ryan's struct patch for gcc 2.95

[taylor/freespace2.git] / src / ship / aibig.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/AiBig.cpp $
 * $Revision$
 * $Date$
 * $Author$
 *
 * C module for AI code related to large ships
 *
 * $Log$
 * 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 07:12:33  relnev
 * a few NDEBUG updates.
 *
 * removed a few warnings.
 *
 * Revision 1.2  2002/05/07 03:16:51  theoddone33
 * The Great Newline Fix
 *
 * Revision 1.1.1.1  2002/05/03 03:28:10  root
 * Initial import.
 *
 * 
 * 13    8/31/99 4:24p Andsager
 * Reduce collisions when attacking big ships.
 * 
 * 12    7/19/99 2:18p Mikeb
 * DA:  DOH!!
 * 
 * 11    7/19/99 2:11p Mikeb
 * DA: sometimes big_ship_attack_normal is not known
 * 
 * 10    6/14/99 3:21p Andsager
 * Allow collisions between ship and its debris.  Fix up collision pairs
 * when large ship is warping out.
 * 
 * 9     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
 * 
 * 8     5/13/99 2:31p Jamesa
 * DA:  Temp fix when attacking subsys of big ship and BS is blown up.
 * 
 * 7     5/06/99 11:46a Andsager
 * Bug fixes.  Don't get into illegal strafe submode.  Don't choose turret
 * enemy objnum for beam protected.
 * 
 * 6     4/23/99 12:01p Johnson
 * Added SIF_HUGE_SHIP
 * 
 * 5     4/20/99 3:40p Andsager
 * Changes to big ship ai.  Uses bounding box as limit where to fly to
 * when flying away.
 * 
 * 4     4/16/99 5:54p Dave
 * Support for on/off style "stream" weapons. Real early support for
 * target-painting lasers.
 * 
 * 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
 * 
 * 77    5/25/98 12:12a Mike
 * Improve big ship avoidance to avoid big ships when in a nearby dock
 * mode.  Fixes very dumb looking behavior in sm2-01a.  Verified sm1-08a
 * not too dumb at start.
 * 
 * 76    5/23/98 2:38a Mike
 * Improve balance of cheat-firing Synaptics.
 * 
 * 75    5/23/98 12:40a Mike
 * Hook for Delta wing to fire Synaptic bombs in sm3-09a.
 * 
 * 74    5/22/98 12:08p Mike
 * Force reset of aspect locking when AI ships switch banks due to
 * good-time-to-unload-secondaries
 * 
 * 73    5/21/98 1:25p Lawrance
 * Fix exception in ai_bpap() when no verts are in closest octant
 * 
 * 72    5/21/98 9:57a Mike
 * Massively improve firing of bombs at big ships.  Improve willingness to
 * take incoming fire to deliver bomb.  Make a little easier to gain
 * aspect lock.
 * 
 * 71    5/12/98 10:06a Mike
 * Fix a jillion bugs preventing ships from firing bombs at Lucifer in
 * sm3-09.
 * 
 * 70    5/10/98 11:30p Mike
 * Better firing of bombs, less likely to go into strafe mode.
 * 
 * 69    5/10/98 3:41a Lawrance
 * Fix bug that was preventing ships from leaving strafe mode
 * 
 * 68    5/08/98 4:39p Mike
 * Make ships match bank when attacking large ships.
 * 
 * 67    5/07/98 11:59p Mike
 * Remove unneeded code, computation of num_verts.
 * 
 * 66    4/29/98 5:01p Mike
 * Large overhaul in how turrets fire.
 * 
 * 65    4/27/98 11:59p Mike
 * Intermediate checkin.  Getting big ship turrets firing at big ships to
 * use pick_big_attack_point.
 * 
 * 64    4/23/98 12:32a Mike
 * Fix bogus math which looked at (1-fov) instead of fov.
 * 
 * 63    4/13/98 4:52p Allender
 * remove AI_frametime and us flFrametime instead.  Make lock warning work
 * in multiplayer for aspect seeking missiles.  Debris fixups
 * 
 * 62    4/13/98 3:27p Lawrance
 * Fix bug that caused ships to leave strafe mode right away since they
 * hadn't taken damage for a while
 * 
 * 61    4/12/98 2:02p Mike
 * Make small ships avoid big ships.
 * Turn on Collide_friendly flag.
 * 
 * 60    4/01/98 9:21p John
 * Made NDEBUG, optimized build with no warnings or errors.
 * 
 * 59    3/25/98 12:00a Allender
 * MK: make sure that output from function gets a valid valud (ai_pbap I
 * think)
 * 
 * 58    3/24/98 10:07p Adam
 * AL: Add another Assert() to try and catch bogus wp->big_attack_point
 * 
 * 57    3/24/98 9:56p Adam
 * AL: Assert that local_attack_point is valid in ai_bpap
 * 
 * 56    3/21/98 3:36p Mike
 * Fix/optimize attacking of big ships.
 * 
 * 55    3/16/98 5:17p Mike
 * Make ships not get stuck on big ships when attacking.
 * 
 * 54    3/16/98 12:03a Mike
 * Add support for kamikaze mode.  Add AIF_NO_DYNAMIC which means
 * relentlessly pursue current goal.
 * 
 * 53    3/12/98 4:04p Lawrance
 * Leave strafe mode if haven't been hit for a while and no enemy
 * fighter/bombers are close by.
 * 
 * 52    3/09/98 5:12p Mike
 * Make sure Pl_objp uses are valid.
 * Throw asteroids at ships in asteroid field, not "Gal"
 * Support ships warp out if no goals after 30 seconds.
 * 
 * 51    3/03/98 11:51p Lawrance
 * Ensure target is a ship before looking at SIF flags
 * 
 * 50    3/02/98 11:35a Mike
 * Fix logic with ai_do_default_behavior -- return after call.
 * 
 * 49    2/19/98 7:37p Lawrance
 * Fix bug that was causing problems with subsystem path following.
 * 
 * 48    2/14/98 3:38p Mike
 * Make bombs have arm time, drop for 1/2 second, have hull_strength.
 * Make them not fired until closer to target.
 * 
 * 47    2/13/98 3:56p Mike
 * Make ships more likely to stick to player orders, not get so distracted
 * by getting hit by someone else.
 * 
 * 46    2/11/98 4:30p Lawrance
 * Improve disarm/disable behavior.
 * 
 * 45    2/11/98 1:16a Mike
 * Mods to AI behavior to make it harder to stay on a ship's tail.  Not
 * too much improvement.
 * 
 * 44    2/05/98 12:51a Mike
 * Early asteroid stuff.
 * 
 * 43    1/30/98 11:28a Comet
 * Fix indexing problem into verts in ai_bpap()
 * 
 * 42    1/29/98 10:46p Mike
 * In ai_big_pick_attack_point, handle case of octant with no points.
 * 
 * 41    1/29/98 1:39p Mike
 * Better heat seeking homing on big ships.
 * 
 * 40    1/27/98 4:18p Mike
 * Not fire weapons too early when attacking large ships.  Aspect lock
 * take proper amount of time for AI ships.
 * 
 * 39    1/22/98 5:14p Lawrance
 * clean up ai_big code, clear path info when stop attacking a subsystem
 * 
 * 38    1/20/98 11:41p Mike
 * Ships use new system of preferred big weapons to fire.  Also, support
 * AIF_UNLOAD_SECONDARIES which means fire as fast as possible.
 * 
 * 37    1/20/98 9:47a Mike
 * Suppress optimized compiler warnings.
 * Some secondary weapon work.
 * 
 * 36    1/17/98 4:45p Mike
 * Better support for AI selection of secondary weapons.
 * 
 * 35    1/16/98 3:57p Mike
 * Clean up some bugs with attacking of protected ships.  Make turrets
 * only fire at targets that are within range.
 * 
 * 34    1/16/98 11:32a Mike
 * Fix bug when a ship is attacking a dead subsystem on a protected ship.
 * 
 * 33    1/07/98 1:32p Lawrance
 * Remove some nprintf output
 * 
 * 32    1/07/98 1:21p Sandeep
 * Fix bug where accessing uninited pointer
 * 
 * 31    1/06/98 6:58p Lawrance
 * Attack turrets (sometimes) when fired upon while attacking a ship.
 * 
 * 30    12/31/97 6:28p Lawrance
 * Improve attacking subsystems on moving ships.
 * 
 * 29    12/31/97 4:16p Lawrance
 * Use different fov's for attacking subsystems depending if ship is
 * moving
 * 
 * 28    12/31/97 4:05p Mike
 * Support for all teams optionally attacking all teams.
 * Lead big ships when attacking their hull.
 * 
 * 27    12/31/97 12:26p Lawrance
 * Don't enter strafe mode for transports, fix bug that prevented strafe
 * mode from getting entered.
 * 
 * 26    12/30/97 5:20p Mike
 * Don't fire secondaries at a protected ship if its hull is very weak.
 * 
 * 25    12/30/97 4:26p Lawrance
 * Take out some debug statements
 * 
 * 24    12/15/97 7:16p Lawrance
 * improving subsystem attacking
 * 
 * 23    12/02/97 11:58a Lawrance
 * avoid during strafe mode only when endangered by a weapon
 * 
 * 22    12/01/97 5:11p Lawrance
 * make strafe mode more effective... slow down when approaching and use
 * afterburner in avoids
 * 
 * 21    11/27/97 4:21p Lawrance
 * set submode to -1 when switching to AIM_NONE from AIM_STRAFE
 * 
 * 20    11/24/97 2:27a Lawrance
 * if attacking a big ship and moving very slow, enter strafe mode if
 * enemy fighter/bombers are close by
 * 
 * 19    11/14/97 11:27a Johnson
 * if goal_objnum is -1, and in STRAFE, return 1 from
 * ai_maybe_follow_subsys_path(), so break out of STRAFE code
 * 
 * 18    11/13/97 11:51a Johnson
 * ALAN: comment out Int3() in AiBig... need to test on my own machine
 * 
 * 17    11/12/97 11:51p Lawrance
 * only check target_objnum == goal_objnum when following path
 * 
 * 16    11/12/97 11:01p Lawrance
 * change call to ai_find_path()
 * ensure goal_objnum == target_objnum in STRAFE
 * 
 * 15    11/12/97 11:18a Lawrance
 * fix bug in path following of subsystems
 * 
 * 14    11/11/97 5:22p Mike
 * Don't allow ships to attack navbuoys.
 * Make ships lead big ships with dumbfire.
 * Make ships smarter about leaving evade weapon mode.
 * Fix a couple Assert() bugs.
 * 
 * 13    11/06/97 6:27p Lawrance
 * fix bug that was messing up retreat point in STRAFE mode
 * 
 * 12    11/06/97 4:53p Mike
 * Limit number of ships that can simultaneously attack another.  Make
 * turrets inherit AI class from parent ship.
 * 
 * 11    11/06/97 12:27a Mike
 * Better avoid behavior.
 * Modify ai_turn_towards_vector() to take a flag parameter.
 * 
 * 10    11/02/97 10:55p Lawrance
 * removed some unused code, added some comments
 * 
 * 9     11/01/97 4:01p Mike
 * Adapt to new ai_find_path().
 * 
 * 8     10/31/97 11:24a Lawrance
 * If taget changes from a big ship to small ship while in AIM_STRAFE,
 * switch to AIM_CHASE
 * 
 * 7     10/30/97 10:06p Lawrance
 * chg some timing values so ship will reach retreat point
 * 
 * 6     10/30/97 9:17p Lawrance
 * work on getting AIM_STRAFE working well with disable/disarm, try to
 * balance
 * 
 * 5     10/30/97 12:32a Lawrance
 * further work on AIM_STRAFE
 * 
 * 4     10/29/97 6:25p Lawrance
 * add AIM_STRAFE functionality
 * 
 * 3     10/26/97 4:19p Lawrance
 * added ai_get_weapon_dist()
 * 
 * 2     10/26/97 3:24p Lawrance
 * split off large ship ai code into AiBig.cpp
 *
 * $NoKeywords: $
 */

#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 "aibig.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 "missionparse.h"

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

#define SCAN_FIGHTERS_INTERVAL  2000            // how often an AI fighter/bomber should scan for enemy fighter/bombers
                                                                                                                // if sitting still and pounding on a big ship.  If enemy fighters are
                                                                                                                // close ( < ENTER_STRAFE_THREAT_DIST ), then enter AIM_STRAFE

#define ENTER_STRAFE_THREAT_DIST_SQUARED        360000  // use squared distance, instead of 600

#define MIN_DOT_TO_ATTACK_SUBSYS                                0.7f
#define MIN_DOT_TO_ATTACK_MOVING_SUBSYS 0.97f

// AI BIG MAGIC NUMBERS
#define STRAFE_RETREAT_COLLIDE_TIME     2.0             // when anticipated collision time is less than this, begin retreat
#define STRAFE_RETREAT_COLLIDE_DIST     100             // when perpendicular distance to *surface* is less than this, begin retreat
#define STRAFE_RETREAT_BOX_DIST                 300             // distance beyond the bounding box to retreat

#define EVADE_BOX_BASE_DISTANCE                 300             // standard distance to end evade submode
#define EVADE_BOX_MIN_DISTANCE                  200             // minimun distance to end evade submode, after long time

#define ATTACK_STOP_DISTANCE                            150             // when distance to target is less than this, put on brakes

#define ATTACK_COLLIDE_BASE_DIST                300             // absolute distance at which to begin checking for possible collision
#define ATTACK_COLLIDE_AVOID_DIST               60                      // perpendicular distance to attack surface at which begin avoiding
#define ATTACK_COLLIDE_AVOID_TIME               1.0             // anticipated collision time at which to begin evade
#define ATTACK_COLLIDE_SLOW_DIST                150             // perpendicular distance to attack surface at which begin slowing down
#define ATTACK_COLLIDE_SLOW_TIME                1.5             // anticipated collision time at which to begin slowing down


// forward declarations
void    ai_big_evade_ship();
void    ai_big_chase_attack(ai_info *aip, ship_info *sip, vector *enemy_pos, float dist_to_enemy);
void    ai_big_avoid_ship();
int     ai_big_maybe_follow_subsys_path(int do_dot_check=1);

extern int model_which_octant_distant_many( vector *pnt, int model_num,matrix *model_orient, vector * model_pos, polymodel **pm, int *octs);
extern void compute_desired_rvec(vector *rvec, vector *goal_pos, vector *cur_pos);
extern void big_ship_collide_recover_start(object *objp, object *big_objp, vector *collide_pos, vector *collision_normal);


//      Called by ai_big_pick_attack_point.
//      Generates a random attack point.
//      If truly_random flag set (haha), then generate a pretty random number.  Otherwise, generate a static rand which
//      tends to not change from frame to frame.
//      Try four times and choose nearest point to increase chance of getting a good point.
void ai_bpap(object *objp, vector *attacker_objp_pos, vector *attacker_objp_fvec, vector *attack_point, vector *local_attack_point, float fov, float weapon_travel_dist, vector *surface_normal)
{
        float           nearest_dist;
        vector  result_point, best_point;
        vector  rel_point;
        int             num_tries;
        model_octant    *octp;
        polymodel       *pm;
        int             i, q, octs[4];  

        best_point = objp->pos;
        nearest_dist = weapon_travel_dist;

        model_which_octant_distant_many(attacker_objp_pos, Ships[objp->instance].modelnum, &objp->orient, &objp->pos, &pm, octs);

        num_tries = (int) (vm_vec_dist(&objp->pos, attacker_objp_pos)/objp->radius);

        if (num_tries >= 4)
                num_tries = 1;
        else
                num_tries = 4 - num_tries;

        //      Index #0 is best one.
        if ( pm->octants[octs[0]].verts ) {
                *local_attack_point = *pm->octants[octs[0]].verts[0];   //      Set just in case it doesn't get set below.
        } else {
                vm_vec_zero(local_attack_point);
        }

        for (q=0; q<4; q++) {
                octp = &pm->octants[octs[q]];
                if (octp->nverts > 0) {

                        if (num_tries > octp->nverts)
                                num_tries = octp->nverts;

                        if (num_tries > octp->nverts)
                                num_tries = octp->nverts;

                        int     best_index = -1;

                        for (i=0; i<num_tries; i++) {
                                int     index;
                                float   dist, dot;
                                vector  v2p;

                                index = (int) (frand() * (octp->nverts));

                                rel_point = *octp->verts[index];
                                vm_vec_unrotate(&result_point, &rel_point, &objp->orient);
                                vm_vec_add2(&result_point, &objp->pos);

                                dist = vm_vec_normalized_dir(&v2p, &result_point, attacker_objp_pos);
                                dot = vm_vec_dot(&v2p, attacker_objp_fvec);

                                if (dot > fov) {
                                        if (dist < nearest_dist) {
                                                best_index = index;
                                                nearest_dist = dist;
                                                best_point = result_point;
                                                *local_attack_point = rel_point;
                                                Assert( !vm_is_vec_nan(local_attack_point) );
                                                if (dot > (1.0f + fov)/2.0f)    //      If this point is quite good, quit searching for a better one.
                                                        goto done_1;
                                        }
                                }
                        }
                }
        }
done_1:

        *attack_point = best_point;

        // Cast from attack_objp_pos to local_attack_pos and check for nearest collision.
        // If no collision, cast to (0,0,0) [center of big ship]**  [best_point initialized to 000]

        // do in world coords to get attack point, then translate to local for local_attack_point
        vector attack_dir, end_point, temp;
        float dist;
        dist = vm_vec_normalized_dir(&attack_dir, attack_point, attacker_objp_pos);

        if (dist > 0.1) {
                vm_vec_scale_add(&end_point, attack_point, &attack_dir, 30.0f);
        } else {
                vm_vec_scale_add(&end_point, attack_point, attacker_objp_fvec, 30.0f);
        }
        
        mc_info mc;
        mc.model_num = Ships[objp->instance].modelnum;
        mc.orient = &objp->orient;
        mc.pos = &objp->pos;
        mc.p0 = attacker_objp_pos;
        mc.p1 = &end_point;
        mc.flags = MC_CHECK_MODEL;
        mc.radius = 0.0f;
        model_collide(&mc);

        if (mc.num_hits > 0) {
                *attack_point = mc.hit_point_world;
                vm_vec_sub(&temp, attack_point, &objp->pos);
                vm_vec_rotate(local_attack_point, &temp, &objp->orient);
                if (surface_normal) {
                        vm_vec_unrotate(surface_normal, &mc.hit_normal, &objp->orient);
                }
        } else {
                vm_vec_zero(local_attack_point);
                *attack_point = objp->pos;
                if (surface_normal) {
                        vm_vec_zero(surface_normal);
                }
        }
}

//      Stuff a point to attack based on nearest octant.
//      If no points in that octant, leave attack_point unmodified.
//
//      Note: Default value for fov is 1.0f  1.0f means don't use fov parameter.
//      If fov != 1.0f, try up to four times to find a point that's in the field of view.
void ai_big_pick_attack_point_turret(object *objp, ship_subsys *ssp, vector *gpos, vector *gvec, vector *attack_point, float fov, float weapon_travel_dist)
{
        if (!timestamp_elapsed(ssp->turret_pick_big_attack_point_timestamp)) {
                vector  result_point;
                vm_vec_unrotate(&result_point, &ssp->turret_big_attack_point, &objp->orient);
                vm_vec_add(attack_point, &result_point, &objp->pos);
        } else {
                vector  local_attack_point;
                ssp->turret_pick_big_attack_point_timestamp = timestamp(2000 + (int) (frand()*500.0f));
                ai_bpap(objp, gpos, gvec, attack_point, &local_attack_point, fov, weapon_travel_dist, NULL);
                ssp->turret_big_attack_point = local_attack_point;
        }
}

//      Stuff a point to attack based on nearest octant.
//      If no points in that octant, leave attack_point unmodified.
//
//      Note: Default value for fov is 1.0f  1.0f means don't use fov parameter.
//      If fov != 1.0f, try up to four times to find a point that's in the field of view.
//      Note, attacker_objp can be a ship or a weapon.
void ai_big_pick_attack_point(object *objp, object *attacker_objp, vector *attack_point, float fov)
{
        Assert(objp->instance > -1);
        Assert(objp->type == OBJ_SHIP);

        vector  local_attack_point;

        switch (attacker_objp->type) {
        case OBJ_SHIP: {
                ai_info *attacker_aip;
                attacker_aip = &Ai_info[Ships[attacker_objp->instance].ai_index];
                if (!timestamp_elapsed(attacker_aip->pick_big_attack_point_timestamp)) {
                        vector  result_point;

                        vm_vec_unrotate(&result_point, &attacker_aip->big_attack_point, &objp->orient);
                        vm_vec_add(attack_point, &result_point, &objp->pos);

                        return;
                }
        
                attacker_aip->pick_big_attack_point_timestamp = timestamp(2000 + (int) (frand()*500.0f));
                break;
                                                }
        case OBJ_WEAPON: {
                weapon  *wp = &Weapons[attacker_objp->instance];

                if (!timestamp_elapsed(wp->pick_big_attack_point_timestamp)) {
                        vector  result_point;

                        vm_vec_unrotate(&result_point, &wp->big_attack_point, &objp->orient);
                        vm_vec_add(attack_point, &result_point, &objp->pos);

                        return;
                }
                wp->pick_big_attack_point_timestamp = timestamp(2000 + (int) (frand()*500.0f));
        
                break;
                                                  }
        }

        // checks valid line to target
        vector surface_normal;
        ai_bpap(objp, &attacker_objp->pos, &attacker_objp->orient.v.fvec, attack_point, &local_attack_point, fov, 99999.9f, &surface_normal);

        switch (attacker_objp->type) {
        case OBJ_SHIP: {
                ai_info *attacker_aip;
                // if we can't find a new local_attack_point don't change local_attack_point
                if (vm_vec_mag_squared(&local_attack_point) < 1) {
                        return;
                }

                attacker_aip = &Ai_info[Ships[attacker_objp->instance].ai_index];
                attacker_aip->big_attack_point = local_attack_point;
                attacker_aip->big_attack_surface_normal = surface_normal;
                break;
                                                }
        case OBJ_WEAPON: {
                weapon  *wp = &Weapons[attacker_objp->instance];
                wp->big_attack_point = local_attack_point;
                Assert( !vm_is_vec_nan(&wp->big_attack_point) );
                break;
                                                  }
        }

        return;
}

// Handler for SM_EVADE submode ( called from ai_big_chase() )
void ai_big_evade_ship()
{
        vector  player_pos, enemy_pos;
        float           dist;
        ship            *shipp = &Ships[Pl_objp->instance];
        ai_info *aip = &Ai_info[shipp->ai_index];
        vector  randvec, semi_enemy_pos;

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

        dist = vm_vec_dist_quick(&player_pos, &enemy_pos);
        vm_vec_rand_vec_quick(&randvec);
        if ((Missiontime>>14) & 1) {
                vm_vec_scale_add(&semi_enemy_pos, &enemy_pos, &randvec, dist/2.0f);
                aip->prev_goal_point = semi_enemy_pos;
        } else {
                semi_enemy_pos = aip->prev_goal_point;
        }
        
        accelerate_ship(aip, 1.0f - ((Missiontime>>8) & 0x3f)/128.0f );
        turn_away_from_point(Pl_objp, &semi_enemy_pos, 0.0f);

        float box_dist;
        vector box_vec;
        int is_inside;
        box_dist = get_world_closest_box_point_with_delta(&box_vec, En_objp, &player_pos, &is_inside, EVADE_BOX_BASE_DISTANCE);
        if (box_dist > EVADE_BOX_BASE_DISTANCE) {
                aip->submode = SM_ATTACK;
                aip->submode_start_time = Missiontime;
        } else if ((box_dist > EVADE_BOX_MIN_DISTANCE) && (Missiontime - aip->submode_start_time > i2f(5)) ) {
                aip->submode = SM_ATTACK;
                aip->submode_start_time = Missiontime;
        }

        //TODO TEST

/*      if (dist > 4*En_objp->radius) {
                aip->submode = SM_ATTACK;
                aip->submode_start_time = Missiontime;
        } else if (dist > En_objp->radius) {
                if (Missiontime - aip->submode_start_time > i2f(5)) {
                        aip->submode = SM_ATTACK;
                        aip->submode_start_time = Missiontime;
                }
        } */
}

// Handler for SM_AVOID submode ( called from ai_big_chase() )
void ai_big_avoid_ship()
{
        ai_big_evade_ship();
}

// reset path following information
void ai_big_subsys_path_cleanup(ai_info *aip)
{
        if ( aip->ai_flags & AIF_ON_SUBSYS_PATH ) {
                aip->ai_flags &= ~AIF_ON_SUBSYS_PATH;
                aip->path_goal_dist = -1;
                aip->path_start = -1;
                aip->path_cur = -1;
                aip->path_length = 0;
        }
}

// Maybe Pl_objp needs to follow a path to get in line-of-sight to a subsystem
// input:       do_dot_check    =>      default value 0, flag to indicate whether check should be done to ensure
//                                                                              subsystem is within certain field of view.  We don't want to check fov when
//                                                                              strafing, since ship is weaving to avoid turret fire
int ai_big_maybe_follow_subsys_path(int do_dot_check)
{
        ai_info *aip;
        float           dot = 1.0f, min_dot;
        object  *target_objp;

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

        if ( (aip->targeted_subsys != NULL) && (aip->target_objnum >= 0) && (aip->targeted_subsys->system_info->path_num >= 0) ) {
                polymodel       *pm;
                int                     subsys_path_num, subsys_in_sight, checked_sight;
                float                   dist;

                pm = model_get( Ships[Pl_objp->instance].modelnum );
        
                // If attacking a subsystem, ensure that we have an unobstructed line of sight... if not, then move
                // towards path linked to subsystem
                subsys_in_sight = 0;    // assume Pl_objp doesn't have line of sight to subys

                // only check for subsystem sight every N milliseconds
                checked_sight = 0;
                if ( timestamp_elapsed(aip->path_subsystem_next_check) ) {
                        vector          geye, gsubpos;
                        eye                     *ep;

                        aip->path_subsystem_next_check = timestamp(1500);

                        // get world pos of eye (stored in geye)
                        ep = &(pm->view_positions[0] );
                        model_find_world_point( &geye, &ep->pnt, Ships[Pl_objp->instance].modelnum, 0, &Pl_objp->orient, &Pl_objp->pos );
                        
                        // get world pos of subsystem
                        vm_vec_unrotate(&gsubpos, &aip->targeted_subsys->system_info->pnt, &En_objp->orient);
                        vm_vec_add2(&gsubpos, &En_objp->pos);

                        checked_sight = 1;

                        // Calc dot between subsys normal (based on using path info), and subsys_to_eye vector.  This is
                        // useful later when we want to decide whether we have a realistic line-of-sight to the subsystem.
                        vector subsys_normal, subsys_to_eye;
                        if ( do_dot_check ) {
                                if ( !ship_return_subsys_path_normal(&Ships[target_objp->instance], aip->targeted_subsys, &gsubpos, &subsys_normal) ) {
                                        vm_vec_normalized_dir(&subsys_to_eye, &geye, &gsubpos);
                                        dot = vm_vec_dot(&subsys_normal, &subsys_to_eye);
                                }
                        }

                        if ( ship_subsystem_in_sight(En_objp, aip->targeted_subsys, &geye, &gsubpos, 1) ) {
                                subsys_in_sight = 1;
                        }
                }

                // check if subsystem not in sight
                min_dot = (target_objp->phys_info.fspeed > 5.0f?MIN_DOT_TO_ATTACK_MOVING_SUBSYS:MIN_DOT_TO_ATTACK_SUBSYS);
                if ( (checked_sight && ((!subsys_in_sight) || (dot < min_dot)) ) )  {

                        aip->path_goal_dist = 5;
                        subsys_path_num = aip->targeted_subsys->system_info->path_num;
                        if ( (aip->path_start) == -1 || (aip->mp_index != subsys_path_num) ) {
                                // maybe create a new path
                                if ( subsys_path_num >= 0 ) {
                                        Assert(aip->target_objnum >= 0);
                                        ai_find_path(Pl_objp, aip->target_objnum, subsys_path_num, 0, 1);
                                        if ( aip->path_start >= 0 ) {
                                                aip->ai_flags |= AIF_ON_SUBSYS_PATH;
                                        }
                                }
                        }
                }

                if ( checked_sight && subsys_in_sight && (dot > min_dot) ) {
                        // we've got a clear shot, stay here for a bit
                        aip->path_subsystem_next_check = timestamp_rand(5000,8000);
                }

                // If there is a path that we are tracking, see if ship has gotten to within
                // aip->path_goal_dist units.  If so, then ship can stop following the path.  This
                // is required since we don't want to follow the path all the way to the subsystem,
                // and we want ships to stop different distances from their path destination
                if ( aip->path_length > 0 ) {
                        int path_done=0;
                        int in_view=0;

                        Assert(aip->path_length >= 2);
                        dist = vm_vec_dist_quick(&Path_points[aip->path_start+aip->path_length-2].pos, &Pl_objp->pos);

                        if ( aip->path_cur >= (aip->path_start+aip->path_length-1) ) {
                                path_done=1;
                        }

                        min_dot = (target_objp->phys_info.fspeed > 5.0f?MIN_DOT_TO_ATTACK_MOVING_SUBSYS:MIN_DOT_TO_ATTACK_SUBSYS);
                        if ( (checked_sight && subsys_in_sight) && (dot > min_dot) ) {
                                in_view=1;
                        }

                        // if we've reached the destination, then we can stop following the path
                        if ( path_done || ( dist < aip->path_goal_dist ) || in_view ) {
                                ai_big_subsys_path_cleanup(aip);
                        } else if ( dist > aip->path_goal_dist ) {
                                // If we have a path to follow, follow it and return                    
                                if ( aip->path_start != -1 ) {
                                        // for now, only follow the path to the first point
                                        if ( aip->path_cur < (aip->path_start+aip->path_length-1) ) {
                                                if ( aip->goal_objnum != aip->target_objnum ) {
                                                        //Int3();       // what is going on here? - Get Alan
                                                        aip->previous_mode = aip->mode;
                                                        aip->mode = AIM_NONE;
                                                        aip->submode = -1;
                                                        return 1;
                                                }
                                                ai_path();
                                                return 1;
                                        }
                                }
                        }
                }
        }

        return 0;
}

// This function is only called from ai_big_chase_attack() when a ship is flying very slowly and
// attacking a big ship.  The ship should scan for enemy fighter/bombers... if any are close, then
// return 1, otherwise return 0;
//
// input: aip   =>      ai_info pointer for Pl_objp
//                       sip    =>      ship_info pointer for Pl_objp
//
// exit:                1       =>      ship should enter strafe mode
//                              0       => ship should not change ai mode, no fighter/bomber threats are near
//
// NOTE: uses SCAN_FIGHTERS_INTERVAL and ENTER_STRAFE_THREAT_DIST_SQUARED which are defined in AiBig.h
int ai_big_maybe_start_strafe(ai_info *aip, ship_info *sip)
{
        // if moving slowly (or stopped), and SIF_SMALL_SHIP, then enter STRAFE mode if enemy fighter/bombers
        // are near
        if ( sip->flags & SIF_SMALL_SHIP ) {
                if ( timestamp_elapsed(aip->scan_for_enemy_timestamp) ) {
                        ship_obj        *so;
                        object  *test_objp;
                        ship            *test_sp;
                        float           dist_squared;
                        
                        aip->scan_for_enemy_timestamp = timestamp(SCAN_FIGHTERS_INTERVAL);
                        // iterate through ships, and see if any fighter/bomber from opposite team are near
                        so = GET_FIRST(&Ship_obj_list);
                        while( so != END_OF_LIST(&Ship_obj_list) ) {
                                test_objp = &Objects[so->objnum];
                                test_sp = &Ships[test_objp->instance];

                                if ( test_sp->team != Ships[Pl_objp->instance].team ) {
                                        if ( Ship_info[test_sp->ship_info_index].flags & SIF_SMALL_SHIP ) {
                                                dist_squared = vm_vec_dist_squared(&Pl_objp->pos, &test_objp->pos);
                                                if ( dist_squared < ENTER_STRAFE_THREAT_DIST_SQUARED ) {
                                                        return 1;
                                                }
                                        }
                                }
                                so = GET_NEXT(so);
                        }
                }
        }
        // If we've reached here, there are no enemy fighter/bombers near
        return 0;
}

//      ATTACK submode handler for chase mode.
void ai_big_chase_attack(ai_info *aip, ship_info *sip, vector *enemy_pos, float dist_to_enemy)
{
        int             start_bank;
        float           dot_to_enemy, time_to_hit;
        polymodel *po = model_get( sip->modelnum );

        //      Maybe evade an incoming weapon.
        if (((time_to_hit = ai_endangered_by_weapon(aip)) < 4.0f) && (time_to_hit >= 0.0f)) {
                aip->submode = SM_EVADE_WEAPON;
                aip->submode_start_time = Missiontime;
                aip->prev_goal_point = En_objp->pos;
        } else {
                //      If moving slowly, maybe evade incoming fire.
                if (Pl_objp->phys_info.speed < 3.0f) {
                        object *objp;
                        for ( objp = GET_FIRST(&obj_used_list); objp !=END_OF_LIST(&obj_used_list); objp = GET_NEXT(objp) ) {
                                if ((objp->type == OBJ_WEAPON) && (Weapons[objp->instance].team != Ships[Pl_objp->instance].team))
                                        if (Weapon_info[objp->instance].subtype == WP_LASER) {
                                                vector  in_vec;
                                                float           dist;

                                                vm_vec_sub(&in_vec, &objp->pos, &Pl_objp->pos);
                                                if (vm_vec_dot(&in_vec, &objp->orient.v.fvec) > 0.0f) {
                                                        dist = vm_vec_normalize(&in_vec);
                                                        if ((dist < 200.0f) && (vm_vec_dot(&in_vec, &objp->orient.v.fvec) > 0.95f)) {
                                                                if ((Objects[objp->parent].signature == objp->parent_sig) && (vm_vec_dist_quick(&objp->pos, &Objects[objp->parent].pos) < 300.0f)) {
                                                                        set_target_objnum(aip, objp->parent);
                                                                        aip->submode = SM_ATTACK;
                                                                        aip->submode_start_time = Missiontime;
                                                                } else {
                                                                        aip->submode = SM_EVADE;
                                                                        aip->submode_start_time = Missiontime;
                                                                        aip->prev_goal_point = En_objp->pos;
                                                                }
                                                        }
                                                }
                                        }
                        }
                        
                        // Since ship is moving slowly and attacking a large ship, scan if enemy fighters are near, if so
                        // then enter strafe mode
                        if ( ai_big_maybe_start_strafe(aip, sip) ) {
                                aip->previous_mode = aip->mode;
                                aip->mode = AIM_STRAFE;
                                aip->submode_parm0 = Missiontime;       // use parm0 as time strafe mode entered
                                aip->submode = AIS_STRAFE_ATTACK;
                                aip->submode_start_time = Missiontime;
                                return;
                        }

                } // end if ( Pl_objp->phys_info.speed < 3.0f ) 

                // see if Pl_objp needs to reposition to get a good shot at subsystem which is being attacked
                if ( ai_big_maybe_follow_subsys_path() ) {
                        return;
                }

                vector  *rel_pos, vec_to_enemy;
                float           weapon_travel_dist;

                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;

                dist_to_enemy = vm_vec_normalized_dir(&vec_to_enemy, enemy_pos, &Pl_objp->pos);
                dot_to_enemy = vm_vec_dot(&vec_to_enemy, &Pl_objp->orient.v.fvec);

                vector  rvec_vec, *rvec = &rvec_vec;

                if (dist_to_enemy > 500.0f)
                        compute_desired_rvec(rvec, enemy_pos, &Pl_objp->pos);
                else
                        rvec = NULL;

                ai_turn_towards_vector(enemy_pos, Pl_objp, flFrametime, sip->srotation_time, NULL, rel_pos, 0.0f, 0, rvec);

                // calc range of primary weapon
                weapon_travel_dist = ai_get_weapon_dist(&Ships[Pl_objp->instance].weapons);

                if ( aip->targeted_subsys != NULL ) {
                        if (dist_to_enemy > (weapon_travel_dist-20))
                                accelerate_ship(aip, 1.0f);
                        else {
                                // AL 12-31-97: Move at least as quickly as your target is moving...
                                accelerate_ship(aip, max(1.0f - dot_to_enemy, Objects[aip->target_objnum].phys_info.fspeed/sip->max_speed));
                        }

                } else {
                        float accel;
                        if (dot_to_enemy < 0.0f) {
                                accel = 0.5f;
                        } else if (dot_to_enemy < 0.75f) {
                                accel = 0.75f;
                        } else {
                                if (dist_to_enemy > weapon_travel_dist/2.0f) {
                                        accel = 1.0f;
                                } else {
                                        accel = 1.0f - dot_to_enemy;
                                }
                        }

                        // use dist normal to enemy here (dont break 50 barrier)
                        if (dist_to_enemy < ATTACK_STOP_DISTANCE) {
//                              accelerate_ship(aip, accel * 0.5f);
                                accelerate_ship(aip, -1.0f);
                        } else {
                                accelerate_ship(aip, accel);
                        }

                }
        }
}

// Handler for submode SM_CONTINUOUS_TURN
void ai_big_chase_ct()
{
        ai_chase_ct();
}

extern void ai_select_secondary_weapon(object *objp, ship_weapon *swp, int priority1 = -1, int priority2 = -1);
extern float set_secondary_fire_delay(ai_info *aip, ship *shipp, weapon_info *swip);
extern void ai_choose_secondary_weapon(object *objp, ai_info *aip, object *en_objp);
extern int maybe_avoid_big_ship(object *objp, object *ignore_objp, ai_info *aip, vector *goal_point, float delta_time);

extern void maybe_cheat_fire_synaptic(object *objp, ai_info *aip);

// Determine if Pl_objp should fire weapons at current target, based on input parameters
//
// dist_to_enemy        =>              distance (in m) to attack point on current target
// dot_to_enemy =>              dot product between fvec of Pl_objp and vector from Pl_objp to attack point
//
void ai_big_maybe_fire_weapons(float dist_to_enemy, float dot_to_enemy, vector *firing_pos, vector *enemy_pos, vector *enemy_vel)
{
        ai_info         *aip;
        ship_weapon     *swp;

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

        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;
                        temp_shipp = &Ships[Pl_objp->instance];
                        ship_weapon *tswp = &temp_shipp->weapons;

                        if ( tswp->num_primary_banks > 0 ) {
                                Assert(tswp->current_primary_bank < tswp->num_primary_banks);
                                weapon_info     *wip = &Weapon_info[tswp->primary_bank_weapons[tswp->current_primary_bank]];

                                if (dist_to_enemy < wip->max_speed * wip->lifetime)
                                        ai_fire_primary_weapon(Pl_objp);

                                int     priority1, priority2;

                                priority1 = -1;
                                priority2 = -1;

                                //      Maybe favor selecting a bomb.
                                //      Note, if you're firing a bomb, if it's aspect seeking, the firing conditions can be looser.
                                if (Ship_info[Ships[En_objp->instance].ship_info_index].flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP))
                                        if (En_objp->phys_info.speed * dist_to_enemy < 5000.0f)         //      Don't select a bomb if enemy moving fast relative to distance
                                                priority1 = WIF_BOMB;

                                if (!(En_objp->flags & OF_PROTECTED)) {
                                        //ai_select_secondary_weapon(Pl_objp, tswp, priority1, priority2);      //      Note, need to select to get weapon speed and lifetime

                                        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[current_bank]];

                                        //      If ship is protected and very low on hits, don't fire missiles.
                                        if ((current_bank > -1) &&  (!(En_objp->flags & OF_PROTECTED) || (En_objp->hull_strength > 10*swip->damage))) {
                                                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])) {

                                                        float firing_range = swip->max_speed * swip->lifetime;
                                                        // reduce firing range of secondaries in nebula
                                                        extern int Nebula_sec_range;
                                                        if ((The_mission.flags & MISSION_FLAG_FULLNEB) && Nebula_sec_range) {
                                                                firing_range *= 0.8f;
                                                        }

                                                        float t = 0.25f;        //      default delay in seconds until next fire.

                                                        if (dist_to_enemy < firing_range*1.0f) {


                                                                //vm_vec_scale_add(&future_enemy_pos, enemy_pos, enemy_vel, dist_to_enemy/swip->max_speed);
                                                                //if (vm_vec_dist_quick(&future_enemy_pos, firing_pos) < firing_range * 0.8f) {
                                                                        if (ai_fire_secondary_weapon(Pl_objp)) {
                                                                                if (aip->ai_flags & AIF_UNLOAD_SECONDARIES) {
                                                                                        t = swip->fire_wait;
                                                                                } else {
                                                                                        t = set_secondary_fire_delay(aip, temp_shipp, swip);
                                                                                }

                                                                                swp->next_secondary_fire_stamp[current_bank] = timestamp((int) (t*1000.0f));
                                                                        }
                                                                //}
                                                        }
                                                        swp->next_secondary_fire_stamp[current_bank] = timestamp((int) (t*1000.0f));
                                                }
                                        }
                                }
                        }
                }
        } else {
                aip->time_enemy_in_range *= (1.0f - flFrametime);
        }
}

// switch ai ship into chase mode
void ai_big_switch_to_chase_mode(ai_info *aip)
{
        aip->previous_mode = aip->mode;
        aip->mode = AIM_CHASE;
        aip->submode = SM_ATTACK;
        aip->submode_start_time = Missiontime;
}

extern int ai_big_strafe_maybe_retreat(float dist, vector *target_pos);

// Make object Pl_objp chase object En_objp, which is a big ship, not a small ship.
void ai_big_chase()
{
        float                   dist_to_enemy, dot_to_enemy;
        vector          player_pos, enemy_pos, vec_to_enemy;
        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];
        int                     enemy_ship_type;
        vector          predicted_enemy_pos;

        Assert(aip->mode == AIM_CHASE);

        maybe_cheat_fire_synaptic(Pl_objp, aip);

        enemy_ship_type = Ship_info[Ships[En_objp->instance].ship_info_index].flags;

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

        player_pos = Pl_objp->pos;
        ai_big_pick_attack_point(En_objp, Pl_objp, &enemy_pos, 0.8f);

        //      Compute the predicted position of the center of the ship, then add the delta to the goal pos.
        if (En_objp->phys_info.speed > 3.0f) {
                set_predicted_enemy_pos(&predicted_enemy_pos, Pl_objp, En_objp, aip);
                vm_vec_add2(&enemy_pos, &predicted_enemy_pos);
                vm_vec_sub2(&enemy_pos, &En_objp->pos);
        }       else
                predicted_enemy_pos = En_objp->pos;

        if (aip->targeted_subsys != NULL) {
                get_subsystem_pos(&enemy_pos, En_objp, aip->targeted_subsys);
        }

        dist_to_enemy = vm_vec_normalized_dir(&vec_to_enemy, &enemy_pos, &player_pos); // - En_objp->radius;
        dot_to_enemy = vm_vec_dot(&vec_to_enemy, &Pl_objp->orient.v.fvec);

        if (aip->ai_flags & AIF_TARGET_COLLISION) {
                if ( ai_big_strafe_maybe_retreat(dist_to_enemy, &enemy_pos) ) {
                        aip->mode = AIM_STRAFE;
                        aip->submode = AIS_STRAFE_AVOID;
                        aip->submode_parm0 = Missiontime;       // use parm0 as time strafe mode entered
                        return;
                }
        }

        if (aip->ai_flags & AIF_KAMIKAZE) {
                //nprintf(("AI", "Kamikaze: %7.3f %7.3f\n", dot_to_enemy, dist_to_enemy));
                accelerate_ship(aip, 1.0f);
                if ((dist_to_enemy < 400.0f) && ai_maybe_fire_afterburner(Pl_objp, aip)) {
                        afterburners_start(Pl_objp);
                        aip->afterburner_stop_time = Missiontime + 3*F1_0;
                }
        }

        //      If just acquired target, or target is not in reasonable cone, don't refine believed enemy position.
        if ((dot_to_enemy < 0.25f) || (aip->target_time < 1.0f) || (aip->ai_flags & AIF_SEEK_LOCK)) {
                update_aspect_lock_information(aip, &vec_to_enemy, dist_to_enemy - En_objp->radius, En_objp->radius);
        } else if (aip->targeted_subsys != NULL) {              
                Assert(aip->targeted_subsys != NULL);
                get_subsystem_pos(&enemy_pos, En_objp, aip->targeted_subsys);
                vm_vec_add2(&enemy_pos, &predicted_enemy_pos);
                vm_vec_sub2(&enemy_pos, &En_objp->pos);
                dist_to_enemy = vm_vec_normalized_dir(&vec_to_enemy, &enemy_pos, &player_pos); // - En_objp->radius;
                dot_to_enemy = vm_vec_dot(&vec_to_enemy, &Pl_objp->orient.v.fvec);
                update_aspect_lock_information(aip, &vec_to_enemy, dist_to_enemy, En_objp->radius);
        } else if (En_objp->flags & OF_PROTECTED) {     //      If protected and we're not attacking a subsystem, stop attacking!
                update_aspect_lock_information(aip, &vec_to_enemy, dist_to_enemy - En_objp->radius, En_objp->radius);
                aip->target_objnum = -1;
                if (find_enemy(Pl_objp-Objects, MAX_ENEMY_DISTANCE, Skill_level_max_attackers[Game_skill_level]) == -1) {
                        ai_do_default_behavior(Pl_objp);
                        return;
                }
        } else {
                update_aspect_lock_information(aip, &vec_to_enemy, dist_to_enemy - En_objp->radius, En_objp->radius);
        }

        //      If recently acquired target and not looking at target, just turn a bit.
        switch (aip->submode) {
        case SM_ATTACK:
        case SM_SUPER_ATTACK:
                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;
                }

                if (aip->target_time < 2.0f)
                        if ((dot_to_enemy < 0.9f) || (dist_to_enemy > 300.0f)) {
                                aip->submode = SM_CONTINUOUS_TURN;
                                aip->submode_start_time = Missiontime - fl2f(2.75f);    //      This backdated start time allows immediate switchout.
                                if (dot_to_enemy > 0.0f)
                                        aip->target_time += flFrametime * dot_to_enemy;
                        }
                break;
        }

        //
        //      Set turn and acceleration based on submode.
        //
        switch (aip->submode) {
        case SM_CONTINUOUS_TURN:
                ai_big_chase_ct();
                break;

        case SM_ATTACK:
        case SM_SUPER_ATTACK:
        case SM_ATTACK_FOREVER:
                ai_big_chase_attack(aip, sip, &enemy_pos, dist_to_enemy);
                break;

        case SM_EVADE:
                ai_big_evade_ship();
                break;

        case SM_AVOID:
                ai_big_avoid_ship();
                break;

        case SM_EVADE_WEAPON:
                evade_weapon();
                break;

        default:
                aip->last_attack_time = Missiontime;
                aip->submode = SM_ATTACK;
                break;
        }

        // maybe Pl_objp was forced into strafe mode, if so return now
        if ( aip->mode == AIM_STRAFE )
                return;

        //      Maybe choose a new submode.
        if (aip->submode != SM_AVOID && aip->submode != SM_EVADE ) {
                //      If a very long time since attacked, attack no matter what!
                if (aip->submode != SM_SUPER_ATTACK) {
                        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!
                float dist_normal_to_enemy;

                if (vm_vec_mag_squared(&aip->big_attack_surface_normal) > 0.9) {
                        dist_normal_to_enemy = fl_abs((dist_to_enemy * vm_vec_dot(&vec_to_enemy, &aip->big_attack_surface_normal)));
                } else {
                        // don;t have normal so use a conservative value here
                        dist_normal_to_enemy = 0.3f * dist_to_enemy;
                }

//              float time_to_enemy = dist_normal_to_enemy / Pl_objp->phys_info.speed * fl_abs(vm_vec_dot(&Pl_objp->phys_info.vel, &aip->big_attack_surface_normal));
//              if (Framecount % 30 == 1) {
//                      mprintf(("normal dist; %.1f, time: %.1f\n", dist_normal_to_enemy, time_to_enemy));
//              }
                
                // since we're not in strafe and we may get a bad normal, cap dist_normal_to_enemy as min(0.3*dist_to_enemy, self)
                // this will allow us to get closer on a bad normal
                dist_normal_to_enemy = max(0.3f*dist_to_enemy, dist_normal_to_enemy);

                if (dist_to_enemy < ATTACK_COLLIDE_BASE_DIST) {
                        // within 50m or 1sec
                        float time_to_enemy;
                        if (vm_vec_mag_squared(&aip->big_attack_surface_normal) > 0.9) {
                                if (Pl_objp->phys_info.speed > 0.1) {
                                        time_to_enemy = dist_normal_to_enemy / fl_abs(vm_vec_dot(&Pl_objp->phys_info.vel, &aip->big_attack_surface_normal));
                                } else {
                                        // a big time
                                        time_to_enemy = 100.0f;
                                }
                        } else {
                                if (Pl_objp->phys_info.speed > 0.1) {
                                        time_to_enemy = dist_normal_to_enemy / Pl_objp->phys_info.speed;
                                } else {
                                        // a big time
                                        time_to_enemy = 100.0f;
                                }
                        }

                        float speed_dist = max(0.0f, (Pl_objp->phys_info.speed-50) * 2);
                        if ((dist_normal_to_enemy < ATTACK_COLLIDE_AVOID_DIST + speed_dist) || (time_to_enemy < ATTACK_COLLIDE_AVOID_TIME) ) {
                                // get away, simulate crsh recovery (don't use avoid)
//                              accelerate_ship(aip, -1.0f);
                                big_ship_collide_recover_start(Pl_objp, En_objp, &Pl_objp->pos, NULL);
//                              aip->submode = SM_AVOID;
//                              aip->submode_start_time = Missiontime;
                        } else if ((dist_normal_to_enemy < ATTACK_COLLIDE_SLOW_DIST) || (time_to_enemy < ATTACK_COLLIDE_SLOW_TIME) ) {
                                // slow down
                                accelerate_ship(aip, -1.0f);
                        }
                }

                /*
                if ((dot_to_enemy > 1.0f - 0.1f * En_objp->radius/(dist_to_enemy + 1.0f)) && (Pl_objp->phys_info.speed > dist_to_enemy/5.0f)) {
                        if (might_collide_with_ship(Pl_objp, En_objp, dot_to_enemy, dist_to_enemy, (aip->targeted_subsys == NULL)*2.0f + 1.5f)) {
                                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:
        case SM_ATTACK_FOREVER:
                break;
                
        case SM_EVADE:
                if (dist_to_enemy > 4*En_objp->radius) {
                        aip->submode = SM_ATTACK;
                        aip->submode_start_time = Missiontime;
                        aip->last_attack_time = Missiontime;
                }
                break;

        case SM_SUPER_ATTACK:
                break;

        case SM_AVOID:
                // if outside box by > 300 m
                // DA 4/20/98  can never get here attacking a big ship
                {
                int is_inside;
                float box_dist = get_world_closest_box_point_with_delta(NULL, En_objp, &Pl_objp->pos, &is_inside, 0.0f);
                
                if (box_dist > 300) {
                        aip->submode = SM_ATTACK;
                        aip->last_attack_time = Missiontime;
                        aip->submode_start_time = Missiontime;
                }
                }
                break;

/*              if (dot_to_enemy > -0.2f) {
                        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_ATTACK;
                                aip->last_attack_time = Missiontime;
                                aip->submode_start_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;

        default:
                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));

        // AL: add condition that Pl_objp must not be following a path to fire.  This may be too extreme, but
        //     I noticed AI ships firing inappropriately when following a path near a big ship.
        //               TODO: investigate why ships fire (and aren't close to hitting ship) when following a path near
        //                               a big ship
        if (aip->mode != AIM_EVADE && aip->path_start == -1 ) {
                ai_big_maybe_fire_weapons(dist_to_enemy, dot_to_enemy, &player_pos, &predicted_enemy_pos, &En_objp->phys_info.vel);
        } else
                aip->time_enemy_in_range *= (1.0f - flFrametime);
}

void ai_big_ship(object *objp)
{
        // do nothing
}

// all three parms are output parameters
//      Enemy object is En_objp
// pos  =>              world pos of attack point
// dist =>              distance from Pl_objp front to attack point
// dot  =>              dot of Pl_objp fvec and vector to attack point
//      fire_pos =>     world pos from which firing
void ai_big_attack_get_data(vector *enemy_pos, float *dist_to_enemy, float *dot_to_enemy)
{
        vector          player_pos, vec_to_enemy, predicted_enemy_pos;  
        ship                    *shipp = &Ships[Pl_objp->instance];     
        ai_info         *aip = &Ai_info[shipp->ai_index];
        ship_info       *esip = &Ship_info[Ships[En_objp->instance].ship_info_index];

        Assert(aip->mode == AIM_STRAFE);

        // ensure that Pl_objp is still targeting a big ship
        if ( !(esip->flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP)) ) {
                ai_big_switch_to_chase_mode(aip);
                return;
        }

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

        player_pos = Pl_objp->pos;

        if (aip->targeted_subsys != NULL) {
                Assert(aip->targeted_subsys != NULL);
                get_subsystem_pos(enemy_pos, En_objp, aip->targeted_subsys);
        } else {
                // checks valid line to target
                ai_big_pick_attack_point(En_objp, Pl_objp, enemy_pos, 0.8f);
        }

        // Take player pos to be center of ship + ship_radius
        vm_vec_scale_add2(&player_pos, &Pl_objp->orient.v.fvec, Pl_objp->radius); 

        //      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.
        vm_vec_normalized_dir(&vec_to_enemy, enemy_pos, &player_pos);
        *dot_to_enemy=vm_vec_dot(&vec_to_enemy, &Pl_objp->orient.v.fvec);
        if ((*dot_to_enemy < 0.25f) || (aip->target_time < 1.0f) || (aip->ai_flags & AIF_SEEK_LOCK)) {
                predicted_enemy_pos=*enemy_pos;
        } else {
                vector  gun_pos, pnt;
                polymodel *po = model_get( Ship_info[shipp->ship_info_index].modelnum );
                float           weapon_speed;

                //      Compute position of gun in absolute space and use that as fire position.
                pnt = po->gun_banks[0].pnt[0];
                vm_vec_unrotate(&gun_pos, &pnt, &Pl_objp->orient);
                vm_vec_add2(&gun_pos, &Pl_objp->pos);
                weapon_speed = ai_get_weapon_speed(&shipp->weapons);
                
                set_predicted_enemy_pos_turret(&predicted_enemy_pos, &gun_pos, Pl_objp, enemy_pos, &En_objp->phys_info.vel, weapon_speed, aip->time_enemy_in_range);
        }

        *dist_to_enemy = vm_vec_normalized_dir(&vec_to_enemy, &predicted_enemy_pos, &player_pos);
        *dot_to_enemy = vm_vec_dot(&vec_to_enemy, &Pl_objp->orient.v.fvec);
        update_aspect_lock_information(aip, &vec_to_enemy, *dist_to_enemy, En_objp->radius);

        *enemy_pos = predicted_enemy_pos;
}

// check to see if Pl_objp has gotten too close to attacking point.. if so, break off by entering
// AIS_STRAFE_RETREAT
int ai_big_strafe_maybe_retreat(float dist, vector *target_pos)
{
        ai_info *aip;
        aip = &Ai_info[Ships[Pl_objp->instance].ai_index];

        vector vec_to_target;
        vm_vec_sub(&vec_to_target, target_pos, &Pl_objp->pos);

        float dist_to_target, dist_normal_to_target, time_to_target;
        dist_to_target = vm_vec_mag_quick(&vec_to_target);
        if (vm_vec_mag_quick(&aip->big_attack_surface_normal) > 0.9) {
                dist_normal_to_target = -vm_vec_dotprod(&vec_to_target, &aip->big_attack_surface_normal);
        } else {
                dist_normal_to_target = 0.2f * vm_vec_mag_quick(&vec_to_target);
        }

        dist_normal_to_target = max(0.2f*dist_to_target, dist_normal_to_target);
        time_to_target = dist_normal_to_target / Pl_objp->phys_info.speed;

        // add distance penalty for going too fast
        float speed_to_dist_penalty = max(0.0f, (Pl_objp->phys_info.speed-50));

        //if ((dot_to_enemy > 1.0f - 0.1f * En_objp->radius/(dist_to_enemy + 1.0f)) && (Pl_objp->phys_info.speed > dist_to_enemy/5.0f))

        // Inside 2 sec retreat, setting goal point to box point + 300m
        // If collision, use std collision resolution.
        if ( !(aip->ai_flags & AIF_KAMIKAZE) && ((aip->ai_flags & AIF_TARGET_COLLISION) || (time_to_target < STRAFE_RETREAT_COLLIDE_TIME) || (dist_normal_to_target < STRAFE_RETREAT_COLLIDE_DIST + speed_to_dist_penalty)) ) {
                if (aip->ai_flags & AIF_TARGET_COLLISION) {
                        // use standard collision resolution
                        aip->ai_flags &= ~AIF_TARGET_COLLISION;
                        big_ship_collide_recover_start(Pl_objp, En_objp, &Pl_objp->pos, NULL);
                } else {
                        // too close for comfort so fly to box point + 300
                        aip->submode = AIS_STRAFE_RETREAT1;
                        aip->submode_start_time = Missiontime;

                        float box_dist;
                        int is_inside;
                        vector goal_point;
                        box_dist = get_world_closest_box_point_with_delta(&goal_point, En_objp, &Pl_objp->pos, &is_inside, STRAFE_RETREAT_BOX_DIST);

                        // set goal point
                        aip->goal_point = goal_point;

                        if (ai_maybe_fire_afterburner(Pl_objp, aip)) {
                                afterburners_start(Pl_objp);
                                aip->afterburner_stop_time = Missiontime + 3*F1_0;
                        }
                }

                return 1;
        } else {
                return 0;
        }
}

// attack directly to the turret and fire weapons 
void ai_big_strafe_attack()
{
        ai_info *aip;
        vector  target_pos;
        vector  rand_vec;
        float           target_dist, target_dot, accel, t;
        object  *target_objp;

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

        if ( ai_big_maybe_follow_subsys_path(0) ) {
                return;
        }

        ai_big_attack_get_data(&target_pos, &target_dist, &target_dot);
        if ( ai_big_strafe_maybe_retreat(target_dist, &target_pos) )
                return;

        target_objp = &Objects[aip->target_objnum];

        if (aip->ai_flags & AIF_KAMIKAZE) {
                if (target_dist < 1200.0f) {
                        //nprintf(("AI", "Kamikaze: %7.3f %7.3f\n", target_dot, target_dist));
                        ai_turn_towards_vector(&target_pos, Pl_objp, flFrametime, Ship_info[Ships[Pl_objp->instance].ship_info_index].srotation_time, NULL, NULL, 0.0f, 0);
                        accelerate_ship(aip, 1.0f);
                        if ((target_dist < 400.0f) && ai_maybe_fire_afterburner(Pl_objp, aip)) {
                                afterburners_start(Pl_objp);
                                aip->afterburner_stop_time = Missiontime + 3*F1_0;
                        }
                        return;
                }
        }

        if (!(aip->ai_flags & AIF_SEEK_LOCK) || (aip->aspect_locked_time < 2.0f)) {
                t  = ai_endangered_by_weapon(aip);
                if ( t > 0.0f && t < 1.5f ) {
                        // set up goal_point for avoid path to turn towards
                        aip->goal_point = Pl_objp->pos;
                        switch(rand()%4) {
                        case 0:
                                vm_vec_scale_add(&rand_vec, &Pl_objp->orient.v.fvec, &Pl_objp->orient.v.uvec, 2.0f);
                                break;
                        case 1:
                                vm_vec_scale_add(&rand_vec, &Pl_objp->orient.v.fvec, &Pl_objp->orient.v.uvec, -2.0f);
                                break;
                        case 2:
                                vm_vec_scale_add(&rand_vec, &Pl_objp->orient.v.fvec, &Pl_objp->orient.v.rvec, 2.0f);
                                break;
                        case 3:
                                vm_vec_scale_add(&rand_vec, &Pl_objp->orient.v.fvec, &Pl_objp->orient.v.rvec, -2.0f);
                                break;
                        } // end switch

                        vm_vec_scale(&rand_vec, 1000.0f);
                        vm_vec_add2(&aip->goal_point, &rand_vec);

                        aip->submode = AIS_STRAFE_AVOID;
                        aip->submode_start_time = Missiontime;
        //              nprintf(("Alan","Ship %s entering AIS_STRAFE_AVOID at frame %d\n", Ships[aip->shipnum].ship_name, Framecount));

                        if (ai_maybe_fire_afterburner(Pl_objp, aip)) {
                                afterburners_start(Pl_objp);
                                aip->afterburner_stop_time = Missiontime + fl2f(0.5f);
                        }
                }
        }

        // maybe fire weapons at target
        ai_big_maybe_fire_weapons(target_dist, target_dot, &Pl_objp->pos, &En_objp->pos, &En_objp->phys_info.vel);
        turn_towards_point(Pl_objp, &target_pos, NULL, 0.0f);

        // Slow down if we've not been hit for a while
        fix last_hit = Missiontime - aip->last_hit_time;
        if ( target_dist > 1200 || last_hit < F1_0*6) {
                accel = 1.0f;
        } else {
                float attack_time;
                attack_time = f2fl(Missiontime - aip->submode_start_time);
                if ( attack_time > 15 ) {
                        accel = 0.2f;
                } else if ( attack_time > 10 ) {
                        accel = 0.4f;
                } else if ( attack_time > 8 ) {
                        accel = 0.6f;
                } else if ( attack_time > 5 ) {
                        accel = 0.8f;
                } else {
                        accel = 1.0f;
                }
        }

        accel = 1.0f;
        accelerate_ship(aip, accel);

        // if haven't been hit in quite a while, leave strafe mode
        fix long_enough;
        long_enough = F1_0*20;
        if ( (last_hit > long_enough) && ( (Missiontime - aip->submode_parm0) > long_enough) ) {
                ai_big_switch_to_chase_mode(aip);
        }
}

// pick a new attack point when entering this state, and keep using it
void ai_big_strafe_avoid()
{
        ai_info *aip;
        vector  target_pos;
        float           target_dist, target_dot;
        fix             mode_time;

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

        mode_time = Missiontime - aip->submode_start_time;

        ai_big_attack_get_data(&target_pos, &target_dist, &target_dot);
        if ( ai_big_strafe_maybe_retreat(target_dist, &target_pos) )
                return;

        if ( mode_time > fl2f(0.5)) {
                aip->submode = AIS_STRAFE_ATTACK;
                aip->submode_start_time = Missiontime;
//              nprintf(("Alan","Ship %s entering AIS_STRAFE_ATTACK at frame %d\n", Ships[aip->shipnum].ship_name, Framecount));
        }

        turn_towards_point(Pl_objp, &aip->goal_point, NULL, 0.0f);
        accelerate_ship(aip, 1.0f);
}

// move towards aip->goal_point in an evasive manner
void ai_big_strafe_retreat1()
{
        float dist;
        ai_info *aip;
        vector  rand_vec;

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

        dist = vm_vec_dist_quick(&Pl_objp->pos, &aip->goal_point);
        if ( dist < 70 ) {
                aip->submode = AIS_STRAFE_POSITION;
                aip->submode_start_time = Missiontime;
//              nprintf(("Alan","Ship %s entering AIS_STRAFE_POSITION\n", Ships[aip->shipnum].ship_name));
                return;
        }

        if (Missiontime - aip->submode_start_time > fl2f(1.50f)) {
                // set up goal_point for avoid path to turn towards
                aip->prev_goal_point = Pl_objp->pos;
                switch(rand()%4) {
                case 0:
                        vm_vec_add(&rand_vec, &Pl_objp->orient.v.fvec, &Pl_objp->orient.v.uvec);
                        break;
                case 1:
                        vm_vec_scale_add(&rand_vec, &Pl_objp->orient.v.fvec, &Pl_objp->orient.v.uvec, -1.0f);
                        break;
                case 2:
                        vm_vec_add(&rand_vec, &Pl_objp->orient.v.fvec, &Pl_objp->orient.v.rvec);
                        break;
                case 3:
                        vm_vec_scale_add(&rand_vec, &Pl_objp->orient.v.fvec, &Pl_objp->orient.v.rvec, -1.0f);
                        break;
                } // end switch

                //vm_vec_scale(&rand_vec, 200.0f);
                //vm_vec_add2(&aip->prev_goal_point, &rand_vec);
                vm_vec_scale_add(&aip->prev_goal_point, &aip->goal_point, &rand_vec, 200.0f);

                aip->submode = AIS_STRAFE_RETREAT2;
                aip->submode_start_time = Missiontime;
        }

        turn_towards_point(Pl_objp, &aip->goal_point, NULL, 0.0f);
        accelerate_ship(aip, 1.0f);
}

void ai_big_strafe_retreat2()
{
        float dist;
        ai_info *aip;

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

        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);
                }
        }

        dist = vm_vec_dist_quick(&Pl_objp->pos, &aip->goal_point);
        if ( dist < 70 ) {
                aip->submode = AIS_STRAFE_POSITION;
                aip->submode_start_time = Missiontime;
//              nprintf(("Alan","Ship %s entering AIS_STRAFE_POSITION\n", Ships[aip->shipnum].ship_name));
                return;
        }

        if (Missiontime - aip->submode_start_time > fl2f(0.70f)) {
                aip->submode = AIS_STRAFE_RETREAT1;
                aip->submode_start_time = Missiontime;

                if ( (Missiontime - aip->last_hit_time) < F1_0*5 ) {
                        if (ai_maybe_fire_afterburner(Pl_objp, aip)) {
                                afterburners_start(Pl_objp);
                                aip->afterburner_stop_time = Missiontime + F1_0;
                        }
                }
        }

        turn_towards_point(Pl_objp, &aip->prev_goal_point, NULL, 0.0f);
        accelerate_ship(aip, 1.0f);
}

// reposition self to begin another strafing run
void ai_big_strafe_position()
{
        ai_info *aip;
        aip = &Ai_info[Ships[Pl_objp->instance].ai_index];
        // TODO: loop around or something!!

        aip->submode = AIS_STRAFE_ATTACK;
        aip->submode_start_time = Missiontime;
//      nprintf(("Alan","Ship %s entering AIS_STRAFE_ATTACK\n", Ships[aip->shipnum].ship_name));
}

//      --------------------------------------------------------------------------
// #define      AIS_STRAFE_ATTACK               201     // fly towards target and attack
// #define      AIS_STRAFE_AVOID                202     // fly evasive vector to avoid incoming fire
// #define      AIS_STRAFE_RETREAT1     203     // fly away from attack point (directly)
// #define      AIS_STRAFE_RETREAT1     204     // fly away from attack point (on an avoid vector)
// #define      AIS_STRAFE_POSITION     205     // re-position to resume strafing attack
//
void ai_big_strafe()
{
        ai_info *aip;

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

        Assert(aip->mode == AIM_STRAFE);

/*
        if ( aip->goal_objnum != aip->target_objnum ) {
                Int3(); // what is going on here? - Get Alan
                aip->mode = AIM_NONE;
                return;
        }
*/

        // check if target is still a big ship... if not enter chase mode
        if ( !(Ship_info[Ships[En_objp->instance].ship_info_index].flags & (SIF_BIG_SHIP|SIF_HUGE_SHIP)) ) {
                ai_big_switch_to_chase_mode(aip);
                return;
        }
        
        switch (aip->submode) {
        case AIS_STRAFE_ATTACK:
                ai_big_strafe_attack();
                break;
        case AIS_STRAFE_AVOID:
                ai_big_strafe_avoid();
                break;
        case AIS_STRAFE_RETREAT1:
                ai_big_strafe_retreat1();
                break;
        case AIS_STRAFE_RETREAT2:
                ai_big_strafe_retreat2();
                break;
        case AIS_STRAFE_POSITION:
                ai_big_strafe_position();
                break;
        default:

                Int3();         //      Illegal submode for AIM_STRAFE
                break;
        }
}

// See if Pl_objp should enter strafe mode (This is called from maybe_evade_dumbfire_weapon(), and the
// weapon_objnum is for a weapon that is about to collide with Pl_objp
//
// Check if weapon_objnum was fired by Pl_objp's target, and whether Pl_objp's target is a big ship, if
// so, enter AIM_STRAFE
int ai_big_maybe_enter_strafe_mode(object *pl_objp, int weapon_objnum, int consider_target_only)
{
        ai_info         *aip;
        ship_info       *sip;
        object          *weapon_objp, *parent_objp;

        aip = &Ai_info[Ships[pl_objp->instance].ai_index];
        Assert(aip->mode != AIM_STRAFE);                // can't happen

        // if Pl_objp has no target, then we can't enter strafe mode
        if ( aip->target_objnum < 0 ) {
                return 0;
        }

        // if target is not a ship, stafe mode is not possible
        if ( Objects[aip->target_objnum].type != OBJ_SHIP ) {
                return 0;
        }

        sip = &Ship_info[Ships[Objects[aip->target_objnum].instance].ship_info_index];

        // if Pl_objp's target is not a big/capital ship, then cannot enter strafe mode
        // AL 12-31-97: Even though transports are considered big ships, don't enter strafe mode on them
        if ( !(sip->flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP)) || (sip->flags & SIF_TRANSPORT) ) {
                return 0;
        }

        //      If Pl_objp not a fighter or bomber, don't enter strafe mode. -- MK, 11/11/97.
        if ( !(Ship_info[Ships[pl_objp->instance].ship_info_index].flags & (SIF_FIGHTER | SIF_BOMBER)) ) {
                return 0;
        }

        Assert(weapon_objnum >= 0 && weapon_objnum < MAX_OBJECTS);
        weapon_objp = &Objects[weapon_objnum];
        Assert(weapon_objp->type == OBJ_WEAPON);

        Assert(weapon_objp->parent >= 0 && weapon_objp->parent < MAX_OBJECTS);
        parent_objp = &Objects[weapon_objp->parent];
        if ( (parent_objp->signature != weapon_objp->parent_sig) || (parent_objp->type != OBJ_SHIP) ) {
                return 0;
        }

        // Maybe the ship which fired the weapon isn't the current target
        if ( OBJ_INDEX(parent_objp) != aip->target_objnum ) {

//JAS IMPOSSIBLE                if (1) { // consider_target_only ) {
//JAS IMPOSSIBLE                        return 0;
//JAS IMPOSSIBLE                } else {
                        // switch targets
                        sip = &Ship_info[Ships[parent_objp->instance].ship_info_index];
                        if ( !(sip->flags & (SIF_BIG_SHIP | SIF_HUGE_SHIP)) || (sip->flags & SIF_TRANSPORT) ) {
                                return 0;
                        }
                        set_target_objnum(aip, OBJ_INDEX(parent_objp));
//JAS IMPOSSIBLE                }
        }

        ai_big_strafe_maybe_attack_turret(pl_objp, weapon_objp);

        // if we've got this far, the weapon must have come from the player's target, and it is a 
        // big/capital ship... so enter strafe mode
        aip->previous_mode = aip->mode;
        aip->mode = AIM_STRAFE;
        aip->submode_parm0 = Missiontime;       // use parm0 as time strafe mode entered
        aip->submode = AIS_STRAFE_AVOID;
        aip->submode_start_time = Missiontime;
//      nprintf(("Alan","%s Accepted strafe mode\n", Ships[pl_objp->instance].ship_name));

        return 1;
}

// Consider attacking a turret, if a turret actually fired the weapon
// input:       ship_objp       =>      ship that will attack the turret
//                              weapon_objp     =>      
void ai_big_strafe_maybe_attack_turret(object *ship_objp, object *weapon_objp)
{
        ai_info *aip;
        object  *parent_objp;

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

        // Make decision to attack turret based on AI class.  The better AI ships will realize that
        // it is better to take out the turrets first on a big ship.
        if ( (frand()*100) > (aip->ai_courage-15) )
                return;

        // If ship is already attacking a subsystem, don't switch
        if ( aip->targeted_subsys != NULL ) {
                return;
        }

        // If the weapon is not from a turret, return
        if ( Weapons[weapon_objp->instance].turret_subsys == NULL ) {
                return;
        }

        // Only attack turret if it sits on current target
        Assert(weapon_objp->parent >= 0 && weapon_objp->parent < MAX_OBJECTS);
        parent_objp = &Objects[weapon_objp->parent];
        if ( (parent_objp->signature != weapon_objp->parent_sig) || (parent_objp->type != OBJ_SHIP) ) {
                return;
        }

        if ( aip->target_objnum != OBJ_INDEX(parent_objp) ) {
                return;
        }

        // attack the turret
        set_targeted_subsys(aip, Weapons[weapon_objp->instance].turret_subsys, OBJ_INDEX(parent_objp));
}