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 #ifndef SERVER
  26 #include "clientenvironment.h"
  27 #endif
  28 #include "serverenvironment.h"
  29 #include "serverobject.h"
  30 #include "util/timetaker.h"
  31 #include "profiler.h"
  32
  33 // float error is 10 - 9.96875 = 0.03125
  34 //#define COLL_ZERO 0.032 // broken unit tests
  35 #define COLL_ZERO 0
  36
  37
  38 struct NearbyCollisionInfo {
  39         NearbyCollisionInfo(bool is_ul, bool is_obj, int bouncy,
  40                         const v3s16 &pos, const aabb3f &box) :
  41                 is_unloaded(is_ul),
  42                 is_step_up(false),
  43                 is_object(is_obj),
  44                 bouncy(bouncy),
  45                 position(pos),
  46                 box(box)
  47         {}
  48
  49         bool is_unloaded;
  50         bool is_step_up;
  51         bool is_object;
  52         int bouncy;
  53         v3s16 position;
  54         aabb3f box;
  55 };
  56
  57
  58 // Helper function:
  59 // Checks for collision of a moving aabbox with a static aabbox
  60 // Returns -1 if no collision, 0 if X collision, 1 if Y collision, 2 if Z collision
  61 // The time after which the collision occurs is stored in dtime.
  62 int axisAlignedCollision(
  63                 const aabb3f &staticbox, const aabb3f &movingbox,
  64                 const v3f &speed, f32 d, f32 *dtime)
  65 {
  66         //TimeTaker tt("axisAlignedCollision");
  67
  68         f32 xsize = (staticbox.MaxEdge.X - staticbox.MinEdge.X) - COLL_ZERO;     // reduce box size for solve collision stuck (flying sand)
  69         f32 ysize = (staticbox.MaxEdge.Y - staticbox.MinEdge.Y); // - COLL_ZERO; // Y - no sense for falling, but maybe try later
  70         f32 zsize = (staticbox.MaxEdge.Z - staticbox.MinEdge.Z) - COLL_ZERO;
  71
  72         aabb3f relbox(
  73                         movingbox.MinEdge.X - staticbox.MinEdge.X,
  74                         movingbox.MinEdge.Y - staticbox.MinEdge.Y,
  75                         movingbox.MinEdge.Z - staticbox.MinEdge.Z,
  76                         movingbox.MaxEdge.X - staticbox.MinEdge.X,
  77                         movingbox.MaxEdge.Y - staticbox.MinEdge.Y,
  78                         movingbox.MaxEdge.Z - staticbox.MinEdge.Z
  79         );
  80
  81         if(speed.X > 0) // Check for collision with X- plane
  82         {
  83                 if (relbox.MaxEdge.X <= d) {
  84                         *dtime = -relbox.MaxEdge.X / speed.X;
  85                         if ((relbox.MinEdge.Y + speed.Y * (*dtime) < ysize) &&
  86                                         (relbox.MaxEdge.Y + speed.Y * (*dtime) > COLL_ZERO) &&
  87                                         (relbox.MinEdge.Z + speed.Z * (*dtime) < zsize) &&
  88                                         (relbox.MaxEdge.Z + speed.Z * (*dtime) > COLL_ZERO))
  89                                 return 0;
  90                 }
  91                 else if(relbox.MinEdge.X > xsize)
  92                 {
  93                         return -1;
  94                 }
  95         }
  96         else if(speed.X < 0) // Check for collision with X+ plane
  97         {
  98                 if (relbox.MinEdge.X >= xsize - d) {
  99                         *dtime = (xsize - relbox.MinEdge.X) / speed.X;
 100                         if ((relbox.MinEdge.Y + speed.Y * (*dtime) < ysize) &&
 101                                         (relbox.MaxEdge.Y + speed.Y * (*dtime) > COLL_ZERO) &&
 102                                         (relbox.MinEdge.Z + speed.Z * (*dtime) < zsize) &&
 103                                         (relbox.MaxEdge.Z + speed.Z * (*dtime) > COLL_ZERO))
 104                                 return 0;
 105                 }
 106                 else if(relbox.MaxEdge.X < 0)
 107                 {
 108                         return -1;
 109                 }
 110         }
 111
 112         // NO else if here
 113
 114         if(speed.Y > 0) // Check for collision with Y- plane
 115         {
 116                 if (relbox.MaxEdge.Y <= d) {
 117                         *dtime = -relbox.MaxEdge.Y / speed.Y;
 118                         if ((relbox.MinEdge.X + speed.X * (*dtime) < xsize) &&
 119                                         (relbox.MaxEdge.X + speed.X * (*dtime) > COLL_ZERO) &&
 120                                         (relbox.MinEdge.Z + speed.Z * (*dtime) < zsize) &&
 121                                         (relbox.MaxEdge.Z + speed.Z * (*dtime) > COLL_ZERO))
 122                                 return 1;
 123                 }
 124                 else if(relbox.MinEdge.Y > ysize)
 125                 {
 126                         return -1;
 127                 }
 128         }
 129         else if(speed.Y < 0) // Check for collision with Y+ plane
 130         {
 131                 if (relbox.MinEdge.Y >= ysize - d) {
 132                         *dtime = (ysize - relbox.MinEdge.Y) / speed.Y;
 133                         if ((relbox.MinEdge.X + speed.X * (*dtime) < xsize) &&
 134                                         (relbox.MaxEdge.X + speed.X * (*dtime) > COLL_ZERO) &&
 135                                         (relbox.MinEdge.Z + speed.Z * (*dtime) < zsize) &&
 136                                         (relbox.MaxEdge.Z + speed.Z * (*dtime) > COLL_ZERO))
 137                                 return 1;
 138                 }
 139                 else if(relbox.MaxEdge.Y < 0)
 140                 {
 141                         return -1;
 142                 }
 143         }
 144
 145         // NO else if here
 146
 147         if(speed.Z > 0) // Check for collision with Z- plane
 148         {
 149                 if (relbox.MaxEdge.Z <= d) {
 150                         *dtime = -relbox.MaxEdge.Z / speed.Z;
 151                         if ((relbox.MinEdge.X + speed.X * (*dtime) < xsize) &&
 152                                         (relbox.MaxEdge.X + speed.X * (*dtime) > COLL_ZERO) &&
 153                                         (relbox.MinEdge.Y + speed.Y * (*dtime) < ysize) &&
 154                                         (relbox.MaxEdge.Y + speed.Y * (*dtime) > COLL_ZERO))
 155                                 return 2;
 156                 }
 157                 //else if(relbox.MinEdge.Z > zsize)
 158                 //{
 159                 //      return -1;
 160                 //}
 161         }
 162         else if(speed.Z < 0) // Check for collision with Z+ plane
 163         {
 164                 if (relbox.MinEdge.Z >= zsize - d) {
 165                         *dtime = (zsize - relbox.MinEdge.Z) / speed.Z;
 166                         if ((relbox.MinEdge.X + speed.X * (*dtime) < xsize) &&
 167                                         (relbox.MaxEdge.X + speed.X * (*dtime) > COLL_ZERO) &&
 168                                         (relbox.MinEdge.Y + speed.Y * (*dtime) < ysize) &&
 169                                         (relbox.MaxEdge.Y + speed.Y * (*dtime) > COLL_ZERO))
 170                                 return 2;
 171                 }
 172                 //else if(relbox.MaxEdge.Z < 0)
 173                 //{
 174                 //      return -1;
 175                 //}
 176         }
 177
 178         return -1;
 179 }
 180
 181 // Helper function:
 182 // Checks if moving the movingbox up by the given distance would hit a ceiling.
 183 bool wouldCollideWithCeiling(
 184                 const std::vector<NearbyCollisionInfo> &cinfo,
 185                 const aabb3f &movingbox,
 186                 f32 y_increase, f32 d)
 187 {
 188         //TimeTaker tt("wouldCollideWithCeiling");
 189
 190         assert(y_increase >= 0);        // pre-condition
 191
 192         for (std::vector<NearbyCollisionInfo>::const_iterator it = cinfo.begin();
 193                         it != cinfo.end(); ++it) {
 194                 const aabb3f &staticbox = it->box;
 195                 if ((movingbox.MaxEdge.Y - d <= staticbox.MinEdge.Y) &&
 196                                 (movingbox.MaxEdge.Y + y_increase > staticbox.MinEdge.Y) &&
 197                                 (movingbox.MinEdge.X < staticbox.MaxEdge.X) &&
 198                                 (movingbox.MaxEdge.X > staticbox.MinEdge.X) &&
 199                                 (movingbox.MinEdge.Z < staticbox.MaxEdge.Z) &&
 200                                 (movingbox.MaxEdge.Z > staticbox.MinEdge.Z))
 201                         return true;
 202         }
 203
 204         return false;
 205 }
 206
 207 static inline void getNeighborConnectingFace(v3s16 p, INodeDefManager *nodedef,
 208                 Map *map, MapNode n, int v, int *neighbors)
 209 {
 210         MapNode n2 = map->getNodeNoEx(p);
 211         if (nodedef->nodeboxConnects(n, n2, v))
 212                 *neighbors |= v;
 213 }
 214
 215 collisionMoveResult collisionMoveSimple(Environment *env, IGameDef *gamedef,
 216                 f32 pos_max_d, const aabb3f &box_0,
 217                 f32 stepheight, f32 dtime,
 218                 v3f *pos_f, v3f *speed_f,
 219                 v3f accel_f, ActiveObject *self,
 220                 bool collideWithObjects)
 221 {
 222         static bool time_notification_done = false;
 223         Map *map = &env->getMap();
 224         //TimeTaker tt("collisionMoveSimple");
 225         ScopeProfiler sp(g_profiler, "collisionMoveSimple avg", SPT_AVG);
 226
 227         collisionMoveResult result;
 228
 229         /*
 230                 Calculate new velocity
 231         */
 232         if (dtime > 0.5) {
 233                 if (!time_notification_done) {
 234                         time_notification_done = true;
 235                         infostream << "collisionMoveSimple: maximum step interval exceeded,"
 236                                         " lost movement details!"<<std::endl;
 237                 }
 238                 dtime = 0.5;
 239         } else {
 240                 time_notification_done = false;
 241         }
 242         *speed_f += accel_f * dtime;
 243
 244         // If there is no speed, there are no collisions
 245         if (speed_f->getLength() == 0)
 246                 return result;
 247
 248         // Limit speed for avoiding hangs
 249         speed_f->Y = rangelim(speed_f->Y, -5000, 5000);
 250         speed_f->X = rangelim(speed_f->X, -5000, 5000);
 251         speed_f->Z = rangelim(speed_f->Z, -5000, 5000);
 252
 253         /*
 254                 Collect node boxes in movement range
 255         */
 256         std::vector<NearbyCollisionInfo> cinfo;
 257         {
 258         //TimeTaker tt2("collisionMoveSimple collect boxes");
 259         ScopeProfiler sp(g_profiler, "collisionMoveSimple collect boxes avg", SPT_AVG);
 260
 261         v3s16 oldpos_i = floatToInt(*pos_f, BS);
 262         v3s16 newpos_i = floatToInt(*pos_f + *speed_f * dtime, BS);
 263         s16 min_x = MYMIN(oldpos_i.X, newpos_i.X) + (box_0.MinEdge.X / BS) - 1;
 264         s16 min_y = MYMIN(oldpos_i.Y, newpos_i.Y) + (box_0.MinEdge.Y / BS) - 1;
 265         s16 min_z = MYMIN(oldpos_i.Z, newpos_i.Z) + (box_0.MinEdge.Z / BS) - 1;
 266         s16 max_x = MYMAX(oldpos_i.X, newpos_i.X) + (box_0.MaxEdge.X / BS) + 1;
 267         s16 max_y = MYMAX(oldpos_i.Y, newpos_i.Y) + (box_0.MaxEdge.Y / BS) + 1;
 268         s16 max_z = MYMAX(oldpos_i.Z, newpos_i.Z) + (box_0.MaxEdge.Z / BS) + 1;
 269
 270         bool any_position_valid = false;
 271
 272         for(s16 x = min_x; x <= max_x; x++)
 273         for(s16 y = min_y; y <= max_y; y++)
 274         for(s16 z = min_z; z <= max_z; z++)
 275         {
 276                 v3s16 p(x,y,z);
 277
 278                 bool is_position_valid;
 279                 MapNode n = map->getNodeNoEx(p, &is_position_valid);
 280
 281                 if (is_position_valid) {
 282                         // Object collides into walkable nodes
 283
 284                         any_position_valid = true;
 285                         INodeDefManager *nodedef = gamedef->getNodeDefManager();
 286                         const ContentFeatures &f = nodedef->get(n);
 287                         if(f.walkable == false)
 288                                 continue;
 289                         int n_bouncy_value = itemgroup_get(f.groups, "bouncy");
 290
 291                         int neighbors = 0;
 292                         if (f.drawtype == NDT_NODEBOX && f.node_box.type == NODEBOX_CONNECTED) {
 293                                 v3s16 p2 = p;
 294
 295                                 p2.Y++;
 296                                 getNeighborConnectingFace(p2, nodedef, map, n, 1, &neighbors);
 297
 298                                 p2 = p;
 299                                 p2.Y--;
 300                                 getNeighborConnectingFace(p2, nodedef, map, n, 2, &neighbors);
 301
 302                                 p2 = p;
 303                                 p2.Z--;
 304                                 getNeighborConnectingFace(p2, nodedef, map, n, 4, &neighbors);
 305
 306                                 p2 = p;
 307                                 p2.X--;
 308                                 getNeighborConnectingFace(p2, nodedef, map, n, 8, &neighbors);
 309
 310                                 p2 = p;
 311                                 p2.Z++;
 312                                 getNeighborConnectingFace(p2, nodedef, map, n, 16, &neighbors);
 313
 314                                 p2 = p;
 315                                 p2.X++;
 316                                 getNeighborConnectingFace(p2, nodedef, map, n, 32, &neighbors);
 317                         }
 318                         std::vector<aabb3f> nodeboxes;
 319                         n.getCollisionBoxes(gamedef->ndef(), &nodeboxes, neighbors);
 320                         for(std::vector<aabb3f>::iterator
 321                                         i = nodeboxes.begin();
 322                                         i != nodeboxes.end(); ++i)
 323                         {
 324                                 aabb3f box = *i;
 325                                 box.MinEdge += v3f(x, y, z)*BS;
 326                                 box.MaxEdge += v3f(x, y, z)*BS;
 327                                 cinfo.push_back(NearbyCollisionInfo(false,
 328                                         false, n_bouncy_value, p, box));
 329                         }
 330                 } else {
 331                         // Collide with unloaded nodes
 332                         aabb3f box = getNodeBox(p, BS);
 333                         cinfo.push_back(NearbyCollisionInfo(true, false, 0, p, box));
 334                 }
 335         }
 336
 337         // Do not move if world has not loaded yet, since custom node boxes
 338         // are not available for collision detection.
 339         if (!any_position_valid) {
 340                 *speed_f = v3f(0, 0, 0);
 341                 return result;
 342         }
 343
 344         } // tt2
 345
 346         if(collideWithObjects)
 347         {
 348                 ScopeProfiler sp(g_profiler, "collisionMoveSimple objects avg", SPT_AVG);
 349                 //TimeTaker tt3("collisionMoveSimple collect object boxes");
 350
 351                 /* add object boxes to cinfo */
 352
 353                 std::vector<ActiveObject*> objects;
 354 #ifndef SERVER
 355                 ClientEnvironment *c_env = dynamic_cast<ClientEnvironment*>(env);
 356                 if (c_env != 0) {
 357                         f32 distance = speed_f->getLength();
 358                         std::vector<DistanceSortedActiveObject> clientobjects;
 359                         c_env->getActiveObjects(*pos_f, distance * 1.5, clientobjects);
 360                         for (size_t i=0; i < clientobjects.size(); i++) {
 361                                 if ((self == 0) || (self != clientobjects[i].obj)) {
 362                                         objects.push_back((ActiveObject*)clientobjects[i].obj);
 363                                 }
 364                         }
 365                 }
 366                 else
 367 #endif
 368                 {
 369                         ServerEnvironment *s_env = dynamic_cast<ServerEnvironment*>(env);
 370                         if (s_env != NULL) {
 371                                 f32 distance = speed_f->getLength();
 372                                 std::vector<u16> s_objects;
 373                                 s_env->getObjectsInsideRadius(s_objects, *pos_f, distance * 1.5);
 374                                 for (std::vector<u16>::iterator iter = s_objects.begin(); iter != s_objects.end(); ++iter) {
 375                                         ServerActiveObject *current = s_env->getActiveObject(*iter);
 376                                         if ((self == 0) || (self != current)) {
 377                                                 objects.push_back((ActiveObject*)current);
 378                                         }
 379                                 }
 380                         }
 381                 }
 382
 383                 for (std::vector<ActiveObject*>::const_iterator iter = objects.begin();
 384                                 iter != objects.end(); ++iter) {
 385                         ActiveObject *object = *iter;
 386
 387                         if (object != NULL) {
 388                                 aabb3f object_collisionbox;
 389                                 if (object->getCollisionBox(&object_collisionbox) &&
 390                                                 object->collideWithObjects()) {
 391                                         cinfo.push_back(NearbyCollisionInfo(false, true, 0, v3s16(), object_collisionbox));
 392                                 }
 393                         }
 394                 }
 395         } //tt3
 396
 397         /*
 398                 Collision detection
 399         */
 400
 401         /*
 402                 Collision uncertainty radius
 403                 Make it a bit larger than the maximum distance of movement
 404         */
 405         f32 d = pos_max_d * 1.1;
 406         // A fairly large value in here makes moving smoother
 407         //f32 d = 0.15*BS;
 408
 409         // This should always apply, otherwise there are glitches
 410         assert(d > pos_max_d);  // invariant
 411
 412         int loopcount = 0;
 413
 414         while(dtime > BS * 1e-10) {
 415                 //TimeTaker tt3("collisionMoveSimple dtime loop");
 416                 ScopeProfiler sp(g_profiler, "collisionMoveSimple dtime loop avg", SPT_AVG);
 417
 418                 // Avoid infinite loop
 419                 loopcount++;
 420                 if (loopcount >= 100) {
 421                         warningstream << "collisionMoveSimple: Loop count exceeded, aborting to avoid infiniite loop" << std::endl;
 422                         break;
 423                 }
 424
 425                 aabb3f movingbox = box_0;
 426                 movingbox.MinEdge += *pos_f;
 427                 movingbox.MaxEdge += *pos_f;
 428
 429                 int nearest_collided = -1;
 430                 f32 nearest_dtime = dtime;
 431                 int nearest_boxindex = -1;
 432
 433                 /*
 434                         Go through every nodebox, find nearest collision
 435                 */
 436                 for (u32 boxindex = 0; boxindex < cinfo.size(); boxindex++) {
 437                         NearbyCollisionInfo box_info = cinfo[boxindex];
 438                         // Ignore if already stepped up this nodebox.
 439                         if (box_info.is_step_up)
 440                                 continue;
 441
 442                         // Find nearest collision of the two boxes (raytracing-like)
 443                         f32 dtime_tmp;
 444                         int collided = axisAlignedCollision(box_info.box,
 445                                         movingbox, *speed_f, d, &dtime_tmp);
 446
 447                         if (collided == -1 || dtime_tmp >= nearest_dtime)
 448                                 continue;
 449
 450                         nearest_dtime = dtime_tmp;
 451                         nearest_collided = collided;
 452                         nearest_boxindex = boxindex;
 453                 }
 454
 455                 if (nearest_collided == -1) {
 456                         // No collision with any collision box.
 457                         *pos_f += *speed_f * dtime;
 458                         dtime = 0;  // Set to 0 to avoid "infinite" loop due to small FP numbers
 459                 } else {
 460                         // Otherwise, a collision occurred.
 461                         NearbyCollisionInfo &nearest_info = cinfo[nearest_boxindex];
 462                         const aabb3f& cbox = nearest_info.box;
 463                         // Check for stairs.
 464                         bool step_up = (nearest_collided != 1) && // must not be Y direction
 465                                         (movingbox.MinEdge.Y < cbox.MaxEdge.Y) &&
 466                                         (movingbox.MinEdge.Y + stepheight > cbox.MaxEdge.Y) &&
 467                                         (!wouldCollideWithCeiling(cinfo, movingbox,
 468                                                         cbox.MaxEdge.Y - movingbox.MinEdge.Y,
 469                                                         d));
 470
 471                         // Get bounce multiplier
 472                         bool bouncy = (nearest_info.bouncy >= 1);
 473                         float bounce = -(float)nearest_info.bouncy / 100.0;
 474
 475                         // Move to the point of collision and reduce dtime by nearest_dtime
 476                         if (nearest_dtime < 0) {
 477                                 // Handle negative nearest_dtime (can be caused by the d allowance)
 478                                 if (!step_up) {
 479                                         if (nearest_collided == 0)
 480                                                 pos_f->X += speed_f->X * nearest_dtime;
 481                                         if (nearest_collided == 1)
 482                                                 pos_f->Y += speed_f->Y * nearest_dtime;
 483                                         if (nearest_collided == 2)
 484                                                 pos_f->Z += speed_f->Z * nearest_dtime;
 485                                 }
 486                         } else {
 487                                 *pos_f += *speed_f * nearest_dtime;
 488                                 dtime -= nearest_dtime;
 489                         }
 490
 491                         bool is_collision = true;
 492                         if (nearest_info.is_unloaded)
 493                                 is_collision = false;
 494
 495                         CollisionInfo info;
 496                         if (nearest_info.is_object)
 497                                 info.type = COLLISION_OBJECT;
 498                         else
 499                                 info.type = COLLISION_NODE;
 500
 501                         info.node_p = nearest_info.position;
 502                         info.bouncy = bouncy;
 503                         info.old_speed = *speed_f;
 504
 505                         // Set the speed component that caused the collision to zero
 506                         if (step_up) {
 507                                 // Special case: Handle stairs
 508                                 nearest_info.is_step_up = true;
 509                                 is_collision = false;
 510                         } else if (nearest_collided == 0) { // X
 511                                 if (fabs(speed_f->X) > BS * 3)
 512                                         speed_f->X *= bounce;
 513                                 else
 514                                         speed_f->X = 0;
 515                                 result.collides = true;
 516                                 result.collides_xz = true;
 517                         } else if (nearest_collided == 1) { // Y
 518                                 if(fabs(speed_f->Y) > BS * 3)
 519                                         speed_f->Y *= bounce;
 520                                 else
 521                                         speed_f->Y = 0;
 522                                 result.collides = true;
 523                         } else if (nearest_collided == 2) { // Z
 524                                 if (fabs(speed_f->Z) > BS * 3)
 525                                         speed_f->Z *= bounce;
 526                                 else
 527                                         speed_f->Z = 0;
 528                                 result.collides = true;
 529                                 result.collides_xz = true;
 530                         }
 531
 532                         info.new_speed = *speed_f;
 533                         if (info.new_speed.getDistanceFrom(info.old_speed) < 0.1 * BS)
 534                                 is_collision = false;
 535
 536                         if (is_collision) {
 537                                 result.collisions.push_back(info);
 538                         }
 539                 }
 540         }
 541
 542         /*
 543                 Final touches: Check if standing on ground, step up stairs.
 544         */
 545         aabb3f box = box_0;
 546         box.MinEdge += *pos_f;
 547         box.MaxEdge += *pos_f;
 548         for (u32 boxindex = 0; boxindex < cinfo.size(); boxindex++) {
 549                 NearbyCollisionInfo &box_info = cinfo[boxindex];
 550                 const aabb3f &cbox = box_info.box;
 551
 552                 /*
 553                         See if the object is touching ground.
 554
 555                         Object touches ground if object's minimum Y is near node's
 556                         maximum Y and object's X-Z-area overlaps with the node's
 557                         X-Z-area.
 558
 559                         Use 0.15*BS so that it is easier to get on a node.
 560                 */
 561                 if (cbox.MaxEdge.X - d > box.MinEdge.X && cbox.MinEdge.X + d < box.MaxEdge.X &&
 562                                 cbox.MaxEdge.Z - d > box.MinEdge.Z &&
 563                                 cbox.MinEdge.Z + d < box.MaxEdge.Z) {
 564                         if (box_info.is_step_up) {
 565                                 pos_f->Y += cbox.MaxEdge.Y - box.MinEdge.Y;
 566                                 box = box_0;
 567                                 box.MinEdge += *pos_f;
 568                                 box.MaxEdge += *pos_f;
 569                         }
 570                         if (fabs(cbox.MaxEdge.Y - box.MinEdge.Y) < 0.15 * BS) {
 571                                 result.touching_ground = true;
 572
 573                                 if (box_info.is_object)
 574                                         result.standing_on_object = true;
 575                                 if (box_info.is_unloaded)
 576                                         result.standing_on_unloaded = true;
 577                         }
 578                 }
 579         }
 580
 581         return result;
 582 }