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 // broken unit tests
  36 #define COLL_ZERO 0
  37
  38 // Helper function:
  39 // Checks for collision of a moving aabbox with a static aabbox
  40 // Returns -1 if no collision, 0 if X collision, 1 if Y collision, 2 if Z collision
  41 // The time after which the collision occurs is stored in dtime.
  42 int axisAlignedCollision(
  43                 const aabb3f &staticbox, const aabb3f &movingbox,
  44                 const v3f &speed, f32 d, f32 &dtime)
  45 {
  46         //TimeTaker tt("axisAlignedCollision");
  47
  48         f32 xsize = (staticbox.MaxEdge.X - staticbox.MinEdge.X) - COLL_ZERO;     // reduce box size for solve collision stuck (flying sand)
  49         f32 ysize = (staticbox.MaxEdge.Y - staticbox.MinEdge.Y); // - COLL_ZERO; // Y - no sense for falling, but maybe try later
  50         f32 zsize = (staticbox.MaxEdge.Z - staticbox.MinEdge.Z) - COLL_ZERO;
  51
  52         aabb3f relbox(
  53                         movingbox.MinEdge.X - staticbox.MinEdge.X,
  54                         movingbox.MinEdge.Y - staticbox.MinEdge.Y,
  55                         movingbox.MinEdge.Z - staticbox.MinEdge.Z,
  56                         movingbox.MaxEdge.X - staticbox.MinEdge.X,
  57                         movingbox.MaxEdge.Y - staticbox.MinEdge.Y,
  58                         movingbox.MaxEdge.Z - staticbox.MinEdge.Z
  59         );
  60
  61         if(speed.X > 0) // Check for collision with X- plane
  62         {
  63                 if(relbox.MaxEdge.X <= d)
  64                 {
  65                         dtime = - relbox.MaxEdge.X / speed.X;
  66                         if((relbox.MinEdge.Y + speed.Y * dtime < ysize) &&
  67                                         (relbox.MaxEdge.Y + speed.Y * dtime > COLL_ZERO) &&
  68                                         (relbox.MinEdge.Z + speed.Z * dtime < zsize) &&
  69                                         (relbox.MaxEdge.Z + speed.Z * dtime > COLL_ZERO))
  70                                 return 0;
  71                 }
  72                 else if(relbox.MinEdge.X > xsize)
  73                 {
  74                         return -1;
  75                 }
  76         }
  77         else if(speed.X < 0) // Check for collision with X+ plane
  78         {
  79                 if(relbox.MinEdge.X >= xsize - d)
  80                 {
  81                         dtime = (xsize - relbox.MinEdge.X) / speed.X;
  82                         if((relbox.MinEdge.Y + speed.Y * dtime < ysize) &&
  83                                         (relbox.MaxEdge.Y + speed.Y * dtime > COLL_ZERO) &&
  84                                         (relbox.MinEdge.Z + speed.Z * dtime < zsize) &&
  85                                         (relbox.MaxEdge.Z + speed.Z * dtime > COLL_ZERO))
  86                                 return 0;
  87                 }
  88                 else if(relbox.MaxEdge.X < 0)
  89                 {
  90                         return -1;
  91                 }
  92         }
  93
  94         // NO else if here
  95
  96         if(speed.Y > 0) // Check for collision with Y- plane
  97         {
  98                 if(relbox.MaxEdge.Y <= d)
  99                 {
 100                         dtime = - relbox.MaxEdge.Y / speed.Y;
 101                         if((relbox.MinEdge.X + speed.X * dtime < xsize) &&
 102                                         (relbox.MaxEdge.X + speed.X * dtime > COLL_ZERO) &&
 103                                         (relbox.MinEdge.Z + speed.Z * dtime < zsize) &&
 104                                         (relbox.MaxEdge.Z + speed.Z * dtime > COLL_ZERO))
 105                                 return 1;
 106                 }
 107                 else if(relbox.MinEdge.Y > ysize)
 108                 {
 109                         return -1;
 110                 }
 111         }
 112         else if(speed.Y < 0) // Check for collision with Y+ plane
 113         {
 114                 if(relbox.MinEdge.Y >= ysize - d)
 115                 {
 116                         dtime = (ysize - relbox.MinEdge.Y) / speed.Y;
 117                         if((relbox.MinEdge.X + speed.X * dtime < xsize) &&
 118                                         (relbox.MaxEdge.X + speed.X * dtime > COLL_ZERO) &&
 119                                         (relbox.MinEdge.Z + speed.Z * dtime < zsize) &&
 120                                         (relbox.MaxEdge.Z + speed.Z * dtime > COLL_ZERO))
 121                                 return 1;
 122                 }
 123                 else if(relbox.MaxEdge.Y < 0)
 124                 {
 125                         return -1;
 126                 }
 127         }
 128
 129         // NO else if here
 130
 131         if(speed.Z > 0) // Check for collision with Z- plane
 132         {
 133                 if(relbox.MaxEdge.Z <= d)
 134                 {
 135                         dtime = - relbox.MaxEdge.Z / speed.Z;
 136                         if((relbox.MinEdge.X + speed.X * dtime < xsize) &&
 137                                         (relbox.MaxEdge.X + speed.X * dtime > COLL_ZERO) &&
 138                                         (relbox.MinEdge.Y + speed.Y * dtime < ysize) &&
 139                                         (relbox.MaxEdge.Y + speed.Y * dtime > COLL_ZERO))
 140                                 return 2;
 141                 }
 142                 //else if(relbox.MinEdge.Z > zsize)
 143                 //{
 144                 //      return -1;
 145                 //}
 146         }
 147         else if(speed.Z < 0) // Check for collision with Z+ plane
 148         {
 149                 if(relbox.MinEdge.Z >= zsize - d)
 150                 {
 151                         dtime = (zsize - relbox.MinEdge.Z) / speed.Z;
 152                         if((relbox.MinEdge.X + speed.X * dtime < xsize) &&
 153                                         (relbox.MaxEdge.X + speed.X * dtime > COLL_ZERO) &&
 154                                         (relbox.MinEdge.Y + speed.Y * dtime < ysize) &&
 155                                         (relbox.MaxEdge.Y + speed.Y * dtime > COLL_ZERO))
 156                                 return 2;
 157                 }
 158                 //else if(relbox.MaxEdge.Z < 0)
 159                 //{
 160                 //      return -1;
 161                 //}
 162         }
 163
 164         return -1;
 165 }
 166
 167 // Helper function:
 168 // Checks if moving the movingbox up by the given distance would hit a ceiling.
 169 bool wouldCollideWithCeiling(
 170                 const std::vector<aabb3f> &staticboxes,
 171                 const aabb3f &movingbox,
 172                 f32 y_increase, f32 d)
 173 {
 174         //TimeTaker tt("wouldCollideWithCeiling");
 175
 176         assert(y_increase >= 0);
 177
 178         for(std::vector<aabb3f>::const_iterator
 179                         i = staticboxes.begin();
 180                         i != staticboxes.end(); i++)
 181         {
 182                 const aabb3f& staticbox = *i;
 183                 if((movingbox.MaxEdge.Y - d <= staticbox.MinEdge.Y) &&
 184                                 (movingbox.MaxEdge.Y + y_increase > staticbox.MinEdge.Y) &&
 185                                 (movingbox.MinEdge.X < staticbox.MaxEdge.X) &&
 186                                 (movingbox.MaxEdge.X > staticbox.MinEdge.X) &&
 187                                 (movingbox.MinEdge.Z < staticbox.MaxEdge.Z) &&
 188                                 (movingbox.MaxEdge.Z > staticbox.MinEdge.Z))
 189                         return true;
 190         }
 191
 192         return false;
 193 }
 194
 195
 196 collisionMoveResult collisionMoveSimple(Environment *env, IGameDef *gamedef,
 197                 f32 pos_max_d, const aabb3f &box_0,
 198                 f32 stepheight, f32 dtime,
 199                 v3f &pos_f, v3f &speed_f,
 200                 v3f &accel_f,ActiveObject* self,
 201                 bool collideWithObjects)
 202 {
 203         Map *map = &env->getMap();
 204         //TimeTaker tt("collisionMoveSimple");
 205     ScopeProfiler sp(g_profiler, "collisionMoveSimple avg", SPT_AVG);
 206
 207         collisionMoveResult result;
 208
 209         /*
 210                 Calculate new velocity
 211         */
 212         if( dtime > 0.5 ) {
 213                 infostream<<"collisionMoveSimple: WARNING: maximum step interval exceeded, lost movement details!"<<std::endl;
 214                 dtime = 0.5;
 215         }
 216         speed_f += accel_f * dtime;
 217
 218         // If there is no speed, there are no collisions
 219         if(speed_f.getLength() == 0)
 220                 return result;
 221
 222         // Limit speed for avoiding hangs
 223         speed_f.Y=rangelim(speed_f.Y,-5000,5000);
 224         speed_f.X=rangelim(speed_f.X,-5000,5000);
 225         speed_f.Z=rangelim(speed_f.Z,-5000,5000);
 226
 227         /*
 228                 Collect node boxes in movement range
 229         */
 230         std::vector<aabb3f> cboxes;
 231         std::vector<bool> is_unloaded;
 232         std::vector<bool> is_step_up;
 233         std::vector<bool> is_object;
 234         std::vector<int> bouncy_values;
 235         std::vector<v3s16> node_positions;
 236         {
 237         //TimeTaker tt2("collisionMoveSimple collect boxes");
 238     ScopeProfiler sp(g_profiler, "collisionMoveSimple collect boxes avg", SPT_AVG);
 239
 240         v3s16 oldpos_i = floatToInt(pos_f, BS);
 241         v3s16 newpos_i = floatToInt(pos_f + speed_f * dtime, BS);
 242         s16 min_x = MYMIN(oldpos_i.X, newpos_i.X) + (box_0.MinEdge.X / BS) - 1;
 243         s16 min_y = MYMIN(oldpos_i.Y, newpos_i.Y) + (box_0.MinEdge.Y / BS) - 1;
 244         s16 min_z = MYMIN(oldpos_i.Z, newpos_i.Z) + (box_0.MinEdge.Z / BS) - 1;
 245         s16 max_x = MYMAX(oldpos_i.X, newpos_i.X) + (box_0.MaxEdge.X / BS) + 1;
 246         s16 max_y = MYMAX(oldpos_i.Y, newpos_i.Y) + (box_0.MaxEdge.Y / BS) + 1;
 247         s16 max_z = MYMAX(oldpos_i.Z, newpos_i.Z) + (box_0.MaxEdge.Z / BS) + 1;
 248
 249         for(s16 x = min_x; x <= max_x; x++)
 250         for(s16 y = min_y; y <= max_y; y++)
 251         for(s16 z = min_z; z <= max_z; z++)
 252         {
 253                 v3s16 p(x,y,z);
 254                 try{
 255                         // Object collides into walkable nodes
 256                         MapNode n = map->getNode(p);
 257                         const ContentFeatures &f = gamedef->getNodeDefManager()->get(n);
 258                         if(f.walkable == false)
 259                                 continue;
 260                         int n_bouncy_value = itemgroup_get(f.groups, "bouncy");
 261
 262                         std::vector<aabb3f> nodeboxes = n.getNodeBoxes(gamedef->ndef());
 263                         for(std::vector<aabb3f>::iterator
 264                                         i = nodeboxes.begin();
 265                                         i != nodeboxes.end(); i++)
 266                         {
 267                                 aabb3f box = *i;
 268                                 box.MinEdge += v3f(x, y, z)*BS;
 269                                 box.MaxEdge += v3f(x, y, z)*BS;
 270                                 cboxes.push_back(box);
 271                                 is_unloaded.push_back(false);
 272                                 is_step_up.push_back(false);
 273                                 bouncy_values.push_back(n_bouncy_value);
 274                                 node_positions.push_back(p);
 275                                 is_object.push_back(false);
 276                         }
 277                 }
 278                 catch(InvalidPositionException &e)
 279                 {
 280                         // Collide with unloaded nodes
 281                         aabb3f box = getNodeBox(p, BS);
 282                         cboxes.push_back(box);
 283                         is_unloaded.push_back(true);
 284                         is_step_up.push_back(false);
 285                         bouncy_values.push_back(0);
 286                         node_positions.push_back(p);
 287                         is_object.push_back(false);
 288                 }
 289         }
 290         } // tt2
 291
 292         if(collideWithObjects)
 293         {
 294                 ScopeProfiler sp(g_profiler, "collisionMoveSimple objects avg", SPT_AVG);
 295                 //TimeTaker tt3("collisionMoveSimple collect object boxes");
 296
 297                 /* add object boxes to cboxes */
 298
 299
 300                 std::list<ActiveObject*> objects;
 301 #ifndef SERVER
 302                 ClientEnvironment *c_env = dynamic_cast<ClientEnvironment*>(env);
 303                 if (c_env != 0)
 304                 {
 305                         f32 distance = speed_f.getLength();
 306                         std::vector<DistanceSortedActiveObject> clientobjects;
 307                         c_env->getActiveObjects(pos_f,distance * 1.5,clientobjects);
 308                         for (size_t i=0; i < clientobjects.size(); i++)
 309                         {
 310                                 if ((self == 0) || (self != clientobjects[i].obj)) {
 311                                         objects.push_back((ActiveObject*)clientobjects[i].obj);
 312                                 }
 313                         }
 314                 }
 315                 else
 316 #endif
 317                 {
 318                         ServerEnvironment *s_env = dynamic_cast<ServerEnvironment*>(env);
 319                         if (s_env != 0)
 320                         {
 321                                 f32 distance = speed_f.getLength();
 322                                 std::set<u16> s_objects = s_env->getObjectsInsideRadius(pos_f,distance * 1.5);
 323                                 for (std::set<u16>::iterator iter = s_objects.begin(); iter != s_objects.end(); iter++)
 324                                 {
 325                                         ServerActiveObject *current = s_env->getActiveObject(*iter);
 326                                         if ((self == 0) || (self != current)) {
 327                                                 objects.push_back((ActiveObject*)current);
 328                                         }
 329                                 }
 330                         }
 331                 }
 332
 333                 for (std::list<ActiveObject*>::const_iterator iter = objects.begin();iter != objects.end(); ++iter)
 334                 {
 335                         ActiveObject *object = *iter;
 336
 337                         if (object != NULL)
 338                         {
 339                                 aabb3f object_collisionbox;
 340                                 if (object->getCollisionBox(&object_collisionbox) &&
 341                                                 object->collideWithObjects())
 342                                 {
 343                                         cboxes.push_back(object_collisionbox);
 344                                         is_unloaded.push_back(false);
 345                                         is_step_up.push_back(false);
 346                                         bouncy_values.push_back(0);
 347                                         node_positions.push_back(v3s16(0,0,0));
 348                                         is_object.push_back(true);
 349                                 }
 350                         }
 351                 }
 352         } //tt3
 353
 354         assert(cboxes.size() == is_unloaded.size());
 355         assert(cboxes.size() == is_step_up.size());
 356         assert(cboxes.size() == bouncy_values.size());
 357         assert(cboxes.size() == node_positions.size());
 358         assert(cboxes.size() == is_object.size());
 359
 360         /*
 361                 Collision detection
 362         */
 363
 364         /*
 365                 Collision uncertainty radius
 366                 Make it a bit larger than the maximum distance of movement
 367         */
 368         f32 d = pos_max_d * 1.1;
 369         // A fairly large value in here makes moving smoother
 370         //f32 d = 0.15*BS;
 371
 372         // This should always apply, otherwise there are glitches
 373         assert(d > pos_max_d);
 374
 375         int loopcount = 0;
 376
 377         while(dtime > BS*1e-10)
 378         {
 379                 //TimeTaker tt3("collisionMoveSimple dtime loop");
 380         ScopeProfiler sp(g_profiler, "collisionMoveSimple dtime loop avg", SPT_AVG);
 381
 382                 // Avoid infinite loop
 383                 loopcount++;
 384                 if(loopcount >= 100)
 385                 {
 386                         infostream<<"collisionMoveSimple: WARNING: Loop count exceeded, aborting to avoid infiniite loop"<<std::endl;
 387                         dtime = 0;
 388                         break;
 389                 }
 390
 391                 aabb3f movingbox = box_0;
 392                 movingbox.MinEdge += pos_f;
 393                 movingbox.MaxEdge += pos_f;
 394
 395                 int nearest_collided = -1;
 396                 f32 nearest_dtime = dtime;
 397                 u32 nearest_boxindex = -1;
 398
 399                 /*
 400                         Go through every nodebox, find nearest collision
 401                 */
 402                 for(u32 boxindex = 0; boxindex < cboxes.size(); boxindex++)
 403                 {
 404                         // Ignore if already stepped up this nodebox.
 405                         if(is_step_up[boxindex])
 406                                 continue;
 407
 408                         // Find nearest collision of the two boxes (raytracing-like)
 409                         f32 dtime_tmp;
 410                         int collided = axisAlignedCollision(
 411                                         cboxes[boxindex], movingbox, speed_f, d, dtime_tmp);
 412
 413                         if(collided == -1 || dtime_tmp >= nearest_dtime)
 414                                 continue;
 415
 416                         nearest_dtime = dtime_tmp;
 417                         nearest_collided = collided;
 418                         nearest_boxindex = boxindex;
 419                 }
 420
 421                 if(nearest_collided == -1)
 422                 {
 423                         // No collision with any collision box.
 424                         pos_f += speed_f * dtime;
 425                         dtime = 0;  // Set to 0 to avoid "infinite" loop due to small FP numbers
 426                 }
 427                 else
 428                 {
 429                         // Otherwise, a collision occurred.
 430
 431                         const aabb3f& cbox = cboxes[nearest_boxindex];
 432
 433                         // Check for stairs.
 434                         bool step_up = (nearest_collided != 1) && // must not be Y direction
 435                                         (movingbox.MinEdge.Y < cbox.MaxEdge.Y) &&
 436                                         (movingbox.MinEdge.Y + stepheight > cbox.MaxEdge.Y) &&
 437                                         (!wouldCollideWithCeiling(cboxes, movingbox,
 438                                                         cbox.MaxEdge.Y - movingbox.MinEdge.Y,
 439                                                         d));
 440
 441                         // Get bounce multiplier
 442                         bool bouncy = (bouncy_values[nearest_boxindex] >= 1);
 443                         float bounce = -(float)bouncy_values[nearest_boxindex] / 100.0;
 444
 445                         // Move to the point of collision and reduce dtime by nearest_dtime
 446                         if(nearest_dtime < 0)
 447                         {
 448                                 // Handle negative nearest_dtime (can be caused by the d allowance)
 449                                 if(!step_up)
 450                                 {
 451                                         if(nearest_collided == 0)
 452                                                 pos_f.X += speed_f.X * nearest_dtime;
 453                                         if(nearest_collided == 1)
 454                                                 pos_f.Y += speed_f.Y * nearest_dtime;
 455                                         if(nearest_collided == 2)
 456                                                 pos_f.Z += speed_f.Z * nearest_dtime;
 457                                 }
 458                         }
 459                         else
 460                         {
 461                                 pos_f += speed_f * nearest_dtime;
 462                                 dtime -= nearest_dtime;
 463                         }
 464
 465                         bool is_collision = true;
 466                         if(is_unloaded[nearest_boxindex])
 467                                 is_collision = false;
 468
 469                         CollisionInfo info;
 470                         if (is_object[nearest_boxindex]) {
 471                                 info.type = COLLISION_OBJECT;
 472                         }
 473                         else {
 474                                 info.type = COLLISION_NODE;
 475                         }
 476                         info.node_p = node_positions[nearest_boxindex];
 477                         info.bouncy = bouncy;
 478                         info.old_speed = speed_f;
 479
 480                         // Set the speed component that caused the collision to zero
 481                         if(step_up)
 482                         {
 483                                 // Special case: Handle stairs
 484                                 is_step_up[nearest_boxindex] = true;
 485                                 is_collision = false;
 486                         }
 487                         else if(nearest_collided == 0) // X
 488                         {
 489                                 if(fabs(speed_f.X) > BS*3)
 490                                         speed_f.X *= bounce;
 491                                 else
 492                                         speed_f.X = 0;
 493                                 result.collides = true;
 494                                 result.collides_xz = true;
 495                         }
 496                         else if(nearest_collided == 1) // Y
 497                         {
 498                                 if(fabs(speed_f.Y) > BS*3)
 499                                         speed_f.Y *= bounce;
 500                                 else
 501                                         speed_f.Y = 0;
 502                                 result.collides = true;
 503                         }
 504                         else if(nearest_collided == 2) // Z
 505                         {
 506                                 if(fabs(speed_f.Z) > BS*3)
 507                                         speed_f.Z *= bounce;
 508                                 else
 509                                         speed_f.Z = 0;
 510                                 result.collides = true;
 511                                 result.collides_xz = true;
 512                         }
 513
 514                         info.new_speed = speed_f;
 515                         if(info.new_speed.getDistanceFrom(info.old_speed) < 0.1*BS)
 516                                 is_collision = false;
 517
 518                         if(is_collision){
 519                                 result.collisions.push_back(info);
 520                         }
 521                 }
 522         }
 523
 524         /*
 525                 Final touches: Check if standing on ground, step up stairs.
 526         */
 527         aabb3f box = box_0;
 528         box.MinEdge += pos_f;
 529         box.MaxEdge += pos_f;
 530         for(u32 boxindex = 0; boxindex < cboxes.size(); boxindex++)
 531         {
 532                 const aabb3f& cbox = cboxes[boxindex];
 533
 534                 /*
 535                         See if the object is touching ground.
 536
 537                         Object touches ground if object's minimum Y is near node's
 538                         maximum Y and object's X-Z-area overlaps with the node's
 539                         X-Z-area.
 540
 541                         Use 0.15*BS so that it is easier to get on a node.
 542                 */
 543                 if(
 544                                 cbox.MaxEdge.X-d > box.MinEdge.X &&
 545                                 cbox.MinEdge.X+d < box.MaxEdge.X &&
 546                                 cbox.MaxEdge.Z-d > box.MinEdge.Z &&
 547                                 cbox.MinEdge.Z+d < box.MaxEdge.Z
 548                 ){
 549                         if(is_step_up[boxindex])
 550                         {
 551                                 pos_f.Y += (cbox.MaxEdge.Y - box.MinEdge.Y);
 552                                 box = box_0;
 553                                 box.MinEdge += pos_f;
 554                                 box.MaxEdge += pos_f;
 555                         }
 556                         if(fabs(cbox.MaxEdge.Y-box.MinEdge.Y) < 0.15*BS)
 557                         {
 558                                 result.touching_ground = true;
 559                                 if(is_unloaded[boxindex])
 560                                         result.standing_on_unloaded = true;
 561                         }
 562                 }
 563         }
 564
 565         return result;
 566 }
 567
 568 #if 0
 569 // This doesn't seem to work and isn't used
 570 collisionMoveResult collisionMovePrecise(Map *map, IGameDef *gamedef,
 571                 f32 pos_max_d, const aabb3f &box_0,
 572                 f32 stepheight, f32 dtime,
 573                 v3f &pos_f, v3f &speed_f, v3f &accel_f)
 574 {
 575         //TimeTaker tt("collisionMovePrecise");
 576     ScopeProfiler sp(g_profiler, "collisionMovePrecise avg", SPT_AVG);
 577
 578         collisionMoveResult final_result;
 579
 580         // If there is no speed, there are no collisions
 581         if(speed_f.getLength() == 0)
 582                 return final_result;
 583
 584         // Don't allow overly huge dtime
 585         if(dtime > 2.0)
 586                 dtime = 2.0;
 587
 588         f32 dtime_downcount = dtime;
 589
 590         u32 loopcount = 0;
 591         do
 592         {
 593                 loopcount++;
 594
 595                 // Maximum time increment (for collision detection etc)
 596                 // time = distance / speed
 597                 f32 dtime_max_increment = 1.0;
 598                 if(speed_f.getLength() != 0)
 599                         dtime_max_increment = pos_max_d / speed_f.getLength();
 600
 601                 // Maximum time increment is 10ms or lower
 602                 if(dtime_max_increment > 0.01)
 603                         dtime_max_increment = 0.01;
 604
 605                 f32 dtime_part;
 606                 if(dtime_downcount > dtime_max_increment)
 607                 {
 608                         dtime_part = dtime_max_increment;
 609                         dtime_downcount -= dtime_part;
 610                 }
 611                 else
 612                 {
 613                         dtime_part = dtime_downcount;
 614                         /*
 615                                 Setting this to 0 (no -=dtime_part) disables an infinite loop
 616                                 when dtime_part is so small that dtime_downcount -= dtime_part
 617                                 does nothing
 618                         */
 619                         dtime_downcount = 0;
 620                 }
 621
 622                 collisionMoveResult result = collisionMoveSimple(map, gamedef,
 623                                 pos_max_d, box_0, stepheight, dtime_part,
 624                                 pos_f, speed_f, accel_f);
 625
 626                 if(result.touching_ground)
 627                         final_result.touching_ground = true;
 628                 if(result.collides)
 629                         final_result.collides = true;
 630                 if(result.collides_xz)
 631                         final_result.collides_xz = true;
 632                 if(result.standing_on_unloaded)
 633                         final_result.standing_on_unloaded = true;
 634         }
 635         while(dtime_downcount > 0.001);
 636
 637         return final_result;
 638 }
 639 #endif