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 <cmath>
  22 #include "mapblock.h"
  23 #include "map.h"
  24 #include "nodedef.h"
  25 #include "gamedef.h"
  26 #ifndef SERVER
  27 #include "client/clientenvironment.h"
  28 #include "client/localplayer.h"
  29 #endif
  30 #include "serverenvironment.h"
  31 #include "server/serveractiveobject.h"
  32 #include "util/timetaker.h"
  33 #include "profiler.h"
  34
  35 #ifdef __FAST_MATH__
  36 #warning "-ffast-math is known to cause bugs in collision code, do not use!"
  37 #endif
  38
  39 struct NearbyCollisionInfo {
  40         NearbyCollisionInfo(bool is_ul, bool is_obj, int bouncy,
  41                         const v3s16 &pos, const aabb3f &box) :
  42                 is_unloaded(is_ul),
  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 = false;
  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 CollisionAxis axisAlignedCollision(
  63                 const aabb3f &staticbox, const aabb3f &movingbox,
  64                 const v3f &speed, f32 *dtime)
  65 {
  66         //TimeTaker tt("axisAlignedCollision");
  67
  68         aabb3f relbox(
  69                         movingbox.MaxEdge.X - movingbox.MinEdge.X + staticbox.MaxEdge.X - staticbox.MinEdge.X,                                          // sum of the widths
  70                         movingbox.MaxEdge.Y - movingbox.MinEdge.Y + staticbox.MaxEdge.Y - staticbox.MinEdge.Y,
  71                         movingbox.MaxEdge.Z - movingbox.MinEdge.Z + staticbox.MaxEdge.Z - staticbox.MinEdge.Z,
  72                         std::max(movingbox.MaxEdge.X, staticbox.MaxEdge.X) - std::min(movingbox.MinEdge.X, staticbox.MinEdge.X),        //outer bounding 'box' dimensions
  73                         std::max(movingbox.MaxEdge.Y, staticbox.MaxEdge.Y) - std::min(movingbox.MinEdge.Y, staticbox.MinEdge.Y),
  74                         std::max(movingbox.MaxEdge.Z, staticbox.MaxEdge.Z) - std::min(movingbox.MinEdge.Z, staticbox.MinEdge.Z)
  75         );
  76
  77         const f32 dtime_max = *dtime;
  78         const f32 inner_margin = -1.5f;
  79         f32 distance;
  80         f32 time;
  81
  82         if (speed.X) {
  83                 distance = relbox.MaxEdge.X - relbox.MinEdge.X;
  84
  85                 *dtime = distance >= 0 ? std::abs(distance / speed.X) : -std::abs(distance / speed.X);
  86                 time = std::max(*dtime, 0.0f);
  87
  88                 if (distance > inner_margin) {
  89                         if (*dtime <= dtime_max) {
  90                                 if ((speed.X > 0 && staticbox.MaxEdge.X > movingbox.MaxEdge.X) ||
  91                                                 (speed.X < 0 && staticbox.MinEdge.X < movingbox.MinEdge.X)) {
  92                                         if (
  93                                                 (std::max(movingbox.MaxEdge.Y + speed.Y * time, staticbox.MaxEdge.Y)
  94                                                         - std::min(movingbox.MinEdge.Y + speed.Y * time, staticbox.MinEdge.Y)
  95                                                         - relbox.MinEdge.Y < 0) &&
  96                                                 (std::max(movingbox.MaxEdge.Z + speed.Z * time, staticbox.MaxEdge.Z)
  97                                                         - std::min(movingbox.MinEdge.Z + speed.Z * time, staticbox.MinEdge.Z)
  98                                                         - relbox.MinEdge.Z < 0)
  99                                                 )
 100                                                 return COLLISION_AXIS_X;
 101                                 }
 102                         } else {
 103                                 return COLLISION_AXIS_NONE;
 104                         }
 105                 }
 106         }
 107
 108         // NO else if here
 109
 110         if (speed.Y) {
 111                 distance = relbox.MaxEdge.Y - relbox.MinEdge.Y;
 112
 113                 *dtime = distance >= 0 ? std::abs(distance / speed.Y) : -std::abs(distance / speed.Y);
 114                 time = std::max(*dtime, 0.0f);
 115
 116                 if (distance > inner_margin) {
 117                         if (*dtime <= dtime_max) {
 118                                 if ((speed.Y > 0 && staticbox.MaxEdge.Y > movingbox.MaxEdge.Y) ||
 119                                                 (speed.Y < 0 && staticbox.MinEdge.Y < movingbox.MinEdge.Y)) {
 120                                         if (
 121                                                 (std::max(movingbox.MaxEdge.X + speed.X * time, staticbox.MaxEdge.X)
 122                                                         - std::min(movingbox.MinEdge.X + speed.X * time, staticbox.MinEdge.X)
 123                                                         - relbox.MinEdge.X < 0) &&
 124                                                 (std::max(movingbox.MaxEdge.Z + speed.Z * time, staticbox.MaxEdge.Z)
 125                                                         - std::min(movingbox.MinEdge.Z + speed.Z * time, staticbox.MinEdge.Z)
 126                                                         - relbox.MinEdge.Z < 0)
 127                                                 )
 128                                                 return COLLISION_AXIS_Y;
 129                                 }
 130                         } else {
 131                                 return COLLISION_AXIS_NONE;
 132                         }
 133                 }
 134         }
 135
 136         // NO else if here
 137
 138         if (speed.Z) {
 139                 distance = relbox.MaxEdge.Z - relbox.MinEdge.Z;
 140
 141                 *dtime = distance >= 0 ? std::abs(distance / speed.Z) : -std::abs(distance / speed.Z);
 142                 time = std::max(*dtime, 0.0f);
 143
 144                 if (distance > inner_margin) {
 145                         if (*dtime <= dtime_max) {
 146                                 if ((speed.Z > 0 && staticbox.MaxEdge.Z > movingbox.MaxEdge.Z) ||
 147                                                 (speed.Z < 0 && staticbox.MinEdge.Z < movingbox.MinEdge.Z)) {
 148                                         if (
 149                                                 (std::max(movingbox.MaxEdge.X + speed.X * time, staticbox.MaxEdge.X)
 150                                                         - std::min(movingbox.MinEdge.X + speed.X * time, staticbox.MinEdge.X)
 151                                                         - relbox.MinEdge.X < 0) &&
 152                                                 (std::max(movingbox.MaxEdge.Y + speed.Y * time, staticbox.MaxEdge.Y)
 153                                                         - std::min(movingbox.MinEdge.Y + speed.Y * time, staticbox.MinEdge.Y)
 154                                                         - relbox.MinEdge.Y < 0)
 155                                                 )
 156                                                 return COLLISION_AXIS_Z;
 157                                 }
 158                         }
 159                 }
 160         }
 161
 162         return COLLISION_AXIS_NONE;
 163 }
 164
 165 // Helper function:
 166 // Checks if moving the movingbox up by the given distance would hit a ceiling.
 167 bool wouldCollideWithCeiling(
 168                 const std::vector<NearbyCollisionInfo> &cinfo,
 169                 const aabb3f &movingbox,
 170                 f32 y_increase, f32 d)
 171 {
 172         //TimeTaker tt("wouldCollideWithCeiling");
 173
 174         assert(y_increase >= 0);        // pre-condition
 175
 176         for (const auto &it : cinfo) {
 177                 const aabb3f &staticbox = it.box;
 178                 if ((movingbox.MaxEdge.Y - d <= staticbox.MinEdge.Y) &&
 179                                 (movingbox.MaxEdge.Y + y_increase > staticbox.MinEdge.Y) &&
 180                                 (movingbox.MinEdge.X < staticbox.MaxEdge.X) &&
 181                                 (movingbox.MaxEdge.X > staticbox.MinEdge.X) &&
 182                                 (movingbox.MinEdge.Z < staticbox.MaxEdge.Z) &&
 183                                 (movingbox.MaxEdge.Z > staticbox.MinEdge.Z))
 184                         return true;
 185         }
 186
 187         return false;
 188 }
 189
 190 static inline void getNeighborConnectingFace(const v3s16 &p,
 191         const NodeDefManager *nodedef, Map *map, MapNode n, int v, int *neighbors)
 192 {
 193         MapNode n2 = map->getNode(p);
 194         if (nodedef->nodeboxConnects(n, n2, v))
 195                 *neighbors |= v;
 196 }
 197
 198 collisionMoveResult collisionMoveSimple(Environment *env, IGameDef *gamedef,
 199                 f32 pos_max_d, const aabb3f &box_0,
 200                 f32 stepheight, f32 dtime,
 201                 v3f *pos_f, v3f *speed_f,
 202                 v3f accel_f, ActiveObject *self,
 203                 bool collideWithObjects)
 204 {
 205         static bool time_notification_done = false;
 206         Map *map = &env->getMap();
 207
 208         ScopeProfiler sp(g_profiler, "collisionMoveSimple()", SPT_AVG);
 209
 210         collisionMoveResult result;
 211
 212         /*
 213                 Calculate new velocity
 214         */
 215         if (dtime > 0.5f) {
 216                 if (!time_notification_done) {
 217                         time_notification_done = true;
 218                         infostream << "collisionMoveSimple: maximum step interval exceeded,"
 219                                         " lost movement details!"<<std::endl;
 220                 }
 221                 dtime = 0.5f;
 222         } else {
 223                 time_notification_done = false;
 224         }
 225         *speed_f += accel_f * dtime;
 226
 227         // If there is no speed, there are no collisions
 228         if (speed_f->getLength() == 0)
 229                 return result;
 230
 231         // Limit speed for avoiding hangs
 232         speed_f->Y = rangelim(speed_f->Y, -5000, 5000);
 233         speed_f->X = rangelim(speed_f->X, -5000, 5000);
 234         speed_f->Z = rangelim(speed_f->Z, -5000, 5000);
 235
 236         /*
 237                 Collect node boxes in movement range
 238         */
 239         std::vector<NearbyCollisionInfo> cinfo;
 240         {
 241         //TimeTaker tt2("collisionMoveSimple collect boxes");
 242         ScopeProfiler sp2(g_profiler, "collisionMoveSimple(): collect boxes", SPT_AVG);
 243
 244         v3f newpos_f = *pos_f + *speed_f * dtime;
 245         v3f minpos_f(
 246                 MYMIN(pos_f->X, newpos_f.X),
 247                 MYMIN(pos_f->Y, newpos_f.Y) + 0.01f * BS, // bias rounding, player often at +/-n.5
 248                 MYMIN(pos_f->Z, newpos_f.Z)
 249         );
 250         v3f maxpos_f(
 251                 MYMAX(pos_f->X, newpos_f.X),
 252                 MYMAX(pos_f->Y, newpos_f.Y),
 253                 MYMAX(pos_f->Z, newpos_f.Z)
 254         );
 255         v3s16 min = floatToInt(minpos_f + box_0.MinEdge, BS) - v3s16(1, 1, 1);
 256         v3s16 max = floatToInt(maxpos_f + box_0.MaxEdge, BS) + v3s16(1, 1, 1);
 257
 258         bool any_position_valid = false;
 259
 260         v3s16 p;
 261         for (p.X = min.X; p.X <= max.X; p.X++)
 262         for (p.Y = min.Y; p.Y <= max.Y; p.Y++)
 263         for (p.Z = min.Z; p.Z <= max.Z; p.Z++) {
 264                 bool is_position_valid;
 265                 MapNode n = map->getNode(p, &is_position_valid);
 266
 267                 if (is_position_valid && n.getContent() != CONTENT_IGNORE) {
 268                         // Object collides into walkable nodes
 269
 270                         any_position_valid = true;
 271                         const NodeDefManager *nodedef = gamedef->getNodeDefManager();
 272                         const ContentFeatures &f = nodedef->get(n);
 273
 274                         if (!f.walkable)
 275                                 continue;
 276
 277                         int n_bouncy_value = itemgroup_get(f.groups, "bouncy");
 278
 279                         int neighbors = 0;
 280                         if (f.drawtype == NDT_NODEBOX &&
 281                                 f.node_box.type == NODEBOX_CONNECTED) {
 282                                 v3s16 p2 = p;
 283
 284                                 p2.Y++;
 285                                 getNeighborConnectingFace(p2, nodedef, map, n, 1, &neighbors);
 286
 287                                 p2 = p;
 288                                 p2.Y--;
 289                                 getNeighborConnectingFace(p2, nodedef, map, n, 2, &neighbors);
 290
 291                                 p2 = p;
 292                                 p2.Z--;
 293                                 getNeighborConnectingFace(p2, nodedef, map, n, 4, &neighbors);
 294
 295                                 p2 = p;
 296                                 p2.X--;
 297                                 getNeighborConnectingFace(p2, nodedef, map, n, 8, &neighbors);
 298
 299                                 p2 = p;
 300                                 p2.Z++;
 301                                 getNeighborConnectingFace(p2, nodedef, map, n, 16, &neighbors);
 302
 303                                 p2 = p;
 304                                 p2.X++;
 305                                 getNeighborConnectingFace(p2, nodedef, map, n, 32, &neighbors);
 306                         }
 307                         std::vector<aabb3f> nodeboxes;
 308                         n.getCollisionBoxes(gamedef->ndef(), &nodeboxes, neighbors);
 309
 310                         // Calculate float position only once
 311                         v3f posf = intToFloat(p, BS);
 312                         for (auto box : nodeboxes) {
 313                                 box.MinEdge += posf;
 314                                 box.MaxEdge += posf;
 315                                 cinfo.emplace_back(false, false, n_bouncy_value, p, box);
 316                         }
 317                 } else {
 318                         // Collide with unloaded nodes (position invalid) and loaded
 319                         // CONTENT_IGNORE nodes (position valid)
 320                         aabb3f box = getNodeBox(p, BS);
 321                         cinfo.emplace_back(true, false, 0, p, box);
 322                 }
 323         }
 324
 325         // Do not move if world has not loaded yet, since custom node boxes
 326         // are not available for collision detection.
 327         // This also intentionally occurs in the case of the object being positioned
 328         // solely on loaded CONTENT_IGNORE nodes, no matter where they come from.
 329         if (!any_position_valid) {
 330                 *speed_f = v3f(0, 0, 0);
 331                 return result;
 332         }
 333
 334         } // tt2
 335
 336         if(collideWithObjects)
 337         {
 338                 /* add object boxes to cinfo */
 339
 340                 std::vector<ActiveObject*> objects;
 341 #ifndef SERVER
 342                 ClientEnvironment *c_env = dynamic_cast<ClientEnvironment*>(env);
 343                 if (c_env != 0) {
 344                         // Calculate distance by speed, add own extent and 1.5m of tolerance
 345                         f32 distance = speed_f->getLength() * dtime +
 346                                 box_0.getExtent().getLength() + 1.5f * BS;
 347                         std::vector<DistanceSortedActiveObject> clientobjects;
 348                         c_env->getActiveObjects(*pos_f, distance, clientobjects);
 349
 350                         for (auto &clientobject : clientobjects) {
 351                                 // Do collide with everything but itself and the parent CAO
 352                                 if (!self || (self != clientobject.obj &&
 353                                                 self != clientobject.obj->getParent())) {
 354                                         objects.push_back((ActiveObject*) clientobject.obj);
 355                                 }
 356                         }
 357                 }
 358                 else
 359 #endif
 360                 {
 361                         ServerEnvironment *s_env = dynamic_cast<ServerEnvironment*>(env);
 362                         if (s_env != NULL) {
 363                                 // Calculate distance by speed, add own extent and 1.5m of tolerance
 364                                 f32 distance = speed_f->getLength() * dtime +
 365                                         box_0.getExtent().getLength() + 1.5f * BS;
 366
 367                                 // search for objects which are not us, or we are not its parent
 368                                 // we directly use the callback to populate the result to prevent
 369                                 // a useless result loop here
 370                                 auto include_obj_cb = [self, &objects] (ServerActiveObject *obj) {
 371                                         if (!self || (self != obj && self != obj->getParent())) {
 372                                                 objects.push_back((ActiveObject *)obj);
 373                                         }
 374                                         return false;
 375                                 };
 376
 377                                 std::vector<ServerActiveObject *> s_objects;
 378                                 s_env->getObjectsInsideRadius(s_objects, *pos_f, distance, include_obj_cb);
 379                         }
 380                 }
 381
 382                 for (std::vector<ActiveObject*>::const_iterator iter = objects.begin();
 383                                 iter != objects.end(); ++iter) {
 384                         ActiveObject *object = *iter;
 385
 386                         if (object) {
 387                                 aabb3f object_collisionbox;
 388                                 if (object->getCollisionBox(&object_collisionbox) &&
 389                                                 object->collideWithObjects()) {
 390                                         cinfo.emplace_back(false, true, 0, v3s16(), object_collisionbox);
 391                                 }
 392                         }
 393                 }
 394 #ifndef SERVER
 395                 if (self && c_env) {
 396                         LocalPlayer *lplayer = c_env->getLocalPlayer();
 397                         if (lplayer->getParent() == nullptr) {
 398                                 aabb3f lplayer_collisionbox = lplayer->getCollisionbox();
 399                                 v3f lplayer_pos = lplayer->getPosition();
 400                                 lplayer_collisionbox.MinEdge += lplayer_pos;
 401                                 lplayer_collisionbox.MaxEdge += lplayer_pos;
 402                                 cinfo.emplace_back(false, true, 0, v3s16(), lplayer_collisionbox);
 403                         }
 404                 }
 405 #endif
 406         } //tt3
 407
 408         /*
 409                 Collision detection
 410         */
 411
 412         f32 d = 0.0f;
 413
 414         int loopcount = 0;
 415
 416         while(dtime > BS * 1e-10f) {
 417                 // Avoid infinite loop
 418                 loopcount++;
 419                 if (loopcount >= 100) {
 420                         warningstream << "collisionMoveSimple: Loop count exceeded, aborting to avoid infiniite loop" << std::endl;
 421                         break;
 422                 }
 423
 424                 aabb3f movingbox = box_0;
 425                 movingbox.MinEdge += *pos_f;
 426                 movingbox.MaxEdge += *pos_f;
 427
 428                 CollisionAxis nearest_collided = COLLISION_AXIS_NONE;
 429                 f32 nearest_dtime = dtime;
 430                 int nearest_boxindex = -1;
 431
 432                 /*
 433                         Go through every nodebox, find nearest collision
 434                 */
 435                 for (u32 boxindex = 0; boxindex < cinfo.size(); boxindex++) {
 436                         const NearbyCollisionInfo &box_info = cinfo[boxindex];
 437                         // Ignore if already stepped up this nodebox.
 438                         if (box_info.is_step_up)
 439                                 continue;
 440
 441                         // Find nearest collision of the two boxes (raytracing-like)
 442                         f32 dtime_tmp = nearest_dtime;
 443                         CollisionAxis collided = axisAlignedCollision(box_info.box,
 444                                         movingbox, *speed_f, &dtime_tmp);
 445
 446                         if (collided == -1 || dtime_tmp >= nearest_dtime)
 447                                 continue;
 448
 449                         nearest_dtime = dtime_tmp;
 450                         nearest_collided = collided;
 451                         nearest_boxindex = boxindex;
 452                 }
 453
 454                 if (nearest_collided == COLLISION_AXIS_NONE) {
 455                         // No collision with any collision box.
 456                         *pos_f += *speed_f * dtime;
 457                         dtime = 0;  // Set to 0 to avoid "infinite" loop due to small FP numbers
 458                 } else {
 459                         // Otherwise, a collision occurred.
 460                         NearbyCollisionInfo &nearest_info = cinfo[nearest_boxindex];
 461                         const aabb3f& cbox = nearest_info.box;
 462
 463                         //movingbox except moved to the horizontal position it would be after step up
 464                         aabb3f stepbox = movingbox;
 465                         stepbox.MinEdge.X += speed_f->X * dtime;
 466                         stepbox.MinEdge.Z += speed_f->Z * dtime;
 467                         stepbox.MaxEdge.X += speed_f->X * dtime;
 468                         stepbox.MaxEdge.Z += speed_f->Z * dtime;
 469                         // Check for stairs.
 470                         bool step_up = (nearest_collided != COLLISION_AXIS_Y) && // must not be Y direction
 471                                         (movingbox.MinEdge.Y < cbox.MaxEdge.Y) &&
 472                                         (movingbox.MinEdge.Y + stepheight > cbox.MaxEdge.Y) &&
 473                                         (!wouldCollideWithCeiling(cinfo, stepbox,
 474                                                         cbox.MaxEdge.Y - movingbox.MinEdge.Y,
 475                                                         d));
 476
 477                         // Get bounce multiplier
 478                         float bounce = -(float)nearest_info.bouncy / 100.0f;
 479
 480                         // Move to the point of collision and reduce dtime by nearest_dtime
 481                         if (nearest_dtime < 0) {
 482                                 // Handle negative nearest_dtime
 483                                 if (!step_up) {
 484                                         if (nearest_collided == COLLISION_AXIS_X)
 485                                                 pos_f->X += speed_f->X * nearest_dtime;
 486                                         if (nearest_collided == COLLISION_AXIS_Y)
 487                                                 pos_f->Y += speed_f->Y * nearest_dtime;
 488                                         if (nearest_collided == COLLISION_AXIS_Z)
 489                                                 pos_f->Z += speed_f->Z * nearest_dtime;
 490                                 }
 491                         } else {
 492                                 *pos_f += *speed_f * nearest_dtime;
 493                                 dtime -= nearest_dtime;
 494                         }
 495
 496                         bool is_collision = true;
 497                         if (nearest_info.is_unloaded)
 498                                 is_collision = false;
 499
 500                         CollisionInfo info;
 501                         if (nearest_info.is_object)
 502                                 info.type = COLLISION_OBJECT;
 503                         else
 504                                 info.type = COLLISION_NODE;
 505
 506                         info.node_p = nearest_info.position;
 507                         info.old_speed = *speed_f;
 508                         info.plane = nearest_collided;
 509
 510                         // Set the speed component that caused the collision to zero
 511                         if (step_up) {
 512                                 // Special case: Handle stairs
 513                                 nearest_info.is_step_up = true;
 514                                 is_collision = false;
 515                         } else if (nearest_collided == COLLISION_AXIS_X) {
 516                                 if (fabs(speed_f->X) > BS * 3)
 517                                         speed_f->X *= bounce;
 518                                 else
 519                                         speed_f->X = 0;
 520                                 result.collides = true;
 521                         } else if (nearest_collided == COLLISION_AXIS_Y) {
 522                                 if(fabs(speed_f->Y) > BS * 3)
 523                                         speed_f->Y *= bounce;
 524                                 else
 525                                         speed_f->Y = 0;
 526                                 result.collides = true;
 527                         } else if (nearest_collided == COLLISION_AXIS_Z) {
 528                                 if (fabs(speed_f->Z) > BS * 3)
 529                                         speed_f->Z *= bounce;
 530                                 else
 531                                         speed_f->Z = 0;
 532                                 result.collides = true;
 533                         }
 534
 535                         info.new_speed = *speed_f;
 536                         if (info.new_speed.getDistanceFrom(info.old_speed) < 0.1f * BS)
 537                                 is_collision = false;
 538
 539                         if (is_collision) {
 540                                 info.axis = nearest_collided;
 541                                 result.collisions.push_back(info);
 542                         }
 543                 }
 544         }
 545
 546         /*
 547                 Final touches: Check if standing on ground, step up stairs.
 548         */
 549         aabb3f box = box_0;
 550         box.MinEdge += *pos_f;
 551         box.MaxEdge += *pos_f;
 552         for (const auto &box_info : cinfo) {
 553                 const aabb3f &cbox = box_info.box;
 554
 555                 /*
 556                         See if the object is touching ground.
 557
 558                         Object touches ground if object's minimum Y is near node's
 559                         maximum Y and object's X-Z-area overlaps with the node's
 560                         X-Z-area.
 561                 */
 562
 563                 if (cbox.MaxEdge.X - d > box.MinEdge.X && cbox.MinEdge.X + d < box.MaxEdge.X &&
 564                                 cbox.MaxEdge.Z - d > box.MinEdge.Z &&
 565                                 cbox.MinEdge.Z + d < box.MaxEdge.Z) {
 566                         if (box_info.is_step_up) {
 567                                 pos_f->Y += cbox.MaxEdge.Y - box.MinEdge.Y;
 568                                 box = box_0;
 569                                 box.MinEdge += *pos_f;
 570                                 box.MaxEdge += *pos_f;
 571                         }
 572                         if (std::fabs(cbox.MaxEdge.Y - box.MinEdge.Y) < 0.05f) {
 573                                 result.touching_ground = true;
 574
 575                                 if (box_info.is_object)
 576                                         result.standing_on_object = true;
 577                         }
 578                 }
 579         }
 580
 581         return result;
 582 }