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