth_visible(guard_objp, hitter_objp) != STEALTH_VISIBLE ) {
                                        return;
                                }
                        }
                }
        }

        if (aip->target_objnum == -1) {
                aip->ok_to_target_timestamp = timestamp(0);
        }

        if ((aip->submode == AIS_GUARD_PATROL) || (aip->submode == AIS_GUARD_STATIC)) {

                if ( hitter_objp->type == OBJ_SHIP ) {
                        if (!(Ship_info[Ships[guard_objp->instance].ship_info_index].flags & SIF_SMALL_SHIP)) {
                                return;
                        }

                        // limit the number of ships attacking hitter_objnum (for now, only if hitter_objnum is player)
                        if ( ai_maybe_limit_attackers(hitter_objnum) == 1 ) {
                                return;
                        }
                }

                if (aip->target_objnum != hitter_objnum) {
                        aip->aspect_locked_time = 0.0f;
                }

                aip->ok_to_target_timestamp = timestamp(0);

                set_target_objnum(aip, hitter_objnum);
                //if (aip->target_objnum == -1) nprintf(("AI", "Frame %i: Attacking NONE\n",Framecount)); else nprintf(("AI", "Frame %i: Attacking %s\n", Framecount, Ships[Objects[aip->target_objnum].instance].ship_name));
                aip->previous_mode = AIM_GUARD;
                aip->previous_submode = aip->submode;
                aip->mode = AIM_CHASE;
                aip->submode = SM_ATTACK;
                aip->submode_start_time = Missiontime;
                aip->active_goal = AI_ACTIVE_GOAL_DYNAMIC;
        } else if (aip->previous_mode == AIM_GUARD) {
                if (aip->target_objnum == -1) {

                        if ( hitter_objp->type == OBJ_SHIP ) {
                                // limit the number of ships attacking hitter_objnum (for now, only if hitter_objnum is player)
                                if ( ai_maybe_limit_attackers(hitter_objnum) == 1 ) {
                                        return;
                                }
                        }

                        set_target_objnum(aip, hitter_objnum);
                //if (aip->target_objnum == -1) nprintf(("AI", "Frame %i: Attacking NONE\n",Framecount)); else nprintf(("AI", "Frame %i: Attacking %s\n", Framecount, Ships[Objects[aip->target_objnum].instance].ship_name));
                        aip->mode = AIM_CHASE;
                        aip->submode = SM_ATTACK;
                        aip->submode_start_time = Missiontime;
                        aip->active_goal = AI_ACTIVE_GOAL_DYNAMIC;
                } else {
                        int     num_attacking_cur, num_attacking_new;

                        num_attacking_cur = num_ships_attacking(aip->target_objnum);
                        if (num_attacking_cur > 1) {
                                num_attacking_new = num_ships_attacking(hitter_objnum);

                                if (num_attacking_new < num_attacking_cur) {

                                        if ( hitter_objp->type == OBJ_SHIP ) {
                                                // limit the number of ships attacking hitter_objnum (for now, only if hitter_objnum is player)
                                                if ( ai_maybe_limit_attackers(hitter_objnum) == 1 ) {
                                                        return;
                                                }
                                        }
                                        set_target_objnum(aip, hitter_objp-Objects);
                //if (aip->target_objnum == -1) nprintf(("AI", "Frame %i: Attacking NONE\n",Framecount)); else nprintf(("AI", "Frame %i: Attacking %s\n", Framecount, Ships[Objects[aip->target_objnum].instance].ship_name));
                                        aip->mode = AIM_CHASE;
                                        aip->submode = SM_ATTACK;
                                        aip->submode_start_time = Missiontime;
                                        aip->active_goal = AI_ACTIVE_GOAL_DYNAMIC;
                                }
                        }
                }
        }
}

//      Ship object *hit_objp was hit by ship object *hitter_objp.
//      See if anyone is guarding hit_objp and, if so, do something useful.
void maybe_update_guard_object(object *hit_objp, object *hitter_objp)
{
        object  *objp;
        ship_obj        *so;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                objp = &Objects[so->objnum];
                if (objp->instance != -1) {
                        ai_info *aip;
                        aip = &Ai_info[Ships[objp->instance].ai_index];

                        if ((aip->mode == AIM_GUARD) || (aip->active_goal == AI_ACTIVE_GOAL_DYNAMIC)) {
                                if (aip->guard_objnum == hit_objp-Objects) {
                                        guard_object_was_hit(objp, hitter_objp);
                                } else if ((aip->guard_wingnum != -1) && (aip->guard_wingnum == Ai_info[Ships[hit_objp->instance].ai_index].wing)) {
                                        guard_object_was_hit(objp, hitter_objp);
                                }
                        }
                }
        }
}

// Scan missile list looking for bombs homing on guarded_objp
// return 1 if bomb is found (and targeted by guarding_objp), otherwise return 0
int ai_guard_find_nearby_bomb(object *guarding_objp, object *guarded_objp)
{       
        missile_obj     *mo;
        object          *bomb_objp, *closest_bomb_objp=NULL;
        float                   dist, dist_to_guarding_obj,closest_dist_to_guarding_obj=999999.0f;
        weapon          *wp;
        weapon_info     *wip;

        for ( mo = GET_NEXT(&Missile_obj_list); mo != END_OF_LIST(&Missile_obj_list); mo = GET_NEXT(mo) ) {
                Assert(mo->objnum >= 0 && mo->objnum < MAX_OBJECTS);
                bomb_objp = &Objects[mo->objnum];

                wp = &Weapons[bomb_objp->instance];
                wip = &Weapon_info[wp->weapon_info_index];

                if ( !(wip->wi_flags & WIF_BOMB) ) {
                        continue;
                }

                if ( wp->homing_object != guarded_objp ) {
                        continue;
                }

                dist = vm_vec_dist_quick(&bomb_objp->pos, &guarded_objp->pos);

                if (dist < (MAX_GUARD_DIST + guarded_objp->radius)*3) {
                        dist_to_guarding_obj = vm_vec_dist_quick(&bomb_objp->pos, &guarding_objp->pos);
                        if ( dist_to_guarding_obj < closest_dist_to_guarding_obj ) {
                                closest_dist_to_guarding_obj = dist_to_guarding_obj;
                                closest_bomb_objp = bomb_objp;
                        }
                }
        }

        if ( closest_bomb_objp ) {
                guard_object_was_hit(guarding_objp, closest_bomb_objp);
                return 1;
        }

        return 0;
}

//      Scan enemy ships and see if one is near enough to guard object to be pursued.
void ai_guard_find_nearby_ship(object *guarding_objp, object *guarded_objp)
{
        ship            *guarding_shipp = &Ships[guarding_objp->instance];
        ai_info *guarding_aip = &Ai_info[guarding_shipp->ai_index];
        ship_obj        *so;
        object  *enemy_objp;
        float           dist;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                enemy_objp = &Objects[so->objnum];

                if (enemy_objp->instance < 0) {
                        continue;
                }

                ship    *eshipp = &Ships[enemy_objp->instance];

                //      Don't attack a cargo container or other harmless ships
                if (!(Ship_info[eshipp->ship_info_index].flags & SIF_HARMLESS)) {
                        if (guarding_shipp->team != eshipp->team)       {
                                dist = vm_vec_dist_quick(&enemy_objp->pos, &guarded_objp->pos);
                                if (dist < (MAX_GUARD_DIST + guarded_objp->radius)*3) {
                                        guard_object_was_hit(guarding_objp, enemy_objp);
                                } else if ((dist < 3000.0f) && (Ai_info[eshipp->ai_index].target_objnum == guarding_aip->guard_objnum)) {
                                        //nprintf(("AI", "%i: Enemy %s targeting guard object (%s), %s will attack!!\n", Framecount, eshipp->ship_name, Ships[Objects[guarding_aip->guard_objnum].instance].ship_name, guarding_shipp->ship_name));
                                        guard_object_was_hit(guarding_objp, enemy_objp);
                                }
                        }
                }
        }
}

// Scan for nearby asteroids.  Favor asteroids which have their collide_objnum set to that of the
// guarded ship.  Also, favor asteroids that are closer to the guarding ship, since it looks cooler
// when a ship blows up an asteroid then goes after the pieces that break off.
void ai_guard_find_nearby_asteroid(object *guarding_objp, object *guarded_objp)
{       
        float           dist;

        object  *closest_asteroid_objp=NULL, *danger_asteroid_objp=NULL, *asteroid_objp;
        float           dist_to_self, closest_danger_asteroid_dist=999999.0f, closest_asteroid_dist=999999.0f;

        for ( asteroid_objp = GET_FIRST(&obj_used_list); asteroid_objp != END_OF_LIST(&obj_used_list); asteroid_objp = GET_NEXT(asteroid_objp) ) {
                if ( asteroid_objp->type == OBJ_ASTEROID ) {
                        // Attack asteroid if near guarded ship
                        dist = vm_vec_dist_quick(&asteroid_objp->pos, &guarded_objp->pos);
                        if ( dist < (MAX_GUARD_DIST + guarded_objp->radius)*2) {
                                dist_to_self = vm_vec_dist_quick(&asteroid_objp->pos, &guarding_objp->pos);
                                if ( OBJ_INDEX(guarded_objp) == asteroid_collide_objnum(asteroid_objp) ) {
                                        if( dist_to_self < closest_danger_asteroid_dist ) {
                                                danger_asteroid_objp=asteroid_objp;
                                                closest_danger_asteroid_dist=dist_to_self;
                                        }
                                } 
                                if ( dist_to_self < closest_asteroid_dist ) {
                                        // only attack if moving slower than own max speed
                                        if ( vm_vec_mag_quick(&asteroid_objp->phys_info.vel) < guarding_objp->phys_info.max_vel.xyz.z ) {
                                                closest_asteroid_dist = dist_to_self;
                                                closest_asteroid_objp = asteroid_objp;
                                        }
                                }
                        }
                }
        }

        if ( danger_asteroid_objp ) {
                guard_object_was_hit(guarding_objp, danger_asteroid_objp);
        } else if ( closest_asteroid_objp ) {
                guard_object_was_hit(guarding_objp, closest_asteroid_objp);
        }
}

//      Scan potential harmful objects and see if one is near enough to guard object to be pursued.
void ai_guard_find_nearby_object()
{
        ship                    *shipp = &Ships[Pl_objp->instance];
        ai_info         *aip = &Ai_info[shipp->ai_index];
        object          *guardobjp;
        int                     bomb_found=0;

        guardobjp = &Objects[aip->guard_objnum];
        
        // highest priority is a bomb fired on guarded ship
        bomb_found = ai_guard_find_nearby_bomb(Pl_objp, guardobjp);

        if ( !bomb_found ) {
                // check for ships if there are no bombs fired at guarded ship
                ai_guard_find_nearby_ship(Pl_objp, guardobjp);

                // if not attacking anything, go for asteroid close to guarded ship
                if ( (aip->target_objnum == -1) && asteroid_count() ) {
                        ai_guard_find_nearby_asteroid(Pl_objp, guardobjp);
                }
        }
}

// gets closest point on extended axis of cylinder, r_vec, and radius of cylinder
// returns z of axis_point in cyl_objp reference frame
float get_cylinder_points(object *other_objp, object *cyl_objp, vector *axis_pt, vector *r_vec, float *radius)
{
        Assert(other_objp->type == OBJ_SHIP);
        Assert(cyl_objp->type == OBJ_SHIP);

        // get radius of cylinder
        polymodel *pm = model_get(Ships[cyl_objp->instance].modelnum);
        float tempx, tempy;
        tempx = max(-pm->mins.xyz.x, pm->maxs.xyz.x);
        tempy = max(-pm->mins.xyz.y, pm->maxs.xyz.y);
        *radius = max(tempx, tempy);

        // get vec from cylinder to other_obj
        vector r_sph;
        vm_vec_sub(&r_sph, &other_objp->pos, &cyl_objp->pos);

        // get point on axis and on cylinder
        // extended_cylinder_z is along extended cylinder
        // cylinder_z is capped within cylinder
        float extended_cylinder_z = vm_vec_dotprod(&r_sph, &cyl_objp->orient.v.fvec);

        // get pt on axis of extended cylinder
        vm_vec_scale_add(axis_pt, &cyl_objp->pos, &cyl_objp->orient.v.fvec, extended_cylinder_z);

        // get r_vec (pos - axis_pt) normalized
        vm_vec_normalized_dir(r_vec, &other_objp->pos, axis_pt);

        return extended_cylinder_z;
}

// handler for guard behavior when guarding BIG ships
//      When someone has attacked guarded ship, then attack that ship.
// To attack another ship, switch out of guard mode into chase mode.
void ai_big_guard()
{
        
        ship                    *shipp = &Ships[Pl_objp->instance];
        ai_info         *aip = &Ai_info[shipp->ai_index];
        object          *guard_objp;

        // sanity checks already done in ai_guard()
        guard_objp = &Objects[aip->guard_objnum];

        switch (aip->submode) {
        case AIS_GUARD_STATIC:
        case AIS_GUARD_PATROL:
                {
                vector axis_pt, r_vec, theta_vec;
                float radius, extended_z;

                // get random [0 to 1] based on OBJNUM
                float objval = static_randf(Pl_objp-Objects);

                // get position relative to cylinder of guard_objp              
                extended_z = get_cylinder_points(Pl_objp, guard_objp, &axis_pt, &r_vec, &radius);
                vm_vec_crossprod(&theta_vec, &guard_objp->orient.v.fvec, &r_vec);

                // half ships circle each way
                if (objval > 0.5f) {
                        vm_vec_negate(&theta_vec);
                }

                float min_guard_dist = radius + Pl_objp->radius + 50.0f;
                float desired_guard_dist = min_guard_dist + 0.5f * ((1.0f + objval) * MAX_GUARD_DIST);
                float max_guard_dist =     min_guard_dist + 1.0f * ((1.0f + objval) * MAX_GUARD_DIST);

                // get z extents
                float min_z, max_z, length;
                polymodel *pm = model_get(Ships[guard_objp->instance].modelnum);
                min_z = pm->mins.xyz.z;
                max_z = pm->maxs.xyz.z;
                length = max_z - min_z;

                // get desired z
                // how often to choose new desired_z
                // 1*(64) sec < 2000, 2*(64) < 2-4000 3*(64) > 4-8000, etc (Missiontime >> 22 is 64 sec intervals)
                int time_choose = int(floor(log(length * 0.001) / log(2)));
                float desired_z = min_z + length * static_randf( Pl_objp-Objects ^ (Missiontime >> (22 + time_choose)) );

                // get r from guard_ship
                float cur_guard_rad = vm_vec_dist(&Pl_objp->pos, &axis_pt);

                // is ship within extents of cylinder of ship it is guarding
                int inside = (extended_z > min_z) && (extended_z < min_z + length);

                vector goal_pt;
                // maybe go into orbit mode
                if (cur_guard_rad < max_guard_dist) {
                        if ( cur_guard_rad > min_guard_dist ) {
                                if (inside) {
                                        // orbit
                                        vm_vec_scale_add(&goal_pt, &axis_pt, &r_vec, desired_guard_dist);
                                        vm_vec_scale_add2(&goal_pt, &theta_vec, desired_guard_dist);
                                } else {
                                        // move to where I can orbit
                                        if (extended_z < min_z) {
                                                vm_vec_scale_add(&goal_pt, &guard_objp->pos, &guard_objp->orient.v.fvec, min_z);
                                        } else {
                                                vm_vec_scale_add(&goal_pt, &guard_objp->pos, &guard_objp->orient.v.fvec, max_z);
                                        }
                                        vm_vec_scale_add2(&goal_pt, &r_vec, desired_guard_dist);
                                        vm_vec_scale_add2(&goal_pt, &theta_vec, desired_guard_dist);
                                }
                        } else {
                                // too close for orbit mode
                                if (inside) {
                                        // inside (fly straight out and return circle)
                                        vm_vec_scale_add(&goal_pt, &axis_pt, &r_vec, max_guard_dist);
                                } else {
                                        // outside (fly to edge and circle)
                                        if (extended_z < min_z) {
                                                vm_vec_scale_add(&goal_pt, &guard_objp->pos, &guard_objp->orient.v.fvec, min_z);
                                        } else {
                                                vm_vec_scale_add(&goal_pt, &guard_objp->pos, &guard_objp->orient.v.fvec, max_z);
                                        }
                                        vm_vec_scale_add2(&goal_pt, &r_vec, max_guard_dist);
                                        vm_vec_scale_add2(&goal_pt, &theta_vec, desired_guard_dist);
                                }
                        }

                        if (Pl_objp->phys_info.fspeed > 0) {
                                // modify goal_pt to take account moving guard objp
                                float dist = vm_vec_dist_quick(&Pl_objp->pos, &goal_pt);
                                float time = dist / Pl_objp->phys_info.fspeed;
                                vm_vec_scale_add2(&goal_pt, &guard_objp->phys_info.vel, time);

                                // now modify to move to desired z (at a max of 20 m/s)
                                float delta_z = desired_z - extended_z;
                                float v_z = delta_z * 0.2f;
                                if (v_z < -20) {
                                        v_z = -20.0f;
                                } else if (v_z > 20) {
                                        v_z = 20.0f;
                                }

                                vm_vec_scale_add2(&goal_pt, &guard_objp->orient.v.fvec, v_z*time);
                        }

                } else {
                        // cast vector to center of guard_ship adjusted by desired_z
                        float delta_z = desired_z - extended_z;
                        vm_vec_scale_add(&goal_pt, &guard_objp->pos, &guard_objp->orient.v.fvec, delta_z);
                }

                // try not to bump into things along the way
                if ( (cur_guard_rad > max_guard_dist) || (extended_z < min_z) || (extended_z > max_z) ) {
                        if (maybe_avoid_big_ship(Pl_objp, guard_objp, aip, &goal_pt, 5.0f)) {
                                return;
                        }

                        if (avoid_player(Pl_objp, &goal_pt)) {
                                return;
                        }
                } else {
                        if (maybe_avoid_big_ship(Pl_objp, guard_objp, aip, &goal_pt, 5.0f)) {
                                return;
                        }
                }

                // got the point, now let's go there
                ai_turn_towards_vector(&goal_pt, Pl_objp, flFrametime, Ship_info[Ships[Pl_objp->instance].ship_info_index].srotation_time, NULL, NULL, 0.0f, 0);
//              aip->goal_point = goal_pt;
                accelerate_ship(aip, 1.0f);

                //      Periodically, scan for a nearby ship to attack.
                if (((AI_FrameCount ^ (Pl_objp-Objects)) & 0x07) == 0) {
                        ai_guard_find_nearby_object();
                }
                }
                break;

        case AIS_GUARD_ATTACK:
                //      The guarded ship has been attacked.  Do something useful!
                ai_chase();
                break;

        default:
                //Int3();       //      Illegal submode for Guard mode.
                // AL 06/03/97 comment out Int3() to allow milestone to get out the door
                aip->submode = AIS_GUARD_PATROL;
                break;
        }
}

//      Main handler for guard behavior.
//      When someone has attacked guarded ship, then attack that ship.
// To attack another ship, switch out of guard mode into chase mode.
void ai_guard()
{
        ship                    *shipp = &Ships[Pl_objp->instance];
        ai_info         *aip = &Ai_info[shipp->ai_index];
        object          *guard_objp;    
        ship                    *gshipp;
        float                   dist_to_guardobj, dot_to_guardobj;
        vector          vec_to_guardobj;

        /*      //      Debug code, find an object to guard.
        int finding_guard_objnum = 0;   //      Debug code, to see if body of "if" below gets executed. 
        if (aip->guard_objnum == -1) {
                finding_guard_objnum = 1;
                debug_find_guard_object();
                if (aip->guard_objnum == -1)
                        return;
        }
*/
        if (aip->guard_objnum == -1) {
                aip->mode = AIM_NONE;
                return;
        }

        Assert(aip->guard_objnum != -1);

        guard_objp = &Objects[aip->guard_objnum];

        if (guard_objp == Pl_objp) {
                Int3();         //      This seems illegal.  Why is a ship guarding itself?
                aip->guard_objnum = -1;
                return;
        }

        // check that I have someone to guard
        if (guard_objp->instance == -1) {
                return;
        }

        //      Not sure whether this should be impossible, or a reasonable cleanup condition.
        //      For now (3/31/97), it's getting trapped by an Assert, so clean it up.
        if (guard_objp->type != OBJ_SHIP) {
                aip->guard_objnum = -1;
                return;
        }

        // handler for gurad object with BIG radius
        if (guard_objp->radius > BIG_GUARD_RADIUS) {
                ai_big_guard();
                return;
        }

        gshipp = &Ships[guard_objp->instance];

        float                   objval;
        vector          goal_point;
        vector          rel_vec;
        float                   dist_to_goal_point, dot_to_goal_point, accel_scale;
        vector          v2g, rvec;

        // get random [0 to 1] based on OBJNUM
        objval = static_randf(Pl_objp-Objects);

        switch (aip->submode) {
        case AIS_GUARD_STATIC:
        case AIS_GUARD_PATROL:
                //      Stay near ship
                dist_to_guardobj = vm_vec_normalized_dir(&vec_to_guardobj, &guard_objp->pos, &Pl_objp->pos);
                dot_to_guardobj = vm_vec_dot(&Pl_objp->orient.v.fvec, &vec_to_guardobj);

                rel_vec = aip->guard_vec;
                vm_vec_add(&goal_point, &guard_objp->pos, &rel_vec);

                vm_vec_normalized_dir(&v2g, &goal_point, &Pl_objp->pos);
                dist_to_goal_point = vm_vec_dist_quick(&goal_point, &Pl_objp->pos);
                dot_to_goal_point = vm_vec_dot(&v2g, &Pl_objp->orient.v.fvec);
                accel_scale = (1.0f + dot_to_goal_point)/2.0f;

                //      If far away, get closer
                if (dist_to_goal_point > MAX_GUARD_DIST + 1.5 * (Pl_objp->radius + guard_objp->radius)) {
                        if (maybe_avoid_big_ship(Pl_objp, guard_objp, aip, &goal_point, 5.0f)) {
                                return;
                        }

                        if (avoid_player(Pl_objp, &goal_point)) {
                                return;
                        }

                        // quite far away, so try to go straight to 
                        compute_desired_rvec(&rvec, &goal_point, &Pl_objp->pos);
                        ai_turn_towards_vector(&goal_point, Pl_objp, flFrametime, Ship_info[shipp->ship_info_index].srotation_time, NULL, NULL, 0.0f, 0, &rvec);

                        accelerate_ship(aip, accel_scale * (0.25f + dist_to_goal_point/700.0f));
                } else {
                        if (maybe_avoid_big_ship(Pl_objp, guard_objp, aip, &goal_point, 2.0f)) {
                                return;
                        }

                        // get max of guard_objp (1) normal speed (2) dock speed
                        float speed = guard_objp->phys_info.speed;

                        if (guard_objp->type == OBJ_SHIP) {
                                ai_info *guard_aip = &Ai_info[Ships[guard_objp->instance].ai_index];

                                if (guard_aip->dock_objnum != -1) {
                                        speed = max(speed, Objects[guard_aip->dock_objnum].phys_info.speed);
                                }
                        }
                        
                        //      Deal with guarding a small object.
                        //      If going to guard_vec might cause a collision with guarded object, pick a new guard point.
                        if (vm_vec_dot(&v2g, &vec_to_guardobj) > 0.8f) {
                                if (dist_to_guardobj < dist_to_goal_point) {
                                        ai_set_guard_vec(Pl_objp, guard_objp);  //      OK to return here.
                                        return;
                                }
                        } 

                        if (speed > 10.0f) {
                                //      If goal ship is moving more than a tiny bit, don't orbit it, get near it.
                                if (vm_vec_dist_quick(&goal_point, &Pl_objp->pos) > 40.0f) {
                                        if (vm_vec_dot(&Pl_objp->orient.v.fvec, &v2g) < 0.0f) {
                                                //      Just slow down, don't turn.
                                                set_accel_for_target_speed(Pl_objp, guard_objp->phys_info.speed - dist_to_goal_point/10.0f);
                                        } else {
                                                //      Goal point is in front.

                                                //      If close to goal point, don't change direction, just change speed.
                                                if (dist_to_goal_point > Pl_objp->radius + 10.0f) {
                                                        turn_towards_point(Pl_objp, &goal_point, NULL, 0.0f);
                                                }
                                                
                                                set_accel_for_target_speed(Pl_objp, guard_objp->phys_info.speed + (dist_to_goal_point-40.0f)/20.0f);
                                        }
                                } else {
                                        if (dot_to_goal_point > 0.8f) {
                                                turn_towards_point(Pl_objp, &goal_point, NULL, 0.0f);
                                                set_accel_for_target_speed(Pl_objp, guard_objp->phys_info.speed + dist_to_goal_point*0.1f);
                                        } else {
                                                set_accel_for_target_speed(Pl_objp, guard_objp->phys_info.speed - dist_to_goal_point*0.1f - 1.0f);
                                        }
                                }
                        // consider guard object STILL
                        } else if (guard_objp->radius < 50.0f) {
                                if (dist_to_goal_point > 15.0f) {
                                        turn_towards_point(Pl_objp, &goal_point, NULL, 0.0f);
                                        set_accel_for_target_speed(Pl_objp, (dist_to_goal_point-10.0f)/2.0f);
                                } else if (Pl_objp->phys_info.speed < 1.0f) {
                                        turn_away_from_point(Pl_objp, &guard_objp->pos, 0.0f);
                                }
                                //      It's a big ship
                        } else if (dist_to_guardobj > MAX_GUARD_DIST + Pl_objp->radius + guard_objp->radius) {
                                //      Orbiting ship, too far away
                                float dot = turn_towards_tangent(Pl_objp, &guard_objp->pos, (1.0f + objval/2) * guard_objp->radius);
                                accelerate_ship(aip, (1.0f + dot)/2.0f);
                        } else if (dist_to_guardobj < Pl_objp->radius + guard_objp->radius) {
                                //      Orbiting ship, got too close
                                turn_away_from_point(Pl_objp, &guard_objp->pos, 0.0f);
                                if ((dist_to_guardobj > guard_objp->radius + Pl_objp->radius + 50.0f) && (guard_objp->phys_info.speed > Pl_objp->phys_info.speed - 1.0f))
                                        change_acceleration(aip, 0.25f);
                                else
                                        accelerate_ship(aip, 0.5f + objval/4.0f);
                        } else {
                                //      Orbiting ship, about the right distance away.
                                float dot = turn_towards_tangent(Pl_objp, &guard_objp->pos, (1.5f + objval/2.0f)*guard_objp->radius);
                                if ((dist_to_guardobj > guard_objp->radius + Pl_objp->radius + 50.0f) && (guard_objp->phys_info.speed > Pl_objp->phys_info.speed - 1.0f))
                                        set_accel_for_target_speed(Pl_objp, (0.5f * (1.0f + dot)) * (guard_objp->phys_info.speed + (dist_to_guardobj - guard_objp->radius - Pl_objp->radius)/10.0f));
                                else
                                        accelerate_ship(aip, 0.5f * (1.0f + dot) * (0.3f + objval/3.0f));
                        }
                }

                //      Periodically, scan for a nearby ship to attack.
                if (((AI_FrameCount ^ (Pl_objp-Objects)) & 0x07) == 0) {
                        ai_guard_find_nearby_object();
                }
                break;

        case AIS_GUARD_ATTACK:
                //      The guarded ship has been attacked.  Do something useful!
                ai_chase();

                break;
        default:
                //Int3();       //      Illegal submode for Guard mode.
                // AL 06/03/97 comment out Int3() to allow milestone to get out the door
                aip->submode = AIS_GUARD_PATROL;
                break;
        }

}

// Return the object of the ship that the given object is docked
// with.  Currently, we know a ship is docked when his ai_mode is AIM_DOCK,
// and his submode is AIS_DOCK_3.  I suppose that this is likely to change though.
// Also, the objnum that was is passed in may not be the object that actually
// performed the docking maneuver.  This code will account for that case.
object *ai_find_docked_object( object *docker )
{
        ai_info *aip;

        // we are trying to find the dockee of docker.  (Note that that these terms
        // are totally relative to what is passed in as a parameter.)

        // first thing to attempt is to check and see if this object is docked with something.
        Assert( docker->type == OBJ_SHIP );             // this had probably better be a ship!!!
        aip = &Ai_info[Ships[docker->instance].ai_index];
        if ( !(aip->ai_flags & AIF_DOCKED) )            // flag not set if not docked with anything
                return NULL;

        if ( aip->dock_objnum == -1 ) {
                Int3();                                                                                 // mwa says this is wrong wrong wrong
                ai_do_objects_undocked_stuff( docker, NULL );
                return NULL;
        }

        return &Objects[aip->dock_objnum];

}


// define for the points subtracted from score for a rearm started on a player.
#define REPAIR_PENALTY          50


// function to clean up ai flags, variables, and other interesting information
// for a ship that was getting repaired.  The how parameter is useful for multiplayer
// only in that it tells us why the repaired ship is being cleaned up.
void ai_do_objects_repairing_stuff( object *repaired_objp, object *repair_objp, int how )
{
        ai_info *aip, *repair_aip;
        int             stamp = -1;

        Assert( repaired_objp->type == OBJ_SHIP);
        aip = &Ai_info[Ships[repaired_objp->instance].ai_index];

        // multiplayer
        int p_index;
        p_index = -1;
        if(Game_mode & GM_MULTIPLAYER){
                p_index = multi_find_player_by_object(repaired_objp);           
        }               
        else {          
                if(repaired_objp == Player_obj){
                        p_index = Player_num;
                }
        }

        switch( how ) {
        case REPAIR_INFO_BEGIN:
                aip->ai_flags |= AIF_BEING_REPAIRED;
                aip->ai_flags &= ~AIF_AWAITING_REPAIR;
                stamp = timestamp(-1);

                // if this is a player ship, then subtract the repair penalty from this player's score
                if ( repaired_objp->flags & OF_PLAYER_SHIP ) {
                        if ( !(Game_mode & GM_MULTIPLAYER) ) {
                                Player->stats.m_score -= (int)(REPAIR_PENALTY * scoring_get_scale_factor());                    // subtract the penalty
                        } else {
                                /*
                                int pnum;

                                // multiplayer game -- find the player, then subtract the score
                                pnum = multi_find_player_by_object( repaired_objp );
                                if ( pnum != -1 ) {
                                        Net_players[pnum].player->stats.m_score -= (int)(REPAIR_PENALTY * scoring_get_scale_factor());

                                        // squad war
                                        multi_team_maybe_add_score(-(int)(REPAIR_PENALTY * scoring_get_scale_factor()), Net_players[pnum].p_info.team);
                                } else {
                                        nprintf(("Network", "Couldn't find player for ship %s for repair penalty\n", Ships[repaired_objp->instance].ship_name));
                                }
                                */
                        }
                }
                break;

        case REPAIR_INFO_BROKEN:
                aip->ai_flags &= ~AIF_BEING_REPAIRED;
                aip->ai_flags |= AIF_AWAITING_REPAIR;
                stamp = timestamp((int) ((30 + 10*frand()) * 1000));
                break;

        case REPAIR_INFO_END:
                // when only awaiting repair, and the repair is ended, then set dock_objnum to -1.
                if ( aip->ai_flags & AIF_AWAITING_REPAIR ){
                        aip->dock_objnum = -1;
                }
                aip->ai_flags &= ~(AIF_AWAITING_REPAIR | AIF_BEING_REPAIRED );
                stamp = timestamp((int) ((30 + 10*frand()) * 1000));
                break;

        case REPAIR_INFO_QUEUE:
                aip->ai_flags |= AIF_AWAITING_REPAIR;
                if ( aip == Player_ai ){
                        hud_support_view_start();
                }
                stamp = timestamp(-1);
                break;

        case REPAIR_INFO_ABORT:
        case REPAIR_INFO_KILLED:
                // 5/4/98 -- MWA -- Need to set dock objnum to -1 to let code know this guy who was getting
                // repaired (or queued for repair), isn't really going to be docked with anyone anymore.
                aip->dock_objnum = -1;
                aip->ai_flags &= ~AIF_DOCKED;
                aip->ai_flags &= ~(AIF_AWAITING_REPAIR | AIF_BEING_REPAIRED );
                if (repair_objp != NULL) {
                        repair_aip = &Ai_info[Ships[repair_objp->instance].ai_index];
                        repair_aip->ai_flags &= ~(AIF_AWAITING_REPAIR | AIF_BEING_REPAIRED );
                }               

                if ( p_index >= 0 ) {
                        hud_support_view_abort();

                        // send appropriate message to player here
                        if ( how == REPAIR_INFO_KILLED ){
                                message_send_builtin_to_player( MESSAGE_SUPPORT_KILLED, NULL, MESSAGE_PRIORITY_HIGH, MESSAGE_TIME_SOON, 0, 0, p_index, -1 );
                        } else {
                                if ( repair_objp ){
                                        message_send_builtin_to_player( MESSAGE_REPAIR_ABORTED, &Ships[repair_objp->instance], MESSAGE_PRIORITY_NORMAL, MESSAGE_TIME_SOON, 0, 0, p_index, -1 );
                                }
                        }
                }

                // add log entry if this is a player
                if ( repaired_objp->flags & OF_PLAYER_SHIP ){
                        mission_log_add_entry(LOG_PLAYER_REARM_ABORT, Ships[repaired_objp->instance].ship_name, NULL);
                }

                stamp = timestamp((int) ((30 + 10*frand()) * 1000));
                break;

        case REPAIR_INFO_COMPLETE:
                // clear the being repaired flag -- and 
                if ( p_index >= 0 ) {
                        Assert( repair_objp );
                        
                        hud_support_view_stop();                        

                        message_send_builtin_to_player(MESSAGE_REPAIR_DONE, &Ships[repair_objp->instance], MESSAGE_PRIORITY_LOW, MESSAGE_TIME_SOON, 0, 0, p_index, -1);
                }
                stamp = timestamp((int) ((30 + 10*frand()) * 1000));
                break;

        case REPAIR_INFO_ONWAY:
                // need to set the dock_signature so that clients in multiplayer games rearm correctly
                Assert( repair_objp );
                aip->dock_signature = repair_objp->signature; 
                aip->dock_objnum = OBJ_INDEX(repair_objp);
                stamp = timestamp(-1);
                break;

        default:
                Int3();                 // bogus type of repair info
        }

        if (repair_objp){
                Ai_info[Ships[repair_objp->instance].ai_index].warp_out_timestamp = stamp;
        }

        // repair_objp might be NULL is we are cleaning up this mode because of the support ship
        // getting killed.
        if ( repair_objp ) {
                aip = &Ai_info[Ships[repair_objp->instance].ai_index];
                switch ( how ) {
                case REPAIR_INFO_ONWAY:
                        Assert( repaired_objp != NULL );
                        aip->goal_objnum = OBJ_INDEX(repaired_objp);
                        aip->ai_flags |= AIF_REPAIRING;
                        break;

                case REPAIR_INFO_BROKEN:
                        break;

                case REPAIR_INFO_END:
                case REPAIR_INFO_ABORT:
                case REPAIR_INFO_KILLED:
                        if ( how == REPAIR_INFO_ABORT )
                                aip->goal_objnum = -1;

                        aip->ai_flags &= ~AIF_REPAIRING;
                        break;
                        
                case REPAIR_INFO_QUEUE:
                        ai_add_rearm_goal( repaired_objp, repair_objp );
                        break;

                case REPAIR_INFO_BEGIN:
                case REPAIR_INFO_COMPLETE:
                        break;

                default:
                        Int3();         // bogus type of repair info
                }
        }

        multi_maybe_send_repair_info( repaired_objp, repair_objp, how );
}

//      Cleanup AI stuff for when a ship was supposed to dock with another, but the ship
//      it was supposed to dock with is no longer valid.
void ai_cleanup_dock_mode(ai_info *aip, ship *shipp)
{
        object *objp;

        objp = &Objects[shipp->objnum];
        aip->mode = AIM_NONE;

        if (aip->ai_flags & AIF_REPAIRING) {
                Assert( aip->goal_objnum != -1 );
                ai_do_objects_repairing_stuff( &Objects[aip->goal_objnum], &Objects[shipp->objnum], REPAIR_INFO_KILLED );
        } else if ( aip->ai_flags & AIF_BEING_REPAIRED ) {
                // MWA -- note that we have to use dock_objnum here instead of goal_objnum.
                Assert( aip->dock_objnum != -1 );
                ai_do_objects_repairing_stuff( &Objects[shipp->objnum], &Objects[aip->dock_objnum], REPAIR_INFO_KILLED );
        } else if ( aip->ai_flags & AIF_AWAITING_REPAIR ) {
                // need to find the support ship that has me as a goal_objnum
                // MWA -- note that we have to use dock_objnum here instead of goal_objnum.
                // MWA -- 3/38/98  Check to see if this guy is queued for a support ship, or there is already
                // one in the mission
                if ( mission_is_repair_scheduled(objp) ) {
                        mission_remove_scheduled_repair( objp );                        // this function will notify multiplayer clients.
                } else {
                        if ( aip->dock_objnum != -1 )
                                ai_do_objects_repairing_stuff( objp, &Objects[aip->dock_objnum], REPAIR_INFO_ABORT );
                        else
                                ai_do_objects_repairing_stuff( objp, NULL, REPAIR_INFO_ABORT );
                }
        }

        if ( aip->ai_flags & AIF_DOCKED ) {
                ai_info *other_aip;

                Assert( aip->dock_objnum != -1 );

                // if docked, and the dock_objnum is not undocking, force them to near last stage
                other_aip = &Ai_info[Ships[Objects[aip->dock_objnum].instance].ai_index];
                if ( (other_aip->mode == AIM_DOCK) && (other_aip->submode < AIS_UNDOCK_3) )
                        other_aip->submode = AIS_UNDOCK_3;
                ai_do_objects_undocked_stuff( objp, &Objects[aip->dock_objnum] );
        }
}

/*
//      Make dockee_objp shake a bit due to docking.
void ai_dock_shake(object *docker_objp, object *dockee_objp)
{
        vector  tangles;
        matrix  rotmat, tmp;
        float           scale;
        angles  *ap;

        scale = 0.25f;          //      Compute this based on mass and speed at time of docking.

        vm_vec_rand_vec_quick(&tangles);
        vm_vec_scale(&tangles, scale);

        ap = (angles *) &tangles;

        vm_angles_2_matrix(&rotmat, ap);
        vm_matrix_x_matrix( &tmp, &dockee_objp->orient, &rotmat );
        dockee_objp->orient = tmp;

        vm_orthogonalize_matrix(&dockee_objp->orient);

        dock_orient_and_approach(docker_objp, dockee_objp, DOA_DOCK_STAY);

}
*/

//      Make Pl_objp point at aip->goal_point.
void ai_still()
{
        ship    *shipp;
        ai_info *aip;

        Assert(Pl_objp->type == OBJ_SHIP);
        Assert((Pl_objp->instance >= 0) && (Pl_objp->instance < MAX_OBJECTS));

        shipp = &Ships[Pl_objp->instance];
        Assert((shipp->ai_index >= 0) && (shipp->ai_index < MAX_AI_INFO));

        aip = &Ai_info[shipp->ai_index];

        turn_towards_point(Pl_objp, &aip->goal_point, NULL, 0.0f);
}

//      Make *Pl_objp stay near another ship.
void ai_stay_near()
{
        ai_info *aip;
        int             goal_objnum;

        aip = &Ai_info[Ships[Pl_objp->instance].ai_index];

        goal_objnum = aip->goal_objnum;

        if ((goal_objnum < 0) || (Objects[goal_objnum].type != OBJ_SHIP) || (Objects[goal_objnum].signature != aip->goal_signature)) {
                aip->mode = AIM_NONE;
        } else {
                float           dist, max_dist, scale;
                vector  rand_vec, goal_pos, vec_to_goal;
                object  *goal_objp;

                goal_objp = &Objects[goal_objnum];

                //      Make not all ships pursue same point.
                static_randvec(Pl_objp-Objects, &rand_vec);

                //      Make sure point is in front hemisphere (relative to Pl_objp's position.
                vm_vec_sub(&vec_to_goal, &goal_objp->pos, &Pl_objp->pos);
                if (vm_vec_dot(&rand_vec, &vec_to_goal) > 1.0f) {
                        vm_vec_negate(&rand_vec);
                }

                //      Scale the random vector by an amount proportional to the distance from Pl_objp to the true goal.
                dist = vm_vec_dist_quick(&goal_objp->pos, &Pl_objp->pos);
                max_dist = aip->stay_near_distance;
                scale = dist - max_dist/2;
                if (scale < 0.0f)
                        scale = 0.0f;

                vm_vec_scale_add(&goal_pos, &goal_objp->pos, &rand_vec, scale);

                if (max_dist < Pl_objp->radius + goal_objp->radius + 25.0f)
                        max_dist = Pl_objp->radius + goal_objp->radius + 25.0f;

                if (dist > max_dist) {
                        turn_towards_point(Pl_objp, &goal_pos, NULL, 0.0f);
                        accelerate_ship(aip, dist / max_dist - 0.8f);
                }
        
        }

}

//      Warn player if dock path is obstructed.
int maybe_dock_obstructed(object *cur_objp, object *goal_objp, int big_only_flag)
{
        vector  *goalpos, *curpos;
        float           radius;
        ai_info *aip;
        int             collide_objnum;

        aip = &Ai_info[Ships[cur_objp->instance].ai_index];

        Ai_info[Ships[goal_objp->instance].ai_index].ai_flags &= ~AIF_REPAIR_OBSTRUCTED;

        if (goal_objp != Player_obj)
                return -1;

        curpos = &cur_objp->pos;
        radius = cur_objp->radius;
        goalpos = &Path_points[aip->path_cur].pos;
        collide_objnum = pp_collide_any(curpos, goalpos, radius, cur_objp, goal_objp, big_only_flag);

        if (collide_objnum != -1)
                Ai_info[Ships[goal_objp->instance].ai_index].ai_flags |= AIF_REPAIR_OBSTRUCTED;

        return collide_objnum;
}


int Dock_path_warning_given = 0;

//      Docking behavior.
//      Approach a ship, follow path to docking platform, approach platform, after awhile,
//      undock.
void ai_dock()
{
        ship                    *shipp = &Ships[Pl_objp->instance];
        ai_info         *aip = &Ai_info[shipp->ai_index];
        object          *goal_objp;
        ship_info       *sip = &Ship_info[shipp->ship_info_index];

        //      Make sure object we're supposed to dock with still exists.
        if ((aip->goal_objnum == -1) || (Objects[aip->goal_objnum].signature != aip->goal_signature)) {
                ai_cleanup_dock_mode(aip, shipp);
                return;
        }

        goal_objp = &Objects[aip->goal_objnum];

        //      For docking submodes (ie, not undocking), follow path.  Once at second last
        //      point on path (point just before point on dock platform), orient into position.
        // For undocking, first mode pushes docked ship straight back from docking point
        // second mode turns ship and moves to point on docking radius
        switch (aip->submode) {

                //      This mode means to find the path to the docking point.
        case AIS_DOCK_0:
                //aip->path_start = -1;
                //nprintf(("AI", "Time = %7.3f, submode = %i\n", f2fl(Missiontime), aip->submode));
                ai_path();
                if (!Dock_path_warning_given && (aip->path_length < 4)) {
                        Warning( LOCATION, "Ship '%s' has only %i points on dock path.  Docking will look strange.  Contact Adam.", shipp->ship_name, aip->path_length );
                        Dock_path_warning_given = 1;            //      This is on a mission-wide basis, but it's just a hack for now...
                }

                aip->submode = AIS_DOCK_1;
                aip->path_start = -1;
                aip->submode_start_time = Missiontime;
                break;

                //      This mode means to follow the path until just before the end.
        case AIS_DOCK_1: {
                float   dist;
                int     r;

                if ((r = maybe_dock_obstructed(Pl_objp, goal_objp, 1)) != -1) {
                        int     r1;
                        if ((r1 = maybe_avoid_big_ship(Pl_objp, goal_objp, aip, &goal_objp->pos, 7.0f)) != 0) {
                                nprintf(("AI", "Support ship %s avoiding large ship %s\n", Ships[Pl_objp->instance].ship_name, Ships[Objects[r1].instance].ship_name));
                                break;
                        } /*else {
                                nprintf(("AI", "Dock 1: Obstructed by %s\n", Ships[Objects[r].instance].ship_name));
                                accelerate_ship(aip, 0.0f);
                                aip->submode = AIS_DOCK_0;
                        } */
                } //else {
                {
                        dist = ai_path();
                        //nprintf(("AI", "Time = %7.3f, submode = %i\n", f2fl(Missiontime), aip->submode));
                        //nprintf(("AI", "Dock 1: Frame: %i, goal point = %i, dist = %7.3f\n", Framecount, aip->path_cur-aip->path_start, dist));

                        if (aip->path_cur-aip->path_start >= aip->path_length-1) {              //      If got this far, advance no matter what.
                                aip->submode = AIS_DOCK_2;
                                aip->submode_start_time = Missiontime;
                                aip->path_cur--;
                                Assert(aip->path_cur-aip->path_start >= 0);
                        } else if (aip->path_cur-aip->path_start >= aip->path_length-2) {
                                if (Pl_objp->phys_info.speed > goal_objp->phys_info.speed + 1.5f) {
                                        set_accel_for_target_speed(Pl_objp, goal_objp->phys_info.speed);
                                } else {
                                        aip->submode = AIS_DOCK_2;
                                        aip->submode_start_time = Missiontime;
                                }
                        }
                }
                break;
                                          }
        //      This mode means to drag oneself right to the second last point on the path.
        //      Path code allows it to overshoot.
        case AIS_DOCK_2: {
                float           dist;
                int     r;

                if ((r = maybe_dock_obstructed(Pl_objp, goal_objp,0)) != -1) {
                        nprintf(("AI", "Dock 2: Obstructed by %s\n", Ships[Objects[r].instance].ship_name));
                        accelerate_ship(aip, 0.0f);
                        aip->submode = AIS_DOCK_1;
                } else {
                        //nprintf(("AI", "Time = %7.3f, submode = %i\n", f2fl(Missiontime), aip->submode));
                        dist = dock_orient_and_approach(Pl_objp, &Objects[aip->goal_objnum], DOA_APPROACH);
                        Assert(dist != UNINITIALIZED_VALUE);

                        if (dist == DOCK_BACKUP_RETURN_VAL) {
                                int path_num;
                                aip->submode = AIS_DOCK_1;
                                path_num = ai_return_path_num_from_dockbay(&Objects[aip->goal_objnum], aip->dockee_index);
                                Assert(aip->goal_objnum >= 0 && aip->goal_objnum < MAX_OBJECTS);
                                ai_find_path(Pl_objp, aip->goal_objnum, path_num, 0);
                                break;
                        }

                        //nprintf(("AI", "Dock 2: dist = %7.3f\n", vm_vec_dist_quick(&Pl_objp->pos, &goal_point)));
                        float   tolerance;
                        if (Objects[aip->goal_objnum].flags & OF_PLAYER_SHIP)
                                tolerance = 6*flFrametime + 1.0f;
                        else
                                tolerance = 4*flFrametime + 0.5f;

                        if ( dist < tolerance) {
                                aip->submode = AIS_DOCK_3;
                                aip->submode_start_time = Missiontime;
                                aip->path_cur++;
                        }
                }
                break;
                                                  }

        case AIS_DOCK_3:
        case AIS_DOCK_3A:
                {
                Assert(aip->goal_objnum != -1);
                int     r;

                if ((r = maybe_dock_obstructed(Pl_objp, goal_objp,0)) != -1) {
                        nprintf(("AI", "Dock 1: Obstructed by %s\n", Ships[Objects[r].instance].ship_name));
                        accelerate_ship(aip, 0.0f);
                        aip->submode = AIS_DOCK_2;
                } else {

                        //nprintf(("AI", "Time = %7.3f, submode = %i\n", f2fl(Missiontime), aip->submode));
                        float dist = dock_orient_and_approach(Pl_objp, &Objects[aip->goal_objnum], DOA_DOCK);
                        Assert(dist != UNINITIALIZED_VALUE);

                        if (dist == DOCK_BACKUP_RETURN_VAL) {
                                aip->submode = AIS_DOCK_2;
                                break;
                        }

                        //nprintf(("AI", "Dock 3: dist = %7.3f\n", dist));

                        if (dist < 2*flFrametime * (1.0f + fl_sqrt(goal_objp->phys_info.speed))) {
                                // - Removed by MK on 11/7/97, causes errors for ships docked at mission start: maybe_recreate_path(Pl_objp, aip, 1);
                                dist = dock_orient_and_approach(Pl_objp, &Objects[aip->goal_objnum], DOA_DOCK);
                                Assert(dist != UNINITIALIZED_VALUE);

                                physics_ship_init(Pl_objp);

                                ai_do_objects_docked_stuff( Pl_objp, goal_objp );

                                if (aip->submode == AIS_DOCK_3) {
                                        snd_play_3d( &Snds[SND_DOCK_ATTACH], &Pl_objp->pos, &View_position );
                                        hud_maybe_flash_docking_text(Pl_objp);
                                        // ai_dock_shake(Pl_objp, goal_objp);

                                        if ((Pl_objp == Player_obj) || (goal_objp == Player_obj))
                                                joy_ff_docked();  // shake player's joystick a little
                                }

                                //      If this ship is repairing another ship...
                                if (aip->ai_flags & AIF_REPAIRING) {
                                        aip->submode = AIS_DOCK_4;                      //      Special rearming only dock mode.
                                        aip->submode_start_time = Missiontime;
                                } else {
                                        aip->submode = AIS_DOCK_4A;
                                        aip->submode_start_time = Missiontime;
                                }
                        }
                }
                break;
                }

                //      Yes, we just sit here.  We wait for further orders.  No, it's not a bug.
        case AIS_DOCK_4A:
                //nprintf(("AI", "Time = %7.3f, submode = %i\n", f2fl(Missiontime), aip->submode));
                //nprintf(("AI", "."));
                if (aip->active_goal >= 0) {
                        mission_log_add_entry(LOG_SHIP_DOCK, Ships[Pl_objp->instance].ship_name, Ships[goal_objp->instance].ship_name);

                        if (aip->goals[aip->active_goal].ai_mode == AI_GOAL_DOCK) {
                                ai_mission_goal_complete( aip );                                        // Note, this calls ai_set_default_behavior().
                        } 
                } else {        //      Can happen for initially docked ships.
                        ai_do_default_behavior( &Objects[Ships[aip->shipnum].objnum] );         // do the default behavior
                }
                
                break;

        case AIS_DOCK_4: {
                //      This mode is only for rearming/repairing.
                //      The ship that is performing the rearm enters this mode after it docks.
                Assert((aip->goal_objnum >= -1) && (aip->goal_objnum < MAX_OBJECTS));

                //nprintf(("AI", "Time = %7.3f, submode = %i\n", f2fl(Missiontime), aip->submode));
                float dist = dock_orient_and_approach(Pl_objp, &Objects[aip->goal_objnum], DOA_DOCK);
                Assert(dist != UNINITIALIZED_VALUE);

                object  *goal_objp = &Objects[aip->goal_objnum];
                Assert(goal_objp->type == OBJ_SHIP);
                ship                    *goal_shipp = &Ships[goal_objp->instance];              
                ai_info         *goal_aip = &Ai_info[goal_shipp->ai_index];

                //nprintf(("AI", "Dock 4: dist = %7.3f\n", dist));

                //      Make sure repair has not broken off.
                if (dist > 5.0f) {      //      Oops, too far away!
                        if ( goal_aip->ai_flags & AIF_BEING_REPAIRED )
                                ai_do_objects_repairing_stuff( goal_objp, Pl_objp, REPAIR_INFO_BROKEN);

                        if (dist > Pl_objp->radius*2 + goal_objp->radius*2) {
                                //      Got real far away from goal, so move back a couple modes and try again.
                                aip->submode = AIS_DOCK_2;
                                aip->submode_start_time = Missiontime;
                        }
                } else {
                        if ( goal_aip->ai_flags & AIF_AWAITING_REPAIR )
                                ai_do_objects_repairing_stuff( goal_objp, Pl_objp, REPAIR_INFO_BEGIN );
                }

                break;
                                                  }

        case AIS_UNDOCK_0: {
                int path_num;
                //      First stage of undocking.

                //nprintf(("AI", "Undock 0:\n"));

                aip->submode = AIS_UNDOCK_1;
                aip->submode_start_time = Missiontime;
                if (aip->dock_objnum == -1) {
                        aip->submode = AIS_UNDOCK_3;
                } else {

                        // set up the path points for the undocking procedure.  dock_path_index member should
                        // have gotten set in the docking code.
                        Assert( aip->dock_path_index != -1 );
                        path_num = ai_return_path_num_from_dockbay(goal_objp, aip->dock_path_index);
                        ai_find_path(Pl_objp, goal_objp-Objects, path_num, 0);

                        // Play a ship docking detach sound
                        snd_play_3d( &Snds[SND_DOCK_DETACH], &Pl_objp->pos, &View_position );
                }
                break;
                                                         }
        case AIS_UNDOCK_1: {
                //      Using thrusters, exit from dock station to nearest next dock path point.
                float   dist;
                
                //nprintf(("AI", "Undock 1: time in this mode = %7.3f\n", f2fl(Missiontime - aip->submode_start_time)));

                if (Missiontime - aip->submode_start_time < REARM_BREAKOFF_DELAY) {
                        break;          //      Waiting for one second to elapse to let detach sound effect play out.
                }
                else {  // AL - added 05/16/97.  Hack to play depart sound.  Will probably take out.
                                        // Assumes that the submode_start_time is not used for AIS_UNDOCK_1 anymore
                        if ( aip->submode_start_time != 0 )
                                snd_play_3d( &Snds[SND_DOCK_DEPART], &Pl_objp->pos, &View_position );
                        aip->submode_start_time = 0;
                }

                dist = dock_orient_and_approach(Pl_objp, &Objects[aip->goal_objnum], DOA_UNDOCK_1);
                Assert(dist != UNINITIALIZED_VALUE);

                float dist_to_dock_obj = vm_vec_dist_quick(&Pl_objp->pos, &Objects[aip->goal_objnum].pos);

                //      Move to within 0.1 units of second last point on path before orienting, or just plain far away from docked-to ship.
                //      This allows undock to complete if first ship flies away.
                if ((dist < 2*flFrametime) || (dist_to_dock_obj > 2*Pl_objp->radius)) {
                        aip->submode = AIS_UNDOCK_2;
                        aip->submode_start_time = Missiontime;
                }
                break;
                                                         }
        case AIS_UNDOCK_2: {
                float dist;
                ai_info *other_aip;

                // get pointer to docked object's aip to reset flags, etc
                Assert( aip->dock_objnum != -1 );
                other_aip = &Ai_info[Ships[Objects[aip->dock_objnum].instance].ai_index];

                //      Second stage of undocking.
                dist = dock_orient_and_approach(Pl_objp, &Objects[aip->goal_objnum], DOA_UNDOCK_2);
                Assert(dist != UNINITIALIZED_VALUE);


                //nprintf(("AI", "Undock 2: dist = %7.3f\n", dist));
                
                //      If at goal point, or quite far away from dock object
                if ((dist < 2.0f) || (vm_vec_dist_quick(&Pl_objp->pos, &goal_objp->pos) > (Pl_objp->radius + goal_objp->radius)*2) || (goal_objp->phys_info.speed > MAX_UNDOCK_ABORT_SPEED) ) {
                        // reset the dock flags.  If rearm/repair, reset rearm repair flags for those ships as well.
                        if ( sip->flags & SIF_SUPPORT ) {
                                ai_do_objects_repairing_stuff( &Objects[aip->dock_objnum], Pl_objp, REPAIR_INFO_END );
                        }

                        // clear out flags for AIF_DOCKED for both objects.
                        ai_do_objects_undocked_stuff( Pl_objp, goal_objp );
                        physics_ship_init(Pl_objp);
                        aip->submode = AIS_UNDOCK_3;                            //      The do-nothing mode, until another order is issued

                        //aip->ai_flags &= ~AIF_DOCKED;         //      @MK, 9/18/97
                        //other_aip->ai_flags &= ~AIF_DOCKED;
                        //aip->dock_objnum = -1;                                        // invalidate who obj is docked with
                        //other_aip->dock_objnum = -1;                  // MWA 10/07/97 invalide docked objects dock_objnum value as well

                        // don't add undock log entries for support ships.
                        if ( !(sip->flags & SIF_SUPPORT) )
                                mission_log_add_entry(LOG_SHIP_UNDOCK, Ships[Pl_objp->instance].ship_name, Ships[goal_objp->instance].ship_name);

                }
                break;
                }
        case AIS_UNDOCK_3: {
                float dist = dock_orient_and_approach(Pl_objp, &Objects[aip->goal_objnum], DOA_UNDOCK_3);
                Assert(dist != UNINITIALIZED_VALUE);

                if (dist < Pl_objp->radius/2 + 5.0f) {
                        aip->submode = AIS_UNDOCK_4;
                }

                // possible that this flag hasn't been cleared yet.  When aborting a rearm, this submode might
                // be entered directly.
                if ( (sip->flags & SIF_SUPPORT) && (aip->ai_flags & AIF_REPAIRING) ) {
                        ai_do_objects_repairing_stuff( &Objects[aip->goal_objnum], Pl_objp, REPAIR_INFO_ABORT );
                }

                break;
                                                 }
        case AIS_UNDOCK_4: {
                ai_info *other_aip;

                // MWA 10/07/97  I'm slightly confused by the dual use of goal_objnum and dock_objnum.  Seems to me
                // that goal_objnum and dock_objnum are the same through this whole docking/undocking process, although
                // I could be wrong.  dock_objnum was reset in undock_2 submode so try to use goal_objnum here to
                // get other ships ai_info pointer
                Assert( aip->goal_objnum != -1 );
                other_aip = &Ai_info[Ships[Objects[aip->goal_objnum].instance].ai_index];

                aip->mode = AIM_NONE;
                aip->dock_path_index = -1;              // invalidate the docking path index

                // these flags should have been cleared long ago!
                // Get Allender if you hit one of these!!!!!
                // removed by allender on 2/16 since a ship may be docked with some other ship, but still be the
                // goal_objnum of this ship ending it's undocking mode.
                //Assert( !(aip->ai_flags & AIF_DOCKED) );
                //Assert( !(other_aip->ai_flags & AIF_DOCKED) );
                //Assert( !(aip->ai_flags & AIF_REPAIRING) );
                //Assert( !(other_aip->ai_flags & AIF_BEING_REPAIRED) );
                //Assert( !(other_aip->ai_flags & AIF_AWAITING_REPAIR) );

                // only call mission goal complete if this was indeed an undock goal
                if ( aip->active_goal > -1 ) {
                        if ( aip->goals[aip->active_goal].ai_mode == AI_GOAL_UNDOCK )
                                ai_mission_goal_complete( aip );                        // this call should reset the AI mode
                        //else
                        //      aip->active_goal = -1;                                          // this ensures that this ship might get new goal
                }

                break;
                                                         }
        default:
                Int3(); //      Error, bogus submode
        }

}

// TURRET BEGIN

//      Given an object and a turret on that object, return the global position and forward vector
//      of the turret.   The gun normal is the unrotated gun normal, (the center of the FOV cone), not
// the actual gun normal given using the current turret heading.  But it _is_ rotated into the model's orientation
//      in global space.
void ship_get_global_turret_info(object *objp, model_subsystem *tp, vector *gpos, vector *gvec)
{
        matrix  m;
        vm_copy_transpose_matrix(&m, &objp->orient);
//      vm_vec_rotate(gpos, &tp->turret_avg_firing_point, &m);
        vm_vec_rotate(gpos, &tp->pnt, &m);
        vm_vec_add2(gpos, &objp->pos);
        vm_vec_rotate(gvec, &tp->turret_norm, &m);      
}

// Given an object and a turret on that object, return the actual firing point of the gun
// and its normal.   This uses the current turret angles.  We are keeping track of which
// gun to fire next in the ship specific info for this turret subobject.  Use this info
// to determine which position to fire from next.
//      Stuffs:
//              *gpos: absolute position of gun firing point
//              *gvec: vector fro *gpos to *targetp
void ship_get_global_turret_gun_info(object *objp, ship_subsys *ssp, vector *gpos, vector *gvec, int use_angles, vector *targetp)
{
        vector * gun_pos;
        model_subsystem *tp = ssp->system_info;

        ship_model_start(objp);

        gun_pos = &tp->turret_firing_point[ssp->turret_next_fire_pos % tp->turret_num_firing_points];

        model_find_world_point(gpos, gun_pos, tp->model_num, tp->turret_gun_sobj, &objp->orient, &objp->pos );

        if (use_angles)
                model_find_world_dir(gvec, &tp->turret_norm, tp->model_num, tp->turret_gun_sobj, &objp->orient, &objp->pos );
        else {
                //vector        gun_pos2;
                //vm_vec_add(&gun_pos2, gpos, gun_pos);
                vm_vec_normalized_dir(gvec, targetp, gpos);
        }

        ship_model_stop(objp);  
}

//      Rotate a turret towards an enemy.
//      Return TRUE if caller should use angles in subsequent rotations.
//      Some obscure model thing only John Slagel knows about.
//      Sets predicted enemy position.
//      If the turret (*ss) has a subsystem targeted, the subsystem is used as the predicted point.
int aifft_rotate_turret(ship *shipp, int parent_objnum, ship_subsys *ss, object *objp, object *lep, vector *predicted_enemy_pos, vector *gvec)
{
        if (ss->turret_enemy_objnum != -1)      {
                model_subsystem *tp = ss->system_info;
                vector  gun_pos, gun_vec;
                float           weapon_speed;
                float           weapon_system_strength;

                //      weapon_system_strength scales time enemy in range in 0..1.  So, the lower this is, the worse the aiming will be.
                weapon_system_strength = ship_get_subsystem_strength(shipp, SUBSYSTEM_WEAPONS);

                ship_get_global_turret_info(&Objects[parent_objnum], tp, &gun_pos, &gun_vec);

                weapon_speed = Weapon_info[tp->turret_weapon_type].max_speed;
                float weapon_travel_dist = weapon_speed * Weapon_info[tp->turret_weapon_type].lifetime;

                vector  enemy_point;
                if (ss->targeted_subsys != NULL) {
                        if (ss->turret_enemy_objnum != -1) {
                                vm_vec_unrotate(&enemy_point, &ss->targeted_subsys->system_info->pnt, &Objects[ss->turret_enemy_objnum].orient);
                                vm_vec_add2(&enemy_point, &Objects[ss->turret_enemy_objnum].pos);
                        }
                } else {
                        if ((lep->type == OBJ_SHIP) && (Ship_info[Ships[lep->instance].ship_info_index].flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP))) {
                                ai_big_pick_attack_point_turret(lep, ss, &gun_pos, &gun_vec, &enemy_point, tp->turret_fov, min(weapon_travel_dist, Weapon_info[tp->turret_weapon_type].weapon_range));
                        } else {
                                enemy_point = lep->pos;
                        }
                }

                set_predicted_enemy_pos_turret(predicted_enemy_pos, &gun_pos, objp, &enemy_point, &lep->phys_info.vel, weapon_speed, ss->turret_time_enemy_in_range * (weapon_system_strength + 1.0f)/2.0f);

                if (weapon_system_strength < 0.7f) {
                        vector  rand_vec;

                        static_randvec(Missiontime >> 18, &rand_vec);   //      Return same random number for two seconds.
                        //      Add to predicted_enemy_pos value in .45 to 1.5x radius of enemy ship, so will often miss, but not by a huge amount.
                        vm_vec_scale_add2(predicted_enemy_pos, &rand_vec, (1.0f - weapon_system_strength)*1.5f * lep->radius);
                }

                vector  v2e;
                vm_vec_normalized_dir(&v2e, predicted_enemy_pos, &gun_pos);
                if (vm_vec_dot(&v2e, gvec) > tp->turret_fov) {
                        int     rval;

                        rval = model_rotate_gun(shipp->modelnum, ss->system_info, &Objects[parent_objnum].orient, 
                                &ss->submodel_info_1.angs, &ss->submodel_info_2.angs,
                                &Objects[parent_objnum].pos, predicted_enemy_pos);
                }
        }

        return 0;
}

//      Determine if subsystem *enemy_subsysp is hittable from objp.
//      If so, return dot product of vector from point abs_gunposp to *enemy_subsysp
float   aifft_compute_turret_dot(object *objp, object *enemy_objp, vector *abs_gunposp, ship_subsys *turret_subsysp, ship_subsys *enemy_subsysp)
{
        float   dot_out;
        vector  subobj_pos, vector_out;

        vm_vec_unrotate(&subobj_pos, &enemy_subsysp->system_info->pnt, &enemy_objp->orient);
        vm_vec_add2(&subobj_pos, &enemy_objp->pos);

        if (ship_subsystem_in_sight(enemy_objp, enemy_subsysp, abs_gunposp, &subobj_pos, 1, &dot_out, &vector_out)) {
                vector  turret_norm;

                vm_vec_rotate(&turret_norm, &turret_subsysp->system_info->turret_norm, &objp->orient);
                return vm_vec_dot(&turret_norm, &vector_out);
        } else
                return -1.0f;

}

#define MAX_AIFFT_TURRETS                       60
ship_subsys *aifft_list[MAX_AIFFT_TURRETS];
float aifft_rank[MAX_AIFFT_TURRETS];
int aifft_list_size = 0;
int aifft_max_checks = 5;
DCF(mf, "")
{
        dc_get_arg(ARG_INT);
        aifft_max_checks = Dc_arg_int;
}


//      Pick a subsystem to attack on enemy_objp.
//      Only pick one if enemy_objp is a big ship or a capital ship.
//      Returns dot product from turret to subsystem in *dot_out
ship_subsys *aifft_find_turret_subsys(object *objp, ship_subsys *ssp, object *enemy_objp, float *dot_out)
{
        ship    *eshipp, *shipp;
        ship_info       *esip;
        ship_subsys     *best_subsysp = NULL;
        float dot;

        Assert(enemy_objp->type == OBJ_SHIP);

        eshipp = &Ships[enemy_objp->instance];
        esip = &Ship_info[eshipp->ship_info_index];

        shipp = &Ships[objp->instance];

        float   best_dot = 0.0f;
        *dot_out = best_dot;

        //      Compute absolute gun position.
        vector  abs_gun_pos;
        vm_vec_unrotate(&abs_gun_pos, &ssp->system_info->pnt, &objp->orient);
        vm_vec_add2(&abs_gun_pos, &objp->pos);

        //      Only pick a turret to attack on large ships.
        if (!(esip->flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP)))
                return best_subsysp;

        // Make sure big or huge ship *actually* has subsystems  (ie, knossos)
        if (esip->n_subsystems == 0) {
                return best_subsysp;
        }

        // first build up a list subsystems to traverse
        ship_subsys     *pss;
        aifft_list_size = 0;
        for ( pss = GET_FIRST(&eshipp->subsys_list); pss !=END_OF_LIST(&eshipp->subsys_list); pss = GET_NEXT(pss) ) {
                model_subsystem *psub = pss->system_info;

                // if we've reached max turrets bail
                if(aifft_list_size >= MAX_AIFFT_TURRETS){
                        break;
                }

                // Don't process destroyed objects
                if ( pss->current_hits <= 0.0f ){
                        continue;
                }
                
                switch (psub->type) {
                case SUBSYSTEM_WEAPONS:
                        aifft_list[aifft_list_size] = pss;
                        aifft_rank[aifft_list_size++] = 1.4f;
                        break;

                case SUBSYSTEM_TURRET:
                        aifft_list[aifft_list_size] = pss;
                        aifft_rank[aifft_list_size++] = 1.2f;
                        break;

                case SUBSYSTEM_SENSORS:
                case SUBSYSTEM_ENGINE:
                        aifft_list[aifft_list_size] = pss;
                        aifft_rank[aifft_list_size++] = 1.0f;
                        break;
                }
        }

        // DKA:  6/28/99 all subsystems can be destroyed.
        //Assert(aifft_list_size > 0);
        if (aifft_list_size == 0) {
                return best_subsysp;
        }

        // determine a stride value so we're not checking too many turrets
        int stride = aifft_list_size > aifft_max_checks ? aifft_list_size / aifft_max_checks : 1;
        if(stride <= 0){
                stride = 1;
        }
        int offset = (int)frand_range(0.0f, (float)(aifft_list_size % stride));
        int idx;
        for(idx=offset; idx<aifft_list_size; idx+=stride){
                dot = aifft_compute_turret_dot(objp, enemy_objp, &abs_gun_pos, ssp, aifft_list[idx]);                   

                if (dot* aifft_rank[idx] > best_dot) {
                        best_dot = dot*aifft_rank[idx];
                        best_subsysp = aifft_list[idx];
                }
        }

        Assert(best_subsysp != &eshipp->subsys_list);

        *dot_out = best_dot;
        return best_subsysp;
}

// Set active weapon for turret
void ai_turret_select_default_weapon(ship_subsys *turret)
{
        ship_weapon *twp;

        twp = &turret->weapons;

        // If a primary weapon is available, select it
        if ( twp->num_primary_banks > 0 ) {
                turret->system_info->turret_weapon_type = twp->primary_bank_weapons[0];
        } else if ( twp->num_secondary_banks > 0 ) {
                turret->system_info->turret_weapon_type = twp->secondary_bank_weapons[0];
        }
}

// return !0 if the specified target should scan for a new target, otherwise return 0
int turret_should_pick_new_target(ship_subsys *turret)
{
//      int target_type;

        if ( timestamp_elapsed(turret->turret_next_enemy_check_stamp) ) {
                return 1;
        }

        return 0;

/*
        if ( turret->turret_enemy_objnum == -1 ) {
                return 1;
        }
                
        target_type = Objects[turret->turret_enemy_objnum].type;
        if ( (target_type != OBJ_SHIP) && (target_type != OBJ_ASTEROID) ) {
                return 1;
        }

        return 0;
*/
}

// Set the next fire timestamp for a turret, based on weapon type and ai class
void turret_set_next_fire_timestamp(ship_subsys *turret, ai_info *aip)
{
        float   wait;
        int     weapon_id;

        weapon_id = turret->system_info->turret_weapon_type;

        wait = Weapon_info[weapon_id].fire_wait * 1000.0f;

        // make side even for team vs. team
        if ((Game_mode & GM_MULTIPLAYER) && (Netgame.type_flags & NG_TYPE_TEAM)) {
                // flak guns need to fire more rapidly
                if (Weapon_info[weapon_id].wi_flags & WIF_FLAK) {
                        wait *= Ship_fire_delay_scale_friendly[Game_skill_level] * 0.5f;
                        wait += (Num_ai_classes - aip->ai_class - 1) * 40.0f;
                } else {
                        wait *= Ship_fire_delay_scale_friendly[Game_skill_level];
                        wait += (Num_ai_classes - aip->ai_class - 1) * 100.0f;
                }
        } else {
                // flak guns need to fire more rapidly
                if (Weapon_info[weapon_id].wi_flags & WIF_FLAK) {
                        if (Ships[aip->shipnum].team == TEAM_FRIENDLY) {
                                wait *= Ship_fire_delay_scale_friendly[Game_skill_level] * 0.5f;
                        } else {
                                wait *= Ship_fire_delay_scale_hostile[Game_skill_level] * 0.5f;
                        }       
                        wait += (Num_ai_classes - aip->ai_class - 1) * 40.0f;

                } else if (Weapon_info[weapon_id].wi_flags & WIF_HUGE) {
                        // make huge weapons fire independently of team
                        wait *= Ship_fire_delay_scale_friendly[Game_skill_level];
                        wait += (Num_ai_classes - aip->ai_class - 1) * 100.0f;
                } else {
                        // give team friendly an advantage
                        if (Ships[aip->shipnum].team == TEAM_FRIENDLY) {
                                wait *= Ship_fire_delay_scale_friendly[Game_skill_level];
                        } else {
                                wait *= Ship_fire_delay_scale_hostile[Game_skill_level];
                        }       
                        wait += (Num_ai_classes - aip->ai_class - 1) * 100.0f;
                }
        }

        // vary wait time +/- 10%
        wait *= frand_range(0.9f, 1.1f);
        turret->turret_next_fire_stamp = timestamp((int) wait);
}

// Decide  if a turret should launch an aspect seeking missile
int turret_should_fire_aspect(ship_subsys *turret, float dot, int weapon_class)
{
        weapon_info *wip;

        wip = &Weapon_info[weapon_class];

        if ( (dot > AICODE_TURRET_DUMBFIRE_ANGLE) && (turret->turret_time_enemy_in_range >= min(wip->min_lock_time,AICODE_TURRET_MAX_TIME_IN_RANGE)) ) {
                return 1;
        }

        return 0;
}

// Update how long current target has been in this turrets range
void turret_update_enemy_in_range(ship_subsys *turret, float seconds)
{
        turret->turret_time_enemy_in_range += seconds;

        if ( turret->turret_time_enemy_in_range < 0.0f ) {
                turret->turret_time_enemy_in_range = 0.0f;
        }

        if ( turret->turret_time_enemy_in_range > AICODE_TURRET_MAX_TIME_IN_RANGE ) {
                turret->turret_time_enemy_in_range = AICODE_TURRET_MAX_TIME_IN_RANGE;
        }
}



// Fire a weapon from a turret
void turret_fire_weapon(ship_subsys *turret, int parent_objnum, vector *turret_pos, vector *turret_fvec, vector *predicted_pos = NULL)
{
        matrix  turret_orient;
        int             turret_weapon_class, weapon_objnum;
        ai_info *parent_aip;
        ship            *parent_ship;
        beam_fire_info fire_info;
        float flak_range = 0.0f;

        parent_aip = &Ai_info[Ships[Objects[parent_objnum].instance].ai_index];
        parent_ship = &Ships[Objects[parent_objnum].instance];
        turret_weapon_class = turret->system_info->turret_weapon_type;

        if (check_ok_to_fire(parent_objnum, turret->turret_enemy_objnum, &Weapon_info[turret_weapon_class])) {
                vm_vector_2_matrix(&turret_orient, turret_fvec, NULL, NULL);
                turret->turret_last_fire_direction = *turret_fvec;

                // set next fire timestamp for the turret
                turret_set_next_fire_timestamp(turret, parent_aip);

                // if this weapon is a beam weapon, handle it specially
                if(Weapon_info[turret_weapon_class].wi_flags & WIF_BEAM){
                        // if this beam isn't free to fire
                        if (!(turret->weapons.flags & SW_FLAG_BEAM_FREE)) {
                                Int3(); // should never get this far
                                return;
                        }

                        // stuff beam firing info
                        memset(&fire_info, 0, sizeof(beam_fire_info));
                        fire_info.accuracy = 1.0f;
                        fire_info.beam_info_index = turret_weapon_class;
                        fire_info.beam_info_override = NULL;
                        fire_info.shooter = &Objects[parent_objnum];
                        fire_info.target = &Objects[turret->turret_enemy_objnum];
                        fire_info.target_subsys = NULL;
                        fire_info.turret = turret;

                        // fire a beam weapon
                        beam_fire(&fire_info);
                } else {

                        // don't fire swarm, but set up swarm info
                        if (Weapon_info[turret_weapon_class].wi_flags & WIF_SWARM) {
                                turret_swarm_set_up_info(parent_objnum, turret, turret_weapon_class);
                                return;
                        } else {
                                weapon_objnum = weapon_create( turret_pos, &turret_orient, turret_weapon_class, parent_objnum, 0, -1, 1);
                                weapon_set_tracking_info(weapon_objnum, parent_objnum, turret->turret_enemy_objnum, 1, turret->targeted_subsys);                
                        }

                        //nprintf(("AI", "Turret_time_enemy_in_range = %7.3f\n", ss->turret_time_enemy_in_range));              
                        if (weapon_objnum != -1) {
                                Weapons[Objects[weapon_objnum].instance].target_num = turret->turret_enemy_objnum;
                                // AL 1-6-97: Store pointer to turret subsystem
                                Weapons[Objects[weapon_objnum].instance].turret_subsys = turret;

                                if ( Weapon_info[turret_weapon_class].launch_snd != -1 ) {
                                        // Don't play turret firing sound if turret sits on player ship... it gets annoying.
                                        if ( parent_objnum != OBJ_INDEX(Player_obj) ) {                                         
                                                snd_play_3d( &Snds[Weapon_info[turret_weapon_class].launch_snd], turret_pos, &View_position );                                          
                                        }
                                }               

                                // if the gun is a flak gun
                                if(Weapon_info[turret_weapon_class].wi_flags & WIF_FLAK){                       
                                        // show a muzzle flash
                                        flak_muzzle_flash(turret_pos, turret_fvec, turret_weapon_class);

                                        // pick a firing range so that it detonates properly                    
                                        flak_pick_range(&Objects[weapon_objnum], predicted_pos, ship_get_subsystem_strength(parent_ship, SUBSYSTEM_WEAPONS));

                                        // determine what that range was
                                        flak_range = flak_get_range(&Objects[weapon_objnum]);
                                }

                                // in multiplayer (and the master), then send a turret fired packet.
                                if ( MULTIPLAYER_MASTER && (weapon_objnum != -1) ) {
                                        int subsys_index;

                                        subsys_index = ship_get_index_from_subsys(turret, parent_objnum );
                                        Assert( subsys_index != -1 );
                                        if(Weapon_info[turret_weapon_class].wi_flags & WIF_FLAK){                       
                                                send_flak_fired_packet( parent_objnum, subsys_index, weapon_objnum, flak_range );
                                        } else {
                                                send_turret_fired_packet( parent_objnum, subsys_index, weapon_objnum );
                                        }
                                }
                        }
                }
        } else {
                float wait = 1000.0f * frand_range(0.9f, 1.1f);
                turret->turret_next_fire_stamp = timestamp((int) wait);
        }
}

void turret_swarm_fire_from_turret(ship_subsys *turret, int parent_objnum, int target_objnum, ship_subsys *target_subsys)
{
        int turret_weapon_class, weapon_objnum;
        matrix turret_orient;
        vector turret_pos, turret_fvec;

        // parent not alive, quick out.
        if (Objects[parent_objnum].type != OBJ_SHIP) {
                return;
        }

        //      change firing point
        ship_get_global_turret_gun_info(&Objects[parent_objnum], turret, &turret_pos, &turret_fvec, 1, NULL);
        turret->turret_next_fire_pos++;

        // get class [index into Weapon_info array
        turret_weapon_class = turret->system_info->turret_weapon_type;
        Assert(Weapon_info[turret_weapon_class].wi_flags & WIF_SWARM);

        // make turret_orient from turret_fvec -- turret->turret_last_fire_direction
        vm_vector_2_matrix(&turret_orient, &turret_fvec, NULL, NULL);

        // create weapon and homing info
        weapon_objnum = weapon_create(&turret_pos, &turret_orient, turret_weapon_class, parent_objnum, 0, -1, 1);
        weapon_set_tracking_info(weapon_objnum, parent_objnum, target_objnum, 1, target_subsys);

        // do other cool stuff if weapon is created.
        if (weapon_objnum > -1) {
                Weapons[Objects[weapon_objnum].instance].turret_subsys = turret;
                Weapons[Objects[weapon_objnum].instance].target_num = turret->turret_enemy_objnum;

                // maybe sound
                if ( Weapon_info[turret_weapon_class].launch_snd != -1 ) {
                        // Don't play turret firing sound if turret sits on player ship... it gets annoying.
                        if ( parent_objnum != OBJ_INDEX(Player_obj) ) {
                                snd_play_3d( &Snds[Weapon_info[turret_weapon_class].launch_snd], &turret_pos, &View_position );
                        }
                }
                
                // in multiplayer (and the master), then send a turret fired packet.
                if ( MULTIPLAYER_MASTER && (weapon_objnum != -1) ) {
                        int subsys_index;

                        subsys_index = ship_get_index_from_subsys(turret, parent_objnum );
                        Assert( subsys_index != -1 );
                        send_turret_fired_packet( parent_objnum, subsys_index, weapon_objnum );
                }
        }
}

int Num_ai_firing = 0;
int Num_find_turret_enemy = 0;
int Num_turrets_fired = 0;
//      Given a turret tp and its parent parent_objnum, fire from the turret at its enemy.
void ai_fire_from_turret(ship *shipp, ship_subsys *ss, int parent_objnum)
{
        float           weapon_firing_range;
        vector  v2e;
        object  *lep;           //      Last enemy pointer
        model_subsystem *tp = ss->system_info;
        int             use_angles, turret_weapon_class;
        vector  predicted_enemy_pos;
        object  *objp;
        ai_info *aip;

        if (!Ai_firing_enabled) {
                return;
        }

        if (ss->current_hits < 0.0f) {
                return;
        }

        if ( ship_subsys_disrupted(ss) ){               // AL 1/19/98: Make sure turret isn't suffering disruption effects
                return;
        }

        // Check turret free
        if (ss->weapons.flags & SW_FLAG_TURRET_LOCK) {
                return;
        }

        // If beam weapon, check beam free
        if ( (Weapon_info[tp->turret_weapon_type].wi_flags & WIF_BEAM) && !(ss->weapons.flags & SW_FLAG_BEAM_FREE) ) {
                return;
        }

        Assert( shipp->objnum == parent_objnum );

        if ( tp->turret_weapon_type < 0 ){
                return;
        }

        // Monitor number of calls to ai_fire_from_turret
        Num_ai_firing++;

        turret_weapon_class = tp->turret_weapon_type;

        // AL 09/14/97: ensure ss->turret_enemy_objnum != -1 before setting lep
        if ( (ss->turret_enemy_objnum >= 0 && ss->turret_enemy_objnum < MAX_OBJECTS) && (ss->turret_enemy_sig == Objects[ss->turret_enemy_objnum].signature)) {
                lep = &Objects[ss->turret_enemy_objnum];

                // MK -- here is where turret is targeting a bomb.  I simply return for now.  We should force
                // a target change -- or better yet, never pick a weapon when this turret has a "huge" weapon
                // loaded.

                // we only care about targets which are ships.
                //if ( lep->type != OBJ_SHIP )
                //      return;

                //      If targeted a small ship and have a huge weapon, don't fire.  But this shouldn't happen, as a small ship should not get selected.
                if ( Weapon_info[turret_weapon_class].wi_flags & WIF_HUGE ) {
                        if ( lep->type != OBJ_SHIP ) {
                                return;
                        }
                        if ( !(Ship_info[Ships[lep->instance].ship_info_index].flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP)) ) {
                                return;
                        }
                }

                // If targeting protected or beam protected ship, don't fire.  Reset enemy objnum
                if (lep->type == OBJ_SHIP) {
                        // Check if we're targeting a protected ship
                        if (lep->flags & OF_PROTECTED) {
                                ss->turret_enemy_objnum = -1;
                                ss->turret_time_enemy_in_range = 0.0f;
                                return;
                        }

                        // Check if we're targeting a beam protected ship with a beam weapon
                        if ( (lep->flags & OF_BEAM_PROTECTED) && (Weapon_info[turret_weapon_class].wi_flags & WIF_BEAM) ) {
                                ss->turret_enemy_objnum = -1;
                                ss->turret_time_enemy_in_range = 0.0f;
                                return;
                        }
                }
        } else {
                ss->turret_enemy_objnum = -1;
                lep = NULL;
        }
        
        Assert((parent_objnum >= 0) && (parent_objnum < MAX_OBJECTS));
        objp = &Objects[parent_objnum];
        Assert(objp->type == OBJ_SHIP);
        aip = &Ai_info[Ships[objp->instance].ai_index];

        // Use the turret info for all guns, not one gun in particular.
        vector   gvec, gpos;
        ship_get_global_turret_info(&Objects[parent_objnum], tp, &gpos, &gvec);

        // Rotate the turret even if time hasn't elapsed, since it needs to turn to face its target.
        use_angles = aifft_rotate_turret(shipp, parent_objnum, ss, objp, lep, &predicted_enemy_pos, &gvec);

        if ( !timestamp_elapsed(ss->turret_next_fire_stamp)){
                return;
        }

        // Don't try to fire beyond weapon_limit_range
        weapon_firing_range = min(Weapon_info[tp->turret_weapon_type].lifetime * Weapon_info[tp->turret_weapon_type].max_speed, Weapon_info[tp->turret_weapon_type].weapon_range);

        // if beam weapon in nebula and target not tagged, decrase firing range
        extern int Nebula_sec_range;
        if (Weapon_info[turret_weapon_class].wi_flags & WIF_BEAM) {
                if ( !((shipp->tag_left > 0) || (shipp->level2_tag_left > 0)) ) {
                        if (Nebula_sec_range) {
                                weapon_firing_range *= float(BEAM_NEBULA_RANGE_REDUCE_FACTOR);
                        }
                }
        }

        if (ss->turret_enemy_objnum != -1) {
                float dist_to_enemy = vm_vec_normalized_dir(&v2e, &predicted_enemy_pos, &gpos) - lep->radius;
                if (dist_to_enemy > weapon_firing_range) {
                        ss->turret_enemy_objnum = -1;           //      Force picking of new enemy.
                }
        }

        // Turret spawn weapons are a special case.  They fire if there are enough enemies in the 
        // immediate area (not necessarily in the turret fov).
        if ( Weapon_info[turret_weapon_class].wi_flags & WIF_SPAWN ) {
                int num_ships_nearby;
                num_ships_nearby = num_nearby_fighters(get_enemy_team_mask(parent_objnum), &gpos, 1500.0f);
                if (( num_ships_nearby >= 3 ) || ((num_ships_nearby >= 2) && (frand() < 0.1f))) {
                        turret_fire_weapon(ss, parent_objnum, &gpos, &ss->turret_last_fire_direction);
                } else {
                        ss->turret_next_fire_stamp = timestamp(1000);   //      Regardless of firing rate, don't check whether should fire for awhile.
                }
                return;
        }

        //      Maybe pick a new enemy.
        if ( turret_should_pick_new_target(ss) ) {
                Num_find_turret_enemy++;
                int objnum = find_turret_enemy(ss, parent_objnum, &gpos, &gvec, ss->turret_enemy_objnum, tp->turret_fov, Weapon_info[turret_weapon_class].wi_flags & WIF_HUGE);
                Assert(objnum < 0 || is_target_beam_valid(ss, objnum));

                if (objnum != -1) {
                        if (ss->turret_enemy_objnum == -1) {
                                ss->turret_enemy_objnum = objnum;
                                ss->turret_enemy_sig = Objects[objnum].signature;
                                // why return?
                                return;
                        } else {
                                ss->turret_enemy_objnum = objnum;
                                ss->turret_enemy_sig = Objects[objnum].signature;
                        }
                } else {
                        ss->turret_enemy_objnum = -1;
                }

                if (ss->turret_enemy_objnum != -1) {
                        float   dot = 1.0f;
                        lep = &Objects[ss->turret_enemy_objnum];
                        if ( lep->type == OBJ_SHIP ) {
                                ss->targeted_subsys = aifft_find_turret_subsys(objp, ss, lep, &dot);                            
                        }
                        ss->turret_next_enemy_check_stamp = timestamp((int) (max(dot, 0.5f)*2000.0f) + 1000);
                } else {
                        ss->turret_next_enemy_check_stamp = timestamp((int) (2000.0f * frand_range(0.9f, 1.1f)));       //      Check every two seconds
                }
        }

        //      If still don't have an enemy, return.  Or, if enemy is protected, return.
        if (ss->turret_enemy_objnum != -1) {
                //      Don't shoot at ship we're going to dock with.
                if (ss->turret_enemy_objnum == aip->dock_objnum) {
                        ss->turret_enemy_objnum = -1;
                        return;
                }

                if (Objects[ss->turret_enemy_objnum].flags & OF_PROTECTED) {
                        //      This can happen if the enemy was selected before it became protected.
                        ss->turret_enemy_objnum = -1;
                        return;
                }
                lep = &Objects[ss->turret_enemy_objnum];
        } else {
                if (timestamp_until(ss->turret_next_fire_stamp) < 500) {
                        ss->turret_next_fire_stamp = timestamp(500);
                }
                return;
        }

        if ( lep == NULL ){
                return;
        }

        Assert(ss->turret_enemy_objnum != -1);

        float dot = vm_vec_dot(&v2e, &gvec);

        if (dot > tp->turret_fov ) {
                // Ok, the turret is lined up... now line up a particular gun.
                int ok_to_fire = 0;
                float dist_to_enemy;

                // We're ready to fire... now get down to specifics, like where is the
                // actual gun point and normal, not just the one for whole turret.
                ship_get_global_turret_gun_info(&Objects[parent_objnum], ss, &gpos, &gvec, use_angles, &predicted_enemy_pos);
                ss->turret_next_fire_pos++;

                // Fire in the direction the turret is facing, not right at the target regardless of turret dir.
                vm_vec_sub(&v2e, &predicted_enemy_pos, &gpos);
                dist_to_enemy = vm_vec_normalize(&v2e);
                dot = vm_vec_dot(&v2e, &gvec);

                // if the weapon is a flak gun, add some jitter to its aim so it fires in a "cone" to make a cool visual effect
                // and make them less lethal
                if(Weapon_info[turret_weapon_class].wi_flags & WIF_FLAK){
                        flak_jitter_aim(&v2e, dist_to_enemy, ship_get_subsystem_strength(shipp, SUBSYSTEM_WEAPONS));
                }

                // Fire if:
                //              dumbfire and nearly pointing at target.
                //              heat seeking and target in a fairly wide cone.
                //              aspect seeking and target is locked.
                turret_weapon_class = tp->turret_weapon_type;

                // if dumbfire (lasers and non-homing missiles)
                if ( !(Weapon_info[turret_weapon_class].wi_flags & WIF_HOMING) ) {
                        if ((dist_to_enemy < 75.0f) || (dot > AICODE_TURRET_DUMBFIRE_ANGLE )) {
                                turret_update_enemy_in_range(ss, 2*Weapon_info[turret_weapon_class].fire_wait);
                                ok_to_fire = 1;
                        }
                } else if ( Weapon_info[turret_weapon_class].wi_flags & WIF_HOMING_HEAT ) {     // if heat seekers
                        if ((dist_to_enemy < 50.0f) || (dot > AICODE_TURRET_HEATSEEK_ANGLE )) {
                                turret_update_enemy_in_range(ss, 2*Weapon_info[turret_weapon_class].fire_wait);
                                ok_to_fire = 1;
                        }
                } else if ( Weapon_info[turret_weapon_class].wi_flags & WIF_HOMING_ASPECT ) {   // if aspect seeker
                        if ((dist_to_enemy < 50.0f) || (dot > AICODE_TURRET_DUMBFIRE_ANGLE )) {
                                turret_update_enemy_in_range(ss, 2*Weapon_info[turret_weapon_class].fire_wait);
                        }
                        if ( turret_should_fire_aspect(ss, dot, turret_weapon_class) ) {
                                ok_to_fire = 1;
                        }
                }

                if ( ok_to_fire ) {
                        Num_turrets_fired++;
                        
                        turret_fire_weapon(ss, parent_objnum, &gpos, &v2e, &predicted_enemy_pos);                                               
                } else {
                        turret_update_enemy_in_range(ss, -4*Weapon_info[tp->turret_weapon_type].fire_wait);
                        ss->turret_next_fire_stamp = timestamp(500);
                }
        } else {
                // Lost him!
                ss->turret_enemy_objnum = -1;           //      Reset enemy objnum, find a new one next frame.
                ss->turret_time_enemy_in_range = 0.0f;
        }
}

// TURRET END

#ifndef NDEBUG
#define MAX_AI_DEBUG_RENDER_STUFF       100
typedef struct ai_render_stuff {
        ship_subsys     *ss;
        int                     parent_objnum;
} ai_render_stuff;

ai_render_stuff AI_debug_render_stuff[MAX_AI_DEBUG_RENDER_STUFF];

int     Num_AI_debug_render_stuff = 0;

void ai_debug_render_stuff()
{
        vertex  vert1, vert2;
        vector  gpos2;
        int             i;

        for (i=0; i<Num_AI_debug_render_stuff; i++) {
                ship_subsys     *ss;
                int     parent_objnum;
                vector  gpos, gvec;
                model_subsystem *tp;

                ss = AI_debug_render_stuff[i].ss;
                tp = ss->system_info;

                parent_objnum = AI_debug_render_stuff[i].parent_objnum;

                ship_get_global_turret_info(&Objects[parent_objnum], tp, &gpos, &gvec);
                g3_rotate_vertex(&vert1, &gpos);
                vm_vec_scale_add(&gpos2, &gpos, &gvec, 20.0f);
                g3_rotate_vertex(&vert2, &gpos2);
                gr_set_color(0, 0, 255);
                g3_draw_sphere(&vert1, 2.0f);
                gr_set_color(255, 0, 255);
                g3_draw_sphere(&vert2, 2.0f);
                g3_draw_line(&vert1, &vert2);
        }

        // draw from beta to its goal point
/*      for (i=0; i<6; i++) {
                ai_info *aip = &Ai_info[i];
                gr_set_color(0, 0, 255);
                g3_rotate_vertex(&vert1, &Objects[i].pos);
                g3_rotate_vertex(&vert2, &aip->goal_point);
                g3_draw_line(&vert1, &vert2);
        } */
        

        Num_AI_debug_render_stuff = 0;
}

#endif

#ifndef NDEBUG
int     Msg_count_4996 = 0;
#endif

//      --------------------------------------------------------------------------
// Process subobjects of object objnum.
//      Deal with engines disabled.
void process_subobjects(int objnum)
{
        model_subsystem *psub;
        ship_subsys     *pss;
        object  *objp = &Objects[objnum];
        ship            *shipp = &Ships[objp->instance];
        ai_info *aip = &Ai_info[shipp->ai_index];
        ship_info       *sip = &Ship_info[shipp->ship_info_index];

        for ( pss = GET_FIRST(&shipp->subsys_list); pss !=END_OF_LIST(&shipp->subsys_list); pss = GET_NEXT(pss) ) {
                psub = pss->system_info;

                // Don't process destroyed objects
                if ( pss->current_hits <= 0.0f ) 
                        continue;

                switch (psub->type) {
                case SUBSYSTEM_TURRET:
                        if ( psub->turret_num_firing_points > 0 )       {
                                ai_fire_from_turret(shipp, pss, objnum);
                        } else {
#ifndef NDEBUG
                                if (!Msg_count_4996) {
                                        Warning( LOCATION, "Ship '%s' has turrets with no guns!\nProbably a model problem, so get an artist!", shipp->ship_name );
                                        Msg_count_4996++;
                                }
#endif
                                }
                        break;

                case SUBSYSTEM_ENGINE:
                case SUBSYSTEM_NAVIGATION:
                case SUBSYSTEM_COMMUNICATION:
                case SUBSYSTEM_WEAPONS:
                case SUBSYSTEM_SENSORS:
                case SUBSYSTEM_UNKNOWN:
                        break;

                // next set of subsystems may rotation
                case SUBSYSTEM_RADAR:
                case SUBSYSTEM_SOLAR:
                case SUBSYSTEM_GAS_COLLECT:
                case SUBSYSTEM_ACTIVATION:
                        break;
                default:
                        Error(LOCATION, "Illegal subsystem type.\n");
                }

                // do solar/radar/gas/activator rotation here
                if ( psub->flags & MSS_FLAG_ROTATES )   {
                        if (psub->flags & MSS_FLAG_STEPPED_ROTATE       ) {
                                submodel_stepped_rotate(psub, &pss->submodel_info_1);
                        } else {
                                submodel_rotate(psub, &pss->submodel_info_1 );
                        }
                }

        }

        //      Deal with a ship with blown out engines.
        if (ship_get_subsystem_strength(shipp, SUBSYSTEM_ENGINE) == 0.0f) {
                if (sip->flags & (SIF_FIGHTER | SIF_BOMBER)) {
                        // AL: Only attack forever if not trying to depart to a docking bay.  Need to have this in, since
                        //     a ship may get repaired... and it should still try to depart.  Since docking bay departures
                        //     are not handled as goals, we don't want to leave the AIM_BAY_DEPART mode.
                        if ( aip->mode != AIM_BAY_DEPART ) {
                                ai_attack_object(objp, NULL, 99, NULL);         //      Regardless of current mode, enter attack mode.
                                aip->submode = SM_ATTACK_FOREVER;                               //      Never leave attack submode, don't avoid, evade, etc.
                        }
                }
        }


}

//      Given an object and the wing it's in, return its index in the wing list.
//      This defines its location in the wing formation.
//      If the object can't be found in the wing, return -1.
//      *objp           object of interest
//      wingnum the wing *objp is in
int get_wing_index(object *objp, int wingnum)
{
        wing    *wingp;
        int     i;

        Assert((wingnum >= 0) && (wingnum < MAX_WINGS));

        wingp = &Wings[wingnum];

        for (i=wingp->current_count-1; i>=0; i--)
                if ( objp->instance == wingp->ship_index[i] )
                        break;

        return i;               //      Note, returns -1 if string not found.
}

//      Given a wing, return a pointer to the object of its leader.
//      Asserts if object not found.
//      Currently, the wing leader is defined as the first object in the wing.
//      wingnum         Wing number in Wings array.
//      If wing leader is disabled, swap it with another ship.
object * get_wing_leader(int wingnum)
{
        wing            *wingp;
        int             ship_num;

        Assert((wingnum >= 0) && (wingnum < MAX_WINGS));

        wingp = &Wings[wingnum];

        Assert(wingp->current_count != 0);                      //      Make sure there is a leader

        ship_num = wingp->ship_index[0];

        //      If this ship is disabled, try another ship in the wing.
        int n = 0;
        while (ship_get_subsystem_strength(&Ships[ship_num], SUBSYSTEM_ENGINE) == 0.0f) {
                n++;
                if (n >= wingp->current_count)
                        break;  
                ship_num = wingp->ship_index[n];
        }

        if (( n != 0) && (n != wingp->current_count)) {
                int t = wingp->ship_index[0];
                wingp->ship_index[0] = wingp->ship_index[n];
                wingp->ship_index[n] = t;
        }

        return &Objects[Ships[ship_num].objnum];
}

#define DEFAULT_WING_X_DELTA            1.0f
#define DEFAULT_WING_Y_DELTA            0.25f
#define DEFAULT_WING_Z_DELTA            0.75f
#define DEFAULT_WING_MAG                (fl_sqrt(DEFAULT_WING_X_DELTA*DEFAULT_WING_X_DELTA + DEFAULT_WING_Y_DELTA*DEFAULT_WING_Y_DELTA + DEFAULT_WING_Z_DELTA*DEFAULT_WING_Z_DELTA))
// next constant is higher that MAX_SHIPS_IN_WINGS to deal with forming on player's wing
#define MAX_FORMATION_ROWS              4

//      Given a position in a wing, return the desired location of the ship relative to the leader
//      *_delta_vec             OUTPUT.  delta vector based on wing_index
//      wing_index              position in wing.
void get_wing_delta(vector *_delta_vec, int wing_index)
{
        int     wi0;

        Assert(wing_index >= 0);

        int     k, row, column;

        int bank = wing_index / (MAX_FORMATION_ROWS*(MAX_FORMATION_ROWS+1)/2);
        wi0 = wing_index % (MAX_FORMATION_ROWS * (MAX_FORMATION_ROWS+1)/2);

        k = 0;
        for (row=1; row<MAX_FORMATION_ROWS+1; row++) {
                k += row;
                if (wi0 < k)
                        break;
        }

        row--;
        column = wi0 - k + row + 1;

        _delta_vec->xyz.x = ((float) column - (float) row/2.0f) * DEFAULT_WING_X_DELTA/DEFAULT_WING_MAG;
        _delta_vec->xyz.y = ((float)row + (float)bank*2.25f) * DEFAULT_WING_Y_DELTA/DEFAULT_WING_MAG;
        _delta_vec->xyz.z = - ((float)row + 0.5f * (float) bank) * DEFAULT_WING_Z_DELTA/DEFAULT_WING_MAG;
}

//      Compute the largest radius of a ship in a *objp's wing.
float gwlr_1(object *objp, ai_info *aip)
{
        int             wingnum = aip->wing;
        float           max_radius;
        object  *o;
        ship_obj        *so;

        Assert(wingnum >= 0);

        max_radius = objp->radius;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                o = &Objects[so->objnum];
                if (Ai_info[Ships[o->instance].ai_index].wing == wingnum)
                        if (o->radius > max_radius)
                                max_radius = o->radius;
        }

        return max_radius;
}

//      Compute the largest radius of a ship forming on *objp's wing.
float gwlr_object_1(object *objp, ai_info *aip)
{
        float           max_radius;
        object  *o;
        ship_obj        *so;

        max_radius = objp->radius;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                o = &Objects[so->objnum];
                if (Ai_info[Ships[o->instance].ai_index].goal_objnum == OBJ_INDEX(objp))
                        if (o->radius > max_radius)
                                max_radius = o->radius;
        }

        return max_radius;
}

//      For the wing that *objp is part of, return the largest ship radius in that wing.
float get_wing_largest_radius(object *objp, int formation_object_flag)
{
        ship            *shipp;
        ai_info *aip;

        Assert(objp->type == OBJ_SHIP);
        Assert((objp->instance >= 0) && (objp->instance < MAX_OBJECTS));
        shipp = &Ships[objp->instance];
        Assert((shipp->ai_index >= 0) && (shipp->ai_index < MAX_AI_INFO));
        aip = &Ai_info[shipp->ai_index];

        if (formation_object_flag) {
                return gwlr_object_1(objp, aip);
        } else {
                return gwlr_1(objp, aip);
        }

}

float Wing_y_scale = 2.0f;
float Wing_scale = 1.0f;
DCF(wing_y_scale, "")
{
        dc_get_arg(ARG_FLOAT);
        Wing_y_scale = Dc_arg_float;
}

DCF(wing_scale, "")
{
        dc_get_arg(ARG_FLOAT);
        Wing_scale = Dc_arg_float;
}

// Given a wing leader and a position in the wing formation, return the desired absolute location to fly to.
//      Returns result in *result_pos.
void get_absolute_wing_pos(vector *result_pos, object *leader_objp, int wing_index, int formation_object_flag)
{
        vector  wing_delta, rotated_wing_delta;
        float           wing_spread_size;

        get_wing_delta(&wing_delta, wing_index);                //      Desired location in leader's reference frame

        wing_spread_size = max(50.0f, 3.0f * get_wing_largest_radius(leader_objp, formation_object_flag) + 15.0f);

        // for player obj (1) move ships up 20% (2) scale formation up 20%
        if (leader_objp->flags & OF_PLAYER_SHIP) {
                wing_delta.xyz.y *= Wing_y_scale;
                wing_spread_size *= Wing_scale;
        }

        vm_vec_scale(&wing_delta, wing_spread_size * (1.0f + leader_objp->phys_info.speed/70.0f));

        vm_vec_unrotate(&rotated_wing_delta, &wing_delta, &leader_objp->orient);        //      Rotate into leader's reference.

        vm_vec_add(result_pos, &leader_objp->pos, &rotated_wing_delta); //      goal_point is absolute 3-space point.
}

#ifndef NDEBUG
int Debug_render_wing_phantoms;

void render_wing_phantoms(object *objp)
{
        int             i;
        ship            *shipp;
        ai_info *aip;
        int             wingnum;
        int             wing_index;             //      Index in wing struct, defines 3-space location in wing.
        vector  goal_point;
        
        Assert(objp->type == OBJ_SHIP);
        Assert((objp->instance >= 0) && (objp->instance < MAX_SHIPS));

        shipp = &Ships[objp->instance];
        Assert((shipp->ai_index >= 0) && (shipp->ai_index < MAX_AI_INFO));

        aip = &Ai_info[shipp->ai_index];

        wingnum = aip->wing;

        if (wingnum == -1)
                return;

        wing_index = get_wing_index(objp, wingnum);

        //      If this ship is NOT the leader, abort.
        if (wing_index != 0)
                return;

        for (i=0; i<32; i++)
                if (Debug_render_wing_phantoms & (1 << i)) {
                        get_absolute_wing_pos(&goal_point, objp, i, 0);
        
                        vertex  vert;
                        gr_set_color(255, 0, 128);
                        g3_rotate_vertex(&vert, &goal_point);
                        g3_draw_sphere(&vert, 2.0f);
                }

        Debug_render_wing_phantoms = 0;

}

void render_wing_phantoms_all()
{
        object  *objp;
        ship_obj        *so;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                ship            *shipp;
                ai_info *aip;
                int             wingnum;
                int             wing_index;             //      Index in wing struct, defines 3-space location in wing.

                objp = &Objects[so->objnum];
                
                Assert((objp->instance >= 0) && (objp->instance < MAX_SHIPS));
                shipp = &Ships[objp->instance];
                Assert((shipp->ai_index >= 0) && (shipp->ai_index < MAX_AI_INFO));

                aip = &Ai_info[shipp->ai_index];

                wingnum = aip->wing;

                if (wingnum == -1)
                        continue;

                wing_index = get_wing_index(objp, wingnum);

                //      If this ship is NOT the leader, abort.
                if (wing_index != 0)
                        continue;
                
                render_wing_phantoms(objp);

                return;
        }
}

#endif

//      Hook from goals code to AI.
//      Force a wing to fly in formation.
//      Sets AIF_FORMATION bit in ai_flags.
//      wingnum         Wing to force to fly in formation
void ai_fly_in_formation(int wingnum)
{
        object  *objp;
        ship            *shipp;
        ship_obj        *so;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                objp = &Objects[so->objnum];
                Assert((objp->instance >= 0) && (objp->instance < MAX_SHIPS));

                shipp = &Ships[objp->instance];
                Assert((shipp->ai_index >= 0) && (shipp->ai_index < MAX_AI_INFO));

                if (Ai_info[shipp->ai_index].wing == wingnum) {
                        Ai_info[shipp->ai_index].ai_flags |= AIF_FORMATION_WING;
                        Ai_info[shipp->ai_index].ai_flags &= ~AIF_FORMATION_OBJECT;
                }
        }
}

//      Hook from goals code to AI.
//      Force a wing to abandon formation flying.
//      Clears AIF_FORMATION bit in ai_flags.
//      wingnum         Wing to force to fly in formation
void ai_disband_formation(int wingnum)
{
        object  *objp;
        ship            *shipp;
        ship_obj        *so;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                objp = &Objects[so->objnum];
                Assert((objp->instance >= 0) && (objp->instance < MAX_SHIPS));

                shipp = &Ships[objp->instance];
                Assert((shipp->ai_index >= 0) && (shipp->ai_index < MAX_AI_INFO));

                if (Ai_info[shipp->ai_index].wing == wingnum) {
                        Ai_info[shipp->ai_index].ai_flags &= ~AIF_FORMATION_WING;
                }
        }
}

float   Leader_chaos = 0.0f;
int Chaos_frame = -1;

//      Return true if objp is flying in an erratic manner
//      Only true if objp is a player
int formation_is_leader_chaotic(object *objp)
{
        if (Game_mode & GM_MULTIPLAYER)
                return 0;

        if (objp != Player_obj)
                return 0;

        if (Framecount != Chaos_frame) {
                float   speed_scale;
                float   fdot, udot;

                speed_scale = 3.0f + objp->phys_info.speed * 0.1f;

                fdot = 5.0f * (1.0f - vm_vec_dot(&objp->orient.v.fvec, &objp->last_orient.v.fvec)) * flFrametime;
                udot = 8.0f * (1.0f - vm_vec_dot(&objp->orient.v.uvec, &objp->last_orient.v.uvec)) * flFrametime;

                Leader_chaos += fdot * speed_scale + udot * speed_scale;

                Leader_chaos *= (1.0f - flFrametime*0.2f);

                if (Leader_chaos < 0.0f)
                        Leader_chaos = 0.0f;
                else if (Leader_chaos > 1.7f)
                        Leader_chaos = 1.7f;

                //nprintf(("AI", "Frame %i: chaos = %7.4f\n", Framecount, Leader_chaos));

                Chaos_frame = Framecount;
        }

        return (Leader_chaos > 1.0f);
}

// Fly in formation.
//      Make Pl_objp assume its proper place in formation.
//      If the leader of the wing is doing something stupid, like fighting a battle,
//      then the poor sap wingmates will be in for a "world of hurt"
//      Return TRUE if we need to process this object's normal mode
int ai_formation()
{
        object  *leader_objp;
        ship            *shipp;
        ai_info *aip, *laip;
        int             wingnum;
        int             wing_index;             //      Index in wing struct, defines 3-space location in wing.
        int             player_wing;    // index of the players wingnum
        vector  goal_point, future_goal_point_5, future_goal_point_2, future_goal_point_x, future_goal_point_1000x, vec_to_goal, dir_to_goal;
        float           dot_to_goal, dist_to_goal, leader_speed;

        Assert(Pl_objp->type == OBJ_SHIP);
        Assert((Pl_objp->instance >= 0) && (Pl_objp->instance < MAX_SHIPS));

        shipp = &Ships[Pl_objp->instance];

        Assert((shipp->ai_index >= 0) && (shipp->ai_index < MAX_AI_INFO));

        aip = &Ai_info[shipp->ai_index];

        Assert((aip->ai_flags & AIF_FORMATION) != AIF_FORMATION);       //      Make sure not both types of formation flying in effect.

        //      Determine which kind of formation flying.
        //      If tracking an object, not in waypoint mode:
        if (aip->ai_flags & AIF_FORMATION_OBJECT) {
                if ((aip->goal_objnum < 0) || (aip->goal_objnum >= MAX_OBJECTS)) {
                        aip->ai_flags &= ~AIF_FORMATION_OBJECT;
                        return 1;
                }
                
                wing_index = ai_formation_object_get_slotnum(aip->goal_objnum, Pl_objp);
                leader_objp = &Objects[aip->goal_objnum];
        } else {        //      Formation flying in waypoint mode.
                Assert(aip->ai_flags & AIF_FORMATION_WING);
                if (aip->mode != AIM_WAYPOINTS) {
                        aip->ai_flags &= ~AIF_FORMATION_WING;
                        return 1;
                }

                wingnum = aip->wing;

                if (wingnum == -1)
                        return 1;

                // disable formation flying for any ship in the players wing
                player_wing = Ships[Player_obj->instance].wingnum;
                if ( (player_wing != -1) && (wingnum == player_wing) )
                        return 1;

                wing_index = get_wing_index(Pl_objp, wingnum);

                leader_objp = get_wing_leader(wingnum);

        }

        //      If docked with a ship in this wing, only the more massive one actually flies in formation.
        if (aip->dock_objnum != -1) {
                object  *other_objp = &Objects[aip->dock_objnum];
                ai_info *other_aip = &Ai_info[Ships[other_objp->instance].ai_index];

                if (aip->wing == other_aip->wing) {
                        if (Pl_objp->phys_info.mass < other_objp->phys_info.mass)
                                return 0;
                        else if (Pl_objp->phys_info.mass == other_objp->phys_info.mass) {
                                if (Pl_objp->signature < other_objp->signature)
                                        return 0;
                        }
                }
        }

        Assert(leader_objp != NULL);
        laip = &Ai_info[Ships[leader_objp->instance].ai_index];

        //      Make sure we're really in this wing.
        if (wing_index == -1)
                return 1;

        //      If this ship is the leader, abort, as he doesn't have to follow anyone.
        if (wing_index == 0) {
                // nprintf(("AI", "Hmm, wing leader %s in ai_formation for no good reason.\n", shipp->ship_name));
                return 1;
        }

        if (aip->mode == AIM_WAYPOINTS) {
                aip->wp_list = laip->wp_list;
                if (laip->wp_index < Waypoint_lists[laip->wp_list].count)
                        aip->wp_index = laip->wp_index;
                else
                        aip->wp_index = Waypoint_lists[laip->wp_list].count - 1;
                aip->wp_flags = laip->wp_flags;
                aip->wp_dir = laip->wp_dir;
        }

        #ifndef NDEBUG
        Debug_render_wing_phantoms |= (1 << wing_index);
        #endif

        leader_speed = leader_objp->phys_info.speed;
        vector leader_vec = leader_objp->phys_info.vel;

        get_absolute_wing_pos(&goal_point, leader_objp, wing_index, aip->ai_flags & AIF_FORMATION_OBJECT);
        vm_vec_scale_add(&future_goal_point_5, &goal_point, &leader_vec, 10.0f);
        vm_vec_scale_add(&future_goal_point_2, &goal_point, &leader_vec, 5.0f);
        vm_vec_scale_add(&future_goal_point_x, &goal_point, &leader_objp->orient.v.fvec, 10.0f);        //      used when very close to destination
        vm_vec_scale_add(&future_goal_point_1000x, &goal_point, &leader_objp->orient.v.fvec, 1000.0f);  //      used when very close to destination

        //      Now, get information telling this object how to turn and accelerate to get to its
        //      desired location.
        vm_vec_sub(&vec_to_goal, &goal_point, &Pl_objp->pos);
        if ( vm_vec_mag_quick(&vec_to_goal) < AICODE_SMALL_MAGNITUDE )
                vec_to_goal.xyz.x += 0.1f;

        vm_vec_copy_normalize(&dir_to_goal, &vec_to_goal);
        //dot_to_goal = vm_vec_dot(&dir_to_goal, &leader_objp->orient.v.fvec);
        dot_to_goal = vm_vec_dot(&dir_to_goal, &Pl_objp->orient.v.fvec);
        dist_to_goal = vm_vec_dist_quick(&Pl_objp->pos, &goal_point);
        float   dist_to_goal_2 = vm_vec_dist_quick(&Pl_objp->pos, &future_goal_point_2);

        // nprintf(("AI", "dot = %7.3f, dist = %8.3f, speed = %7.3f, leader speed = %7.3f\n", dot_to_goal, dist_to_goal, Pl_objp->phys_info.speed, leader_objp->phys_info.speed));

        int     chaotic_leader = 0;

        chaotic_leader = formation_is_leader_chaotic(leader_objp);      //      Set to 1 if leader is player and flying erratically.  Causes ships to not aggressively pursue formation location.

        if (dist_to_goal > 500.0f) {
                turn_towards_point(Pl_objp, &goal_point, NULL, 0.0f);
                accelerate_ship(aip, 1.0f);
        } else if (dist_to_goal > 200.0f) {
                if (dot_to_goal > -0.5f) {
                        turn_towards_point(Pl_objp, &goal_point, NULL, 0.0f);
                        float range_speed = shipp->current_max_speed - leader_speed;
                        if (range_speed > 0.0f)
                                set_accel_for_target_speed(Pl_objp, leader_speed + range_speed * (dist_to_goal+100.0f)/500.0f);
                        else
                                set_accel_for_target_speed(Pl_objp, shipp->current_max_speed);
                } else {
                        turn_towards_point(Pl_objp, &future_goal_point_5, NULL, 0.0f);
                        if (leader_speed > 10.0f)
                                set_accel_for_target_speed(Pl_objp, leader_speed *(1.0f + dot_to_goal));
                        else
                                set_accel_for_target_speed(Pl_objp, 10.0f);
                }
        } else {
                vector  v2f2;
                float   dot_to_f2;
                float   dist_to_f2;

                dist_to_f2 = vm_vec_normalized_dir(&v2f2, &future_goal_point_2, &Pl_objp->pos);
                dot_to_f2 = vm_vec_dot(&v2f2, &Pl_objp->orient.v.fvec);

                //      Leader flying like a maniac.  Don't try hard to form on wing.
                if (chaotic_leader) {
                        turn_towards_point(Pl_objp, &future_goal_point_2, NULL, 0.0f);
                        set_accel_for_target_speed(Pl_objp, min(leader_speed*0.8f, 20.0f));
                } else if (dist_to_goal > 75.0f) {
                        turn_towards_point(Pl_objp, &future_goal_point_2, NULL, 0.0f);
                        float   delta_speed;
                        float range_speed = shipp->current_max_speed - leader_speed;
                        if (range_speed > 0.0f)
                                delta_speed = dist_to_goal_2/500.0f * range_speed;
                        else
                                delta_speed = shipp->current_max_speed - leader_speed;
                        if (dot_to_goal < 0.0f) {
                                delta_speed = -delta_speed;
                                if (-delta_speed > leader_speed/2)
                                        delta_speed = -leader_speed/2;
                        }

                        if (leader_speed < 5.0f)
                                if (delta_speed < 5.0f)
                                        delta_speed = 5.0f;

                        float scale = dot_to_f2;
                        if (scale < 0.1f)
                                scale = 0.0f;
                        else
                                scale *= scale;

                        set_accel_for_target_speed(Pl_objp, scale * (leader_speed + delta_speed));
                } else {
                        //nprintf(("AI", "Dot = %7.3f\n", dot_to_goal));

                        if (leader_speed < 5.0f) {
                                //      Leader very slow.  If not close to goal point, get very close.  Note, keep trying to get close unless
                                //      moving very slowly, else momentum can carry far away from goal.

                                if ((dist_to_goal > 10.0f) || ((Pl_objp->phys_info.speed > leader_speed + 2.5f) && (dot_to_goal > 0.5f))) {
                                        //nprintf(("MK", "(1) "));
                                        turn_towards_point(Pl_objp, &goal_point, NULL, 0.0f);
                                        set_accel_for_target_speed(Pl_objp, leader_speed + dist_to_goal/10.0f);
                                } else {
                                        if (Pl_objp->phys_info.speed < 0.5f) {
                                                //nprintf(("MK", "(2) "));
                                                turn_towards_point(Pl_objp, &future_goal_point_1000x, NULL, 0.0f);
                                        } else {
                                                //nprintf(("MK", "(3) "));
                                        }
                                        set_accel_for_target_speed(Pl_objp, leader_speed);
                                }
                                //nprintf(("MK", "dist: %7.3f, dot: %6.3f, speed: %7.3f\n", dist_to_goal, dot_to_goal, Pl_objp->phys_info.speed));
                        } else if (dist_to_goal > 10.0f) {
                                float   dv;

                                //future_goal_point_2;

                                turn_towards_point(Pl_objp, &future_goal_point_2, NULL, 0.0f);

                                if (dist_to_goal > 25.0f) {
                                        if (dot_to_goal < 0.3f)
                                                dv = -0.1f;
                                        else
                                                dv = dot_to_goal - 0.2f;

                                        set_accel_for_target_speed(Pl_objp, leader_speed + dist_to_goal/5.0f * dv);
                                } else {
                                        set_accel_for_target_speed(Pl_objp, leader_speed + 1.5f * dot_to_goal - 1.0f);
                                }
                        } else {
                                if (Pl_objp->phys_info.speed < 0.1f)
                                        turn_towards_point(Pl_objp, &future_goal_point_1000x, NULL, 0.0f);
                                else
                                        turn_towards_point(Pl_objp, &future_goal_point_x, NULL, 0.0f);
                                set_accel_for_target_speed(Pl_objp, 0.0f);
                        }
                }

        }

        //      See how different this ship's bank is relative to wing leader
        float   up_dot = vm_vec_dot(&leader_objp->orient.v.uvec, &Pl_objp->orient.v.uvec);
        if (up_dot < 0.996f) {
                vector  w_out;
                matrix  new_orient;
                vector  angular_accel;

                vm_vec_copy_scale(&angular_accel, &Pl_objp->phys_info.max_rotvel, 0.2f);
                vm_matrix_interpolate(&leader_objp->orient, &Pl_objp->orient, &Pl_objp->phys_info.rotvel, flFrametime, &new_orient, &w_out, &Pl_objp->phys_info.max_rotvel, &angular_accel, 1);

        //      nprintf(("AI", "Frame %d Bashing formation orient.  Dot was %6.3f, becomes %6.3f\n", Framecount, up_dot, vm_vec_dot(&leader_objp->orient.v.uvec, &new_orient.v.uvec)));
                Pl_objp->orient = new_orient;
                Pl_objp->phys_info.rotvel = w_out;
        //      Pl_objp->phys_info.desired_rotvel = w_out;
        } else {
                Pl_objp->phys_info.rotvel.xyz.z = 0.0f;
        }

        return 0;
}

//      Return index of object repairing object objnum.
int find_repairing_objnum(int objnum)
{
        object          *objp;
        ship                    *shipp;
        ship_info       *sip;
        ship_obj                *so;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                objp = &Objects[so->objnum];

                Assert((objp->instance >= 0) && (objp->instance < MAX_SHIPS));

                shipp = &Ships[objp->instance];
                sip = &Ship_info[shipp->ship_info_index];

                if (sip->flags & SIF_SUPPORT) {
                        ai_info *aip;

                        aip = &Ai_info[shipp->ai_index];

                        if (aip->goal_objnum == objnum) {
                                return objp-Objects;
                        }
                }
        }

        return -1;
}

//      If object *objp is being repaired, deal with it!
void ai_do_repair_frame(object *objp, ai_info *aip, float frametime)
{
        if (Ships[objp->instance].team == TEAM_TRAITOR) {
                ai_abort_rearm_request(objp);
                return;
        }

        if (aip->ai_flags & (AIF_BEING_REPAIRED | AIF_AWAITING_REPAIR)) {
                int     dock_objnum;
                ai_info *repair_aip;

                dock_objnum = aip->dock_objnum; // find_repairing_objnum(objp-Objects);
                //Assert(dock_objnum != -1);
                if (dock_objnum == -1)
                        return;
                if (Objects[dock_objnum].signature != aip->dock_signature) {
                        Int3();         //      Curious -- object numbers match, but signatures do not.
                                                        //      Must mean original repair ship died and was replaced by current ship.
                        return;
                }
        
                repair_aip = &Ai_info[Ships[Objects[dock_objnum].instance].ai_index];
                //Assert(repair_aip->mode == AIM_DOCK);

                if (aip->ai_flags & AIF_BEING_REPAIRED) {
                        // Assert(repair_aip->submode == AIS_DOCK_4);

                        //      Wait awhile into the mode to synchronize with sound effect.
                        if (Missiontime - repair_aip->submode_start_time > REARM_SOUND_DELAY) {
                                int repaired;

                                repaired = ship_do_rearm_frame( objp, frametime );              // hook to do missile rearming

                                //      See if fully repaired.  If so, cause process to stop.
                                if ( repaired && (repair_aip->submode == AIS_DOCK_4)) {

                                        repair_aip->submode = AIS_UNDOCK_0;
                                        repair_aip->submode_start_time = Missiontime;

                                        // if repairing player object -- tell him done with repair
                                        if ( !MULTIPLAYER_CLIENT ){
                                                ai_do_objects_repairing_stuff( objp, &Objects[dock_objnum], REPAIR_INFO_COMPLETE );
                                        }
                                }
                        }
                } else if (aip->ai_flags & AIF_AWAITING_REPAIR) {
                        //      If this ship has been awaiting repair for 90+ seconds, abort.
                        if ( !MULTIPLAYER_CLIENT ) {
                                if ((Game_mode & GM_MULTIPLAYER) || (objp != Player_obj)) {
                                        if ((repair_aip->goal_objnum == OBJ_INDEX(objp)) && (timestamp_elapsed(aip->abort_rearm_timestamp))) {
                                                ai_abort_rearm_request(objp);
                                                aip->next_rearm_request_timestamp = timestamp(NEXT_REARM_TIMESTAMP);
                                        }
                                }
                        }
                }
        } else {
                // AL 11-24-97: If this is the player ship, ensure the repair sound isn't playing.  We need to
                //              do this check, since this is a looping sound, and may continue on if rearm/repair
                //              finishes abnormally once sound begins looping.
                if ( objp == Player_obj ) {
                        player_stop_repair_sound();
                }
        }
}

//      Shell around dock_orient_and_approach to detect whether dock process should be aborted.
//      obj1 is the ship performing the repair.
//      obj2 is the ship being repaired.
void call_doa(object *obj1, object *obj2, ship_info *sip1)
{
        if (sip1->flags & SIF_SUPPORT) {
                if (obj2->phys_info.speed > MAX_REPAIR_SPEED) {

                        // call the ai_abort rearm request code
                        ai_abort_rearm_request( obj2 );
                } else
                        dock_orient_and_approach(obj1, obj2, DOA_DOCK_STAY);
        } else {
                if (Ship_info[Ships[obj1->instance].ship_info_index].flags & SIF_CARGO)
                        dock_orient_and_approach(obj1, obj2, DOA_DOCK_STAY);
                else if (Ship_info[Ships[obj2->instance].ship_info_index].flags & SIF_CARGO)
                        dock_orient_and_approach(obj2, obj1, DOA_DOCK_STAY);
                else {
                        //mprintf(("Warning: Not sure, but making %s [%s] move to stay docked with %s [%s]\n",
                        //      Ships[obj1->instance].ship_name, Ship_info[Ships[obj1->instance].ship_info_index].name, Ships[obj2->instance].ship_name, Ship_info[Ships[obj2->instance].ship_info_index].name));
                        dock_orient_and_approach(obj1, obj2, DOA_DOCK_STAY);

                }
        }

}

//      Maybe launch a countermeasure.
//      Also, detect a supposed homing missile that no longer exists.
void ai_maybe_launch_cmeasure(object *objp, ai_info *aip)
{
        float                   dist;
        ship_info       *sip;
        ship                    *shipp;

        shipp = &Ships[objp->instance];
        sip = &Ship_info[shipp->ship_info_index];

        if (!(sip->flags & (SIF_SMALL_SHIP | SIF_TRANSPORT)))
                return;

        if (!shipp->cmeasure_count)
                return;

        if ( !timestamp_elapsed(shipp->cmeasure_fire_stamp) )
                return;

        //      If not on player's team and Skill_level + ai_class is low, never fire a countermeasure.  The ship is too dumb.
        if (shipp->team != Player_ship->team) {
                if (Game_skill_level + aip->ai_class < 4){
                        return;
                }
        }

        if ((aip->nearest_locked_object != -1) && (Objects[aip->nearest_locked_object].type == OBJ_WEAPON)) {
                object  *weapon_objp;
                weapon  *weaponp;
                weapon_info     *wip;

                weapon_objp = &Objects[aip->nearest_locked_object];
                weaponp = &Weapons[weapon_objp->instance];
                wip = &Weapon_info[weaponp->weapon_info_index];

                if ((dist = vm_vec_dist_quick(&objp->pos, &weapon_objp->pos)) < weapon_objp->phys_info.speed*2.0f) {
        
                        aip->nearest_locked_distance = dist;
                        //      Verify that this object is really homing on us.
                        object  *weapon_objp;

                        weapon_objp = &Objects[aip->nearest_locked_object];

                        float   fire_chance;

                        //      For ships on player's team, have constant, average chance to fire.
                        //      For enemies, increasing chance with higher skill level.
                        if (shipp->team == Player_ship->team)
                                fire_chance = Cmeasure_fire_chance[NUM_SKILL_LEVELS/2];
                        else
                                fire_chance = Cmeasure_fire_chance[Game_skill_level];

                        //      Decrease chance to fire at lower ai class.
                        fire_chance *= (float) aip->ai_class/Num_ai_classes;

                        float r = frand();
                        if (fire_chance < r) {
                                //nprintf(("AI", "Not firing countermeasure due to skill level: %7.3f < %7.3f\n", fire_chance, r));
                                shipp->cmeasure_fire_stamp = timestamp(CMEASURE_WAIT + (int) (fire_chance*2000));               //      Wait 1/2 second (CMEASURE_WAIT) + additional delay to decrease chance of firing very soon.
                                return;
                        }

                        if (weapon_objp->type == OBJ_WEAPON) {
                                if (weapon_objp->instance >= 0) {
                                        //nprintf(("AI", "Firing countermeasure at time t=%7.3f\n", f2fl(Missiontime)));
                                        ship_launch_countermeasure(objp);
                                        shipp->cmeasure_fire_stamp = timestamp(2*CMEASURE_WAIT);
                                        return;
                                }
                        }
        
                }
        }

        return;
}

//      --------------------------------------------------------------------------
void ai_preprocess_ignore_objnum(object *objp, ai_info *aip)
{
//      if (aip->ignore_objnum == UNUSED_OBJNUM)
//              return;

        if (aip->ai_flags & AIF_TEMPORARY_IGNORE) {
                if (timestamp_elapsed(aip->ignore_expire_timestamp)) {
                        aip->ignore_objnum = UNUSED_OBJNUM;
                }
        }

        if (is_ignore_object(aip, aip->goal_objnum)) {
                aip->goal_objnum = -1;
                // AL 12-11-97: If in STRAFE mode, we need to ensure that target_objnum is also
                //              set to -1
                if ( aip->mode == AIM_STRAFE ) {
                        aip->target_objnum = -1;
                }
        }

        if (is_ignore_object(aip, aip->target_objnum))
                aip->target_objnum = -1;
}

/*
void ai_safety_circle_spot()
{
        vector  goal_point;
        ship_info       *sip;

        sip = &Ship_info[Ships[Pl_objp->instance].ship_info_index];

        goal_point = Ai_info[Ships[Pl_objp->instance].ai_index].goal_point;
        turn_towards_tangent(Pl_objp, &goal_point, 50.0f);

        set_accel_for_target_speed(Pl_objp, sip->max_speed/4.0f);

//      float dist = vm_vec_dist_quick(&goal_point, &Pl_objp->pos);
//      nprintf(("AI", "Ship %s circling %7.3f %7.3f %7.3f.  Distance = %7.3f\n", Ships[Pl_objp->instance].ship_name, goal_point.xyz.x, goal_point.xyz.y, goal_point.xyz.z, dist));

}
*/

#define CHASE_CIRCLE_DIST               100.0f

void ai_chase_circle(object *objp)
{
        float           dist_to_goal;
        float           target_speed;
        vector  goal_point;
        ship_info       *sip;
        ai_info         *aip;

        sip = &Ship_info[Ships[Pl_objp->instance].ship_info_index];

        target_speed = sip->max_speed/4.0f;
        aip = &Ai_info[Ships[Pl_objp->instance].ai_index];

        Assert(vm_vec_mag(&aip->goal_point) >= 0.0f);           //      Supposedly detects bogus vector

        goal_point = aip->goal_point;

        if (aip->ignore_objnum == UNUSED_OBJNUM) {
                dist_to_goal = vm_vec_dist_quick(&aip->goal_point, &objp->pos);

                if (dist_to_goal > 2*CHASE_CIRCLE_DIST) {
                        vector  vec_to_goal;
                        //      Too far from circle goal, create a new goal point.
                        vm_vec_normalized_dir(&vec_to_goal, &aip->goal_point, &objp->pos);
                        vm_vec_scale_add(&aip->goal_point, &objp->pos, &vec_to_goal, CHASE_CIRCLE_DIST);
                }

                goal_point = aip->goal_point;
        } else if (is_ignore_object(aip, aip->ignore_objnum)) {
                object  *ignore_objp = &Objects[aip->ignore_objnum];

                vector  tvec1;
                float           dist;

                dist = vm_vec_normalized_dir(&tvec1, &Pl_objp->pos, &ignore_objp->pos);

                if (dist < ignore_objp->radius*2 + 1500.0f) {
                        vm_vec_scale_add(&goal_point, &Pl_objp->pos, &tvec1, ignore_objp->radius*2 + 1400.0f);
                        if (dist < ignore_objp->radius*2 + 1300.0f)
                                target_speed = sip->max_speed * (1.25f - dist/(ignore_objp->radius*2 + 1500.0f));
                }
        }

        Assert(vm_vec_mag(&aip->goal_point) >= 0.0f);           //      Supposedly detects bogus vector

        turn_towards_tangent(Pl_objp, &goal_point, 10*objp->radius + 200.0f);

        set_accel_for_target_speed(Pl_objp, target_speed);

}

#define SHIELD_BALANCE_RATE     0.2f            //      0.1f -> takes 10 seconds to equalize shield.

//      Transfer shield energy to most recently hit section from others.
void ai_transfer_shield(object *objp, int quadrant_num)
{
        int     i;
        float   transfer_amount;
        float   transfer_delta;
        ship_info       *sip;
        float   max_quadrant_strength;

        sip = &Ship_info[Ships[objp->instance].ship_info_index];
        max_quadrant_strength = sip->shields/MAX_SHIELD_SECTIONS;

        transfer_amount = 0.0f;
        transfer_delta = (SHIELD_BALANCE_RATE/2) * max_quadrant_strength;

        if (objp->shields[quadrant_num] + (MAX_SHIELD_SECTIONS-1)*transfer_delta > max_quadrant_strength)
                transfer_delta = (max_quadrant_strength - objp->shields[quadrant_num])/(MAX_SHIELD_SECTIONS-1);

        for (i=0; i<MAX_SHIELD_SECTIONS; i++)
                if (i != quadrant_num) {
                        if (objp->shields[i] >= transfer_delta) {
                                objp->shields[i] -= transfer_delta;
                                transfer_amount += transfer_delta;
                        } else {
                                transfer_amount += objp->shields[i];
                                objp->shields[i] = 0.0f;
                        }
                }

        objp->shields[quadrant_num] += transfer_amount;
}

void ai_balance_shield(object *objp)
{
        int     i;
        float   shield_strength_avg;
        float   delta;


        shield_strength_avg = get_shield_strength(objp)/MAX_SHIELD_SECTIONS;

        delta = SHIELD_BALANCE_RATE * shield_strength_avg;

        for (i=0; i<MAX_SHIELD_SECTIONS; i++)
                if (objp->shields[i] < shield_strength_avg) {
                        add_shield_strength(objp, delta);
                        if (objp->shields[i] > shield_strength_avg)
                                objp->shields[i] = shield_strength_avg;
                } else {
                        add_shield_strength(objp, -delta);
                        if (objp->shields[i] < shield_strength_avg)
                                objp->shields[i] = shield_strength_avg;
                }
}

//      Manage the shield for this ship.
//      Try to max out the side that was most recently hit.
void ai_manage_shield(object *objp, ai_info *aip)
{
        ship_info *sip;

        sip = &Ship_info[Ships[objp->instance].ship_info_index];

        if (timestamp_elapsed(aip->shield_manage_timestamp)) {
                float           delay;

                //      Scale time until next manage shield based on Skill_level.
                //      Ships on player's team are treated as if Skill_level is average.
                if (Ships[objp->instance].team != Player_ship->team){
                        delay = Shield_manage_delays[Game_skill_level];
                } else {
                        delay = Shield_manage_delays[NUM_SKILL_LEVELS/2];
                }

                //      Scale between 1x and 3x based on ai_class
                delay = delay + delay * (float) (3*(Num_ai_classes - aip->ai_class - 1) / (Num_ai_classes - 1));
                aip->shield_manage_timestamp = timestamp((int) (delay * 1000.0f));

                if (sip->flags & SIF_SMALL_SHIP) {
                        if (Missiontime - aip->last_hit_time < F1_0*10)
                                ai_transfer_shield(objp, aip->last_hit_quadrant);
                        else
                                ai_balance_shield(objp);
                }

                // nprintf(("AI", "Time: %7.3f Next: %7.3f, Shields: %7.3f %7.3f %7.3f %7.3f\n", f2fl(Missiontime), f2fl(Missiontime) + delay, objp->shields[0], objp->shields[1], objp->shields[2], objp->shields[3]));
        }
}

//      See if object *objp should evade an incoming missile.
//      *aip is the ai_info pointer within *objp.
void ai_maybe_evade_locked_missile(object *objp, ai_info *aip)
{
        ship                    *shipp;
        ship_info       *sip;

        shipp = &Ships[objp->instance];
        sip = &Ship_info[shipp->ship_info_index];

        //      Only small ships evade an incoming missile.  Why would a capital ship try to swerve?
        if (!(Ship_info[Ships[objp->instance].ship_info_index].flags & SIF_SMALL_SHIP)) {
                return;
        }

        if (aip->ai_flags & (AIF_NO_DYNAMIC | AIF_KAMIKAZE)) {  //      If not allowed to pursue dynamic objectives, don't evade.  Dumb?  Maybe change. -- MK, 3/15/98
                return;
        }

        if (aip->nearest_locked_object != -1) {
                object  *missile_objp;

                missile_objp = &Objects[aip->nearest_locked_object];

                if (Weapons[missile_objp->instance].homing_object != objp) {
                        //nprintf(("AI", "\nMissile lost home!"));
                        aip->nearest_locked_object = -1;
                        return;
                }

                if ((missile_objp->type == OBJ_WEAPON) && (Weapon_info[Weapons[missile_objp->instance].weapon_info_index].wi_flags & WIF_HOMING)) {
                        float dist = vm_vec_dist_quick(&missile_objp->pos, &objp->pos);
                        float dist2 = 4.0f  * vm_vec_mag_quick(&missile_objp->phys_info.vel);                   
                        if (dist < dist2) {
                                switch (aip->mode) {
                                //      If in AIM_STRAFE mode, don't evade if parent of weapon is targeted ship.
                                case AIM_STRAFE:
                                        if ((missile_objp->parent != -1) && (missile_objp->parent == aip->target_objnum)) {
                                                ;
                                        } else {
                                                ;               //      Alan -- If you want to handle incoming weapons from someone other than the ship
                                                                //      the strafing ship is attacking, do it here.
                                        }
                                        break;
                                case AIM_CHASE:
                                        //      Don't always go into evade weapon mode.  Usually, a countermeasure gets launched.
                                        // If low on countermeasures, more likely to try to evade.  If 8+, never evade due to low cmeasures.
                                        if (((((Missiontime >> 18) ^ OBJ_INDEX(objp)) & 3) == 0) || 
                                                (objp->phys_info.speed < 40.0f) ||
                                                (frand() < 1.0f - (float) shipp->cmeasure_count/8.0f)) {
                                                if (aip->submode != SM_ATTACK_FOREVER) {        //      SM_ATTACK_FOREVER means engines blown.
                                                        aip->submode = SM_EVADE_WEAPON;
                                                        aip->submode_start_time = Missiontime;
                                                }
                                        }
                                        break;
                                case AIM_DOCK:  //      Ships in dock mode can evade iif they are not currently repairing or docked.
                                        if (aip->ai_flags & (AIF_REPAIRING | AIF_DOCKED))
                                                break;
                                case AIM_GUARD:
                                        //      If in guard mode and far away from guard object, don't pursue guy that hit me.
                                        if ((aip->guard_objnum != -1) && (aip->guard_signature == Objects[aip->guard_objnum].signature)) {
                                                if (vm_vec_dist_quick(&objp->pos, &Objects[aip->guard_objnum].pos) > 500.0f) {
                                                        return;
                                                }
                                        }
                                case AIM_EVADE:
                                case AIM_GET_BEHIND:
                                case AIM_STAY_NEAR:
                                case AIM_STILL:
                                case AIM_AVOID:
                                case AIM_WAYPOINTS:
                                case AIM_NONE:
                                case AIM_BIGSHIP:
                                case AIM_PATH:
                                case AIM_BE_REARMED:
                                case AIM_SAFETY:
                                case AIM_BAY_EMERGE:
                                        aip->active_goal = AI_ACTIVE_GOAL_DYNAMIC;
                                        aip->previous_mode = aip->mode;
                                        aip->previous_submode = aip->submode;
                                        aip->mode = AIM_EVADE_WEAPON;
                                        aip->submode = -1;
                                        aip->submode_start_time = Missiontime;
                                        aip->mode_time = timestamp(MAX_EVADE_TIME);     //      Max time to evade.
                                        //nprintf(("AI", "%s Evade weapon in frame #%i\n", Ships[objp->instance].ship_name, AI_FrameCount));
                                        break;
                                case AIM_EVADE_WEAPON:          //      Note: We don't want to change mode on another evasion, or previous_mode will get bashed.
                                case AIM_PLAY_DEAD:
                                case AIM_BAY_DEPART:
                                case AIM_SENTRYGUN:
                                        break;
                                case AIM_WARP_OUT:
                                        break;
                                default:
                                        Int3();                 //      Hey, what mode is it?
                                        break;
                                }
                        }
                } else {
                        aip->nearest_locked_object = -1;
                }
        }
}

//      Maybe evade a dumbfire weapon that was fired when Pl_objp was targeted.
//      Have an 80% chance of evading in a second
void maybe_evade_dumbfire_weapon(ai_info *aip)
{
        //      Only small ships evade an incoming missile.  Why would a capital ship try to swerve?
        if (!(Ship_info[Ships[Pl_objp->instance].ship_info_index].flags & SIF_SMALL_SHIP)) {
                return;
        }

        //      Make sure in a mode in which we evade dumbfire weapons.
        switch (aip->mode) {
        case AIM_CHASE:
                if (aip->submode == SM_ATTACK_FOREVER) {
                        return;
                }
        case AIM_GUARD:
                //      If in guard mode and far away from guard object, don't pursue guy that hit me.
                if ((aip->guard_objnum != -1) && (aip->guard_signature == Objects[aip->guard_objnum].signature)) {
                        if (vm_vec_dist_quick(&Objects[Ships[aip->shipnum].objnum].pos, &Objects[aip->guard_objnum].pos) > 500.0f) {
                                return;
                        }
                }
        case AIM_STILL:
        case AIM_STAY_NEAR:
        case AIM_EVADE:
        case AIM_GET_BEHIND:
        case AIM_AVOID:
        case AIM_PATH:
        case AIM_NONE:
        case AIM_WAYPOINTS:
        case AIM_SAFETY:
                break;
        case AIM_STRAFE:
        case AIM_BIGSHIP:
        case AIM_DOCK:
        case AIM_PLAY_DEAD:
        case AIM_EVADE_WEAPON:
        case AIM_BAY_EMERGE:
        case AIM_BAY_DEPART:
        case AIM_SENTRYGUN:
        case AIM_WARP_OUT:
                return;
        default:
                Int3(); //      Bogus mode!
                return;
        }

        if (is_instructor(&Objects[Ships[aip->shipnum].objnum]))
                return; //      Instructor doesn't evade.

        float t = ai_endangered_by_weapon(aip);
        if ((t > 0.0f) && (t < 1.0f)) {
        // Check if this weapon is from a large ship Pl_objp is attacking... if so, enter strafe mode
                if ( ai_big_maybe_enter_strafe_mode(Pl_objp, aip->danger_weapon_objnum) ) {
                        return;
                }

                switch (aip->mode) {
                case AIM_CHASE:
                        switch (aip->submode) {
                        case SM_EVADE:
                        case SM_ATTACK_FOREVER:
                        case SM_AVOID:
                        case SM_GET_AWAY:
                        case SM_EVADE_WEAPON:
                                break;
                        default:
                                if (ai_near_full_strength(Pl_objp, &Ship_info[Ships[Pl_objp->instance].ship_info_index])) {
                                        //mprintf(("Ship %s entered super mode at %7.3f\n", Ships[Pl_objp->instance].ship_name, 1.0f * Missiontime / (1<<16)));
                                        aip->submode = SM_SUPER_ATTACK;
                                        aip->submode_start_time = Missiontime;
                                        aip->last_attack_time = Missiontime;
                                } else {
                                        //mprintf(("Ship %s entered dumbfire evade mode at %7.3f\n", Ships[Pl_objp->instance].ship_name, 1.0f * Missiontime / (1<<16)));
                                        aip->submode = SM_EVADE_WEAPON;
                                        aip->submode_start_time = Missiontime;
                                }
                                break;
                        }
                        break;
                case AIM_GUARD:
                case AIM_STILL:
                case AIM_STAY_NEAR:
                case AIM_EVADE:
                case AIM_GET_BEHIND:
                case AIM_AVOID:
                case AIM_PATH:
                case AIM_NONE:
                case AIM_WAYPOINTS:
                case AIM_SAFETY:
                        if (!(aip->ai_flags & (AIF_NO_DYNAMIC | AIF_KAMIKAZE)) && (Ship_info[Ships[aip->shipnum].ship_info_index].flags & SIF_SMALL_SHIP)) {
                                aip->active_goal = AI_ACTIVE_GOAL_DYNAMIC;
                                aip->previous_mode = aip->mode;
                                aip->previous_submode = aip->submode;
                                aip->mode = AIM_EVADE_WEAPON;
                                aip->submode = -1;
                                aip->submode_start_time = Missiontime;
                                aip->mode_time = timestamp(MAX_EVADE_TIME);     //      Evade for up to five seconds.
                        }
                        break;
                case AIM_STRAFE:
                case AIM_BIGSHIP:
                case AIM_DOCK:
                case AIM_PLAY_DEAD:
                case AIM_EVADE_WEAPON:
                case AIM_BAY_EMERGE:
                case AIM_BAY_DEPART:
                case AIM_SENTRYGUN:
                        break;
                default:
                        Int3(); //      Bogus mode!
                }
        }
}

// determine what path to use when emerging from a fighter bay
// input:       pl_objp =>      pointer to object for ship that is arriving
//                              pos             =>      output parameter, it is the starting world pos for path choosen
//                              v.fvec          =>      output parameter, this is the forward vector that ship has when arriving
//
// exit:                -1              =>      path could not be located
//                               0              => success
int ai_acquire_emerge_path(object *pl_objp, int parent_objnum, vector *pos, vector *fvec)
{
        int                     path_index, sb_path_index;
        ship                    *parent_sp = NULL;
        polymodel       *pm;
        ai_info         *aip;
        ship_bay                *sb;
        pnode                   *pnp;
        vector          *next_point;

        aip = &Ai_info[Ships[pl_objp->instance].ai_index];

        if ( parent_objnum == -1 ) {
                Int3();
                return -1;
        }

        parent_sp = &Ships[Objects[parent_objnum].instance];

        Assert(parent_sp != NULL);
        pm = model_get( parent_sp->modelnum );
        sb = pm->ship_bay;

        if ( sb == NULL ) 
                return -1;

        if ( sb->num_paths <= 0 ) 
                return -1;

        // try to find a bay path that is not taken
        path_index = -1;
        sb_path_index = Ai_last_arrive_path++;

        if ( sb_path_index >= sb->num_paths ) {
                sb_path_index=0;
                Ai_last_arrive_path=0;
        }

        path_index = sb->paths[sb_path_index];
        if ( path_index == -1 ) 
                return -1;

        // create the path for pl_objp to follow
        create_model_exit_path(pl_objp, &Objects[parent_objnum], path_index, pm->paths[path_index].nverts);
        
        // Set this flag, so we don't bother recreating the path... we won't need to update the path
        // that has just been created.
//      aip->ai_flags |= AIF_USE_STATIC_PATH;

        // now return to the caller what the starting world pos and starting fvec for the ship will be
        Assert((aip->path_start >= 0) && (aip->path_start < MAX_PATH_POINTS));
        pnp = &Path_points[aip->path_start];
        *pos = pnp->pos;

        // calc the forward vector using the starting two points of the path
        pnp = &Path_points[aip->path_start+1];
        next_point = &pnp->pos;
        vm_vec_normalized_dir(fvec, next_point, pos);

        // record the parent objnum, since we'll need it once we're done with following the path
        aip->goal_objnum = parent_objnum;
        aip->goal_signature = Objects[parent_objnum].signature;
        aip->mode = AIM_BAY_EMERGE;
        aip->submode_start_time = Missiontime;

        // set up starting vel
        vector vel;
        float speed;
        speed = Ship_info[Ships[pl_objp->instance].ship_info_index].max_speed;
        vel = *fvec;
        vm_vec_scale( &vel, speed );
        pl_objp->phys_info.vel = vel;
        pl_objp->phys_info.desired_vel = vel;
        pl_objp->phys_info.prev_ramp_vel.xyz.x = 0.0f;
        pl_objp->phys_info.prev_ramp_vel.xyz.y = 0.0f;
        pl_objp->phys_info.prev_ramp_vel.xyz.z = speed;
        pl_objp->phys_info.forward_thrust = 0.0f;               // How much the forward thruster is applied.  0-1.

        return 0;       
}

// clean up path data used for emerging from a fighter bay
void ai_emerge_bay_path_cleanup(ai_info *aip)
{
        aip->path_start = -1;
        aip->path_cur = -1;
        aip->path_length = 0;
        aip->mode = AIM_NONE;
}

// handler for AIM_BAY_EMERGE
void ai_bay_emerge()
{
        ai_info *aip;
        int             parent_died=0;

        aip = &Ai_info[Ships[Pl_objp->instance].ai_index];

        // if no path to follow, leave this mode
        if ( aip->path_start < 0 ) {
                aip->mode = AIM_NONE;
                return;
        }

        // ensure parent ship is still alive
        if ( aip->goal_objnum < 0 ) {
                parent_died=1;
        } 
        if ( !parent_died ) {
                if ( Objects[aip->goal_objnum].signature != aip->goal_signature ) {
                        parent_died=1;
                }
        }

        if ( !parent_died ) {
                Assert(Objects[aip->goal_objnum].type == OBJ_SHIP);
                if ( Ships[Objects[aip->goal_objnum].instance].flags & SF_DYING ) {
                        parent_died = 1;
                }
        }

        if ( parent_died ) {
                ai_emerge_bay_path_cleanup(aip);
                return;
        }

        // follow the path to the final point
        ai_path();

        // New test: must have been in AI_EMERGE mode for at least 10 seconds, and be a minimum distance from the start point
        if ( ( (Missiontime - aip->submode_start_time) > 10*F1_0 ) && (vm_vec_dist_quick(&Pl_objp->pos, &Objects[aip->goal_objnum].pos) > 0.75f * Objects[aip->goal_objnum].radius)) {
                // erase path
                ai_emerge_bay_path_cleanup(aip);
        }

        // 2-25-99: Need this check to fix an assert for supercap ships... maybe we'll only do this check for supercaps 
        if (aip->path_cur > (aip->path_start+aip->path_length-1)) {
                ai_emerge_bay_path_cleanup(aip);
        }       
}

// Select the closest depart path
//
//      input:  aip     =>              ai info pointer to ship seeking to depart
//                              pm              =>              pointer to polymodel for the ship contining the ship bay/depart paths
//
// exit:                >=0     =>              ship bay path index for depart path (ie index into sb->paths[])
//                              -1              =>              no path could be found
//
// NOTE: this function should only be used for calculating closest depart paths for ai mode
//                      AI_BAY_DEPART.  It tries to find the closest path that isn't already in use
int ai_find_closest_depart_path(ai_info *aip, polymodel *pm)
{
        int                     i, j, best_path, best_free_path;
        float                   dist, min_dist, min_free_dist;
        vector          *source;
        model_path      *mp;
        ship_bay                *sb;

        sb = pm->ship_bay;

        best_free_path = best_path = -1;
        min_free_dist = min_dist = 1e20f;
        Assert(aip->shipnum >= 0);
        source = &Objects[Ships[aip->shipnum].objnum].pos;

        for ( i = 0; i < sb->num_paths; i++ ) {


                mp = &pm->paths[sb->paths[i]];
                for ( j = 0; j < mp->nverts; j++ ) {
                        dist = vm_vec_dist_squared(source, &mp->verts[j].pos);

                        if ( dist < min_dist ) {
                                min_dist = dist;
                                best_path = i;
                        }

                        // If this is a free path
                        if ( !(sb->depart_flags & (1<<i)) ) {
                                if ( dist < min_free_dist ) {
                                        min_free_dist = dist;
                                        best_free_path = i;
                                }
                        }
                }
        }

        if ( best_free_path >= 0 ) {
                return best_free_path;          
        }

        return best_path;
}

// determine what path to use when trying to depart to a fighter bay
// NOTE: this should be called when AIM_BAY_DEPART mode is set
//
// input:       pl_objp =>      pointer to object for ship that is departing
//
// exit:                -1      =>      could not find depart path
//                              0       => found depart path
int ai_acquire_depart_path(object *pl_objp, int parent_objnum)
{
        int                     objnum, path_index;
        polymodel       *pm;
        ai_info         *aip;
        ship                    *sp;
        ship_bay                *sb;

        aip = &Ai_info[Ships[pl_objp->instance].ai_index];

        if ( parent_objnum == -1 ) {
                ship_obj        *so;

                // for now just locate a captial ship on the same team:
                so = GET_FIRST(&Ship_obj_list);
                objnum = -1;
                while(so != END_OF_LIST(&Ship_obj_list)){
                        sp = &Ships[Objects[so->objnum].instance];
                        if ( (Ship_info[sp->ship_info_index].flags & (SIF_HUGE_SHIP)) && (sp->team == Ships[pl_objp->instance].team) ) {
                                objnum = so->objnum;
                                break;
                        }
                        so = GET_NEXT(so);
                } 
        } else {
                objnum = parent_objnum;
        }

        aip->path_start = -1;

        if ( objnum == -1 )
                return -1;

        pm = model_get( Ships[Objects[objnum].instance].modelnum );
        sb = pm->ship_bay;

        if ( sb == NULL ) 
                return -1;
        if ( sb->num_paths <= 0 ) 
                return -1;

/*
        
        path_index = -1;
        for ( i = 0; i < sb->num_paths; i++ ) {
                if ( !(sb->depart_flags & (1<<i)) ) {
                        sb->depart_flags |= (1<<i);
                        path_index = sb->paths[i];
                        aip->submode_parm0 = i;                 // use mode-specific parameter to record ship bay path index
                        break;
                }
        }
*/
        
        // take the closest path we can find
        int ship_bay_path;
        ship_bay_path = ai_find_closest_depart_path(aip, pm);
        path_index = sb->paths[ship_bay_path];
        aip->submode_parm0 = ship_bay_path;
        sb->depart_flags |= (1<<ship_bay_path);

        if ( path_index == -1 ) {
                return -1;
        }

        Assert(pm->n_paths > path_index);
        ai_find_path(pl_objp, objnum, path_index, 0);

        // Set this flag, so we don't bother recreating the path... we won't need to update the path
        // that has just been created.
        aip->ai_flags &= ~AIF_USE_STATIC_PATH;

        aip->goal_objnum = objnum;
        aip->goal_signature = Objects[objnum].signature;
        aip->mode = AIM_BAY_DEPART;

        Ships[pl_objp->instance].flags |= SF_DEPART_DOCKBAY;
        return 0;
}

// handler for AIM_BAY_DEPART
void ai_bay_depart()
{
        ai_info *aip;

        aip = &Ai_info[Ships[Pl_objp->instance].ai_index];

        // if no path to follow, leave this mode
        if ( aip->path_start < 0 ) {
                aip->mode = AIM_NONE;
                return;
        }

        // check if parent ship still exists, if not abort depart 
        if ( aip->goal_signature != Objects[aip->goal_objnum].signature ) {
                aip->mode = AIM_NONE;
                return;
        }

        // follow the path to the final point
        ai_path();

        // if the final point is reached, let default AI take over
        if ( aip->path_cur >= (aip->path_start+aip->path_length) ) {
                polymodel       *pm;
                ship_bay                *sb;

                pm = model_get( Ships[Objects[aip->goal_objnum].instance].modelnum );
                sb = pm->ship_bay;
                if ( sb != NULL ) {
                        sb->depart_flags &= ~(1<<aip->submode_parm0);
                }

                // make ship disappear
                Pl_objp->flags |= OF_SHOULD_BE_DEAD;
                ship_departed( Pl_objp->instance );

                // clean up path stuff
                aip->path_start = -1;
                aip->path_cur = -1;
                aip->path_length = 0;
                aip->mode = AIM_NONE;
        }
}

// Handler for AIM_SENTRYGUN.  This AI mode is for sentry guns only (ie floating turrets).
void ai_sentrygun()
{
        // Nothing to do here.  Turret firing is handled via process_subobjects().
        // If you want the sentry guns to do anything beyond firing their turrets at enemies, add it here!
}

//      --------------------------------------------------------------------------
//      Execute behavior given by aip->mode.
void ai_execute_behavior(ai_info *aip)
{
        switch (aip->mode) {
        case AIM_CHASE:
                if (En_objp) {
                        ai_chase();
                } else if (aip->submode == SM_EVADE_WEAPON) {
                        evade_weapon();
                        // maybe reset submode
                        if (aip->danger_weapon_objnum == -1) {
                                aip->submode = SM_ATTACK;
                                aip->submode_start_time = Missiontime;
                                aip->last_attack_time = Missiontime;
                        }
                } else {
                        //      Don't circle if this is the instructor.
                        ship    *shipp = &Ships[aip->shipnum];
                        ship_info       *sip = &Ship_info[shipp->ship_info_index];

                        if (strnicmp(shipp->ship_name, INSTRUCTOR_SHIP_NAME, strlen(INSTRUCTOR_SHIP_NAME))) {
                                if (sip->flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP)) {
                                        aip->mode = AIM_NONE;
                                } else {
                                        ai_chase_circle(Pl_objp);
                                }
                        }
                }
                break;
        case AIM_EVADE:
                if (En_objp) {
                        ai_evade();
                } else {
                        vector  tvec;
                        vm_vec_scale_add(&tvec, &Pl_objp->pos, &Pl_objp->orient.v.rvec, 100.0f);
                        turn_towards_point(Pl_objp, &tvec, NULL, 0.0f);
                        accelerate_ship(aip, 0.5f);
                }
                break;
        case AIM_STILL:
                ai_still();
                break;
        case AIM_STAY_NEAR:
                ai_stay_near();
                break;
        case AIM_GUARD:
                ai_guard();
                break;
        case AIM_WAYPOINTS:
                ai_waypoints();
                break;
        case AIM_DOCK:
                ai_dock();
                break;
        case AIM_NONE:
                // ai_formation();
                break;
        case AIM_BIGSHIP:
                ai_big_ship(Pl_objp);
                break;
        case AIM_PATH: {
                int path_num;
                path_num = ai_return_path_num_from_dockbay(&Objects[aip->goal_objnum], 0);
                ai_find_path(Pl_objp, aip->goal_objnum, path_num, 0);
                ai_path();
                break;
        }
        case AIM_SAFETY:
                ai_safety();
                break;
        case AIM_EVADE_WEAPON:
                evade_weapon();
                break;
        case AIM_STRAFE:
                if (En_objp) {
                        Assert(En_objp->type == OBJ_SHIP);
                        ai_big_strafe();        // strafe a big ship
                } else {
                        aip->mode = AIM_NONE;
                }
                break;
        case AIM_BAY_EMERGE:
                ai_bay_emerge();
                break;
        case AIM_BAY_DEPART:
                ai_bay_depart();
                break;
        case AIM_SENTRYGUN:
                ai_sentrygun();
                break;
        case AIM_WARP_OUT:
                break;          //      Note, handled directly from ai_frame().
        default:
                Int3();         //      This should never happen -- MK, 5/12/97 
                break;
        }

        if ( !(ship_get_SIF(aip->shipnum) & SIF_NOT_FLYABLE) ) {
                maybe_evade_dumbfire_weapon(aip);
        }
}

//      Auxiliary function for maybe_request_support.
//      Return 1 if subsystem "type" is worthy of repair, else return 0.
//      Since subsystems cannot be repaired if they are at 0 strength, don't return 1 if subsystem is dead.
int mrs_subsystem(ship *shipp, int type)
{
        float   t;

        t = ship_get_subsystem_strength(shipp, type);

        if (t > 0.0f) {
                return (int) ((1.0f - t) * 3);
        } else {
                return 3;
        }
}

//      Return number of ships on *objp's team that are currently rearming.
int num_allies_rearming(object *objp)
{
        ship_obj        *so;
        int             team;
        int             count = 0;

        team = Ships[objp->instance].team;

        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                object  *A;
                
                Assert (so->objnum != -1);
                A = &Objects[so->objnum];

                if (Ships[A->instance].team == team) {
                        if (Ai_info[Ships[A->instance].ai_index].ai_flags & (AIF_REPAIRING | AIF_AWAITING_REPAIR)) {
                                count++;
                        }
                }
        }

        return count;
}


//      Maybe ship *objp should request support (rearm/repair).
//      If it does, return TRUE, else return FALSE.
int maybe_request_support(object *objp)
{
        ship_info       *sip;
        ship                    *shipp;
        ai_info         *aip;
        int                     desire;

        Assert(objp->type == OBJ_SHIP);
        shipp = &Ships[objp->instance];
        aip = &Ai_info[shipp->ai_index];
        sip = &Ship_info[shipp->ship_info_index];

        if (!timestamp_elapsed(aip->next_rearm_request_timestamp))
                return 0;

        //      Only fighters and bombers request support.
        if (!(sip->flags & (SIF_FIGHTER | SIF_BOMBER)))
                return 0;

        //      A ship that is currently awaiting does not need support!
        if (aip->ai_flags & (AIF_AWAITING_REPAIR | AIF_BEING_REPAIRED))
                return 0;

        if (!is_support_allowed(objp))
                return 0;

        //if (shipp->team != TEAM_FRIENDLY)
        //      return 0;

        //      Compute a desire value.
        //      Desire of 0 means no reason to request support.
        //      1 is slight, 2 more, etc.  Maximum is around 20.  Anything larger than 3 is pretty strong.
        desire = 0;

        //      Set desire based on hull strength.
        //      No: We no longer repair hull, so this would cause repeated repair requests.
        //desire += 6 - (int) ((objp->hull_strength/sip->initial_hull_strength) * 6.0f);

        //      Set desire based on key subsystems.
        desire += 2*mrs_subsystem(shipp, SUBSYSTEM_ENGINE);     //      Note, disabled engine forces repair request, regardless of nearby enemies.
        desire += mrs_subsystem(shipp, SUBSYSTEM_COMMUNICATION);
        desire += mrs_subsystem(shipp, SUBSYSTEM_WEAPONS);
        desire += mrs_subsystem(shipp, SUBSYSTEM_SENSORS);

        //      Set desire based on percentage of secondary weapons.
        ship_weapon *swp = &shipp->weapons;

        for ( int i = 0; i < swp->num_secondary_banks; i++ ) {
                if (swp->secondary_bank_start_ammo[i] > 0) {
//                      float r = (float) swp->secondary_bank_ammo[i]*Weapon_info[swp->secondary_bank_weapons[i]].cargo_size/swp->secondary_bank_capacity[i];
                        float r = (float) swp->secondary_bank_ammo[i]/swp->secondary_bank_start_ammo[i];
                        desire += (int) ((1.0f - r) * 3.0f);
                }
        }

        //      If no reason to repair, don't bother to see if it's safe to repair.
        if (desire == 0){
                return 0;
        }

        //      Compute danger threshold.
        //      Balance this with desire and maybe request support.
        if (ai_good_time_to_rearm( objp )) {
                ai_issue_rearm_request(objp);
                return 1;
        } else if (num_allies_rearming(objp) < 2) {
                if (desire >= 8) {      //      guarantees disabled will cause repair request
                        ai_issue_rearm_request(objp);
                } else if (desire >= 3) {               //      >= 3 means having a single subsystem fully blown will cause repair.
                        int     count;
                        int objnum = find_nearby_hostile(OBJ_INDEX(objp), get_enemy_team_mask(OBJ_INDEX(objp)), 2000.0f, &count);

                        if ((objnum == -1) || (count < 2) || (vm_vec_dist_quick(&objp->pos, &Objects[objnum].pos) > 3000.0f*count/desire)) {
                                ai_issue_rearm_request(objp);
                                return 1;
                        } else {
                                //nprintf(("AI", "Would like to rearm, but enemy only %7.3f units away.\n", vm_vec_dist_quick(&objp->pos, &Objects[objnum].pos)));
                        }
                }
        }

        return 0;

}

void ai_set_mode_warp_out(object *objp, ai_info *aip)
{
        ai_abort_rearm_request(objp);
        if (aip->mode != AIM_WARP_OUT) {
                aip->mode = AIM_WARP_OUT;
                aip->submode = AIS_WARP_1;
        }
}

//      Maybe warp ship out.
//      Shivan and HoL fighter/bomber warp out if their weapons subsystems have been destroyed.
void ai_maybe_warp_out(object *objp)
{
        ship    *shipp;

        // don't do anything if in a training mission.
        if ( The_mission.game_type & MISSION_TYPE_TRAINING )
                return;

        Assert(objp->type == OBJ_SHIP);

        shipp = &Ships[objp->instance];
        ai_info *aip = &Ai_info[shipp->ai_index];

        if (aip->mode == AIM_WARP_OUT)
                return;

        //      If a support ship with no goals and low hull, warp out.  Be sure that there are no pending goals
        // in the support ships ai_goal array.  Just process this ships goals.
        ship_info       *sip = &Ship_info[shipp->ship_info_index];
        if (sip->flags & SIF_SUPPORT) {
                if ( timestamp_elapsed(aip->warp_out_timestamp) ) {
                        ai_process_mission_orders( OBJ_INDEX(objp), aip );
                        if ( (aip->dock_objnum == -1) && (objp->hull_strength/sip->initial_hull_strength < 0.25f) ) {
                                ai_set_mode_warp_out(objp, aip);
                        }
                }
        }

        //      Friendly don't warp out, they'll eventually request support.
        if (shipp->team == TEAM_FRIENDLY)
                return;

        if (!(shipp->flags & SF_DEPARTING)) {
                ship_info       *sip;

                sip = &Ship_info[shipp->ship_info_index];
                if (sip->flags & (SIF_FIGHTER | SIF_BOMBER)) {
                        if (aip->warp_out_timestamp == 0) {
                                //if (ship_get_subsystem_strength(shipp, SUBSYSTEM_WEAPONS) == 0.0f) {
                                //      aip->warp_out_timestamp = timestamp(((myrand() % 10) + 10) * 1000);
                                //}
                        } else if (timestamp_elapsed(aip->warp_out_timestamp)) {
                                ai_set_mode_warp_out(objp, aip);
                        }
                }
        }
}

//      Warp this ship out.
void ai_warp_out(object *objp)
{
        // if dying, don't warp out.
        if (Ships[objp->instance].flags & SF_DYING) {
                return;
        }

        ai_info *aip;

        aip = &Ai_info[Ships[objp->instance].ai_index];

        switch (aip->submode) {
        case AIS_WARP_1:
                aip->force_warp_time = timestamp(10*1000);      //      Try to avoid a collision for up to ten seconds.
                aip->submode = AIS_WARP_2;
                break;
        case AIS_WARP_2:                        //      Make sure won't collide with any object.
                if (timestamp_elapsed(aip->force_warp_time) || !collide_predict_large_ship(objp, objp->radius*2.0f + 100.0f)) {
                        aip->submode = AIS_WARP_3;

                        // maybe recalculate collision pairs.
                        if (ship_get_warp_speed(objp) > ship_get_max_speed(&Ships[objp->instance])) {
                                // recalculate collision pairs
                                OBJ_RECALC_PAIRS(objp); 
                        }

                        aip->force_warp_time = timestamp(4*1000);               //      Try to attain target speed for up to 4 seconds.
                } else {
                        vector  goal_point;
                        vm_vec_scale_add(&goal_point, &objp->pos, &objp->orient.v.uvec, 100.0f);
                        turn_towards_point(objp, &goal_point, NULL, 0.0f);
                        accelerate_ship(aip, 0.0f);
                }
                break;
        case AIS_WARP_3:
                //      Rampup desired_vel in here from current to desired velocity and set PF_USE_VEL. (not sure this is the right flag)
                //      desired velocity is computed in shipfx_calculate_warp_time().  See shipfx#572 for sample code.
                float   speed, goal_speed;
                float shipfx_calculate_warp_speed(object*);
                goal_speed = shipfx_calculate_warp_speed(objp);

                // HUGE ships go immediately to AIS_WARP_4
                if (Ship_info[Ships[objp->instance].ship_info_index].flags & SIF_HUGE_SHIP) {
                        aip->submode = AIS_WARP_4;
                        break;
                }
                //compute_warpout_stuff(objp, &goal_speed, &warp_time, &warp_pos);
                //goal_speed = 80.0f;
                //set_accel_for_target_speed(objp, 40.0f);
                // DKA 8/11/99 objp->phys_info.flags |= PF_USE_VEL;     This flag is set in object code if warping out and AIS_WARP >= 3, properly accounting for blown engines
                speed = goal_speed * flFrametime + objp->phys_info.speed * (1.0f - flFrametime);
                vm_vec_copy_scale(&objp->phys_info.vel, &objp->orient.v.fvec, speed);
                objp->phys_info.desired_vel = objp->phys_info.vel;
                // nprintf(("AI", "Frame %i, speed = %7.3f, goal = %7.3f\n", Framecount, vm_vec_mag_quick(&objp->phys_info.vel), goal_speed));
                if (timestamp_elapsed(aip->force_warp_time) || (fl_abs(objp->phys_info.speed - goal_speed) < 2.0f))
                        aip->submode = AIS_WARP_4;
                break;
        case AIS_WARP_4: {
                shipfx_warpout_start(objp);
                aip->submode = AIS_WARP_5;
                break;
        }
        case AIS_WARP_5:
                break;
        default:
                Int3();         //      Illegal submode for warping out.
        }
}

//      Return object index of weapon that could produce a shockwave that should be known about to *objp.
//      Return nearest one.
int ai_find_shockwave_weapon(object *objp, ai_info *aip)
{
        missile_obj     *mo;
        float   nearest_dist = 999999.9f;
        int     nearest_index = -1;

        for ( mo = GET_NEXT(&Missile_obj_list); mo != END_OF_LIST(&Missile_obj_list); mo = GET_NEXT(mo) ) {
                object          *A;
                weapon          *wp;
                weapon_info     *wip;
        
                Assert(mo->objnum >= 0 && mo->objnum < MAX_OBJECTS);
                A = &Objects[mo->objnum];

                Assert(A->type == OBJ_WEAPON);
                Assert((A->instance >= 0) && (A->instance < MAX_WEAPONS));
                wp = &Weapons[A->instance];
                wip = &Weapon_info[wp->weapon_info_index];
                Assert( wip->subtype == WP_MISSILE );

                if (wip->shockwave_speed > 0.0f) {
                        float   dist;

                        dist = vm_vec_dist_quick(&objp->pos, &A->pos);
                        if (dist < nearest_dist) {
                                nearest_dist = dist;
                                nearest_index = mo->objnum;
                        }
                }
        }

        return nearest_index;

}

#define EVADE_SHOCKWAVE_DAMAGE_THRESHOLD                100.0f

//      Tell all ships to avoid a big ship that is blowing up.
//      Only avoid if shockwave is fairly large.
//      OK to tell everyone to avoid.  If they're too far away, that gets cleaned up in the frame interval.
void ai_announce_ship_dying(object *dying_objp)
{
        float damage = ship_get_exp_damage(dying_objp);
        if (damage >= EVADE_SHOCKWAVE_DAMAGE_THRESHOLD) {
                ship_obj        *so;

                for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                        if (Ship_info[Ships[Objects[so->objnum].instance].ship_info_index].flags & (SIF_SMALL_SHIP | SIF_FREIGHTER)) {
                                ai_info *aip;

                                aip = &Ai_info[Ships[Objects[so->objnum].instance].ai_index];

                                if ( !(aip->ai_flags & (AIF_DOCKED|AIF_BEING_REPAIRED)) ) {
                                        aip->ai_flags |= AIF_AVOID_SHOCKWAVE_SHIP;
                                }
                        }
                }
        }
}


//      Return object index of weapon that could produce a shockwave that should be known about to *objp.
//      Return nearest one.
int ai_find_shockwave_ship(object *objp, ai_info *aip)
{
        ship_obj        *so;
        float   nearest_dist = 999999.9f;
        int     nearest_index = -1;

        for ( so = GET_NEXT(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                object          *A;
                ship                    *shipp;
        
                Assert(so->objnum >= 0 && so->objnum < MAX_OBJECTS);
                A = &Objects[so->objnum];

                Assert(A->type == OBJ_SHIP);
                Assert((A->instance >= 0) && (A->instance < MAX_SHIPS));
                shipp = &Ships[A->instance];
                //      Only look at objects in the process of dying.
                if (shipp->flags & SF_DYING) {
                        float damage = ship_get_exp_damage(objp);

                        if (damage >= EVADE_SHOCKWAVE_DAMAGE_THRESHOLD) {               //      Only evade quite large blasts
                                float   dist;

                                dist = vm_vec_dist_quick(&objp->pos, &A->pos);
                                if (dist < nearest_dist) {
                                        nearest_dist = dist;
                                        nearest_index = so->objnum;
                                }
                        }
                }
        }

        return nearest_index;

}

int aas_1(object *objp, ai_info *aip, vector *safe_pos)
{
        // MAKE SURE safe_pos DOES NOT TAKE US TOWARD THE A SHIP WE'RE ATTACKING.
        if (aip->ai_flags & AIF_AVOID_SHOCKWAVE_WEAPON) {
                //      If we don't currently know of a weapon to avoid, try to find one.
                //      If we can't find one, then clear the bit so we don't keep coming here.
                if (aip->shockwave_object == -1) {
                        int shockwave_weapon = ai_find_shockwave_weapon(objp, aip);
                        if (shockwave_weapon == -1) {
                                aip->ai_flags &= ~AIF_AVOID_SHOCKWAVE_WEAPON;
                                return 0;
                        } else {
                                aip->shockwave_object = shockwave_weapon;
                        }
                }

                //      OK, we have reason to believe we should avoid aip->shockwave_object.
                Assert(aip->shockwave_object > -1);
                object  *weapon_objp = &Objects[aip->shockwave_object];
                if (weapon_objp->type != OBJ_WEAPON) {
                        aip->ai_flags &= ~AIF_AVOID_SHOCKWAVE_WEAPON;
                        aip->shockwave_object = -1;
                        return 0;
                }

                weapon  *weaponp = &Weapons[weapon_objp->instance];
                weapon_info     *wip = &Weapon_info[weaponp->weapon_info_index];
                object *target_ship_obj = NULL;

                if (wip->shockwave_speed == 0.0f) {
                        aip->ai_flags &= ~AIF_AVOID_SHOCKWAVE_WEAPON;
                        aip->shockwave_object = -1;
                        return 0;
                }

                float   danger_dist;
                vector  expected_pos;           //      Position at which we expect the weapon to detonate.
                int             pos_set = 0;

                danger_dist = wip->outer_radius;
                //      Set predicted position of detonation.
                //      If an aspect locked missile, assume it will detonate at the homing position.
                //      If not, which is not possible in a default FreeSpace weapon, then predict it will detonate at some
                //      time in the future, this time based on max lifetime and life left.
                if (wip->wi_flags & WIF_HOMING_ASPECT) {
                        expected_pos = weaponp->homing_pos;
                        if (weaponp->homing_object && weaponp->homing_object->type == OBJ_SHIP) {
                                target_ship_obj = weaponp->homing_object;
                        }
                        pos_set = 1;
                        if (IS_VEC_NULL(&weaponp->homing_pos)) {
                                pos_set = 0;
                                if (weaponp->target_num != -1) {
                                        if (Objects[weaponp->target_num].type == OBJ_SHIP) {
                                                target_ship_obj = &Objects[weaponp->target_num];
                                                expected_pos = target_ship_obj->pos;
                                                pos_set = 1;
                                        }
                                }
                        }
                }

                if (!pos_set) {
                        float   time_scale;

                        if (wip->lifetime - weaponp->lifeleft > 5.0f) {
                                time_scale = 1.0f;
                        } else {
                                time_scale = weaponp->lifeleft/2.0f;
                        }

                        vm_vec_scale_add(&expected_pos, &weapon_objp->pos, &weapon_objp->orient.v.fvec, time_scale);
                }

                //      See if too far away to care about shockwave.
                if (vm_vec_dist_quick(&objp->pos, &expected_pos) > danger_dist*2.0f) {
                        //aip->ai_flags &= ~AIF_AVOID_SHOCKWAVE_WEAPON;
                        return 0;
                } else {
                        // try to find a safe position
                        vector vec_from_exp;
                        float dir = 1.0f;
                        vm_vec_sub(&vec_from_exp, &objp->pos, &expected_pos);
                        float dot = vm_vec_dotprod(&vec_from_exp, &weapon_objp->orient.v.fvec);
                        if (dot > -30) {
                                // if we're already on the other side of the explosion, don't try to fly behind it
                                dir = -1.0f;
                        }

                        //      Fly towards a point behind the weapon.
                        vm_vec_scale_add(safe_pos, &weapon_objp->pos, &weapon_objp->orient.v.fvec, -50000.0f*dir);

                        // verify safe_pos will not make us collide with our target objnum, else try 2 other vecs
                        // don't bang your head, else go
//                      int go_safe = FALSE;
                        int go_safe = TRUE;
/*                      if (target_ship_obj) {
                                if (pp_collide(&objp->pos, safe_pos, target_ship_obj, objp->radius)) {
                                        // try up to 2 other random directions
                                        vector dir_vec, rand_vec;
                                        int idx;
                                        for (idx=0; idx<2; idx++) {
                                                vm_vec_rand_vec_quick(&rand_vec);
                                                vm_vec_scale_add(&dir_vec, &weapon_objp->orient.v.fvec, &rand_vec, 0.5f);
                                                vm_vec_scale_add(safe_pos, &weapon_objp->pos, &dir_vec, -50000.0f*dir);
                                                if ( !pp_collide(&objp->pos, safe_pos, target_ship_obj, objp->radius) ) {
                                                        go_safe = TRUE;
                                                        break;
                                                }
                                        }
                                } else { // direct path is safe
                                        go_safe = TRUE;
                                }
                        } else { // no target_obj_ship
                                go_safe = TRUE;
                        } */

                        if (go_safe) {
                                return 1;
                        } else {
                                // can't figure out a good way to go
                                return 0;
                        }
                }
        } else if (aip->ai_flags & AIF_AVOID_SHOCKWAVE_SHIP) {
                if (aip->shockwave_object == -1) {
                        int shockwave_ship = ai_find_shockwave_ship(objp, aip);
                        if (shockwave_ship == -1) {
                                aip->ai_flags &= ~AIF_AVOID_SHOCKWAVE_SHIP;
                                return 0;
                        } else {
                                aip->shockwave_object = shockwave_ship;
                        }
                }

                Assert(aip->shockwave_object > -1);
                object  *ship_objp = &Objects[aip->shockwave_object];
                if (ship_objp == objp) {
                        aip->shockwave_object = -1;
                        return 0;
                }

                if (ship_objp->type != OBJ_SHIP) {
                        aip->ai_flags &= ~AIF_AVOID_SHOCKWAVE_SHIP;
                        return 0;
                }

                //      Optimize note! Don't really have to normalize.  We only need a point away from the blowing-up ship.
                vector safe_vec;

                vm_vec_normalized_dir(&safe_vec, &objp->pos, &ship_objp->pos);
                vm_vec_scale_add(safe_pos, &ship_objp->pos, &safe_vec, 50000.0f);       //      Fly away from the ship.

                float outer_rad = ship_get_exp_outer_rad(ship_objp);

                if (vm_vec_dist_quick(&objp->pos, &ship_objp->pos) > outer_rad*1.5f) {
                        aip->ai_flags &= ~AIF_AVOID_SHOCKWAVE_WEAPON;
                        return 0;
                }

                return 1;

        } else {
                Int3(); //      Illegal -- supposedly avoiding a shockwave, but neither ship nor weapon.  What is it!?
        }

        return 0;
}

/*
int rct_done = 0;

void rand_chance_test()
{
        int     i;
        float   frametime;

        if (rct_done)
                return;

        rct_done = 1;

        for (frametime=0.02f; frametime<0.25f; frametime *= 1.25f) {
                float   chance;

                nprintf(("AI", "%6.4f: ", frametime));
                for (chance=0.25f; chance<2.5f; chance += 0.25f) {
                        int count = 0;

                        for (i=0; i<100.0f/frametime; i++) {
                                if (rand_chance(frametime, chance))
                                        count++;
                        }
                        nprintf(("AI", "%3i ", count));
                }
                nprintf(("AI", "\n"));
        }
}
*/

//      --------------------------------------------------------------------------
//      Make object *objp avoid the nearest dangerous shockwave-producing weapon.
//      If it looks like there is no valid shockwave-producing weapon then clear the AIF_AVOID_SHOCKWAVE_WEAPON bit in ai_flags and return.
//      Return 1 if avoiding a shockwave, else return 0.
int ai_avoid_shockwave(object *objp, ai_info *aip)
{
        vector  safe_pos;

        //rand_chance_test();
        // BIG|HUGE do not respond to shockwaves
        if (Ship_info[Ships[objp->instance].ship_info_index].flags & (SIF_BIG_SHIP|SIF_HUGE_SHIP)) {
                // don't come here again
                aip->ai_flags &= ~AIF_AVOID_SHOCKWAVE;
                return 0;
        }

        //      Don't all react right away.
        if (!(aip->ai_flags & AIF_AVOID_SHOCKWAVE_STARTED))
                if (!rand_chance(flFrametime, (float) aip->ai_class/4.0f + 0.25f))      //      Chance to avoid in 1 second is 0.25 + ai_class/4
                        return 0;

        if (!aas_1(objp, aip, &safe_pos)) {
                aip->ai_flags |= AIF_AVOID_SHOCKWAVE_STARTED;
                return 0;
        }

        aip->ai_flags |= AIF_AVOID_SHOCKWAVE_STARTED;

        //      OK, evade the shockwave!
        turn_towards_point(objp, &safe_pos, NULL, 0.0f);
        vector  vec_to_safe_pos;
        float           dot_to_goal;

        vm_vec_normalized_dir(&vec_to_safe_pos, &safe_pos, &objp->pos);

        dot_to_goal = vm_vec_dot(&objp->orient.v.fvec, &vec_to_safe_pos);
        if (dot_to_goal < -0.5f)
                accelerate_ship(aip, 0.3f);
        else {
                accelerate_ship(aip, 1.0f + dot_to_goal);
                if (dot_to_goal > 0.2f) {
                        if (!(objp->phys_info.flags & PF_AFTERBURNER_ON )) {
                                afterburners_start(objp);
                                aip->afterburner_stop_time = Missiontime + 2*F1_0;
                        }
                }
        }

        return 1;
}

//      Awaiting repair.  Be useful.
//      Probably fly towards incoming repair ship.
//      Return true if this ship is close to being repaired, else return false.
int ai_await_repair_frame(object *objp, ai_info *aip)
{
        if (!(aip->ai_flags & (AIF_AWAITING_REPAIR | AIF_BEING_REPAIRED)))
                return 0;

        if (aip->dock_objnum == -1)
                return 0;

        ship    *shipp;
        ship_info       *sip;

        shipp = &Ships[Objects[aip->dock_objnum].instance];
        sip = &Ship_info[shipp->ship_info_index];

        aip->ai_flags &= ~AIF_FORMATION_OBJECT; //      Prevents endless rotation.

        if (!(sip->flags & SIF_SUPPORT))
                return 0;

        vector  goal_point;
        object  *repair_objp;

        repair_objp = &Objects[aip->dock_objnum];

        if (Ships[repair_objp->instance].team == TEAM_TRAITOR) {
                ai_abort_rearm_request(repair_objp);
                return 0;
        }

        vm_vec_scale_add(&goal_point, &repair_objp->pos, &repair_objp->orient.v.uvec, -50.0f);  //      Fly towards point below repair ship.

        vector  vtr;
        float dist = vm_vec_normalized_dir(&vtr, &goal_point, &objp->pos);
        float dot = vm_vec_dot(&vtr, &objp->orient.v.fvec);

        if (dist > 200.0f) {
                //nprintf(("AI", "%s flying towards %s for repair, dist = %7.3f\n", Ships[objp->instance].ship_name, &Ships[repair_objp->instance].ship_name, dist));
                accelerate_ship(aip, (0.9f + dot) * dist/1500.0f);
                turn_towards_point(objp, &goal_point, NULL, 0.0f);
        } else {
                accelerate_ship(aip, 0.0f);
                //nprintf(("AI", "%s sitting still awaiting repair from %s, dist = %7.3f\n", Ships[objp->instance].ship_name, &Ships[repair_objp->instance].ship_name, dist));
        }

        return 1;
}

//      Maybe cause this ship to self-destruct.
//      Currently, any small ship (SIF_SMALL_SHIP) that has been disabled will self-destruct after awhile.
//      Maybe should only do this if they are preventing their wing from re-entering.
void ai_maybe_self_destruct(object *objp, ai_info *aip)
{
        //      Friendly ships can be repaired, so no self-destruct.
        //      In multiplayer, just don't self-destruct.  I figured there would be a problem. -- MK, 3/19/98.
        if ((Ships[objp->instance].team == TEAM_FRIENDLY) || (Game_mode & GM_MULTIPLAYER))
                return;

        //      Small ships in a wing blow themselves up after awhile if engine or weapons system has been destroyed.
        //      Reason: Don't want them to prevent a re-emergence of the wing.
        //      Note: Don't blow up if not in a wing for two reasons: One, won't affect re-emergence of waves and (1) disable the Dragon
        //      mission would be broken.
        if ((Ship_info[Ships[objp->instance].ship_info_index].flags & SIF_SMALL_SHIP) && (Ships[objp->instance].wingnum != -1)) {
                if ((ship_get_subsystem_strength(&Ships[objp->instance], SUBSYSTEM_ENGINE) <= 0.0f) ||
                        (ship_get_subsystem_strength(&Ships[objp->instance], SUBSYSTEM_WEAPONS) <= 0.0f)) {
                        if (aip->self_destruct_timestamp < 0)
                                aip->self_destruct_timestamp = timestamp(90 * 1000);    //      seconds until self-destruct
                } else {
                        aip->self_destruct_timestamp = -1;
                }

                if (aip->self_destruct_timestamp < 0) {
                        return;
                }

                if (timestamp_elapsed(aip->self_destruct_timestamp)) {
                        ship_apply_local_damage( objp, objp, &objp->pos, objp->hull_strength*flFrametime + 1.0f, MISS_SHIELDS);
                }
        }
}

// Determine if pl_objp needs a new target, called from ai_frame()
int ai_need_new_target(object *pl_objp, int target_objnum)
{
        object *objp;

        if ( target_objnum < 0 ) {
                return 1;
        }

        objp = &Objects[target_objnum];

        if ( (objp->type != OBJ_SHIP) && (objp->type != OBJ_ASTEROID) && (objp->type != OBJ_WEAPON) ) {
                return 1;
        }

        if ( objp->type == OBJ_SHIP ) {
                if ( Ships[objp->instance].flags & SF_DYING ) {
                        return 1;
                } else if (Ships[objp->instance].team == Ships[pl_objp->instance].team)
                        return 1;
        }

        return 0;
}

//      If *objp is recovering from a collision with a big ship, handle it.
//      Return true if recovering.
int maybe_big_ship_collide_recover_frame(object *objp, ai_info *aip)
{
        float   dot, dist;
        vector  v2g;
        
        if (aip->ai_flags & AIF_BIG_SHIP_COLLIDE_RECOVER_1) {
                ai_turn_towards_vector(&aip->big_recover_pos_1, objp, flFrametime, Ship_info[Ships[objp->instance].ship_info_index].srotation_time, NULL, NULL, 0.0f, 0, NULL);
                dist = vm_vec_normalized_dir(&v2g, &aip->big_recover_pos_1, &objp->pos);
                dot = vm_vec_dot(&objp->orient.v.fvec, &v2g);
                accelerate_ship(aip, dot);

                //      If close to desired point, or 15+ seconds since entered this mode, continue to next mode.
                if ((timestamp_until(aip->big_recover_timestamp) < -15*1000) || (dist < (0.5f + flFrametime) * objp->phys_info.speed)) {
                        aip->ai_flags &= ~AIF_BIG_SHIP_COLLIDE_RECOVER_1;
                        aip->ai_flags |= AIF_BIG_SHIP_COLLIDE_RECOVER_2;
                }

                return 1;

        } else if (aip->ai_flags & AIF_BIG_SHIP_COLLIDE_RECOVER_2) {
                ai_turn_towards_vector(&aip->big_recover_pos_2, objp, flFrametime, Ship_info[Ships[objp->instance].ship_info_index].srotation_time, NULL, NULL, 0.0f, 0, NULL);
                dist = vm_vec_normalized_dir(&v2g, &aip->big_recover_pos_2, &objp->pos);
                dot = vm_vec_dot(&objp->orient.v.fvec, &v2g);
                accelerate_ship(aip, dot);

                //      If close to desired point, or 30+ seconds since started avoiding collision, done avoiding.
                if ((timestamp_until(aip->big_recover_timestamp) < -30*1000) || (dist < (0.5f + flFrametime) * objp->phys_info.speed)) {
                        aip->ai_flags &= ~AIF_BIG_SHIP_COLLIDE_RECOVER_2;
                        aip->ai_flags &= ~AIF_TARGET_COLLISION;
                }

                return 1;
        }

        if (aip->ai_flags & AIF_TARGET_COLLISION) {
                aip->ai_flags &= ~AIF_TARGET_COLLISION;
        }
        return 0;
}

void validate_mode_submode(ai_info *aip)
{
        switch (aip->mode) {
        case AIM_CHASE:
                // check valid submode
                switch (aip->submode) {
                case SM_CONTINUOUS_TURN:
                case SM_ATTACK:
                case SM_EVADE_SQUIGGLE:
                case SM_EVADE_BRAKE:    
                case SM_EVADE:          
                case SM_SUPER_ATTACK:
                case SM_AVOID:  
                case SM_GET_BEHIND:
                case SM_GET_AWAY:               
                case SM_EVADE_WEAPON:
                case SM_FLY_AWAY:       
                case SM_ATTACK_FOREVER:
                        break;
                default:
                        Int3();
                }
                break;

        case AIM_STRAFE:
                // check valid submode
                switch(aip->submode) {
                case AIS_STRAFE_ATTACK:
                case AIS_STRAFE_AVOID:
                case AIS_STRAFE_RETREAT1:
                case AIS_STRAFE_RETREAT2:
                case AIS_STRAFE_POSITION:
                        break;
                default:
                        Int3();
                }
                break;
        }
}

//      --------------------------------------------------------------------------
// Process AI object "objnum".
void ai_frame(int objnum)
{
        ship            *shipp = &Ships[Objects[objnum].instance];
        ai_info *aip = &Ai_info[shipp->ai_index];
        int             target_objnum;

//      validate_mode_submode(aip);

        Assert((aip->mode != AIM_WAYPOINTS) || (aip->active_goal != AI_ACTIVE_GOAL_DYNAMIC));

        // Set globals defining the current object and its enemy object.
        Pl_objp = &Objects[objnum];

        if (aip->mode == AIM_WARP_OUT) {
                ai_warp_out(Pl_objp);
                return;
        }

/*      //      HACK! TEST! REMOVE ME!
        if (Ship_info[shipp->ship_info_index].flags & SIF_BIG_SHIP)
                if (shipp->team == Player_ship->team)
                        aip->mode = AIM_CHASE;
*/

//      if (!strnicmp(Ships[Pl_objp->instance].ship_name, "cancer", 6))
//              nprintf(("AI", "Ship %s: mode = %s, submode = %i\n", Ships[Pl_objp->instance].ship_name, Mode_text[aip->mode], aip->submode));

        ai_maybe_self_destruct(Pl_objp, aip);

//      if ( timestamp_elapsed(aip->goal_check_time) ) {
                ai_process_mission_orders( objnum, aip );
//              aip->goal_check_time = timestamp_rand(1000,2000);
//      }

        //      Avoid a shockwave, if necessary.  If a shockwave and rearming, stop rearming.
        if (aip->ai_flags & AIF_AVOID_SHOCKWAVE) {
                if (ai_avoid_shockwave(Pl_objp, aip)) {
                        aip->ai_flags &= ~(AIF_BIG_SHIP_COLLIDE_RECOVER_1 | AIF_BIG_SHIP_COLLIDE_RECOVER_2);
                        if (aip->ai_flags & (AIF_AWAITING_REPAIR | AIF_BEING_REPAIRED))
                                ai_abort_rearm_request(Pl_objp);
                        return;
                }
        } else {
                aip->ai_flags &= ~AIF_AVOID_SHOCKWAVE_STARTED;
        }

        // moved call to ai_do_repair frame here from below because of the subsequent if statment returning
        // if the ship is getting repaired
        //      If waiting to be repaired, just stop and sit.
        ai_do_repair_frame(Pl_objp, aip, flFrametime);
        if ((aip->ai_flags & AIF_AWAITING_REPAIR) || (aip->ai_flags & AIF_BEING_REPAIRED)) {
                if (ai_await_repair_frame(Pl_objp, aip))
                        return;
        }

        if (aip->mode == AIM_PLAY_DEAD)
                return;

        //      If recovering from a collision with a big ship, don't continue.
        if (maybe_big_ship_collide_recover_frame(Pl_objp, aip))
                return;

        ai_preprocess_ignore_objnum(Pl_objp, aip);
        target_objnum = set_target_objnum(aip, aip->target_objnum);

        // nprintf(("AI", "Frame %i: Coords = %7.3f %7.3f %7.3f\n", AI_FrameCount, Pl_objp->pos.xyz.x, Pl_objp->pos.xyz.y, Pl_objp->pos.xyz.z));

        Assert(objnum != target_objnum);

        ai_manage_shield(Pl_objp, aip);
        
        if ( maybe_request_support(Pl_objp) ) {
                if ( Ships[Pl_objp->instance].flags & SF_FROM_PLAYER_WING ) {
                        ship_maybe_tell_about_rearm(shipp);
                }
        }

        ai_maybe_warp_out(Pl_objp);

/*
        //      If this ship is attacking an object's subsystems and someone else destroyed
        //      the subsystem, it could continue attacking the ship.  Need to invalidate the objnum.
        if (target_objnum >= 0)
                if (Objects[target_objnum].flags & OF_PROTECTED) {
                        // if (aip->targeted_subsys != NULL)
                        //      ; //nprintf(("AI", "subsys hits = %7.3f\n", aip->targeted_subsys->current_hits));

                        if ((aip->targeted_subsys == NULL) || (aip->targeted_subsys->current_hits <= 0.0f)) {
                                target_objnum = -1;
                                aip->target_objnum = -1;
                        }
                }
*/


        //      Find an enemy if don't already have one.
        En_objp = NULL;
        if ( ai_need_new_target(Pl_objp, target_objnum) ) {
                if ((aip->mode != AIM_EVADE_WEAPON) && (aip->active_goal == AI_ACTIVE_GOAL_DYNAMIC)) {
                        aip->resume_goal_time = -1;
                        aip->active_goal = AI_GOAL_NONE;
                } else if (aip->resume_goal_time == -1) {
                        // AL 12-9-97: Don't allow cargo and navbuoys to set their aip->target_objnum
                        if ( !(Ship_info[shipp->ship_info_index].flags & SIF_HARMLESS) ) {
                                target_objnum = find_enemy(objnum, MAX_ENEMY_DISTANCE, Skill_level_max_attackers[Game_skill_level]);            //      Attack up to 25K units away.
                                if (target_objnum != -1) {
                                        if (aip->target_objnum != target_objnum)
                                                aip->aspect_locked_time = 0.0f;
                                        set_target_objnum(aip, target_objnum);
                                        En_objp = &Objects[target_objnum];
                                }
                        }
                }
        } else if (target_objnum >= 0) {
                En_objp = &Objects[target_objnum];
        }

        // set base stealth info each frame
        aip->ai_flags &= ~AIF_STEALTH_PURSIUT;
        if (En_objp && En_objp->type == OBJ_SHIP) {
                if (Ship_info[Ships[En_objp->instance].ship_info_index].flags & SIF_STEALTH) {
                        int stealth_state = ai_is_stealth_visible(Pl_objp, En_objp);
                        float dist = vm_vec_dist_quick(&En_objp->pos, &Pl_objp->pos);

                        if (stealth_state != STEALTH_FULLY_TARGETABLE) {
                                aip->ai_flags |= AIF_STEALTH_PURSIUT;
                        }

                        if ( (stealth_state == STEALTH_FULLY_TARGETABLE) || (stealth_state == STEALTH_VISIBLE) ) {
                                aip->stealth_last_visible_stamp = timestamp();
                                aip->stealth_last_cheat_visible_stamp = aip->stealth_last_visible_stamp;
                                aip->stealth_last_pos = En_objp->pos;
                                aip->stealth_velocity = En_objp->phys_info.vel;
                        } else if (dist < 100) {
                                // get cheat timestamp
                                aip->stealth_last_cheat_visible_stamp = timestamp();

                                // set approximate pos and vel, with increasing error as time from last_visible_stamp increases
                                update_ai_stealth_info_with_error(aip/*, 0*/);
                        }
                }
        }

        /*      if ((Pl_objp != NULL) && (En_objp != NULL)) {
                slide_face_ship();
                return;
        }
*/
        // AL 12-10-97: ensure that cargo and navbuoys aip->target_objnum is always -1.
        if ( Ship_info[shipp->ship_info_index].flags & SIF_HARMLESS ) {
                aip->target_objnum = -1;
        }

        if ((En_objp != NULL) && (En_objp->pos.xyz.x == Pl_objp->pos.xyz.x) && (En_objp->pos.xyz.y == Pl_objp->pos.xyz.y) && (En_objp->pos.xyz.z == Pl_objp->pos.xyz.z)) {
                mprintf(("Warning: Object and its enemy have same position.  Object #%i\n", Pl_objp-Objects));
                En_objp = NULL;
        }

        if (aip->mode == AIM_CHASE) {
                if (En_objp == NULL) {
                        aip->active_goal = -1;
                }
        }

        //      If there is a goal to resume and enough time has elapsed, resume the goal.
        if ((aip->resume_goal_time > 0) && (aip->resume_goal_time < Missiontime)) {
                aip->active_goal = AI_GOAL_NONE;
                aip->resume_goal_time = -1;
                target_objnum = find_enemy(objnum, 2000.0f, Skill_level_max_attackers[Game_skill_level]);
                if (target_objnum != -1) {
                        if (aip->target_objnum != target_objnum) {
                                aip->aspect_locked_time = 0.0f;
                        }
                        set_target_objnum(aip, target_objnum);
                }
        }

        // check if targeted subsystem has been destroyed, if so, move onto another subsystem
        // if trying to disable or disarm the target
        if ((En_objp != NULL) && ( aip->targeted_subsys != NULL )) {
                Assert(En_objp->type == OBJ_SHIP);
                if ( aip->targeted_subsys->current_hits <= 0.0f ) {
                        int subsys_type;

                        if ( aip->goals[0].ai_mode == AI_GOAL_DISABLE_SHIP ) {
                                subsys_type = SUBSYSTEM_ENGINE;
                        } else if ( aip->goals[0].ai_mode == AI_GOAL_DISARM_SHIP ) {
                                subsys_type = SUBSYSTEM_TURRET;
                        } else {
                                subsys_type = -1;
                        }

                        if ( subsys_type != -1 ) {
                                ship_subsys *new_subsys;
                                new_subsys = ship_return_next_subsys(&Ships[En_objp->instance], subsys_type, &Pl_objp->pos);
                                if ( new_subsys != NULL ) {
                                        set_targeted_subsys(aip, new_subsys, aip->target_objnum);
                                } else {
                                        // AL 12-16-97: no more subsystems to attack... reset targeting info
                                        aip->target_objnum = -1;
                                        set_targeted_subsys(aip, NULL, -1);
                                }
                        } else {
                                // targeted subsys is destroyed, so stop attacking it
                                set_targeted_subsys(aip, NULL, -1);
                        }
                }
        }

        ai_maybe_launch_cmeasure(Pl_objp, aip);
        ai_maybe_evade_locked_missile(Pl_objp, aip);

        aip->target_time += flFrametime;

        int in_formation = 0;
        if (aip->ai_flags & AIF_FORMATION) {
                in_formation = !ai_formation();
        }

        if ( !in_formation ) {
                ai_execute_behavior(aip);
        }

        process_subobjects(objnum);
        maybe_resume_previous_mode(Pl_objp, aip);
        
        if (Pl_objp->phys_info.flags & PF_AFTERBURNER_ON ) {
                if (Missiontime > aip->afterburner_stop_time) {
                        //nprintf(("AI", "Frame %i, turning off afterburner.\n", AI_FrameCount));
                        afterburners_stop(Pl_objp);
                }
        }
//      validate_mode_submode(aip);
}

int Waypoints_created = 0;

//      Find the ship with the name *name in the Ship_info array.
int find_ship_name(char *name)
{
        int     i;

        for (i=0; i<Num_ship_types; i++)
                if (!strcmp(Ship_info[i].name, name))
                        return i;

        return -1;
}

void create_waypoints()
{
        int     i, j, z;

        // Waypoints_created = 1;

        if (Waypoints_created)
                return;

        for (j=0; j<Num_waypoint_lists; j++)
                for (i=0; i<Waypoint_lists[j].count; i++) {
                        z = obj_create(OBJ_WAYPOINT, 0, j * 65536 + i, NULL,
                                &Waypoint_lists[j].waypoints[i], 0.0f, OF_RENDERS);
                }

        Waypoints_created = 1;
}

int Last_ai_obj = -1;

void ai_process( object * obj, int ai_index, float frametime )
{
//      if (Ships[obj->instance].flags & SF_DYING)
//              nprintf(("AI", "Frame: %i Ship %s is dying!\n", Framecount, Ships[obj->instance].ship_name));

        if (obj->flags & OF_SHOULD_BE_DEAD)
                return;

        // return if ship is dead, unless it's a big ship...then its turrets still fire, like I was quoted in a magazine.  -- MK, 5/15/98.
        if ((Ships[obj->instance].flags & SF_DYING ) && !(Ship_info[Ships[obj->instance].ship_info_index].flags & (SIF_HUGE_SHIP | SIF_BIG_SHIP))){
                return;
        }

        int rfc = 1;            //      Assume will be Reading Flying Controls.

        Assert( obj->type == OBJ_SHIP );
        Assert( ai_index >= 0 );

        init_ship_info();

        create_waypoints();

        AI_frametime = frametime;
        if (obj-Objects <= Last_ai_obj) {
                AI_FrameCount++;
        }

        memset( &AI_ci, 0, sizeof(AI_ci) );

        ai_frame(obj-Objects);

        AI_ci.pitch = 0.0f;
        AI_ci.bank = 0.0f;
        AI_ci.heading = 0.0f;

        // the ships maximum velocity now depends on the energy flowing to engines
        obj->phys_info.max_vel.xyz.z = Ships[obj->instance].current_max_speed;
        ai_info *aip = &Ai_info[Ships[obj->instance].ai_index];

        //      In certain circumstances, the AI says don't fly in the normal way.
        //      One circumstance is in docking and undocking, when the ship is moving
        //      under thruster control.
        switch (aip->mode) {
        case AIM_DOCK:
                if ((aip->submode >= AIS_DOCK_2) && (aip->submode != AIS_UNDOCK_3))
                        rfc = 0;
                break;
        case AIM_WARP_OUT:
                if (aip->submode >= AIS_WARP_3)
                        rfc = 0;
                break;
//      case AIM_NONE:
//              if (aip->submode == AIS_NONE_FORMATION)
//                      rfc = 0;
//              break;
        default:
                break;
        }

        if (rfc == 1) {
                vector copy_desired_rotvel = obj->phys_info.rotvel;
                physics_read_flying_controls( &obj->orient, &obj->phys_info, &AI_ci, frametime);
                // if obj is in formation and not flight leader, don't update rotvel
                if (aip->ai_flags & AIF_FORMATION) {
                        if (&Objects[aip->goal_objnum] != obj) {
                                obj->phys_info.desired_rotvel = copy_desired_rotvel;
                                obj->phys_info.rotvel = copy_desired_rotvel;
                        }
                }
        }

        Last_ai_obj = obj-Objects;
}

//      Initialize ai_info struct of object objnum.
void init_ai_object(int objnum)
{
        int     ship_index, ai_index;
        ai_info *aip;
        int ship_type;
        object  *objp;
        vector  near_vec;                       //      A vector nearby and mainly in front of this object.

        objp = &Objects[objnum];
        ship_index = objp->instance;
        ai_index = Ships[ship_index].ai_index;
        Assert((ai_index >= 0) && (ai_index < MAX_AI_INFO));

        aip = &Ai_info[ai_index];

        ship_type = Ships[ship_index].ship_info_index;

        vm_vec_scale_add(&near_vec, &objp->pos, &objp->orient.v.fvec, 100.0f);
        vm_vec_scale_add2(&near_vec, &objp->orient.v.rvec, 10.0f);

        // Things that shouldn't have to get initialized, but initialize them just in case!
        aip->ai_flags = 0;
        aip->previous_mode = AIM_NONE;
        aip->mode_time = -1;
        aip->target_objnum = -1;
        aip->target_signature = -1;
        aip->previous_target_objnum = -1;
        aip->target_time = 0.0f;
        aip->enemy_wing = -1;
        aip->attacker_objnum = -1;
        aip->goal_objnum = -1;
        aip->goal_signature = -1;
        aip->guard_objnum = -1;
        aip->guard_signature = -1;
        aip->guard_wingnum = -1;
        aip->dock_signature = -1;
        aip->submode = 0;
        aip->previous_submode = 0;
        aip->best_dot_to_enemy = -1.0f;
        aip->best_dot_from_enemy = -1.0f;
        aip->best_dot_to_time = 0;
        aip->best_dot_from_time = 0;
        aip->submode_start_time = 0;
        aip->submode_parm0 = 0;
        aip->active_goal = -1;
        aip->goal_check_time = timestamp(0);
        aip->last_predicted_enemy_pos = near_vec;
        aip->prev_goal_point = near_vec;
        aip->goal_point = near_vec;
        aip->time_enemy_in_range = 0.0f;
        aip->last_attack_time = 0;
        aip->last_hit_time = 0;
        aip->last_hit_quadrant = 0;
        aip->hitter_objnum = -1;
        aip->hitter_signature = -1;
        aip->resume_goal_time = -1;
        aip->prev_accel = 0.0f;
        aip->prev_dot_to_goal = 0.0f;

        aip->ignore_objnum = UNUSED_OBJNUM;
        aip->ignore_signature = -1;

        // aip->mode = AIM_NONE;

        // End of Things that shouldn't have to get initialized, but initialize them just in case!

        aip->ai_courage = Ai_classes[Ship_info[ship_type].ai_class].ai_courage[Game_skill_level];
        aip->ai_patience = Ai_classes[Ship_info[ship_type].ai_class].ai_patience[Game_skill_level];
        aip->ai_evasion = Ai_classes[Ship_info[ship_type].ai_class].ai_evasion[Game_skill_level];
        aip->ai_accuracy = Ai_classes[Ship_info[ship_type].ai_class].ai_accuracy[Game_skill_level];

        if (Num_waypoint_lists > 0) {
                aip->wp_index = -1;
                aip->wp_list = -1;
        } else {
                aip->wp_index = -1;
                aip->wp_list = -1;
        }

        aip->attacker_objnum = -1;
        aip->goal_signature = -1;

        Objects[objnum].phys_info.prev_fvec = Objects[objnum].orient.v.fvec;

        aip->last_predicted_enemy_pos.xyz.x = 0.0f;     //      Says this value needs to be recomputed!
        aip->time_enemy_in_range = 0.0f;

        aip->resume_goal_time = -1;                                     //      Say there is no goal to resume.

        aip->active_goal = -1;
        aip->path_start = -1;
        aip->path_goal_dist = -1;
        aip->path_length = 0;
        aip->path_subsystem_next_check = 1;
        aip->dock_path_index = -1;
        aip->dock_index = -1;
        aip->dock_objnum = -1;

        aip->danger_weapon_objnum = -1;
        aip->danger_weapon_signature = -1;

        aip->lead_scale = 0.0f;
        aip->last_hit_target_time = Missiontime;

        aip->nearest_locked_object = -1;
        aip->nearest_locked_distance = 99999.0f;

        aip->targeted_subsys = NULL;
        aip->last_subsys_target = NULL;
        aip->targeted_subsys_parent = -1;

        // The next two fields are used to time the rearming to allow useful sound effects for missile rearming
        aip->rearm_first_missile = TRUE;                //      flag to indicate that next missile to load is the first missile
        aip->rearm_release_delay = 0;                   //      timestamp to delay the separation of docked ships after rearm

        aip->next_predict_pos_time = 0;

        aip->afterburner_stop_time = 0;
        aip->last_objsig_hit = -1;                              // object signature of the ship most recently hit by aip

        aip->path_next_create_time = timestamp(1);
        aip->path_create_pos = Objects[objnum].pos;
        aip->path_create_orient = Objects[objnum].orient;

        aip->ignore_expire_timestamp = timestamp(1);
        aip->warp_out_timestamp = 0;
        aip->next_rearm_request_timestamp = timestamp(1);
        aip->primary_select_timestamp = timestamp(1);
        aip->secondary_select_timestamp = timestamp(1);
        aip->scan_for_enemy_timestamp = timestamp(1);

        aip->choose_enemy_timestamp = timestamp(3*(NUM_SKILL_LEVELS-Game_skill_level) * ((rand_alt() % 500) + 500));

        aip->shockwave_object = -1;
        aip->shield_manage_timestamp = timestamp(1);
        aip->self_destruct_timestamp = -1;      //      This is a flag that we have not yet set this.
        aip->ok_to_target_timestamp = timestamp(1);
        aip->pick_big_attack_point_timestamp = timestamp(1);
        vm_vec_zero(&aip->big_attack_point);

        aip->avoid_check_timestamp = timestamp(1);

        aip->abort_rearm_timestamp = -1;

        // artillery stuff
        aip->artillery_objnum = -1;
        aip->artillery_sig = -1;        

        // waypoint speed cap
        aip->waypoint_speed_cap = -1;

        // set lethality to enemy team
        aip->lethality = 0.0f;
}

void init_ai_objects()
{
        int     i;

        for (i=0; i<num_objects; i++){
                if (Objects[i].type == OBJ_SHIP){
                        init_ai_object(i);
                }
        }
}

void init_ai_system()
{
        // MWA -- removed next line of code on 11/12/97.  When a ship is created
        // it calls init_ai_object() on it's objnum.  Doing this init at the point where
        // this function gets called messes things up.
        //init_ai_objects();

        Ppfp = Path_points;
        Waypoints_created = 0;

        Dock_path_warning_given = 0;

/*      for (int i=0; i<MAX_IGNORE_OBJECTS; i++) {
                Ignore_objects[i].objnum = -1;
                Ignore_objects[i].signature = -1;
        }
*/

}

void ai_set_default_behavior(object *obj, int classnum)
{
        ai_info *aip;

        Assert(obj != NULL);
        Assert(obj->instance != -1);
        Assert(Ships[obj->instance].ai_index != -1);

        aip = &Ai_info[Ships[obj->instance].ai_index];

        aip->behavior = classnum;

}

void ai_do_default_behavior(object *obj)
{
        ai_info *aip;
        int             ship_flags;

        Assert(obj != NULL);
        Assert(obj->instance != -1);
        Assert(Ships[obj->instance].ai_index != -1);

        aip = &Ai_info[Ships[obj->instance].ai_index];

        ship_flags = Ship_info[Ships[obj->instance].ship_info_index].flags;
        if (!is_instructor(obj) && (ship_flags & (SIF_FIGHTER | SIF_BOMBER))) {
                int enemy_objnum = find_enemy(OBJ_INDEX(obj), 1000.0f, Skill_level_max_attackers[Game_skill_level]);
                set_target_objnum(aip, enemy_objnum);
                aip->mode = AIM_CHASE;
                aip->submode = SM_ATTACK;
        } else if (ship_flags & (SIF_SUPPORT)) {
                aip->mode = AIM_SAFETY;
                aip->submode = AISS_1;
                aip->ai_flags &= ~(AIF_REPAIRING);
        } else if ( ship_flags & SIF_SENTRYGUN ) {
                aip->mode = AIM_SENTRYGUN;
        } else {
                aip->mode = AIM_NONE;
        }
        
        aip->submode_start_time = Missiontime;
        aip->active_goal = AI_GOAL_NONE;
}

#define FRIENDLY_DAMAGE_THRESHOLD       50.0f           //      Display a message at this threshold.  Note, this gets scaled by Skill_level

// send the given message from objp.  called from the maybe_process_friendly_hit
// code below when a message must get send to the player when he fires on friendlies
void process_friendly_hit_message( int message, object *objp )
{
        int index;

        // no traitor in multiplayer
        if(Game_mode & GM_MULTIPLAYER){
                return;
        }

        // don't send this message if a player ship was hit.
        if ( objp->flags & OF_PLAYER_SHIP ){
                return;
        }

        // check if objp is a cargo contianer -- if so, then find a new ship to send the message
        index = objp->instance;
        if ( !(Ship_info[Ships[objp->instance].ship_info_index].flags & (SIF_FIGHTER|SIF_BOMBER)) ){
                index = -1;
        }

        // if the message is "oops" (the don't hit me message), always make come from Terran command
        if ( message == MESSAGE_OOPS ){
                index = -1;
        }

        if ( index >= 0){
                message_send_builtin_to_player( message, &Ships[index], MESSAGE_PRIORITY_HIGH, MESSAGE_TIME_ANYTIME, 0, 0, -1, -1 );
        } else {
                message_send_builtin_to_player( message, NULL, MESSAGE_PRIORITY_HIGH, MESSAGE_TIME_ANYTIME, 0, 0, -1, -1 );
        }
}

extern  void ship_set_subsystem_strength( ship *shipp, int type, float strength );

//      Object *objp_weapon, fired by *objp_hitter, hit object *objp_ship.
void maybe_process_friendly_hit(object *objp_hitter, object *objp_hit, object *objp_weapon)
{
        // no turning traitor in multiplayer
        if ( Game_mode & GM_MULTIPLAYER ) {
                return;
        }

        // ditto if mission says no traitors allowed
        if (The_mission.flags & MISSION_FLAG_NO_TRAITOR) {
                return;
        }

        if ((objp_hitter == Player_obj) && (Player_ship->team == TEAM_FRIENDLY)) {

                // AL 12-4-97: It is possible the Player is a OBJ_GHOST at this point.  If so, bail out.
                if ( objp_hitter->type != OBJ_SHIP ) {
                        return;
                }

                Assert(objp_hitter->type == OBJ_SHIP);
                Assert(objp_hit->type == OBJ_SHIP);
                Assert(objp_weapon->type == OBJ_WEAPON);

                ship    *shipp_hitter = &Ships[objp_hitter->instance];
                ship    *shipp_hit = &Ships[objp_hit->instance];

                if (shipp_hitter->team != shipp_hit->team) {
                        return;
                }

                // get the player
                player *pp = &Players[Player_num];

                // wacky stuff here
                if (pp->friendly_hits != 0) {
                        float   time_since_last_hit = f2fl(Missiontime - pp->friendly_last_hit_time);
                        if ((time_since_last_hit >= 0.0f) && (time_since_last_hit < 10000.0f)) {
                                if (time_since_last_hit > 60.0f) {
                                        pp->friendly_hits = 0;
                                        pp->friendly_damage = 0.0f;
                                } else if (time_since_last_hit > 2.0f) {
                                        pp->friendly_hits -= (int) time_since_last_hit/2;
                                        pp->friendly_damage -= time_since_last_hit;
                                }

                                if (pp->friendly_damage < 0.0f) {
                                        pp->friendly_damage = 0.0f;
                                }

                                if (pp->friendly_hits < 0) {
                                        pp->friendly_hits = 0;
                                }
                        }
                }

                float   damage;         //      Damage done by weapon.  Gets scaled down based on size of ship.

                damage = Weapon_info[Weapons[objp_weapon->instance].weapon_info_index].damage;
                
                // wacky stuff here
                ship_info *sip = &Ship_info[Ships[objp_hit->instance].ship_info_index];
                if (sip->initial_hull_strength > 1000.0f) {
                        float factor = sip->initial_hull_strength / 1000.0f;
                        factor = min(100.0f, factor);
                        damage /= factor;
                }

                //      Don't penalize much at all for hitting cargo
                if (sip->flags & (SIF_CARGO | SIF_SENTRYGUN)) {
                        damage /= 10.0f;
                }

                //      Hit ship, but not targeting it, so it's not so heinous, maybe an accident.
                if (Ai_info[shipp_hitter->ai_index].target_objnum != OBJ_INDEX(objp_hit)) {
                        damage /= 5.0f;
                }

                pp->friendly_last_hit_time = Missiontime;
                pp->friendly_hits++;

                // cap damage and number of hits done this frame
                float accredited_damage = min(MAX_BURST_DAMAGE, pp->damage_this_burst + damage) - pp->damage_this_burst;
                pp->friendly_damage += accredited_damage;
                pp->damage_this_burst += accredited_damage;

                // Done with adjustments to damage.  Evaluate based on current friendly_damage
                nprintf(("AI", "Friendly damage: %.1f, threshold: %.1f, inc damage: %.1f, max burst: %d\n", pp->friendly_damage, FRIENDLY_DAMAGE_THRESHOLD * (1.0f + (float) (NUM_SKILL_LEVELS + 1 - Game_skill_level)/3.0f), pp->damage_this_burst, MAX_BURST_DAMAGE ));
                
                if (is_instructor(objp_hit)) {
                        // it's not nice to hit your instructor
                        if (pp->friendly_damage > FRIENDLY_DAMAGE_THRESHOLD) {
                                message_send_builtin_to_player( MESSAGE_INSTRUCTOR_ATTACK, NULL, MESSAGE_PRIORITY_HIGH, MESSAGE_TIME_IMMEDIATE, 0, 0, -1, -1);
                                pp->last_warning_message_time = Missiontime;
                                ship_set_subsystem_strength( Player_ship, SUBSYSTEM_WEAPONS, 0.0f);

                                training_fail();

                                //      Instructor warp out.
                                ai_set_mode_warp_out(objp_hit, &Ai_info[Ships[objp_hit->instance].ai_index]);
                                gameseq_post_event( GS_EVENT_PLAYER_WARPOUT_START_FORCED );     //      Force player to warp out.

                                //ship_apply_global_damage( objp_hitter, objp_hit, NULL, 2*(get_shield_strength(objp_hitter) + Ship_info[shipp_hitter->ship_info_index].initial_hull_strength) );
                                //ship_apply_global_damage( objp_hitter, objp_hit, NULL, 1.0f );
                        } else if (Missiontime - pp->last_warning_message_time > F1_0*4) {
                                // warning every 4 sec
                                // use NULL as the message sender here since it is the Terran Command persona
                                message_send_builtin_to_player( MESSAGE_INSTRUCTOR_HIT, NULL, MESSAGE_PRIORITY_HIGH, MESSAGE_TIME_IMMEDIATE, 0, 0, -1, -1);
                                pp->last_warning_message_time = Missiontime;
                        }

                // not nice to hit your friends
                } else if (pp->friendly_damage > FRIENDLY_DAMAGE_THRESHOLD * (1.0f + (float) (NUM_SKILL_LEVELS + 1 - Game_skill_level)/3.0f)) {
                        process_friendly_hit_message( MESSAGE_HAMMER_SWINE, objp_hit );
                        mission_goal_fail_all();
                        ai_abort_rearm_request( Player_obj );

                        Player_ship->team = TEAM_TRAITOR;

                } else if ((damage > frand()) && (Missiontime - pp->last_warning_message_time > F1_0*4) && (pp->friendly_damage > FRIENDLY_DAMAGE_THRESHOLD)) {
                        // no closer than 4 sec intervals
                        //      Note: (damage > frand()) added on 12/9/97 by MK.  Since damage is now scaled down for big ships, we could get too
                        //      many warnings.  Kind of tedious.  frand() returns a value in 0..1, so this won't affect legit hits.
                        process_friendly_hit_message( MESSAGE_OOPS, objp_hit );
                        pp->last_warning_message_time = Missiontime;
                }
        }
}

//      Maybe make ship with ai_info *aip attack hitter_objnum as a dynamic goal
void maybe_set_dynamic_chase(ai_info *aip, int hitter_objnum)
{
        Assert(Ship_info[Ships[aip->shipnum].ship_info_index].flags & (SIF_FIGHTER | SIF_BOMBER));

        // limit the number of ships attacking hitter_objnum (for now, only if hitter_objnum is player)
        if ( ai_maybe_limit_attackers(hitter_objnum) == 1 ) {
                return;
        }

        // only set as target if can be targeted.
        if (awacs_get_level(&Objects[hitter_objnum], &Ships[aip->shipnum], 1) < 1) {
                return;
        }

        if (aip->target_objnum != hitter_objnum)
                aip->aspect_locked_time = 0.0f;
        set_target_objnum(aip, hitter_objnum);
        aip->resume_goal_time = Missiontime + i2f(20);  //      Only chase up to 20 seconds.
        aip->active_goal = AI_ACTIVE_GOAL_DYNAMIC;

        set_targeted_subsys(aip, NULL, -1);             //      Say not attacking any particular subsystem.

        aip->previous_submode = aip->mode;
        aip->mode = AIM_CHASE;
        aip->submode = SM_ATTACK;
}


//      Return true if *objp has armed an aspect seeking bomb.
//      This function written so a ship with an important bomb to fire will willingly take hits in the face to fire its bomb.
int firing_aspect_seeking_bomb(object *objp)
{
        ship    *shipp;
        int     bank_index;
        ship_weapon     *swp;

        shipp = &Ships[objp->instance];

        swp = &shipp->weapons;

        bank_index = swp->current_secondary_bank;

        if (bank_index != -1)
                if (swp->secondary_bank_ammo[bank_index] > 0) {
                        if (Weapon_info[swp->secondary_bank_weapons[bank_index]].wi_flags & WIF_BOMB) {
                                if (Weapon_info[swp->secondary_bank_weapons[bank_index]].wi_flags & WIF_HOMING_ASPECT) {
                                        return 1;
                                }
                        }
                }

        return 0;
}

//      *objp collided with big ship *big_objp at global point *collide_pos
//      Make it fly away from the collision point.
// collision_normal is NULL, when a collision is imminent and we just want to bug out.
void big_ship_collide_recover_start(object *objp, object *big_objp, vector *collide_pos, vector *collision_normal)
{
        ai_info *aip;

        Assert(objp->type == OBJ_SHIP);

        aip = &Ai_info[Ships[objp->instance].ai_index];

        if (!timestamp_elapsed(aip->big_recover_timestamp) && (aip->ai_flags & AIF_BIG_SHIP_COLLIDE_RECOVER_1))
                return;

        //nprintf(("AI", "Ship %s beginning to avoid ship %s at time %7.3f", Ships[objp->instance].ship_name, Ships[big_objp->instance].ship_name, f2fl(Missiontime)));
        if (collision_normal) {
                aip->big_recover_timestamp = timestamp(2000);
                aip->big_collision_normal = *collision_normal;
        //      nprintf(("AI", " normal\n"));
        } else {
                aip->big_recover_timestamp = timestamp(500);
        //      nprintf(("AI", " no normal\n"));
        }


        aip->ai_flags &= ~AIF_BIG_SHIP_COLLIDE_RECOVER_2;
        aip->ai_flags |= AIF_BIG_SHIP_COLLIDE_RECOVER_1;

//      vector  out_vec;
//      vm_vec_normalized_dir(&out_vec, &objp->pos, collide_pos);

        // big_recover_pos_1 is 100 m out along normal
        vector direction;
        if (collision_normal) {
                direction = *collision_normal;
        } else {
                vm_vec_copy_scale(&direction, &objp->orient.v.fvec, -1.0f);
        }
        vm_vec_scale_add(&aip->big_recover_pos_1, &objp->pos, &direction, 100.0f);

        // go out 200 m from box closest box point
        get_world_closest_box_point_with_delta(&aip->big_recover_pos_2, big_objp, &aip->big_recover_pos_1, NULL, 300.0f);

        accelerate_ship(aip, 0.0f);
/*
        if (vm_vec_dot(collision_normal, &objp->orient.v.fvec) > 0.5f) {
//              vm_vec_scale_add(&aip->big_recover_pos_1, &objp->pos, &out_vec, big_objp->radius/2.0f);
//              vm_vec_scale_add(&aip->big_recover_pos_2, &aip->big_recover_pos_1, &objp->orient.v.uvec, big_objp->radius/2.0f);
//              vm_vec_scale_add(&aip->big_recover_pos_2, &objp->pos, &out_vec, big_objp->radius*2.0f);
                accelerate_ship(aip, 2.0f);
        } else {
//              vm_vec_scale_add(&aip->big_recover_pos_1, &objp->pos, &out_vec, big_objp->radius/2.0f);
//              vm_vec_scale_add(&aip->big_recover_pos_2, &aip->big_recover_pos_1, &objp->orient.v.uvec, big_objp->radius/2.0f);
                accelerate_ship(aip, 0.0f);
        } */
}

float max_lethality = 0.0f;

void ai_update_lethality(object *ship_obj, object *other_obj, float damage)
{
        Assert(ship_obj->type == OBJ_SHIP);
        Assert(other_obj->type == OBJ_WEAPON || other_obj->type == OBJ_SHOCKWAVE);
        int dont_count = FALSE;

        int parent = other_obj->parent;
        if (Objects[parent].type == OBJ_SHIP) {
                if (Objects[parent].signature == other_obj->parent_sig) {

                        // check damage done to enemy team
                        if (Ships[ship_obj->instance].team != Ships[Objects[parent].instance].team) {

                                // other is weapon
                                if (other_obj->type == OBJ_WEAPON) {
                                        weapon *wp = &Weapons[other_obj->instance];
                                        weapon_info *wif = &Weapon_info[wp->weapon_info_index];

                                        // if parent is BIG|HUGE, don't count beam
                                        if (Ship_info[Ships[Objects[parent].instance].ship_info_index].flags & (SIF_BIG_SHIP|SIF_HUGE_SHIP)) {
                                                if (wif->wi_flags & WIF_BEAM) {
                                                        dont_count = TRUE;
                                                }
                                        }
                                }

                                if (!dont_count) {
                                        float lethality = 0.025f * damage;      // 2 cyclops (@2000) put you at 100 lethality

                                        // increase lethality weapon's parent ship
                                        ai_info *aip = &Ai_info[Ships[Objects[parent].instance].ai_index];
                                        aip->lethality += lethality;
                                        aip->lethality = min(110.0f, aip->lethality);
                                        // if you hit, don;t be less than 0
                                        aip->lethality = max(0.0f, aip->lethality);

//                                      if (aip->lethality > max_lethality) {
//                                              max_lethality = aip->lethality;
//                                              mprintf(("new lethalilty high: %.1f\n", max_lethality));
//                                      }

                                        // if parent is player, show his lethality
//                                      if (Objects[parent].flags & OF_PLAYER_SHIP) {
//                                              mprintf(("Player lethality: %.1f\n", aip->lethality));
//                                      }
                                }
                        }
                }
        }
}


//      Object *objp_ship was hit by either weapon *objp_weapon or collided into by ship hit_objp at point *hitpos.
void ai_ship_hit(object *objp_ship, object *hit_objp, vector *hitpos, int shield_quadrant, vector *hit_normal)
{
        int             hitter_objnum = -2;
        object  *objp_hitter = NULL;
        ship            *shipp;
        ai_info *aip, *hitter_aip;

        shipp = &Ships[objp_ship->instance];
        aip = &Ai_info[shipp->ai_index];

        if (objp_ship->flags & OF_PLAYER_SHIP)
                return;

        if ((aip->mode == AIM_WARP_OUT) || (aip->mode == AIM_PLAY_DEAD))
                return;

        if (hit_objp->type == OBJ_SHIP) {
                //      If the object that this ship collided with is a big ship
                if (Ship_info[Ships[hit_objp->instance].ship_info_index].flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP)) {
                        //      And the current object is _not_ a big ship
                        if (!(Ship_info[Ships[objp_ship->instance].ship_info_index].flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP))) {
                                //      Recover from hitting a big ship.  Note, if two big ships collide, they just pound away at each other.  Oh well.  Recovery looks dumb and it's very late.
                                big_ship_collide_recover_start(objp_ship, hit_objp, hitpos, hit_normal);
                        }
                }
        }

        if (hit_objp->type == OBJ_WEAPON) {
                //      Make sure the object that fired this weapon is still alive.  If not, abort.
                // Assert(hit_objp->parent >= 0);
                if(hit_objp->parent < 0){
                        return;
                }
                if ( hit_objp->parent_sig != Objects[hit_objp->parent].signature ){
                        return;
                }

                //      Hit by a protected ship, don't attack it.
                if (Objects[hit_objp->parent].flags & OF_PROTECTED) {
                        if ((Ship_info[shipp->ship_info_index].flags & (SIF_FIGHTER | SIF_BOMBER)) && (aip->target_objnum == -1)) {
                                if (aip->mode == AIM_CHASE) {
                                        if (aip->submode != SM_EVADE_WEAPON) {
                                                aip->mode = AIM_CHASE;
                                                aip->submode = SM_EVADE_WEAPON;
                                                aip->submode_start_time = Missiontime;
                                        }
                                } else if (aip->mode != AIM_EVADE_WEAPON) {
                                        aip->active_goal = AI_ACTIVE_GOAL_DYNAMIC;
                                        aip->previous_mode = aip->mode;
                                        aip->previous_submode = aip->submode;
                                        aip->mode = AIM_EVADE_WEAPON;
                                        aip->submode = -1;
                                        aip->submode_start_time = Missiontime;
                                        aip->mode_time = timestamp(MAX_EVADE_TIME);     //      Evade for up to five seconds.
                                }

                        }
                        return;
                }

                hitter_objnum = hit_objp->parent;
                Assert((hitter_objnum >= 0) && (hitter_objnum < MAX_OBJECTS));
                objp_hitter = &Objects[hitter_objnum];
                maybe_process_friendly_hit(objp_hitter, objp_ship, hit_objp);           //      Deal with player's friendly fire.

                if ( (shipp->team & TEAM_FRIENDLY) && !(Game_mode & GM_MULTIPLAYER) ) {
                        ship_maybe_ask_for_help(shipp);
                }
        } else if (hit_objp->type == OBJ_SHIP) {
                if (shipp->team == Ships[hit_objp->instance].team)              //      Don't have AI react to collisions between teammates.
                        return;
                objp_hitter = hit_objp;
                hitter_objnum = hit_objp-Objects;
        } else {
                Int3(); //      Hmm, what kind of object hit this if not weapon or ship?  Get MikeK.
                return;
        }

        //      Collided into a protected ship, don't attack it.
        if (hit_objp->flags & OF_PROTECTED)
                return;

        Assert(objp_hitter != NULL);
        hitter_aip = &Ai_info[Ships[objp_hitter->instance].ai_index];
        hitter_aip->last_hit_target_time = Missiontime;
        
        // store the object signature of objp_ship into ai_info, since we want to track the last ship hit by 'hitter_objnum'
        hitter_aip->last_objsig_hit = objp_ship->signature; 

        aip->last_hit_time = Missiontime;

        if (aip->ai_flags & (AIF_NO_DYNAMIC | AIF_KAMIKAZE))    //      If not allowed to pursue dynamic objectives, don't evade.  Dumb?  Maybe change. -- MK, 3/15/98
                return;

        //      If this ship is awaiting repair, abort!
        if (aip->ai_flags & (AIF_AWAITING_REPAIR | AIF_BEING_REPAIRED)) {
                ship_info       *sip = &Ship_info[shipp->ship_info_index];

                if (objp_ship->hull_strength/sip->initial_hull_strength < 0.3f) {
                        //      No, only abort if hull below a certain level.
                        aip->next_rearm_request_timestamp = timestamp(NEXT_REARM_TIMESTAMP/2);  //      Might request again after 15 seconds.
                        if ( !(objp_ship->flags & OF_PLAYER_SHIP) )                                             // mwa -- don't abort rearm for a player
                                ai_abort_rearm_request(objp_ship);
                }
        }

        //      If firing a bomb, ignore enemy fire so we can gain lock drop the bomb.
        //      Only ignore fire if aspect_locked_time > 0.5f, as this means we're in range.
        if (firing_aspect_seeking_bomb(objp_ship)) {
                if ((aip->ai_flags & AIF_SEEK_LOCK) && (aip->aspect_locked_time > 0.1f))
                        return;
        }

        //      If in AIM_STRAFE mode and got hit by target, maybe attack turret if appropriate
        if (aip->mode == AIM_STRAFE) {
                Assert(hitter_objnum != -2);
                if (aip->target_objnum == hitter_objnum) {
                        if ( hit_objp->type == OBJ_WEAPON ) {
                                ai_big_strafe_maybe_attack_turret(objp_ship, hit_objp);
                        }
                        return;
                }
                else {
                                // AL 11-10-97:
                        ;       // do nothing here, we'll attack this hitter if it is a fighter or bomber (this is handled
                                // in code later in this function
                }
        }

        if (objp_ship == Player_obj)
                return;         //      We don't do AI for the player.

        maybe_update_guard_object(objp_ship, objp_hitter);

        //      Big ships don't go any further.
        if (!(Ship_info[shipp->ship_info_index].flags & SIF_SMALL_SHIP))
                return;

        //      If the hitter object is the ignore object, don't attack it.
        ship_info       *sip = &Ship_info[shipp->ship_info_index];
        if ((is_ignore_object(aip, objp_hitter-Objects)) && (sip->flags & (SIF_BOMBER | SIF_FIGHTER))) {
                if (aip->mode == AIM_NONE) {
                        aip->mode = AIM_CHASE;  //      This will cause the ship to move, if not attack.
                        aip->submode = SM_EVADE;
                }
                return;
        }

        //      Maybe abort based on mode.
        switch (aip->mode) {
        case AIM_CHASE:
                if (aip->submode == SM_ATTACK_FOREVER)
                        return;

                if ( hit_objp->type == OBJ_WEAPON ) {
                        if ( ai_big_maybe_enter_strafe_mode(objp_ship, OBJ_INDEX(hit_objp), 1) )
                                return;
                }

        case AIM_GUARD:
                //      If in guard mode and far away from guard object, don't pursue guy that hit me.
                        if ((aip->guard_objnum != -1) && (aip->guard_signature == Objects[aip->guard_objnum].signature)) {
                                if (vm_vec_dist_quick(&objp_ship->pos, &Objects[aip->guard_objnum].pos) > 500.0f) {
                                        return;
                                }
                        }
        case AIM_STILL:
        case AIM_STAY_NEAR:
                // Note: Dealt with above, at very top.  case AIM_PLAY_DEAD:
        case AIM_STRAFE:
                break;
        case AIM_EVADE_WEAPON:
        case AIM_EVADE:
        case AIM_GET_BEHIND:
        case AIM_AVOID:
        case AIM_DOCK:
        case AIM_BIGSHIP:
        case AIM_PATH:
        case AIM_NONE:
        case AIM_BAY_DEPART:
        case AIM_SENTRYGUN:
                return;
        case AIM_BAY_EMERGE:
                // If just leaving the docking bay, don't react to enemy fire... just keep flying away from docking bay
                if ( (Missiontime - aip->submode_start_time) < 5*F1_0 ) {
                        return;
                }
                break;
        case AIM_WAYPOINTS:
                if (sip->flags & (SIF_FIGHTER | SIF_BOMBER))
                        break;
                else
                        return;
                break;
        case AIM_SAFETY:
                if ((aip->submode != AISS_1) || (Missiontime - aip->submode_start_time > i2f(1))) {
                        aip->submode = AISS_1;
                        aip->submode_start_time = Missiontime;
                }
                return;
                break;
        case AIM_WARP_OUT:
                return;
                break;
        default:
                Int3(); //      Bogus mode!
        }

        if (timestamp_elapsed(aip->ok_to_target_timestamp))
                aip->ai_flags &= ~AIF_FORMATION;                        //      If flying in formation, bug out!

        aip->hitter_objnum = hitter_objnum;
        aip->hitter_signature = Objects[hitter_objnum].signature;

        //      If the hitter is not on the same team as the hittee, do some stuff.
        if (shipp->team != Ships[objp_hitter->instance].team) {
                //nprintf(("AI", "Object %i attacking %i, who just hit him!\n", objp_ship-Objects, hitter_objnum));

                if ((hitter_objnum != aip->target_objnum) && (sip->flags & (SIF_FIGHTER | SIF_BOMBER))) {
                        maybe_set_dynamic_chase(aip, hitter_objnum);
                        maybe_afterburner_after_ship_hit(objp_ship, aip, &Objects[hitter_objnum]);
                } else {
                        if ((aip->mode == AIM_CHASE) && ((objp_ship->hull_strength/sip->initial_hull_strength > 0.9f) || (get_shield_strength(objp_ship)/sip->shields > 0.8f))) {
                                switch (aip->submode) {
                                case SM_ATTACK:
                                case SM_SUPER_ATTACK:
                                case SM_GET_AWAY:
                                        break;
                                default:
                                        if (sip->flags & (SIF_FIGHTER | SIF_BOMBER)) {
                                                maybe_set_dynamic_chase(aip, hitter_objnum);
                                        }
                                        maybe_afterburner_after_ship_hit(objp_ship, aip, &Objects[hitter_objnum]);
                                        break;
                                }
                        } else if (aip->mode == AIM_CHASE) {
                                switch (aip->submode) {
                                case SM_ATTACK:
                                        aip->submode = SM_EVADE;
                                        aip->submode_start_time = Missiontime;
                                        break;
                                case SM_SUPER_ATTACK:
                                        if (Missiontime - aip->submode_start_time > i2f(1)) {
                                                aip->submode = SM_EVADE;
                                                aip->submode_start_time = Missiontime;
                                        }
                                        break;
                                case SM_EVADE_BRAKE:
                                        break;
                                case SM_EVADE_SQUIGGLE:
                                        aip->submode = SM_EVADE;
                                        aip->submode_start_time = Missiontime;
                                        break;
                                default:
                                        if (sip->flags & (SIF_BOMBER | SIF_FIGHTER)) {
                                                maybe_set_dynamic_chase(aip, hitter_objnum);
                                                maybe_afterburner_after_ship_hit(objp_ship, aip, &Objects[hitter_objnum]);
                                        }

                                        break;
                                }
                        } else {
                                // AL 3-15-98: Prevent escape pods from entering chase mode
                                if ( (sip->flags & (SIF_BOMBER | SIF_FIGHTER)) ) {
                                        maybe_set_dynamic_chase(aip, hitter_objnum);
                                }
                                maybe_afterburner_after_ship_hit(objp_ship, aip, &Objects[hitter_objnum]);
                        }
                }
        }
}

//      Ship shipnum has been destroyed.
//      Cleanup.
// the parameter 'method' is used to tell is this ship was destroyed or it departed normally.
// This function will get called in either case, and there are things that should be done if
// the ship actually gets destroyed which shouldn't get done if it departed.
void ai_ship_destroy(int shipnum, int method)
{
        int             objnum;
        object  *other_objp;
        ship            *shipp;
        ship_obj        *so;
        ai_info *dead_aip;

        Assert((shipnum >= 0) && (shipnum < MAX_SHIPS));
        objnum = Ships[shipnum].objnum;
        dead_aip = &Ai_info[Ships[shipnum].ai_index];

        // if I was getting repaired, or awaiting repair, then cleanup the repair mode.  When awaiting repair, the dock_objnum
        // is -1.  When the support ship is on the way, the dock_objnum >= 0 (points to support ship).
        if ( dead_aip->ai_flags & (AIF_AWAITING_REPAIR | AIF_BEING_REPAIRED) ) {
                if ( dead_aip->dock_objnum >= 0 )
                        ai_do_objects_repairing_stuff( &Objects[objnum], &Objects[dead_aip->dock_objnum], REPAIR_INFO_END);
                else
                        ai_do_objects_repairing_stuff( &Objects[objnum], NULL, REPAIR_INFO_END );
        }

        //      For all objects that had this ship as a target, wipe it out, forcing find of a new enemy.
        for ( so = GET_FIRST(&Ship_obj_list); so != END_OF_LIST(&Ship_obj_list); so = GET_NEXT(so) ) {
                other_objp = &Objects[so->objnum];
                Assert(other_objp->instance != -1);

                shipp = &Ships[other_objp->instance];
                Assert(shipp->ai_index != -1);

                ai_info *aip = &Ai_info[shipp->ai_index];

                // MWA 2/11/98
                // code commented out below is taken care of in ai_cleanup_dock_mode when gets called when the
                // support ship starts it's death roll.

                //      If the destroyed ship was on its way to repair the current ship
                if (aip->dock_objnum == objnum) {

                        // clean up the flags for any kind of docking mode.  If aip was part of a goal of dock/undock
                        // then it will get cleaned up by the goal code.
                        ai_do_objects_undocked_stuff( other_objp, NULL );

                        if ( aip->ai_flags & (AIF_AWAITING_REPAIR | AIF_BEING_REPAIRED) ) {
                                int abort_reason;
                                if ( method == SEF_DEPARTED ) {
                                        abort_reason = REPAIR_INFO_ABORT;
                                } else {
                                        abort_reason = REPAIR_INFO_KILLED;
                                }
                                ai_do_objects_repairing_stuff( other_objp, NULL, abort_reason );
                        }
                }

                if (aip->target_objnum == objnum) {
                        set_target_objnum(aip, -1);
                        //      If this ship had a dynamic goal of chasing the dead ship, clear the dynamic goal.
                        if (aip->resume_goal_time != -1)
                                aip->active_goal = AI_GOAL_NONE;
                }

                if (aip->goal_objnum == objnum) {
                        aip->goal_objnum = -1;
                        aip->goal_signature = -1;
                }

                if (aip->guard_objnum == objnum) {
                        aip->guard_objnum = -1;
                        aip->guard_signature = -1;
                }

                if ((aip->guard_wingnum != -1) && (aip->guard_wingnum == Ai_info[Ships[Objects[objnum].instance].ai_index].wing)) {
                        if (aip->guard_wingnum != aip->wing)
                                ai_set_guard_wing(other_objp, aip->guard_wingnum);
                }

                if (aip->hitter_objnum == objnum)
                        aip->hitter_objnum = -1;

        }

}

/*
//      Interface function to goals code.
//      Make object *objp fly to point *vp and warp out.
void ai_warp_out(object *objp, vector *vp)
{
        ai_info *aip;

        aip = &Ai_info[Ships[objp->instance].ai_index];

        if (aip->mode != AIM_WARP_OUT) {
                ai_set_mode_warp_out(objp, aip);
        }
        float   dist;
        float   dot;
        vector  v2v;
        ai_info *aip;

        dist = vm_vec_normalized_dir(&v2v, vp, &objp->pos);

        if (dist < objp->radius + 5.0f) {

                // Start the warp out effect 
                shipfx_warpout_start(objp);

        } else {
                dot = vm_vec_dot(&objp->orient.v.fvec, &v2v);

                aip = &Ai_info[Ships[objp->instance].ai_index];

                if (dist > 500.0f)
                        accelerate_ship(aip, 1.0f);
                else
                        accelerate_ship(aip, (3*dot + 1.0f)/4.0f);

                turn_towards_point(objp, vp, NULL, 0.0f);
        }
}
*/


//      Do stuff at start of deathroll.
void ai_deathroll_start(object *ship_obj)
{
        ai_info *aip;
        ship            *shipp, *other_ship;

        shipp = &Ships[ship_obj->instance];
        aip = &Ai_info[shipp->ai_index];

        // mark object we are docked with so we can do damage and separate during deathroll
        // keep dock_objnum_when_dead from being changed if already set (only allow to be set when -1)
        if (Ships[ship_obj->instance].dock_objnum_when_dead == -1) {
                Ships[ship_obj->instance].dock_objnum_when_dead = aip->dock_objnum;
                // set other_ship dock_objnum_when_dead, if other_ship exits.
                if (Ships[ship_obj->instance].dock_objnum_when_dead != -1) {
                        other_ship = &Ships[Objects[aip->dock_objnum].instance];
                        other_ship->dock_objnum_when_dead = shipp->objnum;
                }
        }

        ai_cleanup_dock_mode(aip, shipp);

        aip->mode = AIM_NONE;
}

//      Object *requester_objp tells rearm ship to abort rearm.
//      Returns true if it succeeded, else false.
//      To succeed means you were previously rearming.
int ai_abort_rearm_request(object *requester_objp)
{
        ship            *requester_shipp;
        ai_info *requester_aip;

        Assert(requester_objp->type == OBJ_SHIP);
        if(requester_objp->type != OBJ_SHIP){
                return 0;
        }
        Assert((requester_objp->instance >= 0) && (requester_objp->instance < MAX_SHIPS));      
        if((requester_objp->instance < 0) || (requester_objp->instance >= MAX_SHIPS)){
                return 0;
        }
        requester_shipp = &Ships[requester_objp->instance];
        Assert((requester_shipp->ai_index >= 0) && (requester_shipp->ai_index < MAX_AI_INFO));          
        if((requester_shipp->ai_index < 0) || (requester_shipp->ai_index >= MAX_AI_INFO)){
                return 0;
        }       
        requester_aip = &Ai_info[requester_shipp->ai_index];
        
        if (requester_aip->ai_flags & (AIF_AWAITING_REPAIR | AIF_BEING_REPAIRED)){

                // dock_objnum is always valid once a rearm repair has been requested.  It points to the
                // ship that is coming to repair me.
                if (requester_aip->dock_objnum != -1) {
                        object  *repair_objp;
                        ai_info *repair_aip;

                        repair_objp = &Objects[requester_aip->dock_objnum];
                        repair_aip = &Ai_info[Ships[repair_objp->instance].ai_index];

                        //      Make sure signatures match.  This prevents nasty bugs in which an object
                        //      that was repairing another is destroyed and is replaced by another ship
                        //      before this code comes around.
                        if (repair_objp->signature == requester_aip->dock_signature) {

                                Assert( repair_objp->type == OBJ_SHIP );

                                // if support ship is in the process of undocking, don't do anything.
                                if ( repair_aip->submode < AIS_UNDOCK_0 ) {
                                        ai_do_objects_repairing_stuff( requester_objp, repair_objp, REPAIR_INFO_ABORT );

                                        if ( repair_aip->submode == AIS_DOCK_4 )
                                                repair_aip->submode = AIS_UNDOCK_0;
                                        else
                                                repair_aip->submode = AIS_UNDOCK_3;

                                        repair_aip->submode_start_time = Missiontime;
                                } else {
                                        nprintf(("AI", "Not aborting rearm since already undocking\n"));
                                }
                        }
                } else {
                        // setting these flags is the safe things to do.  There may not be a corresponding repair
                        // ship for this guys since a repair ship may be currently repairing someone else.
                        ai_do_objects_repairing_stuff( requester_objp, NULL, REPAIR_INFO_ABORT );

                        // try and remove this guy from an arriving support ship.
                        mission_remove_scheduled_repair(requester_objp);
                }

                return 1;
        } else if ( requester_aip->ai_flags & AIF_REPAIRING ) {
                // a support ship can request to abort when he is told to do something else (like warp out).
                // see if this support ships goal_objnum is valid.  If so, then issue this ai_abort comment
                // for the ship that he is enroute to repair
                if ( requester_aip->goal_objnum != -1 ) {
                        int val;

                        val = ai_abort_rearm_request( &Objects[requester_aip->goal_objnum] );
                        return val;
                }
        }

        return 0;
}

// function which gets called from ai-issue_rearm_request and from code in missionparse.cpp
// to actually issue the rearm goal (support_obj to rearm requester_obj);
void ai_add_rearm_goal( object *requester_objp, object *support_objp )
{
        ship *support_shipp, *requester_shipp;
        ai_info *support_aip, *requester_aip;

        support_shipp = &Ships[support_objp->instance];
        requester_shipp = &Ships[requester_objp->instance];
        requester_aip = &Ai_info[requester_shipp->ai_index];

        Assert( support_shipp->ai_index != -1 );
        support_aip = &Ai_info[support_shipp->ai_index];

        // if the requester is a player object, issue the order as the squadmate messaging code does.  Doing so
        // ensures that the player get a higher priority!
        requester_aip->ai_flags |= AIF_AWAITING_REPAIR; //      Tell that I'm awaiting repair.
        if ( requester_objp->flags & OF_PLAYER_SHIP )
                ai_add_ship_goal_player( AIG_TYPE_PLAYER_SHIP, AI_GOAL_REARM_REPAIR, -1, requester_shipp->ship_name, support_aip );
        else
                ai_add_goal_ship_internal( support_aip, AI_GOAL_REARM_REPAIR, requester_shipp->ship_name, -1, -1 );

}

//      Object *requester_objp requests rearming.
//      Returns objnum of ship coming to repair requester on success
//      Success means you found someone to rearm you and you weren't previously rearming.
int ai_issue_rearm_request(object *requester_objp)
{
        object  *objp;
        ship            *requester_shipp;
        ai_info *requester_aip;

        Assert(requester_objp->type == OBJ_SHIP);
        Assert((requester_objp->instance >= 0) && (requester_objp->instance < MAX_SHIPS));
        requester_shipp = &Ships[requester_objp->instance];
        Assert((requester_shipp->ai_index >= 0) && (requester_shipp->ai_index < MAX_AI_INFO));
        requester_aip = &Ai_info[requester_shipp->ai_index];
        
        //      Make sure not already awaiting repair.
        if (requester_aip->ai_flags & AIF_AWAITING_REPAIR) {
                nprintf(("AI", "Ship %s already awaiting rearm by ship %s.\n", requester_shipp->ship_name, &Ships[Objects[requester_aip->dock_objnum].instance].ship_name));    
                return -1;
        }

        if ( !is_support_allowed(requester_objp) )
                return -1;

        //nprintf(("AI", "Ship %s requesting rearming.\n", requester_shipp->ship_name));
        requester_aip->next_rearm_request_timestamp = timestamp(NEXT_REARM_TIMESTAMP);  //      Might request again after this much time.

        // call ship_find_repair_ship to get a support ship.  If none is found, then we will warp one in.  This
        // function will return the next available ship which can repair requester
        objp = ship_find_repair_ship( requester_objp );
        ai_do_objects_repairing_stuff( requester_objp, objp, REPAIR_INFO_QUEUE );
        if ( objp ) {

                // MWA 5/14/98 -- moved next item into the ai_do_objects_repairing_stuff function so that clients
                // would properly update their hud support view
                //ai_add_rearm_goal( requester_objp, objp );
                return OBJ_INDEX(objp);

        } else {
                // call to warp in repair ship!!!!  for now, warp in any number of ships needed.  Should cap it to
                // some reasonable max (or let support ships warp out).  We should assume here that ship_find_repair_ship()
                // would have returned a valid object if there are too many support ships already in the mission
                mission_warp_in_support_ship( requester_objp );

                return -1;
        }

}

// make objp rearm and repair goal_objp
void ai_rearm_repair( object *objp, object  *goal_objp, int priority, int docker_index, int dockee_index )
{
        ai_info *aip, *goal_aip;

        aip = &Ai_info[Ships[objp->instance].ai_index];
        aip->goal_objnum = goal_objp-Objects;

        // nprintf(("AI", "Ship %s preparing to rearm ship %s.\n", shipp->ship_name, requester_shipp->ship_name));

        ai_dock_with_object(objp, goal_objp, priority, AIDO_DOCK, docker_index, dockee_index);
        aip->ai_flags |= AIF_REPAIRING;                                         //      Tell that repair guy is busy trying to repair someone.

        goal_aip = &Ai_info[Ships[goal_objp->instance].ai_index];
        goal_aip->dock_objnum = objp-Objects;           //      Tell which object is coming to repair.
        goal_aip->dock_signature = objp->signature;

        ai_do_objects_repairing_stuff( goal_objp, objp, REPAIR_INFO_ONWAY );

        goal_aip->abort_rearm_timestamp = timestamp(NEXT_REARM_TIMESTAMP*3/2);
}

// Given a dockee object and the index of the dockbay for that object (ie the dockbay index
// into polymodel->dockbays[] for the model associated with the object), return the index
// of a path_num associated with than dockbay (this is an index into polymodel->paths[])
int ai_return_path_num_from_dockbay(object *dockee_objp, int dockbay_index)
{
        if ( dockbay_index < 0 || dockee_objp == NULL ) {
                Int3();         // should never happen
                return -1;
        }

        if ( dockee_objp->type == OBJ_SHIP ) {
                int                     path_num;
                polymodel       *pm;

                pm = model_get( Ships[dockee_objp->instance].modelnum );

                // sanity checks
                Assert(pm->n_docks > dockbay_index);
                Assert(pm->docking_bays[dockbay_index].num_spline_paths > 0);
                Assert(pm->docking_bays[dockbay_index].splines != NULL);
                if(pm->n_docks <= dockbay_index){
                        return -1;
                }
                if(pm->docking_bays[dockbay_index].num_spline_paths <= 0){
                        return -1;
                }
                if(pm->docking_bays[dockbay_index].splines == NULL){
                        return -1;
                }

                // We only need to return one path for the dockbay, so return the first
                path_num = pm->docking_bays[dockbay_index].splines[0];
                return path_num;
        } else {
                return -1;
        }
}

//      Actually go ahead and fire the synaptics.
void cheat_fire_synaptic(object *objp, ship *shipp, ai_info *aip)
{
        ship_weapon     *swp;
        swp = &shipp->weapons;
        int     current_bank = swp->current_secondary_bank;

        ai_select_secondary_weapon(objp, swp, WIF_SPAWN, 0);
        if (timestamp_elapsed(swp->next_secondary_fire_stamp[current_bank])) {
                if (ship_fire_secondary(objp)) {
                        nprintf(("AI", "ship %s cheat fired synaptic!\n", shipp->ship_name));
                        swp->next_secondary_fire_stamp[current_bank] = timestamp(2500);
                }
        }
}

//      For the subspace mission (sm3-09a)
//              for delta wing
//                      if they're sufficiently far into the mission
//                              if they're near one or more enemies
//                                      every so often
//                                              fire a synaptic if they have one.
void maybe_cheat_fire_synaptic(object *objp, ai_info *aip)
{
        //      Only do in subspace missions.
        if ( The_mission.flags & MISSION_FLAG_SUBSPACE )        {
                ship    *shipp;
                int     num, time;

                shipp = &Ships[objp->instance];

                if (!(strnicmp(shipp->ship_name, NOX("delta"), 5))) {
                        num = shipp->ship_name[6] - '1';

                        if ((num >= 0) && (num <= 3)) {
                                time = Missiontime >> 16;       //      Convert to seconds.

                                time -= 2*60;   //      Subtract off two minutes.

                                if (time > 0) {
                                        int modulus = 17 + num*3;

                                        if ((time % modulus) < 2) {
                                                int count = num_nearby_fighters(get_enemy_team_mask(OBJ_INDEX(objp)), &objp->pos, 1500.0f);

                                                if (count > 0) {
                                                        cheat_fire_synaptic(objp, shipp, aip);
                                                }
                                        }
                                }
                        }
                }
        }

}