src/collision.cpp

   1 /*
   2 Minetest-c55
   3 Copyright (C) 2010 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 General Public License as published by
   7 the Free Software Foundation; either version 2 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 General Public License for more details.
  14
  15 You should have received a copy of the GNU 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
  26 collisionMoveResult collisionMoveSimple(Map *map, IGameDef *gamedef,
  27                 f32 pos_max_d, const core::aabbox3d<f32> &box_0,
  28                 f32 dtime, v3f &pos_f, v3f &speed_f)
  29 {
  30         collisionMoveResult result;
  31
  32         v3f oldpos_f = pos_f;
  33         v3s16 oldpos_i = floatToInt(oldpos_f, BS);
  34
  35         /*
  36                 Calculate new position
  37         */
  38         pos_f += speed_f * dtime;
  39
  40         /*
  41                 Collision detection
  42         */
  43
  44         // position in nodes
  45         v3s16 pos_i = floatToInt(pos_f, BS);
  46
  47         /*
  48                 Collision uncertainty radius
  49                 Make it a bit larger than the maximum distance of movement
  50         */
  51         f32 d = pos_max_d * 1.1;
  52         // A fairly large value in here makes moving smoother
  53         //f32 d = 0.15*BS;
  54
  55         // This should always apply, otherwise there are glitches
  56         assert(d > pos_max_d);
  57
  58         /*
  59                 Calculate collision box
  60         */
  61         core::aabbox3d<f32> box = box_0;
  62         box.MaxEdge += pos_f;
  63         box.MinEdge += pos_f;
  64         core::aabbox3d<f32> oldbox = box_0;
  65         oldbox.MaxEdge += oldpos_f;
  66         oldbox.MinEdge += oldpos_f;
  67
  68         /*
  69                 If the object lies on a walkable node, this is set to true.
  70         */
  71         result.touching_ground = false;
  72
  73         /*
  74                 Go through every node around the object
  75                 TODO: Calculate the range of nodes that need to be checked
  76         */
  77         for(s16 y = oldpos_i.Y - 1; y <= oldpos_i.Y + 2; y++)
  78         for(s16 z = oldpos_i.Z - 1; z <= oldpos_i.Z + 1; z++)
  79         for(s16 x = oldpos_i.X - 1; x <= oldpos_i.X + 1; x++)
  80         {
  81                 try{
  82                         // Object collides into walkable nodes
  83                         MapNode n = map->getNode(v3s16(x,y,z));
  84                         if(gamedef->getNodeDefManager()->get(n).walkable == false)
  85                                 continue;
  86                 }
  87                 catch(InvalidPositionException &e)
  88                 {
  89                         // Doing nothing here will block the object from
  90                         // walking over map borders
  91                 }
  92
  93                 core::aabbox3d<f32> nodebox = getNodeBox(v3s16(x,y,z), BS);
  94
  95                 /*
  96                         See if the object is touching ground.
  97
  98                         Object touches ground if object's minimum Y is near node's
  99                         maximum Y and object's X-Z-area overlaps with the node's
 100                         X-Z-area.
 101
 102                         Use 0.15*BS so that it is easier to get on a node.
 103                 */
 104                 if(
 105                                 //fabs(nodebox.MaxEdge.Y-box.MinEdge.Y) < d
 106                                 fabs(nodebox.MaxEdge.Y-box.MinEdge.Y) < 0.15*BS
 107                                 && nodebox.MaxEdge.X-d > box.MinEdge.X
 108                                 && nodebox.MinEdge.X+d < box.MaxEdge.X
 109                                 && nodebox.MaxEdge.Z-d > box.MinEdge.Z
 110                                 && nodebox.MinEdge.Z+d < box.MaxEdge.Z
 111                 ){
 112                         result.touching_ground = true;
 113                 }
 114
 115                 // If object doesn't intersect with node, ignore node.
 116                 if(box.intersectsWithBox(nodebox) == false)
 117                         continue;
 118
 119                 /*
 120                         Go through every axis
 121                 */
 122                 v3f dirs[3] = {
 123                         v3f(0,0,1), // back-front
 124                         v3f(0,1,0), // top-bottom
 125                         v3f(1,0,0), // right-left
 126                 };
 127                 for(u16 i=0; i<3; i++)
 128                 {
 129                         /*
 130                                 Calculate values along the axis
 131                         */
 132                         f32 nodemax = nodebox.MaxEdge.dotProduct(dirs[i]);
 133                         f32 nodemin = nodebox.MinEdge.dotProduct(dirs[i]);
 134                         f32 objectmax = box.MaxEdge.dotProduct(dirs[i]);
 135                         f32 objectmin = box.MinEdge.dotProduct(dirs[i]);
 136                         f32 objectmax_old = oldbox.MaxEdge.dotProduct(dirs[i]);
 137                         f32 objectmin_old = oldbox.MinEdge.dotProduct(dirs[i]);
 138
 139                         /*
 140                                 Check collision for the axis.
 141                                 Collision happens when object is going through a surface.
 142                         */
 143                         bool negative_axis_collides =
 144                                 (nodemax > objectmin && nodemax <= objectmin_old + d
 145                                         && speed_f.dotProduct(dirs[i]) < 0);
 146                         bool positive_axis_collides =
 147                                 (nodemin < objectmax && nodemin >= objectmax_old - d
 148                                         && speed_f.dotProduct(dirs[i]) > 0);
 149                         bool main_axis_collides =
 150                                         negative_axis_collides || positive_axis_collides;
 151
 152                         /*
 153                                 Check overlap of object and node in other axes
 154                         */
 155                         bool other_axes_overlap = true;
 156                         for(u16 j=0; j<3; j++)
 157                         {
 158                                 if(j == i)
 159                                         continue;
 160                                 f32 nodemax = nodebox.MaxEdge.dotProduct(dirs[j]);
 161                                 f32 nodemin = nodebox.MinEdge.dotProduct(dirs[j]);
 162                                 f32 objectmax = box.MaxEdge.dotProduct(dirs[j]);
 163                                 f32 objectmin = box.MinEdge.dotProduct(dirs[j]);
 164                                 if(!(nodemax - d > objectmin && nodemin + d < objectmax))
 165                                 {
 166                                         other_axes_overlap = false;
 167                                         break;
 168                                 }
 169                         }
 170
 171                         /*
 172                                 If this is a collision, revert the pos_f in the main
 173                                 direction.
 174                         */
 175                         if(other_axes_overlap && main_axis_collides)
 176                         {
 177                                 speed_f -= speed_f.dotProduct(dirs[i]) * dirs[i];
 178                                 pos_f -= pos_f.dotProduct(dirs[i]) * dirs[i];
 179                                 pos_f += oldpos_f.dotProduct(dirs[i]) * dirs[i];
 180                                 result.collides = true;
 181                         }
 182
 183                 }
 184         } // xyz
 185
 186         return result;
 187 }
 188
 189 collisionMoveResult collisionMovePrecise(Map *map, IGameDef *gamedef,
 190                 f32 pos_max_d, const core::aabbox3d<f32> &box_0,
 191                 f32 dtime, v3f &pos_f, v3f &speed_f)
 192 {
 193         collisionMoveResult final_result;
 194
 195         // Maximum time increment (for collision detection etc)
 196         // time = distance / speed
 197         f32 dtime_max_increment = pos_max_d / speed_f.getLength();
 198
 199         // Maximum time increment is 10ms or lower
 200         if(dtime_max_increment > 0.01)
 201                 dtime_max_increment = 0.01;
 202
 203         // Don't allow overly huge dtime
 204         if(dtime > 2.0)
 205                 dtime = 2.0;
 206
 207         f32 dtime_downcount = dtime;
 208
 209         u32 loopcount = 0;
 210         do
 211         {
 212                 loopcount++;
 213
 214                 f32 dtime_part;
 215                 if(dtime_downcount > dtime_max_increment)
 216                 {
 217                         dtime_part = dtime_max_increment;
 218                         dtime_downcount -= dtime_part;
 219                 }
 220                 else
 221                 {
 222                         dtime_part = dtime_downcount;
 223                         /*
 224                                 Setting this to 0 (no -=dtime_part) disables an infinite loop
 225                                 when dtime_part is so small that dtime_downcount -= dtime_part
 226                                 does nothing
 227                         */
 228                         dtime_downcount = 0;
 229                 }
 230
 231                 collisionMoveResult result = collisionMoveSimple(map, gamedef,
 232                                 pos_max_d, box_0, dtime_part, pos_f, speed_f);
 233
 234                 if(result.touching_ground)
 235                         final_result.touching_ground = true;
 236                 if(result.collides)
 237                         final_result.collides = true;
 238         }
 239         while(dtime_downcount > 0.001);
 240
 241
 242         return final_result;
 243 }
 244
 245