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 "clientenvironment.h"
  26 #include "serverenvironment.h"
  27 #include "serverobject.h"
  28 #include "profiler.h"
  29
  30 // float error is 10 - 9.96875 = 0.03125
  31 //#define COLL_ZERO 0.032 // broken unit tests
  32 #define COLL_ZERO 0
  33
  34
  35 struct NearbyCollisionInfo {
  36         NearbyCollisionInfo(bool is_ul, bool is_obj, int bouncy,
  37                         const v3s16 &pos, const aabb3f &box) :
  38                 is_unloaded(is_ul),
  39                 is_step_up(false),
  40                 is_object(is_obj),
  41                 bouncy(bouncy),
  42                 position(pos),
  43                 box(box)
  44         {}
  45
  46         bool is_unloaded;
  47         bool is_step_up;
  48         bool is_object;
  49         int bouncy;
  50         v3s16 position;
  51         aabb3f box;
  52 };
  53
  54
  55 // Helper function:
  56 // Checks for collision of a moving aabbox with a static aabbox
  57 // Returns -1 if no collision, 0 if X collision, 1 if Y collision, 2 if Z collision
  58 // The time after which the collision occurs is stored in dtime.
  59 int axisAlignedCollision(
  60                 const aabb3f &staticbox, const aabb3f &movingbox,
  61                 const v3f &speed, f32 d, f32 *dtime)
  62 {
  63         //TimeTaker tt("axisAlignedCollision");
  64
  65         f32 xsize = (staticbox.MaxEdge.X - staticbox.MinEdge.X) - COLL_ZERO;     // reduce box size for solve collision stuck (flying sand)
  66         f32 ysize = (staticbox.MaxEdge.Y - staticbox.MinEdge.Y); // - COLL_ZERO; // Y - no sense for falling, but maybe try later
  67         f32 zsize = (staticbox.MaxEdge.Z - staticbox.MinEdge.Z) - COLL_ZERO;
  68
  69         aabb3f relbox(
  70                         movingbox.MinEdge.X - staticbox.MinEdge.X,
  71                         movingbox.MinEdge.Y - staticbox.MinEdge.Y,
  72                         movingbox.MinEdge.Z - staticbox.MinEdge.Z,
  73                         movingbox.MaxEdge.X - staticbox.MinEdge.X,
  74                         movingbox.MaxEdge.Y - staticbox.MinEdge.Y,
  75                         movingbox.MaxEdge.Z - staticbox.MinEdge.Z
  76         );
  77
  78         if(speed.X > 0) // Check for collision with X- plane
  79         {
  80                 if (relbox.MaxEdge.X <= d) {
  81                         *dtime = -relbox.MaxEdge.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.MinEdge.X > xsize)
  89                 {
  90                         return -1;
  91                 }
  92         }
  93         else if(speed.X < 0) // Check for collision with X+ plane
  94         {
  95                 if (relbox.MinEdge.X >= xsize - d) {
  96                         *dtime = (xsize - relbox.MinEdge.X) / speed.X;
  97                         if ((relbox.MinEdge.Y + speed.Y * (*dtime) < ysize) &&
  98                                         (relbox.MaxEdge.Y + speed.Y * (*dtime) > COLL_ZERO) &&
  99                                         (relbox.MinEdge.Z + speed.Z * (*dtime) < zsize) &&
 100                                         (relbox.MaxEdge.Z + speed.Z * (*dtime) > COLL_ZERO))
 101                                 return 0;
 102                 }
 103                 else if(relbox.MaxEdge.X < 0)
 104                 {
 105                         return -1;
 106                 }
 107         }
 108
 109         // NO else if here
 110
 111         if(speed.Y > 0) // Check for collision with Y- plane
 112         {
 113                 if (relbox.MaxEdge.Y <= d) {
 114                         *dtime = -relbox.MaxEdge.Y / speed.Y;
 115                         if ((relbox.MinEdge.X + speed.X * (*dtime) < xsize) &&
 116                                         (relbox.MaxEdge.X + speed.X * (*dtime) > COLL_ZERO) &&
 117                                         (relbox.MinEdge.Z + speed.Z * (*dtime) < zsize) &&
 118                                         (relbox.MaxEdge.Z + speed.Z * (*dtime) > COLL_ZERO))
 119                                 return 1;
 120                 }
 121                 else if(relbox.MinEdge.Y > ysize)
 122                 {
 123                         return -1;
 124                 }
 125         }
 126         else if(speed.Y < 0) // Check for collision with Y+ plane
 127         {
 128                 if (relbox.MinEdge.Y >= ysize - d) {
 129                         *dtime = (ysize - relbox.MinEdge.Y) / speed.Y;
 130                         if ((relbox.MinEdge.X + speed.X * (*dtime) < xsize) &&
 131                                         (relbox.MaxEdge.X + speed.X * (*dtime) > COLL_ZERO) &&
 132                                         (relbox.MinEdge.Z + speed.Z * (*dtime) < zsize) &&
 133                                         (relbox.MaxEdge.Z + speed.Z * (*dtime) > COLL_ZERO))
 134                                 return 1;
 135                 }
 136                 else if(relbox.MaxEdge.Y < 0)
 137                 {
 138                         return -1;
 139                 }
 140         }
 141
 142         // NO else if here
 143
 144         if(speed.Z > 0) // Check for collision with Z- plane
 145         {
 146                 if (relbox.MaxEdge.Z <= d) {
 147                         *dtime = -relbox.MaxEdge.Z / speed.Z;
 148                         if ((relbox.MinEdge.X + speed.X * (*dtime) < xsize) &&
 149                                         (relbox.MaxEdge.X + speed.X * (*dtime) > COLL_ZERO) &&
 150                                         (relbox.MinEdge.Y + speed.Y * (*dtime) < ysize) &&
 151                                         (relbox.MaxEdge.Y + speed.Y * (*dtime) > COLL_ZERO))
 152                                 return 2;
 153                 }
 154                 //else if(relbox.MinEdge.Z > zsize)
 155                 //{
 156                 //      return -1;
 157                 //}
 158         }
 159         else if(speed.Z < 0) // Check for collision with Z+ plane
 160         {
 161                 if (relbox.MinEdge.Z >= zsize - d) {
 162                         *dtime = (zsize - relbox.MinEdge.Z) / speed.Z;
 163                         if ((relbox.MinEdge.X + speed.X * (*dtime) < xsize) &&
 164                                         (relbox.MaxEdge.X + speed.X * (*dtime) > COLL_ZERO) &&
 165                                         (relbox.MinEdge.Y + speed.Y * (*dtime) < ysize) &&
 166                                         (relbox.MaxEdge.Y + speed.Y * (*dtime) > COLL_ZERO))
 167                                 return 2;
 168                 }
 169                 //else if(relbox.MaxEdge.Z < 0)
 170                 //{
 171                 //      return -1;
 172                 //}
 173         }
 174
 175         return -1;
 176 }
 177
 178 // Helper function:
 179 // Checks if moving the movingbox up by the given distance would hit a ceiling.
 180 bool wouldCollideWithCeiling(
 181                 const std::vector<NearbyCollisionInfo> &cinfo,
 182                 const aabb3f &movingbox,
 183                 f32 y_increase, f32 d)
 184 {
 185         //TimeTaker tt("wouldCollideWithCeiling");
 186
 187         assert(y_increase >= 0);        // pre-condition
 188
 189         for (std::vector<NearbyCollisionInfo>::const_iterator it = cinfo.begin();
 190                         it != cinfo.end(); ++it) {
 191                 const aabb3f &staticbox = it->box;
 192                 if ((movingbox.MaxEdge.Y - d <= staticbox.MinEdge.Y) &&
 193                                 (movingbox.MaxEdge.Y + y_increase > staticbox.MinEdge.Y) &&
 194                                 (movingbox.MinEdge.X < staticbox.MaxEdge.X) &&
 195                                 (movingbox.MaxEdge.X > staticbox.MinEdge.X) &&
 196                                 (movingbox.MinEdge.Z < staticbox.MaxEdge.Z) &&
 197                                 (movingbox.MaxEdge.Z > staticbox.MinEdge.Z))
 198                         return true;
 199         }
 200
 201         return false;
 202 }
 203
 204 static inline void getNeighborConnectingFace(v3s16 p, INodeDefManager *nodedef,
 205                 Map *map, MapNode n, int v, int *neighbors)
 206 {
 207         MapNode n2 = map->getNodeNoEx(p);
 208         if (nodedef->nodeboxConnects(n, n2, v))
 209                 *neighbors |= v;
 210 }
 211
 212 collisionMoveResult collisionMoveSimple(Environment *env, IGameDef *gamedef,
 213                 f32 pos_max_d, const aabb3f &box_0,
 214                 f32 stepheight, f32 dtime,
 215                 v3f *pos_f, v3f *speed_f,
 216                 v3f accel_f, ActiveObject *self,
 217                 bool collideWithObjects)
 218 {
 219         static bool time_notification_done = false;
 220         Map *map = &env->getMap();
 221         //TimeTaker tt("collisionMoveSimple");
 222         ScopeProfiler sp(g_profiler, "collisionMoveSimple avg", SPT_AVG);
 223
 224         collisionMoveResult result;
 225
 226         /*
 227                 Calculate new velocity
 228         */
 229         if (dtime > 0.5) {
 230                 if (!time_notification_done) {
 231                         time_notification_done = true;
 232                         infostream << "collisionMoveSimple: maximum step interval exceeded,"
 233                                         " lost movement details!"<<std::endl;
 234                 }
 235                 dtime = 0.5;
 236         } else {
 237                 time_notification_done = false;
 238         }
 239         *speed_f += accel_f * dtime;
 240
 241         // If there is no speed, there are no collisions
 242         if (speed_f->getLength() == 0)
 243                 return result;
 244
 245         // Limit speed for avoiding hangs
 246         speed_f->Y = rangelim(speed_f->Y, -5000, 5000);
 247         speed_f->X = rangelim(speed_f->X, -5000, 5000);
 248         speed_f->Z = rangelim(speed_f->Z, -5000, 5000);
 249
 250         /*
 251                 Collect node boxes in movement range
 252         */
 253         std::vector<NearbyCollisionInfo> cinfo;
 254         {
 255         //TimeTaker tt2("collisionMoveSimple collect boxes");
 256         ScopeProfiler sp(g_profiler, "collisionMoveSimple collect boxes avg", SPT_AVG);
 257
 258         v3s16 oldpos_i = floatToInt(*pos_f, BS);
 259         v3s16 newpos_i = floatToInt(*pos_f + *speed_f * dtime, BS);
 260         s16 min_x = MYMIN(oldpos_i.X, newpos_i.X) + (box_0.MinEdge.X / BS) - 1;
 261         s16 min_y = MYMIN(oldpos_i.Y, newpos_i.Y) + (box_0.MinEdge.Y / BS) - 1;
 262         s16 min_z = MYMIN(oldpos_i.Z, newpos_i.Z) + (box_0.MinEdge.Z / BS) - 1;
 263         s16 max_x = MYMAX(oldpos_i.X, newpos_i.X) + (box_0.MaxEdge.X / BS) + 1;
 264         s16 max_y = MYMAX(oldpos_i.Y, newpos_i.Y) + (box_0.MaxEdge.Y / BS) + 1;
 265         s16 max_z = MYMAX(oldpos_i.Z, newpos_i.Z) + (box_0.MaxEdge.Z / BS) + 1;
 266
 267         bool any_position_valid = false;
 268
 269         for(s16 x = min_x; x <= max_x; x++)
 270         for(s16 y = min_y; y <= max_y; y++)
 271         for(s16 z = min_z; z <= max_z; z++)
 272         {
 273                 v3s16 p(x,y,z);
 274
 275                 bool is_position_valid;
 276                 MapNode n = map->getNodeNoEx(p, &is_position_valid);
 277
 278                 if (is_position_valid) {
 279                         // Object collides into walkable nodes
 280
 281                         any_position_valid = true;
 282                         INodeDefManager *nodedef = gamedef->getNodeDefManager();
 283                         const ContentFeatures &f = nodedef->get(n);
 284                         if(f.walkable == false)
 285                                 continue;
 286                         int n_bouncy_value = itemgroup_get(f.groups, "bouncy");
 287
 288                         int neighbors = 0;
 289                         if (f.drawtype == NDT_NODEBOX && f.node_box.type == NODEBOX_CONNECTED) {
 290                                 v3s16 p2 = p;
 291
 292                                 p2.Y++;
 293                                 getNeighborConnectingFace(p2, nodedef, map, n, 1, &neighbors);
 294
 295                                 p2 = p;
 296                                 p2.Y--;
 297                                 getNeighborConnectingFace(p2, nodedef, map, n, 2, &neighbors);
 298
 299                                 p2 = p;
 300                                 p2.Z--;
 301                                 getNeighborConnectingFace(p2, nodedef, map, n, 4, &neighbors);
 302
 303                                 p2 = p;
 304                                 p2.X--;
 305                                 getNeighborConnectingFace(p2, nodedef, map, n, 8, &neighbors);
 306
 307                                 p2 = p;
 308                                 p2.Z++;
 309                                 getNeighborConnectingFace(p2, nodedef, map, n, 16, &neighbors);
 310
 311                                 p2 = p;
 312                                 p2.X++;
 313                                 getNeighborConnectingFace(p2, nodedef, map, n, 32, &neighbors);
 314                         }
 315                         std::vector<aabb3f> nodeboxes;
 316                         n.getCollisionBoxes(gamedef->ndef(), &nodeboxes, neighbors);
 317                         for(std::vector<aabb3f>::iterator
 318                                         i = nodeboxes.begin();
 319                                         i != nodeboxes.end(); ++i)
 320                         {
 321                                 aabb3f box = *i;
 322                                 box.MinEdge += v3f(x, y, z)*BS;
 323                                 box.MaxEdge += v3f(x, y, z)*BS;
 324                                 cinfo.push_back(NearbyCollisionInfo(false,
 325                                         false, n_bouncy_value, p, box));
 326                         }
 327                 } else {
 328                         // Collide with unloaded nodes
 329                         aabb3f box = getNodeBox(p, BS);
 330                         cinfo.push_back(NearbyCollisionInfo(true, false, 0, p, box));
 331                 }
 332         }
 333
 334         // Do not move if world has not loaded yet, since custom node boxes
 335         // are not available for collision detection.
 336         if (!any_position_valid) {
 337                 *speed_f = v3f(0, 0, 0);
 338                 return result;
 339         }
 340
 341         } // tt2
 342
 343         if(collideWithObjects)
 344         {
 345                 ScopeProfiler sp(g_profiler, "collisionMoveSimple objects avg", SPT_AVG);
 346                 //TimeTaker tt3("collisionMoveSimple collect object boxes");
 347
 348                 /* add object boxes to cinfo */
 349
 350                 std::vector<ActiveObject*> objects;
 351 #ifndef SERVER
 352                 ClientEnvironment *c_env = dynamic_cast<ClientEnvironment*>(env);
 353                 if (c_env != 0) {
 354                         f32 distance = speed_f->getLength();
 355                         std::vector<DistanceSortedActiveObject> clientobjects;
 356                         c_env->getActiveObjects(*pos_f, distance * 1.5, clientobjects);
 357                         for (size_t i=0; i < clientobjects.size(); i++) {
 358                                 if ((self == 0) || (self != clientobjects[i].obj)) {
 359                                         objects.push_back((ActiveObject*)clientobjects[i].obj);
 360                                 }
 361                         }
 362                 }
 363                 else
 364 #endif
 365                 {
 366                         ServerEnvironment *s_env = dynamic_cast<ServerEnvironment*>(env);
 367                         if (s_env != NULL) {
 368                                 f32 distance = speed_f->getLength();
 369                                 std::vector<u16> s_objects;
 370                                 s_env->getObjectsInsideRadius(s_objects, *pos_f, distance * 1.5);
 371                                 for (std::vector<u16>::iterator iter = s_objects.begin(); iter != s_objects.end(); ++iter) {
 372                                         ServerActiveObject *current = s_env->getActiveObject(*iter);
 373                                         if ((self == 0) || (self != current)) {
 374                                                 objects.push_back((ActiveObject*)current);
 375                                         }
 376                                 }
 377                         }
 378                 }
 379
 380                 for (std::vector<ActiveObject*>::const_iterator iter = objects.begin();
 381                                 iter != objects.end(); ++iter) {
 382                         ActiveObject *object = *iter;
 383
 384                         if (object != NULL) {
 385                                 aabb3f object_collisionbox;
 386                                 if (object->getCollisionBox(&object_collisionbox) &&
 387                                                 object->collideWithObjects()) {
 388                                         cinfo.push_back(NearbyCollisionInfo(false, true, 0, v3s16(), object_collisionbox));
 389                                 }
 390                         }
 391                 }
 392         } //tt3
 393
 394         /*
 395                 Collision detection
 396         */
 397
 398         /*
 399                 Collision uncertainty radius
 400                 Make it a bit larger than the maximum distance of movement
 401         */
 402         f32 d = pos_max_d * 1.1;
 403         // A fairly large value in here makes moving smoother
 404         //f32 d = 0.15*BS;
 405
 406         // This should always apply, otherwise there are glitches
 407         assert(d > pos_max_d);  // invariant
 408
 409         int loopcount = 0;
 410
 411         while(dtime > BS * 1e-10) {
 412                 //TimeTaker tt3("collisionMoveSimple dtime loop");
 413                 ScopeProfiler sp(g_profiler, "collisionMoveSimple dtime loop avg", SPT_AVG);
 414
 415                 // Avoid infinite loop
 416                 loopcount++;
 417                 if (loopcount >= 100) {
 418                         warningstream << "collisionMoveSimple: Loop count exceeded, aborting to avoid infiniite loop" << std::endl;
 419                         break;
 420                 }
 421
 422                 aabb3f movingbox = box_0;
 423                 movingbox.MinEdge += *pos_f;
 424                 movingbox.MaxEdge += *pos_f;
 425
 426                 int nearest_collided = -1;
 427                 f32 nearest_dtime = dtime;
 428                 int nearest_boxindex = -1;
 429
 430                 /*
 431                         Go through every nodebox, find nearest collision
 432                 */
 433                 for (u32 boxindex = 0; boxindex < cinfo.size(); boxindex++) {
 434                         NearbyCollisionInfo box_info = cinfo[boxindex];
 435                         // Ignore if already stepped up this nodebox.
 436                         if (box_info.is_step_up)
 437                                 continue;
 438
 439                         // Find nearest collision of the two boxes (raytracing-like)
 440                         f32 dtime_tmp;
 441                         int collided = axisAlignedCollision(box_info.box,
 442                                         movingbox, *speed_f, d, &dtime_tmp);
 443
 444                         if (collided == -1 || dtime_tmp >= nearest_dtime)
 445                                 continue;
 446
 447                         nearest_dtime = dtime_tmp;
 448                         nearest_collided = collided;
 449                         nearest_boxindex = boxindex;
 450                 }
 451
 452                 if (nearest_collided == -1) {
 453                         // No collision with any collision box.
 454                         *pos_f += *speed_f * dtime;
 455                         dtime = 0;  // Set to 0 to avoid "infinite" loop due to small FP numbers
 456                 } else {
 457                         // Otherwise, a collision occurred.
 458                         NearbyCollisionInfo &nearest_info = cinfo[nearest_boxindex];
 459                         const aabb3f& cbox = nearest_info.box;
 460                         // Check for stairs.
 461                         bool step_up = (nearest_collided != 1) && // must not be Y direction
 462                                         (movingbox.MinEdge.Y < cbox.MaxEdge.Y) &&
 463                                         (movingbox.MinEdge.Y + stepheight > cbox.MaxEdge.Y) &&
 464                                         (!wouldCollideWithCeiling(cinfo, movingbox,
 465                                                         cbox.MaxEdge.Y - movingbox.MinEdge.Y,
 466                                                         d));
 467
 468                         // Get bounce multiplier
 469                         bool bouncy = (nearest_info.bouncy >= 1);
 470                         float bounce = -(float)nearest_info.bouncy / 100.0;
 471
 472                         // Move to the point of collision and reduce dtime by nearest_dtime
 473                         if (nearest_dtime < 0) {
 474                                 // Handle negative nearest_dtime (can be caused by the d allowance)
 475                                 if (!step_up) {
 476                                         if (nearest_collided == 0)
 477                                                 pos_f->X += speed_f->X * nearest_dtime;
 478                                         if (nearest_collided == 1)
 479                                                 pos_f->Y += speed_f->Y * nearest_dtime;
 480                                         if (nearest_collided == 2)
 481                                                 pos_f->Z += speed_f->Z * nearest_dtime;
 482                                 }
 483                         } else {
 484                                 *pos_f += *speed_f * nearest_dtime;
 485                                 dtime -= nearest_dtime;
 486                         }
 487
 488                         bool is_collision = true;
 489                         if (nearest_info.is_unloaded)
 490                                 is_collision = false;
 491
 492                         CollisionInfo info;
 493                         if (nearest_info.is_object)
 494                                 info.type = COLLISION_OBJECT;
 495                         else
 496                                 info.type = COLLISION_NODE;
 497
 498                         info.node_p = nearest_info.position;
 499                         info.bouncy = bouncy;
 500                         info.old_speed = *speed_f;
 501
 502                         // Set the speed component that caused the collision to zero
 503                         if (step_up) {
 504                                 // Special case: Handle stairs
 505                                 nearest_info.is_step_up = true;
 506                                 is_collision = false;
 507                         } else if (nearest_collided == 0) { // X
 508                                 if (fabs(speed_f->X) > BS * 3)
 509                                         speed_f->X *= bounce;
 510                                 else
 511                                         speed_f->X = 0;
 512                                 result.collides = true;
 513                                 result.collides_xz = true;
 514                         } else if (nearest_collided == 1) { // Y
 515                                 if(fabs(speed_f->Y) > BS * 3)
 516                                         speed_f->Y *= bounce;
 517                                 else
 518                                         speed_f->Y = 0;
 519                                 result.collides = true;
 520                         } else if (nearest_collided == 2) { // Z
 521                                 if (fabs(speed_f->Z) > BS * 3)
 522                                         speed_f->Z *= bounce;
 523                                 else
 524                                         speed_f->Z = 0;
 525                                 result.collides = true;
 526                                 result.collides_xz = true;
 527                         }
 528
 529                         info.new_speed = *speed_f;
 530                         if (info.new_speed.getDistanceFrom(info.old_speed) < 0.1 * BS)
 531                                 is_collision = false;
 532
 533                         if (is_collision) {
 534                                 result.collisions.push_back(info);
 535                         }
 536                 }
 537         }
 538
 539         /*
 540                 Final touches: Check if standing on ground, step up stairs.
 541         */
 542         aabb3f box = box_0;
 543         box.MinEdge += *pos_f;
 544         box.MaxEdge += *pos_f;
 545         for (u32 boxindex = 0; boxindex < cinfo.size(); boxindex++) {
 546                 NearbyCollisionInfo &box_info = cinfo[boxindex];
 547                 const aabb3f &cbox = box_info.box;
 548
 549                 /*
 550                         See if the object is touching ground.
 551
 552                         Object touches ground if object's minimum Y is near node's
 553                         maximum Y and object's X-Z-area overlaps with the node's
 554                         X-Z-area.
 555
 556                         Use 0.15*BS so that it is easier to get on a node.
 557                 */
 558                 if (cbox.MaxEdge.X - d > box.MinEdge.X && cbox.MinEdge.X + d < box.MaxEdge.X &&
 559                                 cbox.MaxEdge.Z - d > box.MinEdge.Z &&
 560                                 cbox.MinEdge.Z + d < box.MaxEdge.Z) {
 561                         if (box_info.is_step_up) {
 562                                 pos_f->Y += cbox.MaxEdge.Y - box.MinEdge.Y;
 563                                 box = box_0;
 564                                 box.MinEdge += *pos_f;
 565                                 box.MaxEdge += *pos_f;
 566                         }
 567                         if (fabs(cbox.MaxEdge.Y - box.MinEdge.Y) < 0.15 * BS) {
 568                                 result.touching_ground = true;
 569
 570                                 if (box_info.is_object)
 571                                         result.standing_on_object = true;
 572                                 if (box_info.is_unloaded)
 573                                         result.standing_on_unloaded = true;
 574                         }
 575                 }
 576         }
 577
 578         return result;
 579 }