src/collision.cpp

   1 /*
   2 Minetest
   3 Copyright (C) 2013 celeron55, Perttu Ahola <celeron55@gmail.com>
   4
   5 This program is free software; you can redistribute it and/or modify
   6 it under the terms of the GNU Lesser General Public License as published by
   7 the Free Software Foundation; either version 2.1 of the License, or
   8 (at your option) any later version.
   9
  10 This program is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 GNU Lesser General Public License for more details.
  14
  15 You should have received a copy of the GNU Lesser General Public License along
  16 with this program; if not, write to the Free Software Foundation, Inc.,
  17 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18 */
  19
  20 #include "collision.h"
  21 #include "mapblock.h"
  22 #include "map.h"
  23 #include "nodedef.h"
  24 #include "gamedef.h"
  25 #include "log.h"
  26 #include "environment.h"
  27 #include "serverobject.h"
  28 #include <vector>
  29 #include <set>
  30 #include "util/timetaker.h"
  31 #include "main.h" // g_profiler
  32 #include "profiler.h"
  33
  34 // float error is 10 - 9.96875 = 0.03125
  35 #define COLL_ZERO 0.032
  36
  37 // Helper function:
  38 // Checks for collision of a moving aabbox with a static aabbox
  39 // Returns -1 if no collision, 0 if X collision, 1 if Y collision, 2 if Z collision
  40 // The time after which the collision occurs is stored in dtime.
  41 int axisAlignedCollision(
  42                 const aabb3f &staticbox, const aabb3f &movingbox,
  43                 const v3f &speed, f32 d, f32 &dtime)
  44 {
  45         //TimeTaker tt("axisAlignedCollision");
  46
  47         f32 xsize = (staticbox.MaxEdge.X - staticbox.MinEdge.X) - COLL_ZERO;     // reduce box size for solve collision stuck (flying sand)
  48         f32 ysize = (staticbox.MaxEdge.Y - staticbox.MinEdge.Y); // - COLL_ZERO; // Y - no sense for falling, but maybe try later
  49         f32 zsize = (staticbox.MaxEdge.Z - staticbox.MinEdge.Z) - COLL_ZERO;
  50
  51         aabb3f relbox(
  52                         movingbox.MinEdge.X - staticbox.MinEdge.X,
  53                         movingbox.MinEdge.Y - staticbox.MinEdge.Y,
  54                         movingbox.MinEdge.Z - staticbox.MinEdge.Z,
  55                         movingbox.MaxEdge.X - staticbox.MinEdge.X,
  56                         movingbox.MaxEdge.Y - staticbox.MinEdge.Y,
  57                         movingbox.MaxEdge.Z - staticbox.MinEdge.Z
  58         );
  59
  60         if(speed.X > 0) // Check for collision with X- plane
  61         {
  62                 if(relbox.MaxEdge.X <= d)
  63                 {
  64                         dtime = - relbox.MaxEdge.X / speed.X;
  65                         if((relbox.MinEdge.Y + speed.Y * dtime < ysize) &&
  66                                         (relbox.MaxEdge.Y + speed.Y * dtime > COLL_ZERO) &&
  67                                         (relbox.MinEdge.Z + speed.Z * dtime < zsize) &&
  68                                         (relbox.MaxEdge.Z + speed.Z * dtime > COLL_ZERO))
  69                                 return 0;
  70                 }
  71                 else if(relbox.MinEdge.X > xsize)
  72                 {
  73                         return -1;
  74                 }
  75         }
  76         else if(speed.X < 0) // Check for collision with X+ plane
  77         {
  78                 if(relbox.MinEdge.X >= xsize - d)
  79                 {
  80                         dtime = (xsize - relbox.MinEdge.X) / speed.X;
  81                         if((relbox.MinEdge.Y + speed.Y * dtime < ysize) &&
  82                                         (relbox.MaxEdge.Y + speed.Y * dtime > COLL_ZERO) &&
  83                                         (relbox.MinEdge.Z + speed.Z * dtime < zsize) &&
  84                                         (relbox.MaxEdge.Z + speed.Z * dtime > COLL_ZERO))
  85                                 return 0;
  86                 }
  87                 else if(relbox.MaxEdge.X < 0)
  88                 {
  89                         return -1;
  90                 }
  91         }
  92
  93         // NO else if here
  94
  95         if(speed.Y > 0) // Check for collision with Y- plane
  96         {
  97                 if(relbox.MaxEdge.Y <= d)
  98                 {
  99                         dtime = - relbox.MaxEdge.Y / speed.Y;
 100                         if((relbox.MinEdge.X + speed.X * dtime < xsize) &&
 101                                         (relbox.MaxEdge.X + speed.X * dtime > COLL_ZERO) &&
 102                                         (relbox.MinEdge.Z + speed.Z * dtime < zsize) &&
 103                                         (relbox.MaxEdge.Z + speed.Z * dtime > COLL_ZERO))
 104                                 return 1;
 105                 }
 106                 else if(relbox.MinEdge.Y > ysize)
 107                 {
 108                         return -1;
 109                 }
 110         }
 111         else if(speed.Y < 0) // Check for collision with Y+ plane
 112         {
 113                 if(relbox.MinEdge.Y >= ysize - d)
 114                 {
 115                         dtime = (ysize - relbox.MinEdge.Y) / speed.Y;
 116                         if((relbox.MinEdge.X + speed.X * dtime < xsize) &&
 117                                         (relbox.MaxEdge.X + speed.X * dtime > COLL_ZERO) &&
 118                                         (relbox.MinEdge.Z + speed.Z * dtime < zsize) &&
 119                                         (relbox.MaxEdge.Z + speed.Z * dtime > COLL_ZERO))
 120                                 return 1;
 121                 }
 122                 else if(relbox.MaxEdge.Y < 0)
 123                 {
 124                         return -1;
 125                 }
 126         }
 127
 128         // NO else if here
 129
 130         if(speed.Z > 0) // Check for collision with Z- plane
 131         {
 132                 if(relbox.MaxEdge.Z <= d)
 133                 {
 134                         dtime = - relbox.MaxEdge.Z / speed.Z;
 135                         if((relbox.MinEdge.X + speed.X * dtime < xsize) &&
 136                                         (relbox.MaxEdge.X + speed.X * dtime > COLL_ZERO) &&
 137                                         (relbox.MinEdge.Y + speed.Y * dtime < ysize) &&
 138                                         (relbox.MaxEdge.Y + speed.Y * dtime > COLL_ZERO))
 139                                 return 2;
 140                 }
 141                 //else if(relbox.MinEdge.Z > zsize)
 142                 //{
 143                 //      return -1;
 144                 //}
 145         }
 146         else if(speed.Z < 0) // Check for collision with Z+ plane
 147         {
 148                 if(relbox.MinEdge.Z >= zsize - d)
 149                 {
 150                         dtime = (zsize - relbox.MinEdge.Z) / speed.Z;
 151                         if((relbox.MinEdge.X + speed.X * dtime < xsize) &&
 152                                         (relbox.MaxEdge.X + speed.X * dtime > COLL_ZERO) &&
 153                                         (relbox.MinEdge.Y + speed.Y * dtime < ysize) &&
 154                                         (relbox.MaxEdge.Y + speed.Y * dtime > COLL_ZERO))
 155                                 return 2;
 156                 }
 157                 //else if(relbox.MaxEdge.Z < 0)
 158                 //{
 159                 //      return -1;
 160                 //}
 161         }
 162
 163         return -1;
 164 }
 165
 166 // Helper function:
 167 // Checks if moving the movingbox up by the given distance would hit a ceiling.
 168 bool wouldCollideWithCeiling(
 169                 const std::vector<aabb3f> &staticboxes,
 170                 const aabb3f &movingbox,
 171                 f32 y_increase, f32 d)
 172 {
 173         //TimeTaker tt("wouldCollideWithCeiling");
 174
 175         assert(y_increase >= 0);
 176
 177         for(std::vector<aabb3f>::const_iterator
 178                         i = staticboxes.begin();
 179                         i != staticboxes.end(); i++)
 180         {
 181                 const aabb3f& staticbox = *i;
 182                 if((movingbox.MaxEdge.Y - d <= staticbox.MinEdge.Y) &&
 183                                 (movingbox.MaxEdge.Y + y_increase > staticbox.MinEdge.Y) &&
 184                                 (movingbox.MinEdge.X < staticbox.MaxEdge.X) &&
 185                                 (movingbox.MaxEdge.X > staticbox.MinEdge.X) &&
 186                                 (movingbox.MinEdge.Z < staticbox.MaxEdge.Z) &&
 187                                 (movingbox.MaxEdge.Z > staticbox.MinEdge.Z))
 188                         return true;
 189         }
 190
 191         return false;
 192 }
 193
 194
 195 collisionMoveResult collisionMoveSimple(Environment *env, IGameDef *gamedef,
 196                 f32 pos_max_d, const aabb3f &box_0,
 197                 f32 stepheight, f32 dtime,
 198                 v3f &pos_f, v3f &speed_f, v3f &accel_f,ActiveObject* self)
 199 {
 200         Map *map = &env->getMap();
 201         //TimeTaker tt("collisionMoveSimple");
 202     ScopeProfiler sp(g_profiler, "collisionMoveSimple avg", SPT_AVG);
 203
 204         collisionMoveResult result;
 205
 206         /*
 207                 Calculate new velocity
 208         */
 209         if( dtime > 0.5 ) {
 210                 infostream<<"collisionMoveSimple: WARNING: maximum step interval exceeded, lost movement details!"<<std::endl;
 211                 dtime = 0.5;
 212         }
 213         speed_f += accel_f * dtime;
 214
 215         // If there is no speed, there are no collisions
 216         if(speed_f.getLength() == 0)
 217                 return result;
 218
 219         // Limit speed for avoiding hangs
 220         speed_f.Y=rangelim(speed_f.Y,-5000,5000);
 221         speed_f.X=rangelim(speed_f.X,-5000,5000);
 222         speed_f.Z=rangelim(speed_f.Z,-5000,5000);
 223
 224         /*
 225                 Collect node boxes in movement range
 226         */
 227         std::vector<aabb3f> cboxes;
 228         std::vector<bool> is_unloaded;
 229         std::vector<bool> is_step_up;
 230         std::vector<bool> is_object;
 231         std::vector<int> bouncy_values;
 232         std::vector<v3s16> node_positions;
 233         {
 234         //TimeTaker tt2("collisionMoveSimple collect boxes");
 235     ScopeProfiler sp(g_profiler, "collisionMoveSimple collect boxes avg", SPT_AVG);
 236
 237         v3s16 oldpos_i = floatToInt(pos_f, BS);
 238         v3s16 newpos_i = floatToInt(pos_f + speed_f * dtime, BS);
 239         s16 min_x = MYMIN(oldpos_i.X, newpos_i.X) + (box_0.MinEdge.X / BS) - 1;
 240         s16 min_y = MYMIN(oldpos_i.Y, newpos_i.Y) + (box_0.MinEdge.Y / BS) - 1;
 241         s16 min_z = MYMIN(oldpos_i.Z, newpos_i.Z) + (box_0.MinEdge.Z / BS) - 1;
 242         s16 max_x = MYMAX(oldpos_i.X, newpos_i.X) + (box_0.MaxEdge.X / BS) + 1;
 243         s16 max_y = MYMAX(oldpos_i.Y, newpos_i.Y) + (box_0.MaxEdge.Y / BS) + 1;
 244         s16 max_z = MYMAX(oldpos_i.Z, newpos_i.Z) + (box_0.MaxEdge.Z / BS) + 1;
 245
 246         for(s16 x = min_x; x <= max_x; x++)
 247         for(s16 y = min_y; y <= max_y; y++)
 248         for(s16 z = min_z; z <= max_z; z++)
 249         {
 250                 v3s16 p(x,y,z);
 251                 try{
 252                         // Object collides into walkable nodes
 253                         MapNode n = map->getNode(p);
 254                         const ContentFeatures &f = gamedef->getNodeDefManager()->get(n);
 255                         if(f.walkable == false)
 256                                 continue;
 257                         int n_bouncy_value = itemgroup_get(f.groups, "bouncy");
 258
 259                         std::vector<aabb3f> nodeboxes = n.getNodeBoxes(gamedef->ndef());
 260                         for(std::vector<aabb3f>::iterator
 261                                         i = nodeboxes.begin();
 262                                         i != nodeboxes.end(); i++)
 263                         {
 264                                 aabb3f box = *i;
 265                                 box.MinEdge += v3f(x, y, z)*BS;
 266                                 box.MaxEdge += v3f(x, y, z)*BS;
 267                                 cboxes.push_back(box);
 268                                 is_unloaded.push_back(false);
 269                                 is_step_up.push_back(false);
 270                                 bouncy_values.push_back(n_bouncy_value);
 271                                 node_positions.push_back(p);
 272                                 is_object.push_back(false);
 273                         }
 274                 }
 275                 catch(InvalidPositionException &e)
 276                 {
 277                         // Collide with unloaded nodes
 278                         aabb3f box = getNodeBox(p, BS);
 279                         cboxes.push_back(box);
 280                         is_unloaded.push_back(true);
 281                         is_step_up.push_back(false);
 282                         bouncy_values.push_back(0);
 283                         node_positions.push_back(p);
 284                         is_object.push_back(false);
 285                 }
 286         }
 287         } // tt2
 288
 289         {
 290                 ScopeProfiler sp(g_profiler, "collisionMoveSimple objects avg", SPT_AVG);
 291                 //TimeTaker tt3("collisionMoveSimple collect object boxes");
 292
 293                 /* add object boxes to cboxes */
 294
 295
 296                 std::list<ActiveObject*> objects;
 297 #ifndef SERVER
 298                 ClientEnvironment *c_env = dynamic_cast<ClientEnvironment*>(env);
 299                 if (c_env != 0)
 300                 {
 301                         f32 distance = speed_f.getLength();
 302                         std::vector<DistanceSortedActiveObject> clientobjects;
 303                         c_env->getActiveObjects(pos_f,distance * 1.5,clientobjects);
 304                         for (size_t i=0; i < clientobjects.size(); i++)
 305                         {
 306                                 if ((self == 0) || (self != clientobjects[i].obj)) {
 307                                         objects.push_back((ActiveObject*)clientobjects[i].obj);
 308                                 }
 309                         }
 310                 }
 311                 else
 312 #endif
 313                 {
 314                         ServerEnvironment *s_env = dynamic_cast<ServerEnvironment*>(env);
 315                         if (s_env != 0)
 316                         {
 317                                 f32 distance = speed_f.getLength();
 318                                 std::set<u16> s_objects = s_env->getObjectsInsideRadius(pos_f,distance * 1.5);
 319                                 for (std::set<u16>::iterator iter = s_objects.begin(); iter != s_objects.end(); iter++)
 320                                 {
 321                                         ServerActiveObject *current = s_env->getActiveObject(*iter);
 322                                         if ((self == 0) || (self != current)) {
 323                                                 objects.push_back((ActiveObject*)current);
 324                                         }
 325                                 }
 326                         }
 327                 }
 328
 329                 for (std::list<ActiveObject*>::const_iterator iter = objects.begin();iter != objects.end(); ++iter)
 330                 {
 331                         ActiveObject *object = *iter;
 332
 333                         if (object != NULL)
 334                         {
 335                                 aabb3f object_collisionbox;
 336                                 if (object->getCollisionBox(&object_collisionbox))
 337                                 {
 338                                         cboxes.push_back(object_collisionbox);
 339                                         is_unloaded.push_back(false);
 340                                         is_step_up.push_back(false);
 341                                         bouncy_values.push_back(0);
 342                                         node_positions.push_back(v3s16(0,0,0));
 343                                         is_object.push_back(true);
 344                                 }
 345                         }
 346                 }
 347         } //tt3
 348
 349         assert(cboxes.size() == is_unloaded.size());
 350         assert(cboxes.size() == is_step_up.size());
 351         assert(cboxes.size() == bouncy_values.size());
 352         assert(cboxes.size() == node_positions.size());
 353         assert(cboxes.size() == is_object.size());
 354
 355         /*
 356                 Collision detection
 357         */
 358
 359         /*
 360                 Collision uncertainty radius
 361                 Make it a bit larger than the maximum distance of movement
 362         */
 363         f32 d = pos_max_d * 1.1;
 364         // A fairly large value in here makes moving smoother
 365         //f32 d = 0.15*BS;
 366
 367         // This should always apply, otherwise there are glitches
 368         assert(d > pos_max_d);
 369
 370         int loopcount = 0;
 371
 372         while(dtime > BS*1e-10)
 373         {
 374                 //TimeTaker tt3("collisionMoveSimple dtime loop");
 375         ScopeProfiler sp(g_profiler, "collisionMoveSimple dtime loop avg", SPT_AVG);
 376
 377                 // Avoid infinite loop
 378                 loopcount++;
 379                 if(loopcount >= 100)
 380                 {
 381                         infostream<<"collisionMoveSimple: WARNING: Loop count exceeded, aborting to avoid infiniite loop"<<std::endl;
 382                         dtime = 0;
 383                         break;
 384                 }
 385
 386                 aabb3f movingbox = box_0;
 387                 movingbox.MinEdge += pos_f;
 388                 movingbox.MaxEdge += pos_f;
 389
 390                 int nearest_collided = -1;
 391                 f32 nearest_dtime = dtime;
 392                 u32 nearest_boxindex = -1;
 393
 394                 /*
 395                         Go through every nodebox, find nearest collision
 396                 */
 397                 for(u32 boxindex = 0; boxindex < cboxes.size(); boxindex++)
 398                 {
 399                         // Ignore if already stepped up this nodebox.
 400                         if(is_step_up[boxindex])
 401                                 continue;
 402
 403                         // Find nearest collision of the two boxes (raytracing-like)
 404                         f32 dtime_tmp;
 405                         int collided = axisAlignedCollision(
 406                                         cboxes[boxindex], movingbox, speed_f, d, dtime_tmp);
 407
 408                         if(collided == -1 || dtime_tmp >= nearest_dtime)
 409                                 continue;
 410
 411                         nearest_dtime = dtime_tmp;
 412                         nearest_collided = collided;
 413                         nearest_boxindex = boxindex;
 414                 }
 415
 416                 if(nearest_collided == -1)
 417                 {
 418                         // No collision with any collision box.
 419                         pos_f += speed_f * dtime;
 420                         dtime = 0;  // Set to 0 to avoid "infinite" loop due to small FP numbers
 421                 }
 422                 else
 423                 {
 424                         // Otherwise, a collision occurred.
 425
 426                         const aabb3f& cbox = cboxes[nearest_boxindex];
 427
 428                         // Check for stairs.
 429                         bool step_up = (nearest_collided != 1) && // must not be Y direction
 430                                         (movingbox.MinEdge.Y < cbox.MaxEdge.Y) &&
 431                                         (movingbox.MinEdge.Y + stepheight > cbox.MaxEdge.Y) &&
 432                                         (!wouldCollideWithCeiling(cboxes, movingbox,
 433                                                         cbox.MaxEdge.Y - movingbox.MinEdge.Y,
 434                                                         d));
 435
 436                         // Get bounce multiplier
 437                         bool bouncy = (bouncy_values[nearest_boxindex] >= 1);
 438                         float bounce = -(float)bouncy_values[nearest_boxindex] / 100.0;
 439
 440                         // Move to the point of collision and reduce dtime by nearest_dtime
 441                         if(nearest_dtime < 0)
 442                         {
 443                                 // Handle negative nearest_dtime (can be caused by the d allowance)
 444                                 if(!step_up)
 445                                 {
 446                                         if(nearest_collided == 0)
 447                                                 pos_f.X += speed_f.X * nearest_dtime;
 448                                         if(nearest_collided == 1)
 449                                                 pos_f.Y += speed_f.Y * nearest_dtime;
 450                                         if(nearest_collided == 2)
 451                                                 pos_f.Z += speed_f.Z * nearest_dtime;
 452                                 }
 453                         }
 454                         else
 455                         {
 456                                 pos_f += speed_f * nearest_dtime;
 457                                 dtime -= nearest_dtime;
 458                         }
 459
 460                         bool is_collision = true;
 461                         if(is_unloaded[nearest_boxindex])
 462                                 is_collision = false;
 463
 464                         CollisionInfo info;
 465                         if (is_object[nearest_boxindex]) {
 466                                 info.type = COLLISION_OBJECT;
 467                         }
 468                         else {
 469                                 info.type = COLLISION_NODE;
 470                         }
 471                         info.node_p = node_positions[nearest_boxindex];
 472                         info.bouncy = bouncy;
 473                         info.old_speed = speed_f;
 474
 475                         // Set the speed component that caused the collision to zero
 476                         if(step_up)
 477                         {
 478                                 // Special case: Handle stairs
 479                                 is_step_up[nearest_boxindex] = true;
 480                                 is_collision = false;
 481                         }
 482                         else if(nearest_collided == 0) // X
 483                         {
 484                                 if(fabs(speed_f.X) > BS*3)
 485                                         speed_f.X *= bounce;
 486                                 else
 487                                         speed_f.X = 0;
 488                                 result.collides = true;
 489                                 result.collides_xz = true;
 490                         }
 491                         else if(nearest_collided == 1) // Y
 492                         {
 493                                 if(fabs(speed_f.Y) > BS*3)
 494                                         speed_f.Y *= bounce;
 495                                 else
 496                                         speed_f.Y = 0;
 497                                 result.collides = true;
 498                         }
 499                         else if(nearest_collided == 2) // Z
 500                         {
 501                                 if(fabs(speed_f.Z) > BS*3)
 502                                         speed_f.Z *= bounce;
 503                                 else
 504                                         speed_f.Z = 0;
 505                                 result.collides = true;
 506                                 result.collides_xz = true;
 507                         }
 508
 509                         info.new_speed = speed_f;
 510                         if(info.new_speed.getDistanceFrom(info.old_speed) < 0.1*BS)
 511                                 is_collision = false;
 512
 513                         if(is_collision){
 514                                 result.collisions.push_back(info);
 515                         }
 516                 }
 517         }
 518
 519         /*
 520                 Final touches: Check if standing on ground, step up stairs.
 521         */
 522         aabb3f box = box_0;
 523         box.MinEdge += pos_f;
 524         box.MaxEdge += pos_f;
 525         for(u32 boxindex = 0; boxindex < cboxes.size(); boxindex++)
 526         {
 527                 const aabb3f& cbox = cboxes[boxindex];
 528
 529                 /*
 530                         See if the object is touching ground.
 531
 532                         Object touches ground if object's minimum Y is near node's
 533                         maximum Y and object's X-Z-area overlaps with the node's
 534                         X-Z-area.
 535
 536                         Use 0.15*BS so that it is easier to get on a node.
 537                 */
 538                 if(
 539                                 cbox.MaxEdge.X-d > box.MinEdge.X &&
 540                                 cbox.MinEdge.X+d < box.MaxEdge.X &&
 541                                 cbox.MaxEdge.Z-d > box.MinEdge.Z &&
 542                                 cbox.MinEdge.Z+d < box.MaxEdge.Z
 543                 ){
 544                         if(is_step_up[boxindex])
 545                         {
 546                                 pos_f.Y += (cbox.MaxEdge.Y - box.MinEdge.Y);
 547                                 box = box_0;
 548                                 box.MinEdge += pos_f;
 549                                 box.MaxEdge += pos_f;
 550                         }
 551                         if(fabs(cbox.MaxEdge.Y-box.MinEdge.Y) < 0.15*BS)
 552                         {
 553                                 result.touching_ground = true;
 554                                 if(is_unloaded[boxindex])
 555                                         result.standing_on_unloaded = true;
 556                         }
 557                 }
 558         }
 559
 560         return result;
 561 }
 562
 563 #if 0
 564 // This doesn't seem to work and isn't used
 565 collisionMoveResult collisionMovePrecise(Map *map, IGameDef *gamedef,
 566                 f32 pos_max_d, const aabb3f &box_0,
 567                 f32 stepheight, f32 dtime,
 568                 v3f &pos_f, v3f &speed_f, v3f &accel_f)
 569 {
 570         //TimeTaker tt("collisionMovePrecise");
 571     ScopeProfiler sp(g_profiler, "collisionMovePrecise avg", SPT_AVG);
 572
 573         collisionMoveResult final_result;
 574
 575         // If there is no speed, there are no collisions
 576         if(speed_f.getLength() == 0)
 577                 return final_result;
 578
 579         // Don't allow overly huge dtime
 580         if(dtime > 2.0)
 581                 dtime = 2.0;
 582
 583         f32 dtime_downcount = dtime;
 584
 585         u32 loopcount = 0;
 586         do
 587         {
 588                 loopcount++;
 589
 590                 // Maximum time increment (for collision detection etc)
 591                 // time = distance / speed
 592                 f32 dtime_max_increment = 1.0;
 593                 if(speed_f.getLength() != 0)
 594                         dtime_max_increment = pos_max_d / speed_f.getLength();
 595
 596                 // Maximum time increment is 10ms or lower
 597                 if(dtime_max_increment > 0.01)
 598                         dtime_max_increment = 0.01;
 599
 600                 f32 dtime_part;
 601                 if(dtime_downcount > dtime_max_increment)
 602                 {
 603                         dtime_part = dtime_max_increment;
 604                         dtime_downcount -= dtime_part;
 605                 }
 606                 else
 607                 {
 608                         dtime_part = dtime_downcount;
 609                         /*
 610                                 Setting this to 0 (no -=dtime_part) disables an infinite loop
 611                                 when dtime_part is so small that dtime_downcount -= dtime_part
 612                                 does nothing
 613                         */
 614                         dtime_downcount = 0;
 615                 }
 616
 617                 collisionMoveResult result = collisionMoveSimple(map, gamedef,
 618                                 pos_max_d, box_0, stepheight, dtime_part,
 619                                 pos_f, speed_f, accel_f);
 620
 621                 if(result.touching_ground)
 622                         final_result.touching_ground = true;
 623                 if(result.collides)
 624                         final_result.collides = true;
 625                 if(result.collides_xz)
 626                         final_result.collides_xz = true;
 627                 if(result.standing_on_unloaded)
 628                         final_result.standing_on_unloaded = true;
 629         }
 630         while(dtime_downcount > 0.001);
 631
 632         return final_result;
 633 }
 634 #endif