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, v3f &accel_f,ActiveObject* self)
 200 {
 201         Map *map = &env->getMap();
 202         //TimeTaker tt("collisionMoveSimple");
 203     ScopeProfiler sp(g_profiler, "collisionMoveSimple avg", SPT_AVG);
 204
 205         collisionMoveResult result;
 206
 207         /*
 208                 Calculate new velocity
 209         */
 210         if( dtime > 0.5 ) {
 211                 infostream<<"collisionMoveSimple: WARNING: maximum step interval exceeded, lost movement details!"<<std::endl;
 212                 dtime = 0.5;
 213         }
 214         speed_f += accel_f * dtime;
 215
 216         // If there is no speed, there are no collisions
 217         if(speed_f.getLength() == 0)
 218                 return result;
 219
 220         // Limit speed for avoiding hangs
 221         speed_f.Y=rangelim(speed_f.Y,-5000,5000);
 222         speed_f.X=rangelim(speed_f.X,-5000,5000);
 223         speed_f.Z=rangelim(speed_f.Z,-5000,5000);
 224
 225         /*
 226                 Collect node boxes in movement range
 227         */
 228         std::vector<aabb3f> cboxes;
 229         std::vector<bool> is_unloaded;
 230         std::vector<bool> is_step_up;
 231         std::vector<bool> is_object;
 232         std::vector<int> bouncy_values;
 233         std::vector<v3s16> node_positions;
 234         {
 235         //TimeTaker tt2("collisionMoveSimple collect boxes");
 236     ScopeProfiler sp(g_profiler, "collisionMoveSimple collect boxes avg", SPT_AVG);
 237
 238         v3s16 oldpos_i = floatToInt(pos_f, BS);
 239         v3s16 newpos_i = floatToInt(pos_f + speed_f * dtime, BS);
 240         s16 min_x = MYMIN(oldpos_i.X, newpos_i.X) + (box_0.MinEdge.X / BS) - 1;
 241         s16 min_y = MYMIN(oldpos_i.Y, newpos_i.Y) + (box_0.MinEdge.Y / BS) - 1;
 242         s16 min_z = MYMIN(oldpos_i.Z, newpos_i.Z) + (box_0.MinEdge.Z / BS) - 1;
 243         s16 max_x = MYMAX(oldpos_i.X, newpos_i.X) + (box_0.MaxEdge.X / BS) + 1;
 244         s16 max_y = MYMAX(oldpos_i.Y, newpos_i.Y) + (box_0.MaxEdge.Y / BS) + 1;
 245         s16 max_z = MYMAX(oldpos_i.Z, newpos_i.Z) + (box_0.MaxEdge.Z / BS) + 1;
 246
 247         for(s16 x = min_x; x <= max_x; x++)
 248         for(s16 y = min_y; y <= max_y; y++)
 249         for(s16 z = min_z; z <= max_z; z++)
 250         {
 251                 v3s16 p(x,y,z);
 252                 try{
 253                         // Object collides into walkable nodes
 254                         MapNode n = map->getNode(p);
 255                         const ContentFeatures &f = gamedef->getNodeDefManager()->get(n);
 256                         if(f.walkable == false)
 257                                 continue;
 258                         int n_bouncy_value = itemgroup_get(f.groups, "bouncy");
 259
 260                         std::vector<aabb3f> nodeboxes = n.getNodeBoxes(gamedef->ndef());
 261                         for(std::vector<aabb3f>::iterator
 262                                         i = nodeboxes.begin();
 263                                         i != nodeboxes.end(); i++)
 264                         {
 265                                 aabb3f box = *i;
 266                                 box.MinEdge += v3f(x, y, z)*BS;
 267                                 box.MaxEdge += v3f(x, y, z)*BS;
 268                                 cboxes.push_back(box);
 269                                 is_unloaded.push_back(false);
 270                                 is_step_up.push_back(false);
 271                                 bouncy_values.push_back(n_bouncy_value);
 272                                 node_positions.push_back(p);
 273                                 is_object.push_back(false);
 274                         }
 275                 }
 276                 catch(InvalidPositionException &e)
 277                 {
 278                         // Collide with unloaded nodes
 279                         aabb3f box = getNodeBox(p, BS);
 280                         cboxes.push_back(box);
 281                         is_unloaded.push_back(true);
 282                         is_step_up.push_back(false);
 283                         bouncy_values.push_back(0);
 284                         node_positions.push_back(p);
 285                         is_object.push_back(false);
 286                 }
 287         }
 288         } // tt2
 289
 290         {
 291                 ScopeProfiler sp(g_profiler, "collisionMoveSimple objects avg", SPT_AVG);
 292                 //TimeTaker tt3("collisionMoveSimple collect object boxes");
 293
 294                 /* add object boxes to cboxes */
 295
 296
 297                 std::list<ActiveObject*> objects;
 298 #ifndef SERVER
 299                 ClientEnvironment *c_env = dynamic_cast<ClientEnvironment*>(env);
 300                 if (c_env != 0)
 301                 {
 302                         f32 distance = speed_f.getLength();
 303                         std::vector<DistanceSortedActiveObject> clientobjects;
 304                         c_env->getActiveObjects(pos_f,distance * 1.5,clientobjects);
 305                         for (size_t i=0; i < clientobjects.size(); i++)
 306                         {
 307                                 if ((self == 0) || (self != clientobjects[i].obj)) {
 308                                         objects.push_back((ActiveObject*)clientobjects[i].obj);
 309                                 }
 310                         }
 311                 }
 312                 else
 313 #endif
 314                 {
 315                         ServerEnvironment *s_env = dynamic_cast<ServerEnvironment*>(env);
 316                         if (s_env != 0)
 317                         {
 318                                 f32 distance = speed_f.getLength();
 319                                 std::set<u16> s_objects = s_env->getObjectsInsideRadius(pos_f,distance * 1.5);
 320                                 for (std::set<u16>::iterator iter = s_objects.begin(); iter != s_objects.end(); iter++)
 321                                 {
 322                                         ServerActiveObject *current = s_env->getActiveObject(*iter);
 323                                         if ((self == 0) || (self != current)) {
 324                                                 objects.push_back((ActiveObject*)current);
 325                                         }
 326                                 }
 327                         }
 328                 }
 329
 330                 for (std::list<ActiveObject*>::const_iterator iter = objects.begin();iter != objects.end(); ++iter)
 331                 {
 332                         ActiveObject *object = *iter;
 333
 334                         if (object != NULL)
 335                         {
 336                                 aabb3f object_collisionbox;
 337                                 if (object->getCollisionBox(&object_collisionbox))
 338                                 {
 339                                         cboxes.push_back(object_collisionbox);
 340                                         is_unloaded.push_back(false);
 341                                         is_step_up.push_back(false);
 342                                         bouncy_values.push_back(0);
 343                                         node_positions.push_back(v3s16(0,0,0));
 344                                         is_object.push_back(true);
 345                                 }
 346                         }
 347                 }
 348         } //tt3
 349
 350         assert(cboxes.size() == is_unloaded.size());
 351         assert(cboxes.size() == is_step_up.size());
 352         assert(cboxes.size() == bouncy_values.size());
 353         assert(cboxes.size() == node_positions.size());
 354         assert(cboxes.size() == is_object.size());
 355
 356         /*
 357                 Collision detection
 358         */
 359
 360         /*
 361                 Collision uncertainty radius
 362                 Make it a bit larger than the maximum distance of movement
 363         */
 364         f32 d = pos_max_d * 1.1;
 365         // A fairly large value in here makes moving smoother
 366         //f32 d = 0.15*BS;
 367
 368         // This should always apply, otherwise there are glitches
 369         assert(d > pos_max_d);
 370
 371         int loopcount = 0;
 372
 373         while(dtime > BS*1e-10)
 374         {
 375                 //TimeTaker tt3("collisionMoveSimple dtime loop");
 376         ScopeProfiler sp(g_profiler, "collisionMoveSimple dtime loop avg", SPT_AVG);
 377
 378                 // Avoid infinite loop
 379                 loopcount++;
 380                 if(loopcount >= 100)
 381                 {
 382                         infostream<<"collisionMoveSimple: WARNING: Loop count exceeded, aborting to avoid infiniite loop"<<std::endl;
 383                         dtime = 0;
 384                         break;
 385                 }
 386
 387                 aabb3f movingbox = box_0;
 388                 movingbox.MinEdge += pos_f;
 389                 movingbox.MaxEdge += pos_f;
 390
 391                 int nearest_collided = -1;
 392                 f32 nearest_dtime = dtime;
 393                 u32 nearest_boxindex = -1;
 394
 395                 /*
 396                         Go through every nodebox, find nearest collision
 397                 */
 398                 for(u32 boxindex = 0; boxindex < cboxes.size(); boxindex++)
 399                 {
 400                         // Ignore if already stepped up this nodebox.
 401                         if(is_step_up[boxindex])
 402                                 continue;
 403
 404                         // Find nearest collision of the two boxes (raytracing-like)
 405                         f32 dtime_tmp;
 406                         int collided = axisAlignedCollision(
 407                                         cboxes[boxindex], movingbox, speed_f, d, dtime_tmp);
 408
 409                         if(collided == -1 || dtime_tmp >= nearest_dtime)
 410                                 continue;
 411
 412                         nearest_dtime = dtime_tmp;
 413                         nearest_collided = collided;
 414                         nearest_boxindex = boxindex;
 415                 }
 416
 417                 if(nearest_collided == -1)
 418                 {
 419                         // No collision with any collision box.
 420                         pos_f += speed_f * dtime;
 421                         dtime = 0;  // Set to 0 to avoid "infinite" loop due to small FP numbers
 422                 }
 423                 else
 424                 {
 425                         // Otherwise, a collision occurred.
 426
 427                         const aabb3f& cbox = cboxes[nearest_boxindex];
 428
 429                         // Check for stairs.
 430                         bool step_up = (nearest_collided != 1) && // must not be Y direction
 431                                         (movingbox.MinEdge.Y < cbox.MaxEdge.Y) &&
 432                                         (movingbox.MinEdge.Y + stepheight > cbox.MaxEdge.Y) &&
 433                                         (!wouldCollideWithCeiling(cboxes, movingbox,
 434                                                         cbox.MaxEdge.Y - movingbox.MinEdge.Y,
 435                                                         d));
 436
 437                         // Get bounce multiplier
 438                         bool bouncy = (bouncy_values[nearest_boxindex] >= 1);
 439                         float bounce = -(float)bouncy_values[nearest_boxindex] / 100.0;
 440
 441                         // Move to the point of collision and reduce dtime by nearest_dtime
 442                         if(nearest_dtime < 0)
 443                         {
 444                                 // Handle negative nearest_dtime (can be caused by the d allowance)
 445                                 if(!step_up)
 446                                 {
 447                                         if(nearest_collided == 0)
 448                                                 pos_f.X += speed_f.X * nearest_dtime;
 449                                         if(nearest_collided == 1)
 450                                                 pos_f.Y += speed_f.Y * nearest_dtime;
 451                                         if(nearest_collided == 2)
 452                                                 pos_f.Z += speed_f.Z * nearest_dtime;
 453                                 }
 454                         }
 455                         else
 456                         {
 457                                 pos_f += speed_f * nearest_dtime;
 458                                 dtime -= nearest_dtime;
 459                         }
 460
 461                         bool is_collision = true;
 462                         if(is_unloaded[nearest_boxindex])
 463                                 is_collision = false;
 464
 465                         CollisionInfo info;
 466                         if (is_object[nearest_boxindex]) {
 467                                 info.type = COLLISION_OBJECT;
 468                         }
 469                         else {
 470                                 info.type = COLLISION_NODE;
 471                         }
 472                         info.node_p = node_positions[nearest_boxindex];
 473                         info.bouncy = bouncy;
 474                         info.old_speed = speed_f;
 475
 476                         // Set the speed component that caused the collision to zero
 477                         if(step_up)
 478                         {
 479                                 // Special case: Handle stairs
 480                                 is_step_up[nearest_boxindex] = true;
 481                                 is_collision = false;
 482                         }
 483                         else if(nearest_collided == 0) // X
 484                         {
 485                                 if(fabs(speed_f.X) > BS*3)
 486                                         speed_f.X *= bounce;
 487                                 else
 488                                         speed_f.X = 0;
 489                                 result.collides = true;
 490                                 result.collides_xz = true;
 491                         }
 492                         else if(nearest_collided == 1) // Y
 493                         {
 494                                 if(fabs(speed_f.Y) > BS*3)
 495                                         speed_f.Y *= bounce;
 496                                 else
 497                                         speed_f.Y = 0;
 498                                 result.collides = true;
 499                         }
 500                         else if(nearest_collided == 2) // Z
 501                         {
 502                                 if(fabs(speed_f.Z) > BS*3)
 503                                         speed_f.Z *= bounce;
 504                                 else
 505                                         speed_f.Z = 0;
 506                                 result.collides = true;
 507                                 result.collides_xz = true;
 508                         }
 509
 510                         info.new_speed = speed_f;
 511                         if(info.new_speed.getDistanceFrom(info.old_speed) < 0.1*BS)
 512                                 is_collision = false;
 513
 514                         if(is_collision){
 515                                 result.collisions.push_back(info);
 516                         }
 517                 }
 518         }
 519
 520         /*
 521                 Final touches: Check if standing on ground, step up stairs.
 522         */
 523         aabb3f box = box_0;
 524         box.MinEdge += pos_f;
 525         box.MaxEdge += pos_f;
 526         for(u32 boxindex = 0; boxindex < cboxes.size(); boxindex++)
 527         {
 528                 const aabb3f& cbox = cboxes[boxindex];
 529
 530                 /*
 531                         See if the object is touching ground.
 532
 533                         Object touches ground if object's minimum Y is near node's
 534                         maximum Y and object's X-Z-area overlaps with the node's
 535                         X-Z-area.
 536
 537                         Use 0.15*BS so that it is easier to get on a node.
 538                 */
 539                 if(
 540                                 cbox.MaxEdge.X-d > box.MinEdge.X &&
 541                                 cbox.MinEdge.X+d < box.MaxEdge.X &&
 542                                 cbox.MaxEdge.Z-d > box.MinEdge.Z &&
 543                                 cbox.MinEdge.Z+d < box.MaxEdge.Z
 544                 ){
 545                         if(is_step_up[boxindex])
 546                         {
 547                                 pos_f.Y += (cbox.MaxEdge.Y - box.MinEdge.Y);
 548                                 box = box_0;
 549                                 box.MinEdge += pos_f;
 550                                 box.MaxEdge += pos_f;
 551                         }
 552                         if(fabs(cbox.MaxEdge.Y-box.MinEdge.Y) < 0.15*BS)
 553                         {
 554                                 result.touching_ground = true;
 555                                 if(is_unloaded[boxindex])
 556                                         result.standing_on_unloaded = true;
 557                         }
 558                 }
 559         }
 560
 561         return result;
 562 }
 563
 564 #if 0
 565 // This doesn't seem to work and isn't used
 566 collisionMoveResult collisionMovePrecise(Map *map, IGameDef *gamedef,
 567                 f32 pos_max_d, const aabb3f &box_0,
 568                 f32 stepheight, f32 dtime,
 569                 v3f &pos_f, v3f &speed_f, v3f &accel_f)
 570 {
 571         //TimeTaker tt("collisionMovePrecise");
 572     ScopeProfiler sp(g_profiler, "collisionMovePrecise avg", SPT_AVG);
 573
 574         collisionMoveResult final_result;
 575
 576         // If there is no speed, there are no collisions
 577         if(speed_f.getLength() == 0)
 578                 return final_result;
 579
 580         // Don't allow overly huge dtime
 581         if(dtime > 2.0)
 582                 dtime = 2.0;
 583
 584         f32 dtime_downcount = dtime;
 585
 586         u32 loopcount = 0;
 587         do
 588         {
 589                 loopcount++;
 590
 591                 // Maximum time increment (for collision detection etc)
 592                 // time = distance / speed
 593                 f32 dtime_max_increment = 1.0;
 594                 if(speed_f.getLength() != 0)
 595                         dtime_max_increment = pos_max_d / speed_f.getLength();
 596
 597                 // Maximum time increment is 10ms or lower
 598                 if(dtime_max_increment > 0.01)
 599                         dtime_max_increment = 0.01;
 600
 601                 f32 dtime_part;
 602                 if(dtime_downcount > dtime_max_increment)
 603                 {
 604                         dtime_part = dtime_max_increment;
 605                         dtime_downcount -= dtime_part;
 606                 }
 607                 else
 608                 {
 609                         dtime_part = dtime_downcount;
 610                         /*
 611                                 Setting this to 0 (no -=dtime_part) disables an infinite loop
 612                                 when dtime_part is so small that dtime_downcount -= dtime_part
 613                                 does nothing
 614                         */
 615                         dtime_downcount = 0;
 616                 }
 617
 618                 collisionMoveResult result = collisionMoveSimple(map, gamedef,
 619                                 pos_max_d, box_0, stepheight, dtime_part,
 620                                 pos_f, speed_f, accel_f);
 621
 622                 if(result.touching_ground)
 623                         final_result.touching_ground = true;
 624                 if(result.collides)
 625                         final_result.collides = true;
 626                 if(result.collides_xz)
 627                         final_result.collides_xz = true;
 628                 if(result.standing_on_unloaded)
 629                         final_result.standing_on_unloaded = true;
 630         }
 631         while(dtime_downcount > 0.001);
 632
 633         return final_result;
 634 }
 635 #endif