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         // node
  41         NearbyCollisionInfo(bool is_ul, int bouncy, const v3s16 &pos,
  42                         const aabb3f &box) :
  43                 is_unloaded(is_ul),
  44                 obj(nullptr),
  45                 bouncy(bouncy),
  46                 position(pos),
  47                 box(box)
  48         {}
  49
  50         // object
  51         NearbyCollisionInfo(ActiveObject *obj, int bouncy,
  52                         const aabb3f &box) :
  53                 is_unloaded(false),
  54                 obj(obj),
  55                 bouncy(bouncy),
  56                 box(box)
  57         {}
  58
  59         inline bool isObject() const { return obj != nullptr; }
  60
  61         bool is_unloaded;
  62         bool is_step_up = false;
  63         ActiveObject *obj;
  64         int bouncy;
  65         v3s16 position;
  66         aabb3f box;
  67 };
  68
  69
  70 // Helper function:
  71 // Checks for collision of a moving aabbox with a static aabbox
  72 // Returns -1 if no collision, 0 if X collision, 1 if Y collision, 2 if Z collision
  73 // The time after which the collision occurs is stored in dtime.
  74 CollisionAxis axisAlignedCollision(
  75                 const aabb3f &staticbox, const aabb3f &movingbox,
  76                 const v3f &speed, f32 *dtime)
  77 {
  78         //TimeTaker tt("axisAlignedCollision");
  79
  80         aabb3f relbox(
  81                         movingbox.MaxEdge.X - movingbox.MinEdge.X + staticbox.MaxEdge.X - staticbox.MinEdge.X,                                          // sum of the widths
  82                         movingbox.MaxEdge.Y - movingbox.MinEdge.Y + staticbox.MaxEdge.Y - staticbox.MinEdge.Y,
  83                         movingbox.MaxEdge.Z - movingbox.MinEdge.Z + staticbox.MaxEdge.Z - staticbox.MinEdge.Z,
  84                         std::max(movingbox.MaxEdge.X, staticbox.MaxEdge.X) - std::min(movingbox.MinEdge.X, staticbox.MinEdge.X),        //outer bounding 'box' dimensions
  85                         std::max(movingbox.MaxEdge.Y, staticbox.MaxEdge.Y) - std::min(movingbox.MinEdge.Y, staticbox.MinEdge.Y),
  86                         std::max(movingbox.MaxEdge.Z, staticbox.MaxEdge.Z) - std::min(movingbox.MinEdge.Z, staticbox.MinEdge.Z)
  87         );
  88
  89         const f32 dtime_max = *dtime;
  90         const f32 inner_margin = -1.5f;
  91         f32 distance;
  92         f32 time;
  93
  94         if (speed.X) {
  95                 distance = relbox.MaxEdge.X - relbox.MinEdge.X;
  96
  97                 *dtime = distance >= 0 ? std::abs(distance / speed.X) : -std::abs(distance / speed.X);
  98                 time = std::max(*dtime, 0.0f);
  99
 100                 if (distance > inner_margin) {
 101                         if (*dtime <= dtime_max) {
 102                                 if ((speed.X > 0 && staticbox.MaxEdge.X > movingbox.MaxEdge.X) ||
 103                                                 (speed.X < 0 && staticbox.MinEdge.X < movingbox.MinEdge.X)) {
 104                                         if (
 105                                                 (std::max(movingbox.MaxEdge.Y + speed.Y * time, staticbox.MaxEdge.Y)
 106                                                         - std::min(movingbox.MinEdge.Y + speed.Y * time, staticbox.MinEdge.Y)
 107                                                         - relbox.MinEdge.Y < 0) &&
 108                                                 (std::max(movingbox.MaxEdge.Z + speed.Z * time, staticbox.MaxEdge.Z)
 109                                                         - std::min(movingbox.MinEdge.Z + speed.Z * time, staticbox.MinEdge.Z)
 110                                                         - relbox.MinEdge.Z < 0)
 111                                                 )
 112                                                 return COLLISION_AXIS_X;
 113                                 }
 114                         } else {
 115                                 return COLLISION_AXIS_NONE;
 116                         }
 117                 }
 118         }
 119
 120         // NO else if here
 121
 122         if (speed.Y) {
 123                 distance = relbox.MaxEdge.Y - relbox.MinEdge.Y;
 124
 125                 *dtime = distance >= 0 ? std::abs(distance / speed.Y) : -std::abs(distance / speed.Y);
 126                 time = std::max(*dtime, 0.0f);
 127
 128                 if (distance > inner_margin) {
 129                         if (*dtime <= dtime_max) {
 130                                 if ((speed.Y > 0 && staticbox.MaxEdge.Y > movingbox.MaxEdge.Y) ||
 131                                                 (speed.Y < 0 && staticbox.MinEdge.Y < movingbox.MinEdge.Y)) {
 132                                         if (
 133                                                 (std::max(movingbox.MaxEdge.X + speed.X * time, staticbox.MaxEdge.X)
 134                                                         - std::min(movingbox.MinEdge.X + speed.X * time, staticbox.MinEdge.X)
 135                                                         - relbox.MinEdge.X < 0) &&
 136                                                 (std::max(movingbox.MaxEdge.Z + speed.Z * time, staticbox.MaxEdge.Z)
 137                                                         - std::min(movingbox.MinEdge.Z + speed.Z * time, staticbox.MinEdge.Z)
 138                                                         - relbox.MinEdge.Z < 0)
 139                                                 )
 140                                                 return COLLISION_AXIS_Y;
 141                                 }
 142                         } else {
 143                                 return COLLISION_AXIS_NONE;
 144                         }
 145                 }
 146         }
 147
 148         // NO else if here
 149
 150         if (speed.Z) {
 151                 distance = relbox.MaxEdge.Z - relbox.MinEdge.Z;
 152
 153                 *dtime = distance >= 0 ? std::abs(distance / speed.Z) : -std::abs(distance / speed.Z);
 154                 time = std::max(*dtime, 0.0f);
 155
 156                 if (distance > inner_margin) {
 157                         if (*dtime <= dtime_max) {
 158                                 if ((speed.Z > 0 && staticbox.MaxEdge.Z > movingbox.MaxEdge.Z) ||
 159                                                 (speed.Z < 0 && staticbox.MinEdge.Z < movingbox.MinEdge.Z)) {
 160                                         if (
 161                                                 (std::max(movingbox.MaxEdge.X + speed.X * time, staticbox.MaxEdge.X)
 162                                                         - std::min(movingbox.MinEdge.X + speed.X * time, staticbox.MinEdge.X)
 163                                                         - relbox.MinEdge.X < 0) &&
 164                                                 (std::max(movingbox.MaxEdge.Y + speed.Y * time, staticbox.MaxEdge.Y)
 165                                                         - std::min(movingbox.MinEdge.Y + speed.Y * time, staticbox.MinEdge.Y)
 166                                                         - relbox.MinEdge.Y < 0)
 167                                                 )
 168                                                 return COLLISION_AXIS_Z;
 169                                 }
 170                         }
 171                 }
 172         }
 173
 174         return COLLISION_AXIS_NONE;
 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 (const auto &it : cinfo) {
 189                 const aabb3f &staticbox = it.box;
 190                 if ((movingbox.MaxEdge.Y - d <= staticbox.MinEdge.Y) &&
 191                                 (movingbox.MaxEdge.Y + y_increase > staticbox.MinEdge.Y) &&
 192                                 (movingbox.MinEdge.X < staticbox.MaxEdge.X) &&
 193                                 (movingbox.MaxEdge.X > staticbox.MinEdge.X) &&
 194                                 (movingbox.MinEdge.Z < staticbox.MaxEdge.Z) &&
 195                                 (movingbox.MaxEdge.Z > staticbox.MinEdge.Z))
 196                         return true;
 197         }
 198
 199         return false;
 200 }
 201
 202 static inline void getNeighborConnectingFace(const v3s16 &p,
 203         const NodeDefManager *nodedef, Map *map, MapNode n, int v, int *neighbors)
 204 {
 205         MapNode n2 = map->getNode(p);
 206         if (nodedef->nodeboxConnects(n, n2, v))
 207                 *neighbors |= v;
 208 }
 209
 210 collisionMoveResult collisionMoveSimple(Environment *env, IGameDef *gamedef,
 211                 f32 pos_max_d, const aabb3f &box_0,
 212                 f32 stepheight, f32 dtime,
 213                 v3f *pos_f, v3f *speed_f,
 214                 v3f accel_f, ActiveObject *self,
 215                 bool collideWithObjects)
 216 {
 217         static bool time_notification_done = false;
 218         Map *map = &env->getMap();
 219
 220         ScopeProfiler sp(g_profiler, "collisionMoveSimple()", SPT_AVG);
 221
 222         collisionMoveResult result;
 223
 224         /*
 225                 Calculate new velocity
 226         */
 227         if (dtime > 0.5f) {
 228                 if (!time_notification_done) {
 229                         time_notification_done = true;
 230                         infostream << "collisionMoveSimple: maximum step interval exceeded,"
 231                                         " lost movement details!"<<std::endl;
 232                 }
 233                 dtime = 0.5f;
 234         } else {
 235                 time_notification_done = false;
 236         }
 237         *speed_f += accel_f * dtime;
 238
 239         // If there is no speed, there are no collisions
 240         if (speed_f->getLength() == 0)
 241                 return result;
 242
 243         // Limit speed for avoiding hangs
 244         speed_f->Y = rangelim(speed_f->Y, -5000, 5000);
 245         speed_f->X = rangelim(speed_f->X, -5000, 5000);
 246         speed_f->Z = rangelim(speed_f->Z, -5000, 5000);
 247
 248         /*
 249                 Collect node boxes in movement range
 250         */
 251         std::vector<NearbyCollisionInfo> cinfo;
 252         {
 253         //TimeTaker tt2("collisionMoveSimple collect boxes");
 254         ScopeProfiler sp2(g_profiler, "collisionMoveSimple(): collect boxes", SPT_AVG);
 255
 256         v3f newpos_f = *pos_f + *speed_f * dtime;
 257         v3f minpos_f(
 258                 MYMIN(pos_f->X, newpos_f.X),
 259                 MYMIN(pos_f->Y, newpos_f.Y) + 0.01f * BS, // bias rounding, player often at +/-n.5
 260                 MYMIN(pos_f->Z, newpos_f.Z)
 261         );
 262         v3f maxpos_f(
 263                 MYMAX(pos_f->X, newpos_f.X),
 264                 MYMAX(pos_f->Y, newpos_f.Y),
 265                 MYMAX(pos_f->Z, newpos_f.Z)
 266         );
 267         v3s16 min = floatToInt(minpos_f + box_0.MinEdge, BS) - v3s16(1, 1, 1);
 268         v3s16 max = floatToInt(maxpos_f + box_0.MaxEdge, BS) + v3s16(1, 1, 1);
 269
 270         bool any_position_valid = false;
 271
 272         v3s16 p;
 273         for (p.X = min.X; p.X <= max.X; p.X++)
 274         for (p.Y = min.Y; p.Y <= max.Y; p.Y++)
 275         for (p.Z = min.Z; p.Z <= max.Z; p.Z++) {
 276                 bool is_position_valid;
 277                 MapNode n = map->getNode(p, &is_position_valid);
 278
 279                 if (is_position_valid && n.getContent() != CONTENT_IGNORE) {
 280                         // Object collides into walkable nodes
 281
 282                         any_position_valid = true;
 283                         const NodeDefManager *nodedef = gamedef->getNodeDefManager();
 284                         const ContentFeatures &f = nodedef->get(n);
 285
 286                         if (!f.walkable)
 287                                 continue;
 288
 289                         int n_bouncy_value = itemgroup_get(f.groups, "bouncy");
 290
 291                         int neighbors = 0;
 292                         if (f.drawtype == NDT_NODEBOX &&
 293                                 f.node_box.type == NODEBOX_CONNECTED) {
 294                                 v3s16 p2 = p;
 295
 296                                 p2.Y++;
 297                                 getNeighborConnectingFace(p2, nodedef, map, n, 1, &neighbors);
 298
 299                                 p2 = p;
 300                                 p2.Y--;
 301                                 getNeighborConnectingFace(p2, nodedef, map, n, 2, &neighbors);
 302
 303                                 p2 = p;
 304                                 p2.Z--;
 305                                 getNeighborConnectingFace(p2, nodedef, map, n, 4, &neighbors);
 306
 307                                 p2 = p;
 308                                 p2.X--;
 309                                 getNeighborConnectingFace(p2, nodedef, map, n, 8, &neighbors);
 310
 311                                 p2 = p;
 312                                 p2.Z++;
 313                                 getNeighborConnectingFace(p2, nodedef, map, n, 16, &neighbors);
 314
 315                                 p2 = p;
 316                                 p2.X++;
 317                                 getNeighborConnectingFace(p2, nodedef, map, n, 32, &neighbors);
 318                         }
 319                         std::vector<aabb3f> nodeboxes;
 320                         n.getCollisionBoxes(gamedef->ndef(), &nodeboxes, neighbors);
 321
 322                         // Calculate float position only once
 323                         v3f posf = intToFloat(p, BS);
 324                         for (auto box : nodeboxes) {
 325                                 box.MinEdge += posf;
 326                                 box.MaxEdge += posf;
 327                                 cinfo.emplace_back(false, n_bouncy_value, p, box);
 328                         }
 329                 } else {
 330                         // Collide with unloaded nodes (position invalid) and loaded
 331                         // CONTENT_IGNORE nodes (position valid)
 332                         aabb3f box = getNodeBox(p, BS);
 333                         cinfo.emplace_back(true, 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         // This also intentionally occurs in the case of the object being positioned
 340         // solely on loaded CONTENT_IGNORE nodes, no matter where they come from.
 341         if (!any_position_valid) {
 342                 *speed_f = v3f(0, 0, 0);
 343                 return result;
 344         }
 345
 346         } // tt2
 347
 348         if(collideWithObjects)
 349         {
 350                 /* add object boxes to cinfo */
 351
 352                 std::vector<ActiveObject*> objects;
 353 #ifndef SERVER
 354                 ClientEnvironment *c_env = dynamic_cast<ClientEnvironment*>(env);
 355                 if (c_env != 0) {
 356                         // Calculate distance by speed, add own extent and 1.5m of tolerance
 357                         f32 distance = speed_f->getLength() * dtime +
 358                                 box_0.getExtent().getLength() + 1.5f * BS;
 359                         std::vector<DistanceSortedActiveObject> clientobjects;
 360                         c_env->getActiveObjects(*pos_f, distance, clientobjects);
 361
 362                         for (auto &clientobject : clientobjects) {
 363                                 // Do collide with everything but itself and the parent CAO
 364                                 if (!self || (self != clientobject.obj &&
 365                                                 self != clientobject.obj->getParent())) {
 366                                         objects.push_back((ActiveObject*) clientobject.obj);
 367                                 }
 368                         }
 369                 }
 370                 else
 371 #endif
 372                 {
 373                         ServerEnvironment *s_env = dynamic_cast<ServerEnvironment*>(env);
 374                         if (s_env != NULL) {
 375                                 // Calculate distance by speed, add own extent and 1.5m of tolerance
 376                                 f32 distance = speed_f->getLength() * dtime +
 377                                         box_0.getExtent().getLength() + 1.5f * BS;
 378
 379                                 // search for objects which are not us, or we are not its parent
 380                                 // we directly use the callback to populate the result to prevent
 381                                 // a useless result loop here
 382                                 auto include_obj_cb = [self, &objects] (ServerActiveObject *obj) {
 383                                         if (!self || (self != obj && self != obj->getParent())) {
 384                                                 objects.push_back((ActiveObject *)obj);
 385                                         }
 386                                         return false;
 387                                 };
 388
 389                                 std::vector<ServerActiveObject *> s_objects;
 390                                 s_env->getObjectsInsideRadius(s_objects, *pos_f, distance, include_obj_cb);
 391                         }
 392                 }
 393
 394                 for (std::vector<ActiveObject*>::const_iterator iter = objects.begin();
 395                                 iter != objects.end(); ++iter) {
 396                         ActiveObject *object = *iter;
 397
 398                         if (object && object->collideWithObjects()) {
 399                                 aabb3f object_collisionbox;
 400                                 if (object->getCollisionBox(&object_collisionbox))
 401                                         cinfo.emplace_back(object, 0, object_collisionbox);
 402                         }
 403                 }
 404 #ifndef SERVER
 405                 if (self && c_env) {
 406                         LocalPlayer *lplayer = c_env->getLocalPlayer();
 407                         if (lplayer->getParent() == nullptr) {
 408                                 aabb3f lplayer_collisionbox = lplayer->getCollisionbox();
 409                                 v3f lplayer_pos = lplayer->getPosition();
 410                                 lplayer_collisionbox.MinEdge += lplayer_pos;
 411                                 lplayer_collisionbox.MaxEdge += lplayer_pos;
 412                                 ActiveObject *obj = (ActiveObject*) lplayer->getCAO();
 413                                 cinfo.emplace_back(obj, 0, lplayer_collisionbox);
 414                         }
 415                 }
 416 #endif
 417         } //tt3
 418
 419         /*
 420                 Collision detection
 421         */
 422
 423         f32 d = 0.0f;
 424
 425         int loopcount = 0;
 426
 427         while(dtime > BS * 1e-10f) {
 428                 // Avoid infinite loop
 429                 loopcount++;
 430                 if (loopcount >= 100) {
 431                         warningstream << "collisionMoveSimple: Loop count exceeded, aborting to avoid infiniite loop" << std::endl;
 432                         break;
 433                 }
 434
 435                 aabb3f movingbox = box_0;
 436                 movingbox.MinEdge += *pos_f;
 437                 movingbox.MaxEdge += *pos_f;
 438
 439                 CollisionAxis nearest_collided = COLLISION_AXIS_NONE;
 440                 f32 nearest_dtime = dtime;
 441                 int nearest_boxindex = -1;
 442
 443                 /*
 444                         Go through every nodebox, find nearest collision
 445                 */
 446                 for (u32 boxindex = 0; boxindex < cinfo.size(); boxindex++) {
 447                         const NearbyCollisionInfo &box_info = cinfo[boxindex];
 448                         // Ignore if already stepped up this nodebox.
 449                         if (box_info.is_step_up)
 450                                 continue;
 451
 452                         // Find nearest collision of the two boxes (raytracing-like)
 453                         f32 dtime_tmp = nearest_dtime;
 454                         CollisionAxis collided = axisAlignedCollision(box_info.box,
 455                                         movingbox, *speed_f, &dtime_tmp);
 456
 457                         if (collided == -1 || dtime_tmp >= nearest_dtime)
 458                                 continue;
 459
 460                         nearest_dtime = dtime_tmp;
 461                         nearest_collided = collided;
 462                         nearest_boxindex = boxindex;
 463                 }
 464
 465                 if (nearest_collided == COLLISION_AXIS_NONE) {
 466                         // No collision with any collision box.
 467                         *pos_f += *speed_f * dtime;
 468                         dtime = 0;  // Set to 0 to avoid "infinite" loop due to small FP numbers
 469                 } else {
 470                         // Otherwise, a collision occurred.
 471                         NearbyCollisionInfo &nearest_info = cinfo[nearest_boxindex];
 472                         const aabb3f& cbox = nearest_info.box;
 473
 474                         //movingbox except moved to the horizontal position it would be after step up
 475                         aabb3f stepbox = movingbox;
 476                         stepbox.MinEdge.X += speed_f->X * dtime;
 477                         stepbox.MinEdge.Z += speed_f->Z * dtime;
 478                         stepbox.MaxEdge.X += speed_f->X * dtime;
 479                         stepbox.MaxEdge.Z += speed_f->Z * dtime;
 480                         // Check for stairs.
 481                         bool step_up = (nearest_collided != COLLISION_AXIS_Y) && // must not be Y direction
 482                                         (movingbox.MinEdge.Y < cbox.MaxEdge.Y) &&
 483                                         (movingbox.MinEdge.Y + stepheight > cbox.MaxEdge.Y) &&
 484                                         (!wouldCollideWithCeiling(cinfo, stepbox,
 485                                                         cbox.MaxEdge.Y - movingbox.MinEdge.Y,
 486                                                         d));
 487
 488                         // Get bounce multiplier
 489                         float bounce = -(float)nearest_info.bouncy / 100.0f;
 490
 491                         // Move to the point of collision and reduce dtime by nearest_dtime
 492                         if (nearest_dtime < 0) {
 493                                 // Handle negative nearest_dtime
 494                                 if (!step_up) {
 495                                         if (nearest_collided == COLLISION_AXIS_X)
 496                                                 pos_f->X += speed_f->X * nearest_dtime;
 497                                         if (nearest_collided == COLLISION_AXIS_Y)
 498                                                 pos_f->Y += speed_f->Y * nearest_dtime;
 499                                         if (nearest_collided == COLLISION_AXIS_Z)
 500                                                 pos_f->Z += speed_f->Z * nearest_dtime;
 501                                 }
 502                         } else {
 503                                 *pos_f += *speed_f * nearest_dtime;
 504                                 dtime -= nearest_dtime;
 505                         }
 506
 507                         bool is_collision = true;
 508                         if (nearest_info.is_unloaded)
 509                                 is_collision = false;
 510
 511                         CollisionInfo info;
 512                         if (nearest_info.isObject())
 513                                 info.type = COLLISION_OBJECT;
 514                         else
 515                                 info.type = COLLISION_NODE;
 516
 517                         info.node_p = nearest_info.position;
 518                         info.object = nearest_info.obj;
 519                         info.old_speed = *speed_f;
 520                         info.plane = nearest_collided;
 521
 522                         // Set the speed component that caused the collision to zero
 523                         if (step_up) {
 524                                 // Special case: Handle stairs
 525                                 nearest_info.is_step_up = true;
 526                                 is_collision = false;
 527                         } else if (nearest_collided == COLLISION_AXIS_X) {
 528                                 if (fabs(speed_f->X) > BS * 3)
 529                                         speed_f->X *= bounce;
 530                                 else
 531                                         speed_f->X = 0;
 532                                 result.collides = true;
 533                         } else if (nearest_collided == COLLISION_AXIS_Y) {
 534                                 if(fabs(speed_f->Y) > BS * 3)
 535                                         speed_f->Y *= bounce;
 536                                 else
 537                                         speed_f->Y = 0;
 538                                 result.collides = true;
 539                         } else if (nearest_collided == COLLISION_AXIS_Z) {
 540                                 if (fabs(speed_f->Z) > BS * 3)
 541                                         speed_f->Z *= bounce;
 542                                 else
 543                                         speed_f->Z = 0;
 544                                 result.collides = true;
 545                         }
 546
 547                         info.new_speed = *speed_f;
 548                         if (info.new_speed.getDistanceFrom(info.old_speed) < 0.1f * BS)
 549                                 is_collision = false;
 550
 551                         if (is_collision) {
 552                                 info.axis = nearest_collided;
 553                                 result.collisions.push_back(info);
 554                         }
 555                 }
 556         }
 557
 558         /*
 559                 Final touches: Check if standing on ground, step up stairs.
 560         */
 561         aabb3f box = box_0;
 562         box.MinEdge += *pos_f;
 563         box.MaxEdge += *pos_f;
 564         for (const auto &box_info : cinfo) {
 565                 const aabb3f &cbox = box_info.box;
 566
 567                 /*
 568                         See if the object is touching ground.
 569
 570                         Object touches ground if object's minimum Y is near node's
 571                         maximum Y and object's X-Z-area overlaps with the node's
 572                         X-Z-area.
 573                 */
 574
 575                 if (cbox.MaxEdge.X - d > box.MinEdge.X && cbox.MinEdge.X + d < box.MaxEdge.X &&
 576                                 cbox.MaxEdge.Z - d > box.MinEdge.Z &&
 577                                 cbox.MinEdge.Z + d < box.MaxEdge.Z) {
 578                         if (box_info.is_step_up) {
 579                                 pos_f->Y += cbox.MaxEdge.Y - box.MinEdge.Y;
 580                                 box = box_0;
 581                                 box.MinEdge += *pos_f;
 582                                 box.MaxEdge += *pos_f;
 583                         }
 584                         if (std::fabs(cbox.MaxEdge.Y - box.MinEdge.Y) < 0.05f) {
 585                                 result.touching_ground = true;
 586
 587                                 if (box_info.isObject())
 588                                         result.standing_on_object = true;
 589                         }
 590                 }
 591         }
 592
 593         return result;
 594 }