main/physics.c

   1 /*
   2 THE COMPUTER CODE CONTAINED HEREIN IS THE SOLE PROPERTY OF PARALLAX
   3 SOFTWARE CORPORATION ("PARALLAX").  PARALLAX, IN DISTRIBUTING THE CODE TO
   4 END-USERS, AND SUBJECT TO ALL OF THE TERMS AND CONDITIONS HEREIN, GRANTS A
   5 ROYALTY-FREE, PERPETUAL LICENSE TO SUCH END-USERS FOR USE BY SUCH END-USERS
   6 IN USING, DISPLAYING,  AND CREATING DERIVATIVE WORKS THEREOF, SO LONG AS
   7 SUCH USE, DISPLAY OR CREATION IS FOR NON-COMMERCIAL, ROYALTY OR REVENUE
   8 FREE PURPOSES.  IN NO EVENT SHALL THE END-USER USE THE COMPUTER CODE
   9 CONTAINED HEREIN FOR REVENUE-BEARING PURPOSES.  THE END-USER UNDERSTANDS
  10 AND AGREES TO THE TERMS HEREIN AND ACCEPTS THE SAME BY USE OF THIS FILE.
  11 COPYRIGHT 1993-1999 PARALLAX SOFTWARE CORPORATION.  ALL RIGHTS RESERVED.
  12 */
  13
  14 #ifdef RCS
  15 static char rcsid[] = "$Id: physics.c,v 1.2 2001-01-20 13:49:17 bradleyb Exp $";
  16 #endif
  17
  18 #include <conf.h>
  19
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22
  23 #include "joy.h"
  24 #include "mono.h"
  25 #include "error.h"
  26
  27 #include "inferno.h"
  28 #include "segment.h"
  29 #include "object.h"
  30 #include "physics.h"
  31 #include "key.h"
  32 #include "game.h"
  33 #include "collide.h"
  34 #include "fvi.h"
  35 #include "newdemo.h"
  36 #include "timer.h"
  37 #include "ai.h"
  38 #include "wall.h"
  39 #include "laser.h"
  40 #include "bm.h"
  41 #include "player.h"
  42
  43 #ifdef TACTILE
  44 #include "tactile.h"
  45 #endif
  46
  47 //Global variables for physics system
  48
  49 #define ROLL_RATE               0x2000
  50 #define DAMP_ANG                        0x400                  //min angle to bank
  51
  52 #define TURNROLL_SCALE  (0x4ec4/2)
  53
  54 #define MAX_OBJECT_VEL i2f(100)
  55
  56 #define BUMP_HACK       1               //if defined, bump player when he gets stuck
  57
  58 //--unused-- int mike_mode=0;
  59
  60 //check point against each side of segment. return bitmask, where bit
  61 //set means behind that side
  62
  63 int Physics_cheat_flag = 0;
  64 extern char BounceCheat;
  65
  66 //##//returns the distance of a point (checkp) from a plane (defined by norm & planep)
  67 //##fix dist_to_plane(vms_vector *checkp,vms_vector *norm,vms_vector *planep)
  68 //##{
  69 //##    vms_vector deltap;
  70 //##
  71 //##    vm_vec_sub(&deltap,checkp,planep);
  72 //##
  73 //##    return vm_vec_dot(&deltap,norm);
  74 //##}
  75
  76 //--unused-- int dpjm_old_joy_x, dpjm_old_joy_y;
  77
  78 int floor_levelling=0;
  79
  80 //--unused-- level_with_floor()
  81 //--unused-- {
  82 //--unused--    floor_levelling=1;
  83 //--unused-- }
  84
  85 //make sure matrix is orthogonal
  86 void check_and_fix_matrix(vms_matrix *m)
  87 {
  88         vms_matrix tempm;
  89
  90         vm_vector_2_matrix(&tempm,&m->fvec,&m->uvec,NULL);
  91         *m  = tempm;
  92 }
  93
  94
  95 void do_physics_align_object( object * obj )
  96 {
  97         vms_vector desired_upvec;
  98         fixang delta_ang,roll_ang;
  99         //vms_vector forvec = {0,0,f1_0};
 100         vms_matrix temp_matrix;
 101         fix d,largest_d=-f1_0;
 102         int i,best_side;
 103
 104         best_side=0;
 105         // bank player according to segment orientation
 106
 107         //find side of segment that player is most alligned with
 108
 109         for (i=0;i<6;i++) {
 110                 #ifdef COMPACT_SEGS
 111                         vms_vector _tv1;
 112                         get_side_normal( &Segments[obj->segnum], i, 0, &_tv1 );
 113                         d = vm_vec_dot(&_tv1,&obj->orient.uvec);
 114                 #else
 115                         d = vm_vec_dot(&Segments[obj->segnum].sides[i].normals[0],&obj->orient.uvec);
 116                 #endif
 117
 118                 if (d > largest_d) {largest_d = d; best_side=i;}
 119         }
 120
 121         if (floor_levelling) {
 122
 123                 // old way: used floor's normal as upvec
 124                 #ifdef COMPACT_SEGS
 125                         get_side_normal(&Segments[obj->segnum], 3, 0, &desired_upvec );
 126                 #else
 127                         desired_upvec = Segments[obj->segnum].sides[3].normals[0];
 128                 #endif
 129
 130         }
 131         else  // new player leveling code: use normal of side closest to our up vec
 132                 if (get_num_faces(&Segments[obj->segnum].sides[best_side])==2) {
 133                         #ifdef COMPACT_SEGS
 134                                 vms_vector normals[2];
 135                                 get_side_normals(&Segments[obj->segnum], best_side, &normals[0], &normals[1] );
 136
 137                                 desired_upvec.x = (normals[0].x + normals[1].x) / 2;
 138                                 desired_upvec.y = (normals[0].y + normals[1].y) / 2;
 139                                 desired_upvec.z = (normals[0].z + normals[1].z) / 2;
 140
 141                                 vm_vec_normalize(&desired_upvec);
 142                         #else
 143                                 side *s = &Segments[obj->segnum].sides[best_side];
 144                                 desired_upvec.x = (s->normals[0].x + s->normals[1].x) / 2;
 145                                 desired_upvec.y = (s->normals[0].y + s->normals[1].y) / 2;
 146                                 desired_upvec.z = (s->normals[0].z + s->normals[1].z) / 2;
 147
 148                                 vm_vec_normalize(&desired_upvec);
 149                         #endif
 150                 }
 151                 else
 152                         #ifdef COMPACT_SEGS
 153                                 get_side_normal(&Segments[obj->segnum], best_side, 0, &desired_upvec );
 154                         #else
 155                                 desired_upvec = Segments[obj->segnum].sides[best_side].normals[0];
 156                         #endif
 157
 158         if (labs(vm_vec_dot(&desired_upvec,&obj->orient.fvec)) < f1_0/2) {
 159                 fixang save_delta_ang;
 160                 vms_angvec tangles;
 161
 162                 vm_vector_2_matrix(&temp_matrix,&obj->orient.fvec,&desired_upvec,NULL);
 163
 164                 save_delta_ang = delta_ang = vm_vec_delta_ang(&obj->orient.uvec,&temp_matrix.uvec,&obj->orient.fvec);
 165
 166                 delta_ang += obj->mtype.phys_info.turnroll;
 167
 168                 if (abs(delta_ang) > DAMP_ANG) {
 169                         vms_matrix rotmat, new_pm;
 170
 171                         roll_ang = fixmul(FrameTime,ROLL_RATE);
 172
 173                         if (abs(delta_ang) < roll_ang) roll_ang = delta_ang;
 174                         else if (delta_ang<0) roll_ang = -roll_ang;
 175
 176                         tangles.p = tangles.h = 0;  tangles.b = roll_ang;
 177                         vm_angles_2_matrix(&rotmat,&tangles);
 178
 179                         vm_matrix_x_matrix(&new_pm,&obj->orient,&rotmat);
 180                         obj->orient = new_pm;
 181                 }
 182                 else floor_levelling=0;
 183         }
 184
 185 }
 186
 187 void set_object_turnroll(object *obj)
 188 {
 189         fixang desired_bank;
 190
 191         desired_bank = -fixmul(obj->mtype.phys_info.rotvel.y,TURNROLL_SCALE);
 192
 193         if (obj->mtype.phys_info.turnroll != desired_bank) {
 194                 fixang delta_ang,max_roll;
 195
 196                 max_roll = fixmul(ROLL_RATE,FrameTime);
 197
 198                 delta_ang = desired_bank - obj->mtype.phys_info.turnroll;
 199
 200                 if (labs(delta_ang) < max_roll)
 201                         max_roll = delta_ang;
 202                 else
 203                         if (delta_ang < 0)
 204                                 max_roll = -max_roll;
 205
 206                 obj->mtype.phys_info.turnroll += max_roll;
 207         }
 208
 209 }
 210
 211 //list of segments went through
 212 int phys_seglist[MAX_FVI_SEGS],n_phys_segs;
 213
 214
 215 #define MAX_IGNORE_OBJS 100
 216
 217 #ifndef NDEBUG
 218 #define EXTRA_DEBUG 1           //no extra debug when NDEBUG is on
 219 #endif
 220
 221 #ifdef EXTRA_DEBUG
 222 object *debug_obj=NULL;
 223 #endif
 224
 225 #define XYZ(v) (v)->x,(v)->y,(v)->z
 226
 227
 228 #ifndef NDEBUG
 229 int     Total_retries=0, Total_sims=0;
 230 int     Dont_move_ai_objects=0;
 231 #endif
 232
 233 #define FT (f1_0/64)
 234
 235 extern int disable_new_fvi_stuff;
 236 //      -----------------------------------------------------------------------------------------------------------
 237 // add rotational velocity & acceleration
 238 void do_physics_sim_rot(object *obj)
 239 {
 240         vms_angvec      tangles;
 241         vms_matrix      rotmat,new_orient;
 242         //fix                   rotdrag_scale;
 243         physics_info *pi;
 244
 245         Assert(FrameTime > 0);  //Get MATT if hit this!
 246
 247         pi = &obj->mtype.phys_info;
 248
 249         if (!(pi->rotvel.x || pi->rotvel.y || pi->rotvel.z || pi->rotthrust.x || pi->rotthrust.y || pi->rotthrust.z))
 250                 return;
 251
 252         if (obj->mtype.phys_info.drag) {
 253                 int count;
 254                 vms_vector accel;
 255                 fix drag,r,k;
 256
 257                 count = FrameTime / FT;
 258                 r = FrameTime % FT;
 259                 k = fixdiv(r,FT);
 260
 261                 drag = (obj->mtype.phys_info.drag*5)/2;
 262
 263                 if (obj->mtype.phys_info.flags & PF_USES_THRUST) {
 264
 265                         vm_vec_copy_scale(&accel,&obj->mtype.phys_info.rotthrust,fixdiv(f1_0,obj->mtype.phys_info.mass));
 266
 267                         while (count--) {
 268
 269                                 vm_vec_add2(&obj->mtype.phys_info.rotvel,&accel);
 270
 271                                 vm_vec_scale(&obj->mtype.phys_info.rotvel,f1_0-drag);
 272                         }
 273
 274                         //do linear scale on remaining bit of time
 275
 276                         vm_vec_scale_add2(&obj->mtype.phys_info.rotvel,&accel,k);
 277                         vm_vec_scale(&obj->mtype.phys_info.rotvel,f1_0-fixmul(k,drag));
 278                 }
 279                 else if (! (obj->mtype.phys_info.flags & PF_FREE_SPINNING)) {
 280                         fix total_drag=f1_0;
 281
 282                         while (count--)
 283                                 total_drag = fixmul(total_drag,f1_0-drag);
 284
 285                         //do linear scale on remaining bit of time
 286
 287                         total_drag = fixmul(total_drag,f1_0-fixmul(k,drag));
 288
 289                         vm_vec_scale(&obj->mtype.phys_info.rotvel,total_drag);
 290                 }
 291
 292         }
 293
 294         //mprintf( (0, "Rot vel = %.3f,%.3f,%.3f\n", f2fl(obj->mtype.phys_info.rotvel.x),f2fl(obj->mtype.phys_info.rotvel.y), f2fl(obj->mtype.phys_info.rotvel.z) ));
 295
 296         //now rotate object
 297
 298         //unrotate object for bank caused by turn
 299         if (obj->mtype.phys_info.turnroll) {
 300                 vms_matrix new_pm;
 301
 302                 tangles.p = tangles.h = 0;
 303                 tangles.b = -obj->mtype.phys_info.turnroll;
 304                 vm_angles_2_matrix(&rotmat,&tangles);
 305                 vm_matrix_x_matrix(&new_pm,&obj->orient,&rotmat);
 306                 obj->orient = new_pm;
 307         }
 308
 309         tangles.p = fixmul(obj->mtype.phys_info.rotvel.x,FrameTime);
 310         tangles.h = fixmul(obj->mtype.phys_info.rotvel.y,FrameTime);
 311         tangles.b  = fixmul(obj->mtype.phys_info.rotvel.z,FrameTime);
 312
 313         vm_angles_2_matrix(&rotmat,&tangles);
 314         vm_matrix_x_matrix(&new_orient,&obj->orient,&rotmat);
 315         obj->orient = new_orient;
 316
 317         if (obj->mtype.phys_info.flags & PF_TURNROLL)
 318                 set_object_turnroll(obj);
 319
 320         //re-rotate object for bank caused by turn
 321         if (obj->mtype.phys_info.turnroll) {
 322                 vms_matrix new_pm;
 323
 324                 tangles.p = tangles.h = 0;
 325                 tangles.b = obj->mtype.phys_info.turnroll;
 326                 vm_angles_2_matrix(&rotmat,&tangles);
 327                 vm_matrix_x_matrix(&new_pm,&obj->orient,&rotmat);
 328                 obj->orient = new_pm;
 329         }
 330
 331         check_and_fix_matrix(&obj->orient);
 332 }
 333
 334 //      -----------------------------------------------------------------------------------------------------------
 335 //Simulate a physics object for this frame
 336 void do_physics_sim(object *obj)
 337 {
 338         int ignore_obj_list[MAX_IGNORE_OBJS],n_ignore_objs;
 339         int iseg;
 340         int try_again;
 341         int fate;
 342         vms_vector frame_vec;                   //movement in this frame
 343         vms_vector new_pos,ipos;                //position after this frame
 344         int count=0;
 345         int objnum;
 346         int WallHitSeg, WallHitSide;
 347         fvi_info hit_info;
 348         fvi_query fq;
 349         vms_vector save_pos;
 350         int save_seg;
 351         fix drag;
 352         fix sim_time,old_sim_time;
 353         vms_vector start_pos;
 354         int obj_stopped=0;
 355         fix moved_time;                 //how long objected moved before hit something
 356         vms_vector save_p0,save_p1;
 357         physics_info *pi;
 358         int orig_segnum = obj->segnum;
 359         int bounced=0;
 360
 361         Assert(obj->type != OBJ_NONE);
 362         Assert(obj->movement_type == MT_PHYSICS);
 363
 364 #ifndef NDEBUG
 365 if (Dont_move_ai_objects)
 366         if (obj->control_type == CT_AI)
 367                 return;
 368 #endif
 369
 370         pi = &obj->mtype.phys_info;
 371
 372         do_physics_sim_rot(obj);
 373
 374         if (!(pi->velocity.x || pi->velocity.y || pi->velocity.z || pi->thrust.x || pi->thrust.y || pi->thrust.z))
 375                 return;
 376
 377         objnum = obj-Objects;
 378
 379         n_phys_segs = 0;
 380
 381         disable_new_fvi_stuff = (obj->type != OBJ_PLAYER);
 382
 383         sim_time = FrameTime;
 384
 385 //debug_obj = obj;
 386
 387         #ifdef EXTRA_DEBUG
 388         if (obj == debug_obj) {
 389                 printf("object %d:\n  start pos = %x %x %x\n",objnum,XYZ(&obj->pos));
 390                 printf("  thrust = %x %x %x\n",XYZ(&obj->mtype.phys_info.thrust));
 391                 printf("  sim_time = %x\n",sim_time);
 392         }
 393
 394         //check for correct object segment
 395         if(!get_seg_masks(&obj->pos,obj->segnum,0).centermask==0) {
 396                 #ifndef NDEBUG
 397                 mprintf((0,"Warning: object %d not in given seg!\n",objnum));
 398                 #endif
 399                 //Int3();  Removed by Rob 10/5/94
 400                 if (!update_object_seg(obj)) {
 401                         #ifndef NDEBUG
 402                         mprintf((0,"Warning: can't find seg for object %d - moving\n",objnum));
 403                         #endif
 404                         if (!(Game_mode & GM_MULTI))
 405                                 Int3();
 406                         compute_segment_center(&obj->pos,&Segments[obj->segnum]);
 407                         obj->pos.x += objnum;
 408                 }
 409         }
 410         #endif
 411
 412         start_pos = obj->pos;
 413
 414         n_ignore_objs = 0;
 415
 416         Assert(obj->mtype.phys_info.brakes==0);         //brakes not used anymore?
 417
 418                 //if uses thrust, cannot have zero drag
 419         Assert(!(obj->mtype.phys_info.flags&PF_USES_THRUST) || obj->mtype.phys_info.drag!=0);
 420
 421 //mprintf((0,"thrust=%x  speed=%x\n",vm_vec_mag(&obj->mtype.phys_info.thrust),vm_vec_mag(&obj->mtype.phys_info.velocity)));
 422
 423         //do thrust & drag
 424
 425         if ((drag = obj->mtype.phys_info.drag) != 0) {
 426
 427                 int count;
 428                 vms_vector accel;
 429                 fix r,k;
 430
 431                 count = sim_time / FT;
 432                 r = sim_time % FT;
 433                 k = fixdiv(r,FT);
 434
 435                 if (obj->mtype.phys_info.flags & PF_USES_THRUST) {
 436
 437                         vm_vec_copy_scale(&accel,&obj->mtype.phys_info.thrust,fixdiv(f1_0,obj->mtype.phys_info.mass));
 438
 439                         while (count--) {
 440
 441                                 vm_vec_add2(&obj->mtype.phys_info.velocity,&accel);
 442
 443                                 vm_vec_scale(&obj->mtype.phys_info.velocity,f1_0-drag);
 444                         }
 445
 446                         //do linear scale on remaining bit of time
 447
 448                         vm_vec_scale_add2(&obj->mtype.phys_info.velocity,&accel,k);
 449
 450                         vm_vec_scale(&obj->mtype.phys_info.velocity,f1_0-fixmul(k,drag));
 451                 }
 452                 else {
 453                         fix total_drag=f1_0;
 454
 455                         while (count--)
 456                                 total_drag = fixmul(total_drag,f1_0-drag);
 457
 458                         //do linear scale on remaining bit of time
 459
 460                         total_drag = fixmul(total_drag,f1_0-fixmul(k,drag));
 461
 462                         vm_vec_scale(&obj->mtype.phys_info.velocity,total_drag);
 463                 }
 464         }
 465
 466         #ifdef EXTRA_DEBUG
 467         if (obj == debug_obj)
 468                 printf("  velocity = %x %x %x\n",XYZ(&obj->mtype.phys_info.velocity));
 469         #endif
 470
 471         do {
 472                 try_again = 0;
 473
 474                 //Move the object
 475                 vm_vec_copy_scale(&frame_vec, &obj->mtype.phys_info.velocity, sim_time);
 476
 477                 #ifdef EXTRA_DEBUG
 478                 if (obj == debug_obj)
 479                         printf("  pass %d, frame_vec = %x %x %x\n",count,XYZ(&frame_vec));
 480                 #endif
 481
 482                 if ( (frame_vec.x==0) && (frame_vec.y==0) && (frame_vec.z==0) )
 483                         break;
 484
 485                 count++;
 486
 487                 //      If retry count is getting large, then we are trying to do something stupid.
 488                 if ( count > 3)         {
 489                         if (obj->type == OBJ_PLAYER) {
 490                                 if (count > 8)
 491                                         break;
 492                         } else
 493                                 break;
 494                 }
 495
 496                 vm_vec_add(&new_pos,&obj->pos,&frame_vec);
 497
 498                 #ifdef EXTRA_DEBUG
 499                 if (obj == debug_obj)
 500                         printf("   desired_pos  = %x %x %x\n",XYZ(&new_pos));
 501                 #endif
 502
 503                 ignore_obj_list[n_ignore_objs] = -1;
 504
 505                 #ifdef EXTRA_DEBUG
 506                 if (obj == debug_obj) {
 507                         printf("   FVI parms: p0 = %8x %8x %8x, segnum=%x, size=%x\n",XYZ(&obj->pos),obj->segnum,obj->size);
 508                         printf("              p1 = %8x %8x %8x\n",XYZ(&new_pos));
 509                 }
 510                 #endif
 511
 512                 fq.p0                                           = &obj->pos;
 513                 fq.startseg                             = obj->segnum;
 514                 fq.p1                                           = &new_pos;
 515                 fq.rad                                  = obj->size;
 516                 fq.thisobjnum                   = objnum;
 517                 fq.ignore_obj_list      = ignore_obj_list;
 518                 fq.flags                                        = FQ_CHECK_OBJS;
 519
 520                 if (obj->type == OBJ_WEAPON)
 521                         fq.flags |= FQ_TRANSPOINT;
 522
 523                 if (obj->type == OBJ_PLAYER)
 524                         fq.flags |= FQ_GET_SEGLIST;
 525
 526 //@@                    if (get_seg_masks(&obj->pos,obj->segnum,0).centermask!=0)
 527 //@@                            Int3();
 528
 529 save_p0 = *fq.p0;
 530 save_p1 = *fq.p1;
 531
 532
 533                 fate = find_vector_intersection(&fq,&hit_info);
 534                 //      Matt: Mike's hack.
 535                 if (fate == HIT_OBJECT) {
 536                         object  *objp = &Objects[hit_info.hit_object];
 537
 538                         if ((objp->type == OBJ_WEAPON) && ((objp->id == PROXIMITY_ID) || (objp->id == SUPERPROX_ID)))
 539                                 count--;
 540                 }
 541
 542                 #ifndef NDEBUG
 543                 if (fate == HIT_BAD_P0) {
 544                         mprintf((0,"Warning: Bad p0 in physics!  Object = %i, type = %i [%s]\n", obj-Objects, obj->type, Object_type_names[obj->type]));
 545                         Int3();
 546                 }
 547                 #endif
 548
 549                 if (obj->type == OBJ_PLAYER) {
 550                         int i;
 551
 552                         if (n_phys_segs && phys_seglist[n_phys_segs-1]==hit_info.seglist[0])
 553                                 n_phys_segs--;
 554
 555                         for (i=0;(i<hit_info.n_segs) && (n_phys_segs<MAX_FVI_SEGS-1);  )
 556                                 phys_seglist[n_phys_segs++] = hit_info.seglist[i++];
 557                 }
 558
 559                 #ifdef EXTRA_DEBUG
 560                 if (obj == debug_obj)
 561                         printf("   fate  = %d, hit_pnt = %8x %8x %8x\n",fate,XYZ(&hit_info.hit_pnt));;
 562                 #endif
 563
 564                 ipos = hit_info.hit_pnt;
 565                 iseg = hit_info.hit_seg;
 566                 WallHitSide = hit_info.hit_side;
 567                 WallHitSeg = hit_info.hit_side_seg;
 568
 569                 if (iseg==-1) {         //some sort of horrible error
 570                         #ifndef NDEBUG
 571                         mprintf((1,"iseg==-1 in physics!  Object = %i, type = %i (%s)\n", obj-Objects, obj->type, Object_type_names[obj->type]));
 572                         #endif
 573                         //Int3();
 574                         //compute_segment_center(&ipos,&Segments[obj->segnum]);
 575                         //ipos.x += objnum;
 576                         //iseg = obj->segnum;
 577                         //fate = HIT_NONE;
 578                         if (obj->type == OBJ_WEAPON)
 579                                 obj->flags |= OF_SHOULD_BE_DEAD;
 580                         break;
 581                 }
 582
 583                 Assert(!((fate==HIT_WALL) && ((WallHitSeg == -1) || (WallHitSeg > Highest_segment_index))));
 584
 585                 //if(!get_seg_masks(&hit_info.hit_pnt,hit_info.hit_seg,0).centermask==0)
 586                 //      Int3();
 587
 588                 save_pos = obj->pos;                    //save the object's position
 589                 save_seg = obj->segnum;
 590
 591                 // update object's position and segment number
 592                 obj->pos = ipos;
 593
 594                 #ifdef EXTRA_DEBUG
 595                 if (obj == debug_obj)
 596                         printf("   new pos = %x %x %x\n",XYZ(&obj->pos));
 597                 #endif
 598
 599                 if ( iseg != obj->segnum )
 600                         obj_relink(objnum, iseg );
 601
 602                 //if start point not in segment, move object to center of segment
 603                 if (get_seg_masks(&obj->pos,obj->segnum,0).centermask!=0) {
 604                         int n;
 605
 606                         if ((n=find_object_seg(obj))==-1) {
 607                                 //Int3();
 608                                 if (obj->type==OBJ_PLAYER && (n=find_point_seg(&obj->last_pos,obj->segnum))!=-1) {
 609                                         obj->pos = obj->last_pos;
 610                                         obj_relink(objnum, n );
 611                                 }
 612                                 else {
 613                                         compute_segment_center(&obj->pos,&Segments[obj->segnum]);
 614                                         obj->pos.x += objnum;
 615                                 }
 616                                 if (obj->type == OBJ_WEAPON)
 617                                         obj->flags |= OF_SHOULD_BE_DEAD;
 618                         }
 619                         return;
 620                 }
 621
 622                 //calulate new sim time
 623                 {
 624                         //vms_vector moved_vec;
 625                         vms_vector moved_vec_n;
 626                         fix attempted_dist,actual_dist;
 627
 628                         old_sim_time = sim_time;
 629
 630                         actual_dist = vm_vec_normalized_dir(&moved_vec_n,&obj->pos,&save_pos);
 631
 632                         if (fate==HIT_WALL && vm_vec_dot(&moved_vec_n,&frame_vec) < 0) {                //moved backwards
 633
 634                                 //don't change position or sim_time
 635
 636 //*******                                       mprintf((0,"Obj %d moved backwards\n",obj-Objects));
 637
 638                                 #ifdef EXTRA_DEBUG
 639                                 if (obj == debug_obj)
 640                                         printf("   Warning: moved backwards!\n");
 641                                 #endif
 642
 643                                 obj->pos = save_pos;
 644
 645                                 //iseg = obj->segnum;           //don't change segment
 646
 647                                 obj_relink(objnum, save_seg );
 648
 649                                 moved_time = 0;
 650                         }
 651                         else {
 652
 653                                 //if (obj == debug_obj)
 654                                 //      printf("   moved_vec = %x %x %x\n",XYZ(&moved_vec));
 655
 656                                 attempted_dist = vm_vec_mag(&frame_vec);
 657
 658                                 sim_time = fixmuldiv(sim_time,attempted_dist-actual_dist,attempted_dist);
 659
 660                                 moved_time = old_sim_time - sim_time;
 661
 662                                 if (sim_time < 0 || sim_time>old_sim_time) {
 663                                         #ifndef NDEBUG
 664                                         mprintf((0,"Bogus sim_time = %x, old = %x\n",sim_time,old_sim_time));
 665                                         if (obj == debug_obj)
 666                                                 printf("   Bogus sim_time = %x, old = %x, attempted_dist = %x, actual_dist = %x\n",sim_time,old_sim_time,attempted_dist,actual_dist);
 667                                         //Int3(); Removed by Rob
 668                                         #endif
 669                                         sim_time = old_sim_time;
 670                                         //WHY DOES THIS HAPPEN??
 671
 672                                         moved_time = 0;
 673                                 }
 674                         }
 675
 676                         #ifdef EXTRA_DEBUG
 677                         if (obj == debug_obj)
 678                                 printf("   new sim_time = %x\n",sim_time);
 679                         #endif
 680
 681                 }
 682
 683
 684                 switch( fate )          {
 685
 686                         case HIT_WALL:          {
 687                                 vms_vector moved_v;
 688                                 //@@fix total_d,moved_d;
 689                                 fix hit_speed,wall_part;
 690
 691                                 // Find hit speed
 692
 693                                 vm_vec_sub(&moved_v,&obj->pos,&save_pos);
 694
 695                                 wall_part = vm_vec_dot(&moved_v,&hit_info.hit_wallnorm);
 696
 697                                 if (wall_part != 0 && moved_time>0 && (hit_speed=-fixdiv(wall_part,moved_time))>0)
 698                                         collide_object_with_wall( obj, hit_speed, WallHitSeg, WallHitSide, &hit_info.hit_pnt );
 699                                 else
 700                                         scrape_object_on_wall(obj, WallHitSeg, WallHitSide, &hit_info.hit_pnt );
 701
 702                                 Assert( WallHitSeg > -1 );
 703                                 Assert( WallHitSide > -1 );
 704
 705                                 if ( !(obj->flags&OF_SHOULD_BE_DEAD) )  {
 706                                         int forcefield_bounce;          //bounce off a forcefield
 707
 708                                         Assert(BounceCheat || !(obj->mtype.phys_info.flags & PF_STICK && obj->mtype.phys_info.flags & PF_BOUNCE));      //can't be bounce and stick
 709
 710                                         forcefield_bounce = (TmapInfo[Segments[WallHitSeg].sides[WallHitSide].tmap_num].flags & TMI_FORCE_FIELD);
 711
 712                                         if (!forcefield_bounce && (obj->mtype.phys_info.flags & PF_STICK)) {            //stop moving
 713
 714                                                 // mprintf((0, "Object %i stuck at %i:%i\n", obj-Objects, WallHitSeg, WallHitSide));
 715                                                 add_stuck_object(obj, WallHitSeg, WallHitSide);
 716
 717                                                 vm_vec_zero(&obj->mtype.phys_info.velocity);
 718                                                 obj_stopped = 1;
 719                                                 try_again = 0;
 720                                         }
 721                                         else {                                  // Slide object along wall
 722                                                 int check_vel=0;
 723
 724                                                 //We're constrained by wall, so subtract wall part from
 725                                                 //velocity vector
 726
 727                                                 wall_part = vm_vec_dot(&hit_info.hit_wallnorm,&obj->mtype.phys_info.velocity);
 728
 729 //                                              mprintf((0, "%d", f2i(vm_vec_mag(&hit_info.hit_wallnorm)) ));
 730
 731                                                 if (forcefield_bounce || (obj->mtype.phys_info.flags & PF_BOUNCE)) {            //bounce off wall
 732                                                         wall_part *= 2; //Subtract out wall part twice to achieve bounce
 733
 734                                                         if (forcefield_bounce) {
 735                                                                 check_vel = 1;                          //check for max velocity
 736                                                                 if (obj->type == OBJ_PLAYER)
 737                                                                         wall_part *= 2;         //player bounce twice as much
 738                                                         }
 739
 740                                                         if ( obj->mtype.phys_info.flags & PF_BOUNCES_TWICE) {
 741                                                                 Assert(obj->mtype.phys_info.flags & PF_BOUNCE);
 742                                                                 if (obj->mtype.phys_info.flags & PF_BOUNCED_ONCE)
 743                                                                         obj->mtype.phys_info.flags &= ~(PF_BOUNCE+PF_BOUNCED_ONCE+PF_BOUNCES_TWICE);
 744                                                                 else
 745                                                                         obj->mtype.phys_info.flags |= PF_BOUNCED_ONCE;
 746                                                         }
 747
 748                                                         bounced = 1;            //this object bounced
 749                                                 }
 750
 751                                                 vm_vec_scale_add2(&obj->mtype.phys_info.velocity,&hit_info.hit_wallnorm,-wall_part);
 752
 753 //                                              mprintf((0, "Velocity at bounce time = %d\n", f2i(vm_vec_mag(&obj->mtype.phys_info.velocity))));
 754
 755 //if (obj==ConsoleObject)
 756 //      mprintf((0,"player vel = %x\n",vm_vec_mag_quick(&obj->mtype.phys_info.velocity)));
 757
 758                                                 if (check_vel) {
 759                                                         fix vel = vm_vec_mag_quick(&obj->mtype.phys_info.velocity);
 760
 761                                                         if (vel > MAX_OBJECT_VEL)
 762                                                                 vm_vec_scale(&obj->mtype.phys_info.velocity,fixdiv(MAX_OBJECT_VEL,vel));
 763                                                 }
 764
 765                                                 if (bounced && obj->type == OBJ_WEAPON)
 766                                                         vm_vector_2_matrix(&obj->orient,&obj->mtype.phys_info.velocity,&obj->orient.uvec,NULL);
 767
 768                                                 #ifdef EXTRA_DEBUG
 769                                                 if (obj == debug_obj) {
 770                                                         printf("   sliding - wall_norm %x %x %x %x\n",wall_part,XYZ(&hit_info.hit_wallnorm));
 771                                                         printf("   wall_part %x, new velocity = %x %x %x\n",wall_part,XYZ(&obj->mtype.phys_info.velocity));
 772                                                 }
 773                                                 #endif
 774
 775                                                 try_again = 1;
 776                                         }
 777                                 }
 778                                 break;
 779                         }
 780
 781                         case HIT_OBJECT:                {
 782                                 vms_vector old_vel;
 783
 784                                 // Mark the hit object so that on a retry the fvi code
 785                                 // ignores this object.
 786
 787                                 Assert(hit_info.hit_object != -1);
 788
 789                                 //      Calculcate the hit point between the two objects.
 790                                 {       vms_vector      *ppos0, *ppos1, pos_hit;
 791                                         fix                     size0, size1;
 792                                         ppos0 = &Objects[hit_info.hit_object].pos;
 793                                         ppos1 = &obj->pos;
 794                                         size0 = Objects[hit_info.hit_object].size;
 795                                         size1 = obj->size;
 796                                         Assert(size0+size1 != 0);       // Error, both sizes are 0, so how did they collide, anyway?!?
 797                                         //vm_vec_scale(vm_vec_sub(&pos_hit, ppos1, ppos0), fixdiv(size0, size0 + size1));
 798                                         //vm_vec_add2(&pos_hit, ppos0);
 799                                         vm_vec_sub(&pos_hit, ppos1, ppos0);
 800                                         vm_vec_scale_add(&pos_hit,ppos0,&pos_hit,fixdiv(size0, size0 + size1));
 801
 802                                         old_vel = obj->mtype.phys_info.velocity;
 803
 804                                         collide_two_objects( obj, &Objects[hit_info.hit_object], &pos_hit);
 805
 806                                 }
 807
 808                                 // Let object continue its movement
 809                                 if ( !(obj->flags&OF_SHOULD_BE_DEAD)  ) {
 810                                         //obj->pos = save_pos;
 811
 812                                         if (obj->mtype.phys_info.flags&PF_PERSISTENT || (old_vel.x == obj->mtype.phys_info.velocity.x && old_vel.y == obj->mtype.phys_info.velocity.y && old_vel.z == obj->mtype.phys_info.velocity.z)) {
 813                                                 //if (Objects[hit_info.hit_object].type == OBJ_POWERUP)
 814                                                         ignore_obj_list[n_ignore_objs++] = hit_info.hit_object;
 815                                                 try_again = 1;
 816                                         }
 817                                 }
 818
 819                                 break;
 820                         }
 821                         case HIT_NONE:
 822                         #ifdef TACTILE
 823                                 if (TactileStick && obj==ConsoleObject && !(FrameCount & 15))
 824                                  Tactile_Xvibrate_clear ();
 825                         #endif
 826                                 break;
 827
 828                         #ifndef NDEBUG
 829                         case HIT_BAD_P0:
 830                                 Int3();         // Unexpected collision type: start point not in specified segment.
 831                                 mprintf((0,"Warning: Bad p0 in physics!!!\n"));
 832                                 break;
 833                         default:
 834                                 // Unknown collision type returned from find_vector_intersection!!
 835                                 Int3();
 836                                 break;
 837                         #endif
 838                 }
 839
 840         } while ( try_again );
 841
 842         //      Pass retry count info to AI.
 843         if (obj->control_type == CT_AI) {
 844                 if (count > 0) {
 845                         Ai_local_info[objnum].retry_count = count-1;
 846                         #ifndef NDEBUG
 847                         Total_retries += count-1;
 848                         Total_sims++;
 849                         #endif
 850                 }
 851         }
 852
 853         //I'm not sure why we do this.  I wish there were a comment that
 854         //explained it.  I think maybe it only needs to be done if the object
 855         //is sliding, but I don't know
 856         if (!obj_stopped && !bounced)   {       //Set velocity from actual movement
 857                 vms_vector moved_vec;
 858
 859                 vm_vec_sub(&moved_vec,&obj->pos,&start_pos);
 860                 vm_vec_copy_scale(&obj->mtype.phys_info.velocity,&moved_vec,fixdiv(f1_0,FrameTime));
 861
 862                 #ifdef BUMP_HACK
 863                 if (obj==ConsoleObject && (obj->mtype.phys_info.velocity.x==0 && obj->mtype.phys_info.velocity.y==0 && obj->mtype.phys_info.velocity.z==0) &&
 864                           !(obj->mtype.phys_info.thrust.x==0 && obj->mtype.phys_info.thrust.y==0 && obj->mtype.phys_info.thrust.z==0)) {
 865                         vms_vector center,bump_vec;
 866
 867                         //bump player a little towards center of segment to unstick
 868
 869                         compute_segment_center(&center,&Segments[obj->segnum]);
 870                         vm_vec_normalized_dir_quick(&bump_vec,&center,&obj->pos);
 871
 872                         //don't bump player toward center of reactor segment
 873                         if (Segment2s[obj->segnum].special == SEGMENT_IS_CONTROLCEN)
 874                                 vm_vec_negate(&bump_vec);
 875
 876                         vm_vec_scale_add2(&obj->pos,&bump_vec,obj->size/5);
 877
 878                         //if moving away from seg, might move out of seg, so update
 879                         if (Segment2s[obj->segnum].special == SEGMENT_IS_CONTROLCEN)
 880                                 update_object_seg(obj);
 881                 }
 882                 #endif
 883         }
 884
 885         //Assert(check_point_in_seg(&obj->pos,obj->segnum,0).centermask==0);
 886
 887         //if (obj->control_type == CT_FLYING)
 888         if (obj->mtype.phys_info.flags & PF_LEVELLING)
 889                 do_physics_align_object( obj );
 890
 891
 892         //hack to keep player from going through closed doors
 893         if (obj->type==OBJ_PLAYER && obj->segnum!=orig_segnum && (Physics_cheat_flag!=0xBADA55) ) {
 894                 int sidenum;
 895
 896                 sidenum = find_connect_side(&Segments[obj->segnum],&Segments[orig_segnum]);
 897
 898                 if (sidenum != -1) {
 899
 900                         if (! (WALL_IS_DOORWAY(&Segments[orig_segnum],sidenum) & WID_FLY_FLAG)) {
 901                                 side *s;
 902                                 int vertnum,num_faces,i;
 903                                 fix dist;
 904                                 int vertex_list[6];
 905
 906                                 //bump object back
 907
 908                                 s = &Segments[orig_segnum].sides[sidenum];
 909
 910                                 if (orig_segnum==-1)
 911                                         Error("orig_segnum == -1 in physics");
 912
 913                                 create_abs_vertex_lists( &num_faces, vertex_list, orig_segnum, sidenum);
 914
 915                                 //let's pretend this wall is not triangulated
 916                                 vertnum = vertex_list[0];
 917                                 for (i=1;i<4;i++)
 918                                         if (vertex_list[i] < vertnum)
 919                                                 vertnum = vertex_list[i];
 920
 921                                 #ifdef COMPACT_SEGS
 922                                         {
 923                                         vms_vector _vn;
 924                                         get_side_normal(&Segments[orig_segnum], sidenum, 0, &_vn );
 925                                         dist = vm_dist_to_plane(&start_pos, &_vn, &Vertices[vertnum]);
 926                                         vm_vec_scale_add(&obj->pos,&start_pos,&_vn,obj->size-dist);
 927                                         }
 928                                 #else
 929                                         dist = vm_dist_to_plane(&start_pos, &s->normals[0], &Vertices[vertnum]);
 930                                         vm_vec_scale_add(&obj->pos,&start_pos,&s->normals[0],obj->size-dist);
 931                                 #endif
 932                                 update_object_seg(obj);
 933
 934                         }
 935                 }
 936         }
 937
 938 //--WE ALWYS WANT THIS IN, MATT AND MIKE DECISION ON 12/10/94, TWO MONTHS AFTER FINAL   #ifndef NDEBUG
 939         //if end point not in segment, move object to last pos, or segment center
 940         if (get_seg_masks(&obj->pos,obj->segnum,0).centermask!=0) {
 941                 if (find_object_seg(obj)==-1) {
 942                         int n;
 943
 944                         //Int3();
 945                         if (obj->type==OBJ_PLAYER && (n=find_point_seg(&obj->last_pos,obj->segnum))!=-1) {
 946                                 obj->pos = obj->last_pos;
 947                                 obj_relink(objnum, n );
 948                         }
 949                         else {
 950                                 compute_segment_center(&obj->pos,&Segments[obj->segnum]);
 951                                 obj->pos.x += objnum;
 952                         }
 953                         if (obj->type == OBJ_WEAPON)
 954                                 obj->flags |= OF_SHOULD_BE_DEAD;
 955                 }
 956         }
 957 //--WE ALWYS WANT THIS IN, MATT AND MIKE DECISION ON 12/10/94, TWO MONTHS AFTER FINAL   #endif
 958
 959
 960 }
 961
 962 //--unused-- //tell us what the given object will do (as far as hiting walls) in
 963 //--unused-- //the given time (in seconds) t.  Igores acceleration (sorry)
 964 //--unused-- //if check_objects is set, check with objects, else just with walls
 965 //--unused-- //returns fate, fills in hit time.  If fate==HIT_NONE, hit_time undefined
 966 //--unused-- int physics_lookahead(object *obj,fix t,int fvi_flags,fix *hit_time, fvi_info *hit_info)
 967 //--unused-- {
 968 //--unused--    vms_vector new_pos;
 969 //--unused--    int objnum,fate;
 970 //--unused--    fvi_query fq;
 971 //--unused--
 972 //--unused--    Assert(obj->movement_type == MT_PHYSICS);
 973 //--unused--
 974 //--unused--    objnum = obj-Objects;
 975 //--unused--
 976 //--unused--    vm_vec_scale_add(&new_pos, &obj->pos, &obj->mtype.phys_info.velocity, t);
 977 //--unused--
 978 //--unused--    fq.p0                                           = &obj->pos;
 979 //--unused--    fq.startseg                             = obj->segnum;
 980 //--unused--    fq.p1                                           = &new_pos;
 981 //--unused--    fq.rad                                  = obj->size;
 982 //--unused--    fq.thisobjnum                   = objnum;
 983 //--unused--    fq.ignore_obj_list      = NULL;
 984 //--unused--    fq.flags                                        = fvi_flags;
 985 //--unused--
 986 //--unused--    fate = find_vector_intersection(&fq,hit_info);
 987 //--unused--
 988 //--unused--    if (fate != HIT_NONE) {
 989 //--unused--            fix dist,speed;
 990 //--unused--
 991 //--unused--            dist = vm_vec_dist(&obj->pos, &hit_info->hit_pnt);
 992 //--unused--
 993 //--unused--            speed = vm_vec_mag(&obj->mtype.phys_info.velocity);
 994 //--unused--
 995 //--unused--            *hit_time = fixdiv(dist,speed);
 996 //--unused--
 997 //--unused--    }
 998 //--unused--
 999 //--unused--    return fate;
1000 //--unused--
1001 //--unused-- }
1002
1003 //Applies an instantaneous force on an object, resulting in an instantaneous
1004 //change in velocity.
1005 void phys_apply_force(object *obj,vms_vector *force_vec)
1006 {
1007
1008         //      Put in by MK on 2/13/96 for force getting applied to Omega blobs, which have 0 mass,
1009         //      in collision with crazy reactor robot thing on d2levf-s.
1010         if (obj->mtype.phys_info.mass == 0)
1011                 return;
1012
1013         if (obj->movement_type != MT_PHYSICS)
1014                 return;
1015
1016 #ifdef TACTILE
1017    if (TactileStick && obj==&Objects[Players[Player_num].objnum])
1018                 Tactile_apply_force (force_vec,&obj->orient);
1019 #endif
1020
1021         //Add in acceleration due to force
1022         vm_vec_scale_add2(&obj->mtype.phys_info.velocity,force_vec,fixdiv(f1_0,obj->mtype.phys_info.mass));
1023
1024
1025 }
1026
1027 //      ----------------------------------------------------------------
1028 //      Do *dest = *delta unless:
1029 //                              *delta is pretty small
1030 //              and     they are of different signs.
1031 void physics_set_rotvel_and_saturate(fix *dest, fix delta)
1032 {
1033         if ((delta ^ *dest) < 0) {
1034                 if (abs(delta) < F1_0/8) {
1035                         // mprintf((0, "D"));
1036                         *dest = delta/4;
1037                 } else
1038                         // mprintf((0, "d"));
1039                         *dest = delta;
1040         } else {
1041                 // mprintf((0, "!"));
1042                 *dest = delta;
1043         }
1044 }
1045
1046 //      ------------------------------------------------------------------------------------------------------
1047 //      Note: This is the old ai_turn_towards_vector code.
1048 //      phys_apply_rot used to call ai_turn_towards_vector until I fixed it, which broke phys_apply_rot.
1049 void physics_turn_towards_vector(vms_vector *goal_vector, object *obj, fix rate)
1050 {
1051         vms_angvec      dest_angles, cur_angles;
1052         fix                     delta_p, delta_h;
1053         vms_vector      *rotvel_ptr = &obj->mtype.phys_info.rotvel;
1054
1055         // Make this object turn towards the goal_vector.  Changes orientation, doesn't change direction of movement.
1056         // If no one moves, will be facing goal_vector in 1 second.
1057
1058         //      Detect null vector.
1059         if ((goal_vector->x == 0) && (goal_vector->y == 0) && (goal_vector->z == 0))
1060                 return;
1061
1062         //      Make morph objects turn more slowly.
1063         if (obj->control_type == CT_MORPH)
1064                 rate *= 2;
1065
1066         vm_extract_angles_vector(&dest_angles, goal_vector);
1067         vm_extract_angles_vector(&cur_angles, &obj->orient.fvec);
1068
1069         delta_p = (dest_angles.p - cur_angles.p);
1070         delta_h = (dest_angles.h - cur_angles.h);
1071
1072         if (delta_p > F1_0/2) delta_p = dest_angles.p - cur_angles.p - F1_0;
1073         if (delta_p < -F1_0/2) delta_p = dest_angles.p - cur_angles.p + F1_0;
1074         if (delta_h > F1_0/2) delta_h = dest_angles.h - cur_angles.h - F1_0;
1075         if (delta_h < -F1_0/2) delta_h = dest_angles.h - cur_angles.h + F1_0;
1076
1077         delta_p = fixdiv(delta_p, rate);
1078         delta_h = fixdiv(delta_h, rate);
1079
1080         if (abs(delta_p) < F1_0/16) delta_p *= 4;
1081         if (abs(delta_h) < F1_0/16) delta_h *= 4;
1082
1083         physics_set_rotvel_and_saturate(&rotvel_ptr->x, delta_p);
1084         physics_set_rotvel_and_saturate(&rotvel_ptr->y, delta_h);
1085         rotvel_ptr->z = 0;
1086 }
1087
1088 //      -----------------------------------------------------------------------------
1089 //      Applies an instantaneous whack on an object, resulting in an instantaneous
1090 //      change in orientation.
1091 void phys_apply_rot(object *obj,vms_vector *force_vec)
1092 {
1093         fix     rate, vecmag;
1094
1095         if (obj->movement_type != MT_PHYSICS)
1096                 return;
1097
1098         vecmag = vm_vec_mag(force_vec)/8;
1099         if (vecmag < F1_0/256)
1100                 rate = 4*F1_0;
1101         else if (vecmag < obj->mtype.phys_info.mass >> 14)
1102                 rate = 4*F1_0;
1103         else {
1104                 rate = fixdiv(obj->mtype.phys_info.mass, vecmag);
1105                 if (obj->type == OBJ_ROBOT) {
1106                         if (rate < F1_0/4)
1107                                 rate = F1_0/4;
1108                         //      Changed by mk, 10/24/95, claw guys should not slow down when attacking!
1109                         if (!Robot_info[obj->id].thief && !Robot_info[obj->id].attack_type) {
1110                                 if (obj->ctype.ai_info.SKIP_AI_COUNT * FrameTime < 3*F1_0/4) {
1111                                         fix     tval = fixdiv(F1_0, 8*FrameTime);
1112                                         int     addval;
1113
1114                                         addval = f2i(tval);
1115
1116                                         if ( (d_rand() * 2) < (tval & 0xffff))
1117                                                 addval++;
1118                                         obj->ctype.ai_info.SKIP_AI_COUNT += addval;
1119                                         // -- mk: too much stuff making hard to see my debug messages...mprintf((0, "FrameTime = %7.3f, addval = %i\n", f2fl(FrameTime), addval));
1120                                 }
1121                         }
1122                 } else {
1123                         if (rate < F1_0/2)
1124                                 rate = F1_0/2;
1125                 }
1126         }
1127
1128         //      Turn amount inversely proportional to mass.  Third parameter is seconds to do 360 turn.
1129         physics_turn_towards_vector(force_vec, obj, rate);
1130
1131
1132 }
1133
1134
1135 //this routine will set the thrust for an object to a value that will
1136 //(hopefully) maintain the object's current velocity
1137 void set_thrust_from_velocity(object *obj)
1138 {
1139         fix k;
1140
1141         Assert(obj->movement_type == MT_PHYSICS);
1142
1143         k = fixmuldiv(obj->mtype.phys_info.mass,obj->mtype.phys_info.drag,(f1_0-obj->mtype.phys_info.drag));
1144
1145         vm_vec_copy_scale(&obj->mtype.phys_info.thrust,&obj->mtype.phys_info.velocity,k);
1146
1147 }
1148
1149