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 "serverobject.h"
  27 #include "profiler.h"
  28
  29 // float error is 10 - 9.96875 = 0.03125
  30 //#define COLL_ZERO 0.032 // broken unit tests
  31 #define COLL_ZERO 0
  32
  33
  34 struct NearbyCollisionInfo {
  35         NearbyCollisionInfo(bool is_ul, bool is_obj, int bouncy,
  36                         const v3s16 &pos, const aabb3f &box) :
  37                 is_unloaded(is_ul),
  38                 is_step_up(false),
  39                 is_object(is_obj),
  40                 bouncy(bouncy),
  41                 position(pos),
  42                 box(box)
  43         {}
  44
  45         bool is_unloaded;
  46         bool is_step_up;
  47         bool is_object;
  48         int bouncy;
  49         v3s16 position;
  50         aabb3f box;
  51 };
  52
  53
  54 // Helper function:
  55 // Checks for collision of a moving aabbox with a static aabbox
  56 // Returns -1 if no collision, 0 if X collision, 1 if Y collision, 2 if Z collision
  57 // The time after which the collision occurs is stored in dtime.
  58 int axisAlignedCollision(
  59                 const aabb3f &staticbox, const aabb3f &movingbox,
  60                 const v3f &speed, f32 d, f32 *dtime)
  61 {
  62         //TimeTaker tt("axisAlignedCollision");
  63
  64         f32 xsize = (staticbox.MaxEdge.X - staticbox.MinEdge.X) - COLL_ZERO;     // reduce box size for solve collision stuck (flying sand)
  65         f32 ysize = (staticbox.MaxEdge.Y - staticbox.MinEdge.Y); // - COLL_ZERO; // Y - no sense for falling, but maybe try later
  66         f32 zsize = (staticbox.MaxEdge.Z - staticbox.MinEdge.Z) - COLL_ZERO;
  67
  68         aabb3f relbox(
  69                         movingbox.MinEdge.X - staticbox.MinEdge.X,
  70                         movingbox.MinEdge.Y - staticbox.MinEdge.Y,
  71                         movingbox.MinEdge.Z - staticbox.MinEdge.Z,
  72                         movingbox.MaxEdge.X - staticbox.MinEdge.X,
  73                         movingbox.MaxEdge.Y - staticbox.MinEdge.Y,
  74                         movingbox.MaxEdge.Z - staticbox.MinEdge.Z
  75         );
  76
  77         if(speed.X > 0) // Check for collision with X- plane
  78         {
  79                 if (relbox.MaxEdge.X <= d) {
  80                         *dtime = -relbox.MaxEdge.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.MinEdge.X > xsize)
  88                 {
  89                         return -1;
  90                 }
  91         }
  92         else if(speed.X < 0) // Check for collision with X+ plane
  93         {
  94                 if (relbox.MinEdge.X >= xsize - d) {
  95                         *dtime = (xsize - relbox.MinEdge.X) / speed.X;
  96                         if ((relbox.MinEdge.Y + speed.Y * (*dtime) < ysize) &&
  97                                         (relbox.MaxEdge.Y + speed.Y * (*dtime) > COLL_ZERO) &&
  98                                         (relbox.MinEdge.Z + speed.Z * (*dtime) < zsize) &&
  99                                         (relbox.MaxEdge.Z + speed.Z * (*dtime) > COLL_ZERO))
 100                                 return 0;
 101                 }
 102                 else if(relbox.MaxEdge.X < 0)
 103                 {
 104                         return -1;
 105                 }
 106         }
 107
 108         // NO else if here
 109
 110         if(speed.Y > 0) // Check for collision with Y- plane
 111         {
 112                 if (relbox.MaxEdge.Y <= d) {
 113                         *dtime = -relbox.MaxEdge.Y / speed.Y;
 114                         if ((relbox.MinEdge.X + speed.X * (*dtime) < xsize) &&
 115                                         (relbox.MaxEdge.X + speed.X * (*dtime) > COLL_ZERO) &&
 116                                         (relbox.MinEdge.Z + speed.Z * (*dtime) < zsize) &&
 117                                         (relbox.MaxEdge.Z + speed.Z * (*dtime) > COLL_ZERO))
 118                                 return 1;
 119                 }
 120                 else if(relbox.MinEdge.Y > ysize)
 121                 {
 122                         return -1;
 123                 }
 124         }
 125         else if(speed.Y < 0) // Check for collision with Y+ plane
 126         {
 127                 if (relbox.MinEdge.Y >= ysize - d) {
 128                         *dtime = (ysize - relbox.MinEdge.Y) / speed.Y;
 129                         if ((relbox.MinEdge.X + speed.X * (*dtime) < xsize) &&
 130                                         (relbox.MaxEdge.X + speed.X * (*dtime) > COLL_ZERO) &&
 131                                         (relbox.MinEdge.Z + speed.Z * (*dtime) < zsize) &&
 132                                         (relbox.MaxEdge.Z + speed.Z * (*dtime) > COLL_ZERO))
 133                                 return 1;
 134                 }
 135                 else if(relbox.MaxEdge.Y < 0)
 136                 {
 137                         return -1;
 138                 }
 139         }
 140
 141         // NO else if here
 142
 143         if(speed.Z > 0) // Check for collision with Z- plane
 144         {
 145                 if (relbox.MaxEdge.Z <= d) {
 146                         *dtime = -relbox.MaxEdge.Z / speed.Z;
 147                         if ((relbox.MinEdge.X + speed.X * (*dtime) < xsize) &&
 148                                         (relbox.MaxEdge.X + speed.X * (*dtime) > COLL_ZERO) &&
 149                                         (relbox.MinEdge.Y + speed.Y * (*dtime) < ysize) &&
 150                                         (relbox.MaxEdge.Y + speed.Y * (*dtime) > COLL_ZERO))
 151                                 return 2;
 152                 }
 153                 //else if(relbox.MinEdge.Z > zsize)
 154                 //{
 155                 //      return -1;
 156                 //}
 157         }
 158         else if(speed.Z < 0) // Check for collision with Z+ plane
 159         {
 160                 if (relbox.MinEdge.Z >= zsize - d) {
 161                         *dtime = (zsize - relbox.MinEdge.Z) / speed.Z;
 162                         if ((relbox.MinEdge.X + speed.X * (*dtime) < xsize) &&
 163                                         (relbox.MaxEdge.X + speed.X * (*dtime) > COLL_ZERO) &&
 164                                         (relbox.MinEdge.Y + speed.Y * (*dtime) < ysize) &&
 165                                         (relbox.MaxEdge.Y + speed.Y * (*dtime) > COLL_ZERO))
 166                                 return 2;
 167                 }
 168                 //else if(relbox.MaxEdge.Z < 0)
 169                 //{
 170                 //      return -1;
 171                 //}
 172         }
 173
 174         return -1;
 175 }
 176
 177 // Helper function:
 178 // Checks if moving the movingbox up by the given distance would hit a ceiling.
 179 bool wouldCollideWithCeiling(
 180                 const std::vector<NearbyCollisionInfo> &cinfo,
 181                 const aabb3f &movingbox,
 182                 f32 y_increase, f32 d)
 183 {
 184         //TimeTaker tt("wouldCollideWithCeiling");
 185
 186         assert(y_increase >= 0);        // pre-condition
 187
 188         for (std::vector<NearbyCollisionInfo>::const_iterator it = cinfo.begin();
 189                         it != cinfo.end(); ++it) {
 190                 const aabb3f &staticbox = it->box;
 191                 if ((movingbox.MaxEdge.Y - d <= staticbox.MinEdge.Y) &&
 192                                 (movingbox.MaxEdge.Y + y_increase > staticbox.MinEdge.Y) &&
 193                                 (movingbox.MinEdge.X < staticbox.MaxEdge.X) &&
 194                                 (movingbox.MaxEdge.X > staticbox.MinEdge.X) &&
 195                                 (movingbox.MinEdge.Z < staticbox.MaxEdge.Z) &&
 196                                 (movingbox.MaxEdge.Z > staticbox.MinEdge.Z))
 197                         return true;
 198         }
 199
 200         return false;
 201 }
 202
 203 static inline void getNeighborConnectingFace(v3s16 p, INodeDefManager *nodedef,
 204                 Map *map, MapNode n, int v, int *neighbors)
 205 {
 206         MapNode n2 = map->getNodeNoEx(p);
 207         if (nodedef->nodeboxConnects(n, n2, v))
 208                 *neighbors |= v;
 209 }
 210
 211 collisionMoveResult collisionMoveSimple(Environment *env, IGameDef *gamedef,
 212                 f32 pos_max_d, const aabb3f &box_0,
 213                 f32 stepheight, f32 dtime,
 214                 v3f *pos_f, v3f *speed_f,
 215                 v3f accel_f, ActiveObject *self,
 216                 bool collideWithObjects)
 217 {
 218         static bool time_notification_done = false;
 219         Map *map = &env->getMap();
 220         //TimeTaker tt("collisionMoveSimple");
 221         ScopeProfiler sp(g_profiler, "collisionMoveSimple avg", SPT_AVG);
 222
 223         collisionMoveResult result;
 224
 225         /*
 226                 Calculate new velocity
 227         */
 228         if (dtime > 0.5) {
 229                 if (!time_notification_done) {
 230                         time_notification_done = true;
 231                         infostream << "collisionMoveSimple: maximum step interval exceeded,"
 232                                         " lost movement details!"<<std::endl;
 233                 }
 234                 dtime = 0.5;
 235         } else {
 236                 time_notification_done = false;
 237         }
 238         *speed_f += accel_f * dtime;
 239
 240         // If there is no speed, there are no collisions
 241         if (speed_f->getLength() == 0)
 242                 return result;
 243
 244         // Limit speed for avoiding hangs
 245         speed_f->Y = rangelim(speed_f->Y, -5000, 5000);
 246         speed_f->X = rangelim(speed_f->X, -5000, 5000);
 247         speed_f->Z = rangelim(speed_f->Z, -5000, 5000);
 248
 249         /*
 250                 Collect node boxes in movement range
 251         */
 252         std::vector<NearbyCollisionInfo> cinfo;
 253         {
 254         //TimeTaker tt2("collisionMoveSimple collect boxes");
 255         ScopeProfiler sp(g_profiler, "collisionMoveSimple collect boxes avg", SPT_AVG);
 256
 257         v3s16 oldpos_i = floatToInt(*pos_f, BS);
 258         v3s16 newpos_i = floatToInt(*pos_f + *speed_f * dtime, BS);
 259         s16 min_x = MYMIN(oldpos_i.X, newpos_i.X) + (box_0.MinEdge.X / BS) - 1;
 260         s16 min_y = MYMIN(oldpos_i.Y, newpos_i.Y) + (box_0.MinEdge.Y / BS) - 1;
 261         s16 min_z = MYMIN(oldpos_i.Z, newpos_i.Z) + (box_0.MinEdge.Z / BS) - 1;
 262         s16 max_x = MYMAX(oldpos_i.X, newpos_i.X) + (box_0.MaxEdge.X / BS) + 1;
 263         s16 max_y = MYMAX(oldpos_i.Y, newpos_i.Y) + (box_0.MaxEdge.Y / BS) + 1;
 264         s16 max_z = MYMAX(oldpos_i.Z, newpos_i.Z) + (box_0.MaxEdge.Z / BS) + 1;
 265
 266         bool any_position_valid = false;
 267
 268         for(s16 x = min_x; x <= max_x; x++)
 269         for(s16 y = min_y; y <= max_y; y++)
 270         for(s16 z = min_z; z <= max_z; z++)
 271         {
 272                 v3s16 p(x,y,z);
 273
 274                 bool is_position_valid;
 275                 MapNode n = map->getNodeNoEx(p, &is_position_valid);
 276
 277                 if (is_position_valid) {
 278                         // Object collides into walkable nodes
 279
 280                         any_position_valid = true;
 281                         INodeDefManager *nodedef = gamedef->getNodeDefManager();
 282                         const ContentFeatures &f = nodedef->get(n);
 283                         if(f.walkable == false)
 284                                 continue;
 285                         int n_bouncy_value = itemgroup_get(f.groups, "bouncy");
 286
 287                         int neighbors = 0;
 288                         if (f.drawtype == NDT_NODEBOX && f.node_box.type == NODEBOX_CONNECTED) {
 289                                 v3s16 p2 = p;
 290
 291                                 p2.Y++;
 292                                 getNeighborConnectingFace(p2, nodedef, map, n, 1, &neighbors);
 293
 294                                 p2 = p;
 295                                 p2.Y--;
 296                                 getNeighborConnectingFace(p2, nodedef, map, n, 2, &neighbors);
 297
 298                                 p2 = p;
 299                                 p2.Z--;
 300                                 getNeighborConnectingFace(p2, nodedef, map, n, 4, &neighbors);
 301
 302                                 p2 = p;
 303                                 p2.X--;
 304                                 getNeighborConnectingFace(p2, nodedef, map, n, 8, &neighbors);
 305
 306                                 p2 = p;
 307                                 p2.Z++;
 308                                 getNeighborConnectingFace(p2, nodedef, map, n, 16, &neighbors);
 309
 310                                 p2 = p;
 311                                 p2.X++;
 312                                 getNeighborConnectingFace(p2, nodedef, map, n, 32, &neighbors);
 313                         }
 314                         std::vector<aabb3f> nodeboxes;
 315                         n.getCollisionBoxes(gamedef->ndef(), &nodeboxes, neighbors);
 316                         for(std::vector<aabb3f>::iterator
 317                                         i = nodeboxes.begin();
 318                                         i != nodeboxes.end(); ++i)
 319                         {
 320                                 aabb3f box = *i;
 321                                 box.MinEdge += v3f(x, y, z)*BS;
 322                                 box.MaxEdge += v3f(x, y, z)*BS;
 323                                 cinfo.push_back(NearbyCollisionInfo(false,
 324                                         false, n_bouncy_value, p, box));
 325                         }
 326                 } else {
 327                         // Collide with unloaded nodes
 328                         aabb3f box = getNodeBox(p, BS);
 329                         cinfo.push_back(NearbyCollisionInfo(true, false, 0, p, box));
 330                 }
 331         }
 332
 333         // Do not move if world has not loaded yet, since custom node boxes
 334         // are not available for collision detection.
 335         if (!any_position_valid) {
 336                 *speed_f = v3f(0, 0, 0);
 337                 return result;
 338         }
 339
 340         } // tt2
 341
 342         if(collideWithObjects)
 343         {
 344                 ScopeProfiler sp(g_profiler, "collisionMoveSimple objects avg", SPT_AVG);
 345                 //TimeTaker tt3("collisionMoveSimple collect object boxes");
 346
 347                 /* add object boxes to cinfo */
 348
 349                 std::vector<ActiveObject*> objects;
 350 #ifndef SERVER
 351                 ClientEnvironment *c_env = dynamic_cast<ClientEnvironment*>(env);
 352                 if (c_env != 0) {
 353                         f32 distance = speed_f->getLength();
 354                         std::vector<DistanceSortedActiveObject> clientobjects;
 355                         c_env->getActiveObjects(*pos_f, distance * 1.5, clientobjects);
 356                         for (size_t i=0; i < clientobjects.size(); i++) {
 357                                 if ((self == 0) || (self != clientobjects[i].obj)) {
 358                                         objects.push_back((ActiveObject*)clientobjects[i].obj);
 359                                 }
 360                         }
 361                 }
 362                 else
 363 #endif
 364                 {
 365                         ServerEnvironment *s_env = dynamic_cast<ServerEnvironment*>(env);
 366                         if (s_env != NULL) {
 367                                 f32 distance = speed_f->getLength();
 368                                 std::vector<u16> s_objects;
 369                                 s_env->getObjectsInsideRadius(s_objects, *pos_f, distance * 1.5);
 370                                 for (std::vector<u16>::iterator iter = s_objects.begin(); iter != s_objects.end(); ++iter) {
 371                                         ServerActiveObject *current = s_env->getActiveObject(*iter);
 372                                         if ((self == 0) || (self != current)) {
 373                                                 objects.push_back((ActiveObject*)current);
 374                                         }
 375                                 }
 376                         }
 377                 }
 378
 379                 for (std::vector<ActiveObject*>::const_iterator iter = objects.begin();
 380                                 iter != objects.end(); ++iter) {
 381                         ActiveObject *object = *iter;
 382
 383                         if (object != NULL) {
 384                                 aabb3f object_collisionbox;
 385                                 if (object->getCollisionBox(&object_collisionbox) &&
 386                                                 object->collideWithObjects()) {
 387                                         cinfo.push_back(NearbyCollisionInfo(false, true, 0, v3s16(), object_collisionbox));
 388                                 }
 389                         }
 390                 }
 391         } //tt3
 392
 393         /*
 394                 Collision detection
 395         */
 396
 397         /*
 398                 Collision uncertainty radius
 399                 Make it a bit larger than the maximum distance of movement
 400         */
 401         f32 d = pos_max_d * 1.1;
 402         // A fairly large value in here makes moving smoother
 403         //f32 d = 0.15*BS;
 404
 405         // This should always apply, otherwise there are glitches
 406         assert(d > pos_max_d);  // invariant
 407
 408         int loopcount = 0;
 409
 410         while(dtime > BS * 1e-10) {
 411                 //TimeTaker tt3("collisionMoveSimple dtime loop");
 412                 ScopeProfiler sp(g_profiler, "collisionMoveSimple dtime loop avg", SPT_AVG);
 413
 414                 // Avoid infinite loop
 415                 loopcount++;
 416                 if (loopcount >= 100) {
 417                         warningstream << "collisionMoveSimple: Loop count exceeded, aborting to avoid infiniite loop" << std::endl;
 418                         break;
 419                 }
 420
 421                 aabb3f movingbox = box_0;
 422                 movingbox.MinEdge += *pos_f;
 423                 movingbox.MaxEdge += *pos_f;
 424
 425                 int nearest_collided = -1;
 426                 f32 nearest_dtime = dtime;
 427                 int nearest_boxindex = -1;
 428
 429                 /*
 430                         Go through every nodebox, find nearest collision
 431                 */
 432                 for (u32 boxindex = 0; boxindex < cinfo.size(); boxindex++) {
 433                         NearbyCollisionInfo box_info = cinfo[boxindex];
 434                         // Ignore if already stepped up this nodebox.
 435                         if (box_info.is_step_up)
 436                                 continue;
 437
 438                         // Find nearest collision of the two boxes (raytracing-like)
 439                         f32 dtime_tmp;
 440                         int collided = axisAlignedCollision(box_info.box,
 441                                         movingbox, *speed_f, d, &dtime_tmp);
 442
 443                         if (collided == -1 || dtime_tmp >= nearest_dtime)
 444                                 continue;
 445
 446                         nearest_dtime = dtime_tmp;
 447                         nearest_collided = collided;
 448                         nearest_boxindex = boxindex;
 449                 }
 450
 451                 if (nearest_collided == -1) {
 452                         // No collision with any collision box.
 453                         *pos_f += *speed_f * dtime;
 454                         dtime = 0;  // Set to 0 to avoid "infinite" loop due to small FP numbers
 455                 } else {
 456                         // Otherwise, a collision occurred.
 457                         NearbyCollisionInfo &nearest_info = cinfo[nearest_boxindex];
 458                         const aabb3f& cbox = nearest_info.box;
 459                         // Check for stairs.
 460                         bool step_up = (nearest_collided != 1) && // must not be Y direction
 461                                         (movingbox.MinEdge.Y < cbox.MaxEdge.Y) &&
 462                                         (movingbox.MinEdge.Y + stepheight > cbox.MaxEdge.Y) &&
 463                                         (!wouldCollideWithCeiling(cinfo, movingbox,
 464                                                         cbox.MaxEdge.Y - movingbox.MinEdge.Y,
 465                                                         d));
 466
 467                         // Get bounce multiplier
 468                         bool bouncy = (nearest_info.bouncy >= 1);
 469                         float bounce = -(float)nearest_info.bouncy / 100.0;
 470
 471                         // Move to the point of collision and reduce dtime by nearest_dtime
 472                         if (nearest_dtime < 0) {
 473                                 // Handle negative nearest_dtime (can be caused by the d allowance)
 474                                 if (!step_up) {
 475                                         if (nearest_collided == 0)
 476                                                 pos_f->X += speed_f->X * nearest_dtime;
 477                                         if (nearest_collided == 1)
 478                                                 pos_f->Y += speed_f->Y * nearest_dtime;
 479                                         if (nearest_collided == 2)
 480                                                 pos_f->Z += speed_f->Z * nearest_dtime;
 481                                 }
 482                         } else {
 483                                 *pos_f += *speed_f * nearest_dtime;
 484                                 dtime -= nearest_dtime;
 485                         }
 486
 487                         bool is_collision = true;
 488                         if (nearest_info.is_unloaded)
 489                                 is_collision = false;
 490
 491                         CollisionInfo info;
 492                         if (nearest_info.is_object)
 493                                 info.type = COLLISION_OBJECT;
 494                         else
 495                                 info.type = COLLISION_NODE;
 496
 497                         info.node_p = nearest_info.position;
 498                         info.bouncy = bouncy;
 499                         info.old_speed = *speed_f;
 500
 501                         // Set the speed component that caused the collision to zero
 502                         if (step_up) {
 503                                 // Special case: Handle stairs
 504                                 nearest_info.is_step_up = true;
 505                                 is_collision = false;
 506                         } else if (nearest_collided == 0) { // X
 507                                 if (fabs(speed_f->X) > BS * 3)
 508                                         speed_f->X *= bounce;
 509                                 else
 510                                         speed_f->X = 0;
 511                                 result.collides = true;
 512                                 result.collides_xz = true;
 513                         } else if (nearest_collided == 1) { // Y
 514                                 if(fabs(speed_f->Y) > BS * 3)
 515                                         speed_f->Y *= bounce;
 516                                 else
 517                                         speed_f->Y = 0;
 518                                 result.collides = true;
 519                         } else if (nearest_collided == 2) { // Z
 520                                 if (fabs(speed_f->Z) > BS * 3)
 521                                         speed_f->Z *= bounce;
 522                                 else
 523                                         speed_f->Z = 0;
 524                                 result.collides = true;
 525                                 result.collides_xz = true;
 526                         }
 527
 528                         info.new_speed = *speed_f;
 529                         if (info.new_speed.getDistanceFrom(info.old_speed) < 0.1 * BS)
 530                                 is_collision = false;
 531
 532                         if (is_collision) {
 533                                 result.collisions.push_back(info);
 534                         }
 535                 }
 536         }
 537
 538         /*
 539                 Final touches: Check if standing on ground, step up stairs.
 540         */
 541         aabb3f box = box_0;
 542         box.MinEdge += *pos_f;
 543         box.MaxEdge += *pos_f;
 544         for (u32 boxindex = 0; boxindex < cinfo.size(); boxindex++) {
 545                 NearbyCollisionInfo &box_info = cinfo[boxindex];
 546                 const aabb3f &cbox = box_info.box;
 547
 548                 /*
 549                         See if the object is touching ground.
 550
 551                         Object touches ground if object's minimum Y is near node's
 552                         maximum Y and object's X-Z-area overlaps with the node's
 553                         X-Z-area.
 554
 555                         Use 0.15*BS so that it is easier to get on a node.
 556                 */
 557                 if (cbox.MaxEdge.X - d > box.MinEdge.X && cbox.MinEdge.X + d < box.MaxEdge.X &&
 558                                 cbox.MaxEdge.Z - d > box.MinEdge.Z &&
 559                                 cbox.MinEdge.Z + d < box.MaxEdge.Z) {
 560                         if (box_info.is_step_up) {
 561                                 pos_f->Y += cbox.MaxEdge.Y - box.MinEdge.Y;
 562                                 box = box_0;
 563                                 box.MinEdge += *pos_f;
 564                                 box.MaxEdge += *pos_f;
 565                         }
 566                         if (fabs(cbox.MaxEdge.Y - box.MinEdge.Y) < 0.15 * BS) {
 567                                 result.touching_ground = true;
 568
 569                                 if (box_info.is_object)
 570                                         result.standing_on_object = true;
 571                                 if (box_info.is_unloaded)
 572                                         result.standing_on_unloaded = true;
 573                         }
 574                 }
 575         }
 576
 577         return result;
 578 }