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 #endif
  29 #include "serverenvironment.h"
  30 #include "serverobject.h"
  31 #include "util/timetaker.h"
  32 #include "profiler.h"
  33
  34 // float error is 10 - 9.96875 = 0.03125
  35 //#define COLL_ZERO 0.032 // broken unit tests
  36 #define COLL_ZERO 0
  37
  38
  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 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 COLLISION_AXIS_X;
  90                 }
  91                 else if(relbox.MinEdge.X > xsize)
  92                 {
  93                         return COLLISION_AXIS_NONE;
  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 COLLISION_AXIS_X;
 105                 }
 106                 else if(relbox.MaxEdge.X < 0)
 107                 {
 108                         return COLLISION_AXIS_NONE;
 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 COLLISION_AXIS_Y;
 123                 }
 124                 else if(relbox.MinEdge.Y > ysize)
 125                 {
 126                         return COLLISION_AXIS_NONE;
 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 COLLISION_AXIS_Y;
 138                 }
 139                 else if(relbox.MaxEdge.Y < 0)
 140                 {
 141                         return COLLISION_AXIS_NONE;
 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 COLLISION_AXIS_Z;
 156                 }
 157                 //else if(relbox.MinEdge.Z > zsize)
 158                 //{
 159                 //      return COLLISION_AXIS_NONE;
 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 COLLISION_AXIS_Z;
 171                 }
 172                 //else if(relbox.MaxEdge.Z < 0)
 173                 //{
 174                 //      return COLLISION_AXIS_NONE;
 175                 //}
 176         }
 177
 178         return COLLISION_AXIS_NONE;
 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 (const auto &it : cinfo) {
 193                 const aabb3f &staticbox = it.box;
 194                 if ((movingbox.MaxEdge.Y - d <= staticbox.MinEdge.Y) &&
 195                                 (movingbox.MaxEdge.Y + y_increase > staticbox.MinEdge.Y) &&
 196                                 (movingbox.MinEdge.X < staticbox.MaxEdge.X) &&
 197                                 (movingbox.MaxEdge.X > staticbox.MinEdge.X) &&
 198                                 (movingbox.MinEdge.Z < staticbox.MaxEdge.Z) &&
 199                                 (movingbox.MaxEdge.Z > staticbox.MinEdge.Z))
 200                         return true;
 201         }
 202
 203         return false;
 204 }
 205
 206 static inline void getNeighborConnectingFace(const v3s16 &p,
 207         const NodeDefManager *nodedef, Map *map, MapNode n, int v, int *neighbors)
 208 {
 209         MapNode n2 = map->getNodeNoEx(p);
 210         if (nodedef->nodeboxConnects(n, n2, v))
 211                 *neighbors |= v;
 212 }
 213
 214 collisionMoveResult collisionMoveSimple(Environment *env, IGameDef *gamedef,
 215                 f32 pos_max_d, const aabb3f &box_0,
 216                 f32 stepheight, f32 dtime,
 217                 v3f *pos_f, v3f *speed_f,
 218                 v3f accel_f, ActiveObject *self,
 219                 bool collideWithObjects)
 220 {
 221         static bool time_notification_done = false;
 222         Map *map = &env->getMap();
 223         //TimeTaker tt("collisionMoveSimple");
 224         ScopeProfiler sp(g_profiler, "collisionMoveSimple avg", SPT_AVG);
 225
 226         collisionMoveResult result;
 227
 228         /*
 229                 Calculate new velocity
 230         */
 231         if (dtime > 0.5f) {
 232                 if (!time_notification_done) {
 233                         time_notification_done = true;
 234                         infostream << "collisionMoveSimple: maximum step interval exceeded,"
 235                                         " lost movement details!"<<std::endl;
 236                 }
 237                 dtime = 0.5f;
 238         } else {
 239                 time_notification_done = false;
 240         }
 241         *speed_f += accel_f * dtime;
 242
 243         // If there is no speed, there are no collisions
 244         if (speed_f->getLength() == 0)
 245                 return result;
 246
 247         // Limit speed for avoiding hangs
 248         speed_f->Y = rangelim(speed_f->Y, -5000, 5000);
 249         speed_f->X = rangelim(speed_f->X, -5000, 5000);
 250         speed_f->Z = rangelim(speed_f->Z, -5000, 5000);
 251
 252         /*
 253                 Collect node boxes in movement range
 254         */
 255         std::vector<NearbyCollisionInfo> cinfo;
 256         {
 257         //TimeTaker tt2("collisionMoveSimple collect boxes");
 258         ScopeProfiler sp2(g_profiler, "collisionMoveSimple collect boxes avg", SPT_AVG);
 259
 260         v3f newpos_f = *pos_f + *speed_f * dtime;
 261         v3f minpos_f(
 262                 MYMIN(pos_f->X, newpos_f.X),
 263                 MYMIN(pos_f->Y, newpos_f.Y) + 0.01f * BS, // bias rounding, player often at +/-n.5
 264                 MYMIN(pos_f->Z, newpos_f.Z)
 265         );
 266         v3f maxpos_f(
 267                 MYMAX(pos_f->X, newpos_f.X),
 268                 MYMAX(pos_f->Y, newpos_f.Y),
 269                 MYMAX(pos_f->Z, newpos_f.Z)
 270         );
 271         v3s16 min = floatToInt(minpos_f + box_0.MinEdge, BS) - v3s16(1, 1, 1);
 272         v3s16 max = floatToInt(maxpos_f + box_0.MaxEdge, BS) + v3s16(1, 1, 1);
 273
 274         bool any_position_valid = false;
 275
 276         v3s16 p;
 277         for (p.X = min.X; p.X <= max.X; p.X++)
 278         for (p.Y = min.Y; p.Y <= max.Y; p.Y++)
 279         for (p.Z = min.Z; p.Z <= max.Z; p.Z++) {
 280                 bool is_position_valid;
 281                 MapNode n = map->getNodeNoEx(p, &is_position_valid);
 282
 283                 if (is_position_valid && n.getContent() != CONTENT_IGNORE) {
 284                         // Object collides into walkable nodes
 285
 286                         any_position_valid = true;
 287                         const NodeDefManager *nodedef = gamedef->getNodeDefManager();
 288                         const ContentFeatures &f = nodedef->get(n);
 289
 290                         if (!f.walkable)
 291                                 continue;
 292
 293                         int n_bouncy_value = itemgroup_get(f.groups, "bouncy");
 294
 295                         int neighbors = 0;
 296                         if (f.drawtype == NDT_NODEBOX &&
 297                                 f.node_box.type == NODEBOX_CONNECTED) {
 298                                 v3s16 p2 = p;
 299
 300                                 p2.Y++;
 301                                 getNeighborConnectingFace(p2, nodedef, map, n, 1, &neighbors);
 302
 303                                 p2 = p;
 304                                 p2.Y--;
 305                                 getNeighborConnectingFace(p2, nodedef, map, n, 2, &neighbors);
 306
 307                                 p2 = p;
 308                                 p2.Z--;
 309                                 getNeighborConnectingFace(p2, nodedef, map, n, 4, &neighbors);
 310
 311                                 p2 = p;
 312                                 p2.X--;
 313                                 getNeighborConnectingFace(p2, nodedef, map, n, 8, &neighbors);
 314
 315                                 p2 = p;
 316                                 p2.Z++;
 317                                 getNeighborConnectingFace(p2, nodedef, map, n, 16, &neighbors);
 318
 319                                 p2 = p;
 320                                 p2.X++;
 321                                 getNeighborConnectingFace(p2, nodedef, map, n, 32, &neighbors);
 322                         }
 323                         std::vector<aabb3f> nodeboxes;
 324                         n.getCollisionBoxes(gamedef->ndef(), &nodeboxes, neighbors);
 325
 326                         // Calculate float position only once
 327                         v3f posf = intToFloat(p, BS);
 328                         for (auto box : nodeboxes) {
 329                                 box.MinEdge += posf;
 330                                 box.MaxEdge += posf;
 331                                 cinfo.emplace_back(false, false, n_bouncy_value, p, box);
 332                         }
 333                 } else {
 334                         // Collide with unloaded nodes (position invalid) and loaded
 335                         // CONTENT_IGNORE nodes (position valid)
 336                         aabb3f box = getNodeBox(p, BS);
 337                         cinfo.emplace_back(true, false, 0, p, box);
 338                 }
 339         }
 340
 341         // Do not move if world has not loaded yet, since custom node boxes
 342         // are not available for collision detection.
 343         // This also intentionally occurs in the case of the object being positioned
 344         // solely on loaded CONTENT_IGNORE nodes, no matter where they come from.
 345         if (!any_position_valid) {
 346                 *speed_f = v3f(0, 0, 0);
 347                 return result;
 348         }
 349
 350         } // tt2
 351
 352         if(collideWithObjects)
 353         {
 354                 ScopeProfiler sp2(g_profiler, "collisionMoveSimple objects avg", SPT_AVG);
 355                 //TimeTaker tt3("collisionMoveSimple collect object boxes");
 356
 357                 /* add object boxes to cinfo */
 358
 359                 std::vector<ActiveObject*> objects;
 360 #ifndef SERVER
 361                 ClientEnvironment *c_env = dynamic_cast<ClientEnvironment*>(env);
 362                 if (c_env != 0) {
 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                         std::vector<DistanceSortedActiveObject> clientobjects;
 367                         c_env->getActiveObjects(*pos_f, distance, clientobjects);
 368
 369                         for (auto &clientobject : clientobjects) {
 370                                 // Do collide with everything but itself and the parent CAO
 371                                 if (!self || (self != clientobject.obj &&
 372                                                 self != clientobject.obj->getParent())) {
 373                                         objects.push_back((ActiveObject*) clientobject.obj);
 374                                 }
 375                         }
 376                 }
 377                 else
 378 #endif
 379                 {
 380                         ServerEnvironment *s_env = dynamic_cast<ServerEnvironment*>(env);
 381                         if (s_env != NULL) {
 382                                 // Calculate distance by speed, add own extent and 1.5m of tolerance
 383                                 f32 distance = speed_f->getLength() * dtime +
 384                                         box_0.getExtent().getLength() + 1.5f * BS;
 385                                 std::vector<u16> s_objects;
 386                                 s_env->getObjectsInsideRadius(s_objects, *pos_f, distance);
 387
 388                                 for (u16 obj_id : s_objects) {
 389                                         ServerActiveObject *current = s_env->getActiveObject(obj_id);
 390
 391                                         if (!self || (self != current &&
 392                                                         self != current->getParent())) {
 393                                                 objects.push_back((ActiveObject*)current);
 394                                         }
 395                                 }
 396                         }
 397                 }
 398
 399                 for (std::vector<ActiveObject*>::const_iterator iter = objects.begin();
 400                                 iter != objects.end(); ++iter) {
 401                         ActiveObject *object = *iter;
 402
 403                         if (object) {
 404                                 aabb3f object_collisionbox;
 405                                 if (object->getCollisionBox(&object_collisionbox) &&
 406                                                 object->collideWithObjects()) {
 407                                         cinfo.emplace_back(false, true, 0, v3s16(), object_collisionbox);
 408                                 }
 409                         }
 410                 }
 411         } //tt3
 412
 413         /*
 414                 Collision detection
 415         */
 416
 417         /*
 418                 Collision uncertainty radius
 419                 Make it a bit larger than the maximum distance of movement
 420         */
 421         f32 d = pos_max_d * 1.1f;
 422         // A fairly large value in here makes moving smoother
 423         //f32 d = 0.15*BS;
 424
 425         // This should always apply, otherwise there are glitches
 426         assert(d > pos_max_d);  // invariant
 427
 428         int loopcount = 0;
 429
 430         while(dtime > BS * 1e-10f) {
 431                 //TimeTaker tt3("collisionMoveSimple dtime loop");
 432                 ScopeProfiler sp2(g_profiler, "collisionMoveSimple dtime loop avg", SPT_AVG);
 433
 434                 // Avoid infinite loop
 435                 loopcount++;
 436                 if (loopcount >= 100) {
 437                         warningstream << "collisionMoveSimple: Loop count exceeded, aborting to avoid infiniite loop" << std::endl;
 438                         break;
 439                 }
 440
 441                 aabb3f movingbox = box_0;
 442                 movingbox.MinEdge += *pos_f;
 443                 movingbox.MaxEdge += *pos_f;
 444
 445                 CollisionAxis nearest_collided = COLLISION_AXIS_NONE;
 446                 f32 nearest_dtime = dtime;
 447                 int nearest_boxindex = -1;
 448
 449                 /*
 450                         Go through every nodebox, find nearest collision
 451                 */
 452                 for (u32 boxindex = 0; boxindex < cinfo.size(); boxindex++) {
 453                         const NearbyCollisionInfo &box_info = cinfo[boxindex];
 454                         // Ignore if already stepped up this nodebox.
 455                         if (box_info.is_step_up)
 456                                 continue;
 457
 458                         // Find nearest collision of the two boxes (raytracing-like)
 459                         f32 dtime_tmp;
 460                         CollisionAxis collided = axisAlignedCollision(box_info.box,
 461                                         movingbox, *speed_f, d, &dtime_tmp);
 462
 463                         if (collided == -1 || dtime_tmp >= nearest_dtime)
 464                                 continue;
 465
 466                         nearest_dtime = dtime_tmp;
 467                         nearest_collided = collided;
 468                         nearest_boxindex = boxindex;
 469                 }
 470
 471                 if (nearest_collided == COLLISION_AXIS_NONE) {
 472                         // No collision with any collision box.
 473                         *pos_f += *speed_f * dtime;
 474                         dtime = 0;  // Set to 0 to avoid "infinite" loop due to small FP numbers
 475                 } else {
 476                         // Otherwise, a collision occurred.
 477                         NearbyCollisionInfo &nearest_info = cinfo[nearest_boxindex];
 478                         const aabb3f& cbox = nearest_info.box;
 479                         // Check for stairs.
 480                         bool step_up = (nearest_collided != COLLISION_AXIS_Y) && // must not be Y direction
 481                                         (movingbox.MinEdge.Y < cbox.MaxEdge.Y) &&
 482                                         (movingbox.MinEdge.Y + stepheight > cbox.MaxEdge.Y) &&
 483                                         (!wouldCollideWithCeiling(cinfo, movingbox,
 484                                                         cbox.MaxEdge.Y - movingbox.MinEdge.Y,
 485                                                         d));
 486
 487                         // Get bounce multiplier
 488                         float bounce = -(float)nearest_info.bouncy / 100.0f;
 489
 490                         // Move to the point of collision and reduce dtime by nearest_dtime
 491                         if (nearest_dtime < 0) {
 492                                 // Handle negative nearest_dtime (can be caused by the d allowance)
 493                                 if (!step_up) {
 494                                         if (nearest_collided == COLLISION_AXIS_X)
 495                                                 pos_f->X += speed_f->X * nearest_dtime;
 496                                         if (nearest_collided == COLLISION_AXIS_Y)
 497                                                 pos_f->Y += speed_f->Y * nearest_dtime;
 498                                         if (nearest_collided == COLLISION_AXIS_Z)
 499                                                 pos_f->Z += speed_f->Z * nearest_dtime;
 500                                 }
 501                         } else {
 502                                 *pos_f += *speed_f * nearest_dtime;
 503                                 dtime -= nearest_dtime;
 504                         }
 505
 506                         bool is_collision = true;
 507                         if (nearest_info.is_unloaded)
 508                                 is_collision = false;
 509
 510                         CollisionInfo info;
 511                         if (nearest_info.is_object)
 512                                 info.type = COLLISION_OBJECT;
 513                         else
 514                                 info.type = COLLISION_NODE;
 515
 516                         info.node_p = nearest_info.position;
 517                         info.old_speed = *speed_f;
 518                         info.plane = nearest_collided;
 519
 520                         // Set the speed component that caused the collision to zero
 521                         if (step_up) {
 522                                 // Special case: Handle stairs
 523                                 nearest_info.is_step_up = true;
 524                                 is_collision = false;
 525                         } else if (nearest_collided == COLLISION_AXIS_X) {
 526                                 if (fabs(speed_f->X) > BS * 3)
 527                                         speed_f->X *= bounce;
 528                                 else
 529                                         speed_f->X = 0;
 530                                 result.collides = true;
 531                         } else if (nearest_collided == COLLISION_AXIS_Y) {
 532                                 if(fabs(speed_f->Y) > BS * 3)
 533                                         speed_f->Y *= bounce;
 534                                 else
 535                                         speed_f->Y = 0;
 536                                 result.collides = true;
 537                         } else if (nearest_collided == COLLISION_AXIS_Z) {
 538                                 if (fabs(speed_f->Z) > BS * 3)
 539                                         speed_f->Z *= bounce;
 540                                 else
 541                                         speed_f->Z = 0;
 542                                 result.collides = true;
 543                         }
 544
 545                         info.new_speed = *speed_f;
 546                         if (info.new_speed.getDistanceFrom(info.old_speed) < 0.1f * BS)
 547                                 is_collision = false;
 548
 549                         if (is_collision) {
 550                                 info.axis = nearest_collided;
 551                                 result.collisions.push_back(info);
 552                         }
 553                 }
 554         }
 555
 556         /*
 557                 Final touches: Check if standing on ground, step up stairs.
 558         */
 559         aabb3f box = box_0;
 560         box.MinEdge += *pos_f;
 561         box.MaxEdge += *pos_f;
 562         for (const auto &box_info : cinfo) {
 563                 const aabb3f &cbox = box_info.box;
 564
 565                 /*
 566                         See if the object is touching ground.
 567
 568                         Object touches ground if object's minimum Y is near node's
 569                         maximum Y and object's X-Z-area overlaps with the node's
 570                         X-Z-area.
 571
 572                         Use 0.15*BS so that it is easier to get on a node.
 573                 */
 574                 if (cbox.MaxEdge.X - d > box.MinEdge.X && cbox.MinEdge.X + d < box.MaxEdge.X &&
 575                                 cbox.MaxEdge.Z - d > box.MinEdge.Z &&
 576                                 cbox.MinEdge.Z + d < box.MaxEdge.Z) {
 577                         if (box_info.is_step_up) {
 578                                 pos_f->Y += cbox.MaxEdge.Y - box.MinEdge.Y;
 579                                 box = box_0;
 580                                 box.MinEdge += *pos_f;
 581                                 box.MaxEdge += *pos_f;
 582                         }
 583                         if (std::fabs(cbox.MaxEdge.Y - box.MinEdge.Y) < 0.15f * BS) {
 584                                 result.touching_ground = true;
 585
 586                                 if (box_info.is_object)
 587                                         result.standing_on_object = true;
 588                         }
 589                 }
 590         }
 591
 592         return result;
 593 }