svbsp.c

   1
   2 // Shadow Volume BSP code written by Forest "LordHavoc" Hale on 2003-11-06 and placed into public domain.
   3 // Modified by LordHavoc (to make it work and other nice things like that) on 2007-01-24 and 2007-01-25
   4
   5 #include <math.h>
   6 #include <string.h>
   7 #include "svbsp.h"
   8 #include "polygon.h"
   9
  10 #define MAX_SVBSP_POLYGONPOINTS 64
  11 #define SVBSP_CLIP_EPSILON (1.0 / 1024.0)
  12
  13 #define SVBSP_DotProduct(a,b) ((a)[0]*(b)[0]+(a)[1]*(b)[1]+(a)[2]*(b)[2])
  14
  15 static void SVBSP_PlaneFromPoints(double *plane4f, const double *p1, const double *p2, const double *p3)
  16 {
  17         double ilength;
  18         // calculate unnormalized plane
  19         plane4f[0] = (p1[1] - p2[1]) * (p3[2] - p2[2]) - (p1[2] - p2[2]) * (p3[1] - p2[1]);
  20         plane4f[1] = (p1[2] - p2[2]) * (p3[0] - p2[0]) - (p1[0] - p2[0]) * (p3[2] - p2[2]);
  21         plane4f[2] = (p1[0] - p2[0]) * (p3[1] - p2[1]) - (p1[1] - p2[1]) * (p3[0] - p2[0]);
  22         plane4f[3] = SVBSP_DotProduct(plane4f, p1);
  23         // normalize the plane normal and adjust distance accordingly
  24         ilength = sqrt(SVBSP_DotProduct(plane4f, plane4f));
  25         if (ilength)
  26                 ilength = 1.0 / ilength;
  27         plane4f[0] *= ilength;
  28         plane4f[1] *= ilength;
  29         plane4f[2] *= ilength;
  30         plane4f[3] *= ilength;
  31 }
  32
  33 void SVBSP_Init(svbsp_t *b, const double *origin, int maxnodes, svbsp_node_t *nodes)
  34 {
  35         memset(b, 0, sizeof(*b));
  36         b->origin[0] = origin[0];
  37         b->origin[1] = origin[1];
  38         b->origin[2] = origin[2];
  39         b->numnodes = 3;
  40         b->maxnodes = maxnodes;
  41         b->nodes = nodes;
  42         b->ranoutofnodes = 0;
  43         b->stat_occluders_rejected = 0;
  44         b->stat_occluders_accepted = 0;
  45         b->stat_occluders_fragments_accepted = 0;
  46         b->stat_occluders_fragments_rejected = 0;
  47         b->stat_queries_rejected = 0;
  48         b->stat_queries_accepted = 0;
  49         b->stat_queries_fragments_accepted = 0;
  50         b->stat_queries_fragments_rejected = 0;
  51
  52         // the bsp tree must be initialized to have two perpendicular splits axes
  53         // through origin, otherwise the polygon insertions would affect the
  54         // opposite side of the tree, which would be disasterous.
  55         //
  56         // so this code has to make 3 nodes and 4 leafs, and since the leafs are
  57         // represented by empty/solid state numbers in this system rather than
  58         // actual structs, we only need to make the 3 nodes.
  59
  60         // root node
  61         // this one splits the world into +X and -X sides
  62         b->nodes[0].plane[0] = 1;
  63         b->nodes[0].plane[1] = 0;
  64         b->nodes[0].plane[2] = 0;
  65         b->nodes[0].plane[3] = origin[0];
  66         b->nodes[0].parent = -1;
  67         b->nodes[0].children[0] = 1;
  68         b->nodes[0].children[1] = 2;
  69
  70         // +X side node
  71         // this one splits the +X half of the world into +Y and -Y
  72         b->nodes[1].plane[0] = 0;
  73         b->nodes[1].plane[1] = 1;
  74         b->nodes[1].plane[2] = 0;
  75         b->nodes[1].plane[3] = origin[1];
  76         b->nodes[1].parent = 0;
  77         b->nodes[1].children[0] = -1;
  78         b->nodes[1].children[1] = -1;
  79
  80         // -X side node
  81         // this one splits the -X half of the world into +Y and -Y
  82         b->nodes[2].plane[0] = 0;
  83         b->nodes[2].plane[1] = 1;
  84         b->nodes[2].plane[2] = 0;
  85         b->nodes[2].plane[3] = origin[1];
  86         b->nodes[2].parent = 0;
  87         b->nodes[2].children[0] = -1;
  88         b->nodes[2].children[1] = -1;
  89 }
  90
  91 static void SVBSP_InsertOccluderPolygonNodes(svbsp_t *b, int *parentnodenumpointer, int parentnodenum, int numpoints, const double *points, void (*fragmentcallback)(void *fragmentcallback_pointer1, int fragmentcallback_number1, svbsp_t *b, int numpoints, const double *points), void *fragmentcallback_pointer1, int fragmentcallback_number1)
  92 {
  93         // now we need to create up to numpoints + 1 new nodes, forming a BSP tree
  94         // describing the occluder polygon's shadow volume
  95         int i, j, p, basenum;
  96         svbsp_node_t *node;
  97
  98         // if there aren't enough nodes remaining, skip it
  99         if (b->numnodes + numpoints + 1 >= b->maxnodes)
 100         {
 101                 b->ranoutofnodes = 1;
 102                 return;
 103         }
 104
 105         // add one node per side, then the actual occluding face node
 106
 107         // thread safety notes:
 108         // DO NOT multithread insertion, it could be made 'safe' but the results
 109         // would be inconsistent.
 110         //
 111         // it is completely safe to multithread queries in all cases.
 112         //
 113         // if an insertion is occurring the query will give intermediate results,
 114         // being blocked by some volumes but not others, which is perfectly okay
 115         // for visibility culling intended only to reduce rendering work
 116
 117         // note down the first available nodenum for the *parentnodenumpointer
 118         // line which is done last to allow multithreaded queries during an
 119         // insertion
 120         basenum = b->numnodes;
 121         for (i = 0, p = numpoints - 1;i < numpoints;p = i, i++)
 122         {
 123 #if 1
 124                 // see if a parent plane describes this side
 125                 for (j = parentnodenum;j >= 0;j = b->nodes[j].parent)
 126                 {
 127                         double *parentnodeplane = b->nodes[j].plane;
 128                         if (fabs(SVBSP_DotProduct(b->origin     , parentnodeplane) - parentnodeplane[3]) < SVBSP_CLIP_EPSILON
 129                          && fabs(SVBSP_DotProduct(points + p * 3, parentnodeplane) - parentnodeplane[3]) < SVBSP_CLIP_EPSILON
 130                          && fabs(SVBSP_DotProduct(points + i * 3, parentnodeplane) - parentnodeplane[3]) < SVBSP_CLIP_EPSILON)
 131                                 break;
 132                 }
 133                 if (j >= 0)
 134                         continue; // already have a matching parent plane
 135 #endif
 136
 137                 // create a side plane
 138                 // anything infront of this is not inside the shadow volume
 139                 node = b->nodes + b->numnodes++;
 140                 SVBSP_PlaneFromPoints(node->plane, b->origin, points + p * 3, points + i * 3);
 141                 // we need to flip the plane if it puts any part of the polygon on the
 142                 // wrong side
 143                 // (in this way this code treats all polygons as double sided)
 144                 //
 145                 // because speed is important this stops as soon as it finds proof
 146                 // that the orientation is right or wrong
 147                 // (we know that the plane is on one edge of the polygon, so there is
 148                 // never a case where points lie on both sides, so the first hint is
 149                 // sufficient)
 150                 for (j = 0;j < numpoints;j++)
 151                 {
 152                         double d = SVBSP_DotProduct(points + j * 3, node->plane) - node->plane[3];
 153                         if (d < -SVBSP_CLIP_EPSILON)
 154                                 break;
 155                         if (d > SVBSP_CLIP_EPSILON)
 156                         {
 157                                 node->plane[0] *= -1;
 158                                 node->plane[1] *= -1;
 159                                 node->plane[2] *= -1;
 160                                 node->plane[3] *= -1;
 161                                 break;
 162                         }
 163                 }
 164                 node->parent = parentnodenum;
 165                 node->children[0] = -1; // empty
 166                 node->children[1] = -1; // empty
 167                 // link this child into the tree
 168                 *parentnodenumpointer = parentnodenum = (int)(node - b->nodes);
 169                 // now point to the child pointer for the next node to update later
 170                 parentnodenumpointer = &node->children[1];
 171         }
 172
 173 #if 1
 174         // see if a parent plane describes the face plane
 175         for (j = parentnodenum;j >= 0;j = b->nodes[j].parent)
 176         {
 177                 double *parentnodeplane = b->nodes[j].plane;
 178                 if (fabs(SVBSP_DotProduct(points    , parentnodeplane) - parentnodeplane[3]) < SVBSP_CLIP_EPSILON
 179                  && fabs(SVBSP_DotProduct(points + 3, parentnodeplane) - parentnodeplane[3]) < SVBSP_CLIP_EPSILON
 180                  && fabs(SVBSP_DotProduct(points + 6, parentnodeplane) - parentnodeplane[3]) < SVBSP_CLIP_EPSILON)
 181                         break;
 182         }
 183         if (j < 0)
 184 #endif
 185         {
 186                 // add the face-plane node
 187                 // infront is empty, behind is shadow
 188                 node = b->nodes + b->numnodes++;
 189                 SVBSP_PlaneFromPoints(node->plane, points, points + 3, points + 6);
 190                 // this is a flip check similar to the one above
 191                 // this one checks if the plane faces the origin, if not, flip it
 192                 if (SVBSP_DotProduct(b->origin, node->plane) - node->plane[3] < -SVBSP_CLIP_EPSILON)
 193                 {
 194                         node->plane[0] *= -1;
 195                         node->plane[1] *= -1;
 196                         node->plane[2] *= -1;
 197                         node->plane[3] *= -1;
 198                 }
 199                 node->parent = parentnodenum;
 200                 node->children[0] = -1; // empty
 201                 node->children[1] = -2; // shadow
 202                 // link this child into the tree
 203                 // (with the addition of this node, queries will now be culled by it)
 204                 *parentnodenumpointer = (int)(node - b->nodes);
 205         }
 206 }
 207
 208 static int SVBSP_AddPolygonNode(svbsp_t *b, int *parentnodenumpointer, int parentnodenum, int numpoints, const double *points, int insertoccluder, void (*fragmentcallback)(void *fragmentcallback_pointer1, int fragmentcallback_number1, svbsp_t *b, int numpoints, const double *points), void *fragmentcallback_pointer1, int fragmentcallback_number1)
 209 {
 210         int i;
 211         int frontnumpoints, backnumpoints;
 212         double frontpoints[MAX_SVBSP_POLYGONPOINTS * 3], backpoints[MAX_SVBSP_POLYGONPOINTS * 3];
 213         if (numpoints < 3)
 214                 return 0;
 215         // recurse through plane nodes
 216         while (*parentnodenumpointer >= 0)
 217         {
 218                 // do a quick check to see if there is any need to split the polygon
 219                 svbsp_node_t *node = b->nodes + *parentnodenumpointer;
 220                 parentnodenum = *parentnodenumpointer;
 221 #if 1
 222                 if (SVBSP_DotProduct(points, node->plane) >= node->plane[3] + SVBSP_CLIP_EPSILON)
 223                 {
 224                         for (i = 1;i < numpoints && SVBSP_DotProduct(points + i * 3, node->plane) >= node->plane[3] + SVBSP_CLIP_EPSILON;i++);
 225                         if (i == numpoints)
 226                         {
 227                                 // no need to split, just go to one side
 228                                 parentnodenumpointer = &node->children[0];
 229                                 continue;
 230                         }
 231                 }
 232                 else if (SVBSP_DotProduct(points, node->plane) <= node->plane[3] - SVBSP_CLIP_EPSILON)
 233                 {
 234                         for (i = 1;i < numpoints && SVBSP_DotProduct(points + i * 3, node->plane) <= node->plane[3] - SVBSP_CLIP_EPSILON;i++);
 235                         if (i == numpoints)
 236                         {
 237                                 // no need to split, just go to one side
 238                                 parentnodenumpointer = &node->children[1];
 239                                 continue;
 240                         }
 241                 }
 242 #endif
 243                 // at this point we know it crosses the plane, so we need to split it
 244                 PolygonD_Divide(numpoints, points, node->plane[0], node->plane[1], node->plane[2], node->plane[3], SVBSP_CLIP_EPSILON, MAX_SVBSP_POLYGONPOINTS, frontpoints, &frontnumpoints, MAX_SVBSP_POLYGONPOINTS, backpoints, &backnumpoints, NULL);
 245                 if (frontnumpoints > MAX_SVBSP_POLYGONPOINTS)
 246                         frontnumpoints = MAX_SVBSP_POLYGONPOINTS;
 247                 if (backnumpoints > MAX_SVBSP_POLYGONPOINTS)
 248                         backnumpoints = MAX_SVBSP_POLYGONPOINTS;
 249                 // recurse the sides and return the resulting bit flags
 250                 i = 0;
 251                 if (frontnumpoints >= 3)
 252                         i |= SVBSP_AddPolygonNode(b, &node->children[0], (int)(node - b->nodes), frontnumpoints, frontpoints, insertoccluder, fragmentcallback, fragmentcallback_pointer1, fragmentcallback_number1);
 253                 if (backnumpoints >= 3)
 254                         i |= SVBSP_AddPolygonNode(b, &node->children[1], (int)(node - b->nodes), backnumpoints , backpoints , insertoccluder, fragmentcallback, fragmentcallback_pointer1, fragmentcallback_number1);
 255                 return i;
 256         }
 257         // leaf node
 258         if (*parentnodenumpointer == -1)
 259         {
 260                 // empty leaf node; and some geometry survived
 261                 // if inserting an occluder, replace this empty leaf with a shadow volume
 262 #if 0
 263                 for (i = 0;i < numpoints-2;i++)
 264                 {
 265                         Debug_PolygonBegin(NULL, DRAWFLAG_ADDITIVE);
 266                         Debug_PolygonVertex(points[0], points[1], points[2], 0, 0, 0.25, 0, 0, 1);
 267                         Debug_PolygonVertex(points[0 + (i + 1) * 3], points[1 + (i + 1) * 3], points[2 + (i + 1) * 3], 0, 0, 0.25, 0, 0, 1);
 268                         Debug_PolygonVertex(points[0 + (i + 2) * 3], points[1 + (i + 2) * 3], points[2 + (i + 2) * 3], 0, 0, 0.25, 0, 0, 1);
 269                         Debug_PolygonEnd();
 270                 }
 271 #endif
 272                 if (insertoccluder)
 273                 {
 274                         b->stat_occluders_fragments_accepted++;
 275                         SVBSP_InsertOccluderPolygonNodes(b, parentnodenumpointer, parentnodenum, numpoints, points, fragmentcallback, fragmentcallback_pointer1, fragmentcallback_number1);
 276                 }
 277                 else
 278                         b->stat_queries_fragments_accepted++;
 279                 if (fragmentcallback)
 280                         fragmentcallback(fragmentcallback_pointer1, fragmentcallback_number1, b, numpoints, points);
 281                 return 2;
 282         }
 283         else
 284         {
 285                 // otherwise it's a solid leaf which destroys all polygons inside it
 286                 if (insertoccluder)
 287                         b->stat_occluders_fragments_rejected++;
 288                 else
 289                         b->stat_queries_fragments_rejected++;
 290 #if 0
 291                 for (i = 0;i < numpoints-2;i++)
 292                 {
 293                         Debug_PolygonBegin(NULL, DRAWFLAG_ADDITIVE);
 294                         Debug_PolygonVertex(points[0], points[1], points[2], 0, 0, 0, 0, 0.25, 1);
 295                         Debug_PolygonVertex(points[0 + (i + 1) * 3], points[1 + (i + 1) * 3], points[2 + (i + 1) * 3], 0, 0, 0, 0, 0.25, 1);
 296                         Debug_PolygonVertex(points[0 + (i + 2) * 3], points[1 + (i + 2) * 3], points[2 + (i + 2) * 3], 0, 0, 0, 0, 0.25, 1);
 297                         Debug_PolygonEnd();
 298                 }
 299 #endif
 300         }
 301         return 1;
 302 }
 303
 304 int SVBSP_AddPolygon(svbsp_t *b, int numpoints, const double *points, int insertoccluder, void (*fragmentcallback)(void *fragmentcallback_pointer1, int fragmentcallback_number1, svbsp_t *b, int numpoints, const double *points), void *fragmentcallback_pointer1, int fragmentcallback_number1)
 305 {
 306         int i;
 307         int nodenum;
 308         // don't even consider an empty polygon
 309         if (numpoints < 3)
 310                 return 0;
 311 #if 0
 312 //if (insertoccluder)
 313         for (i = 0;i < numpoints-2;i++)
 314         {
 315                 Debug_PolygonBegin(NULL, DRAWFLAG_ADDITIVE);
 316                 Debug_PolygonVertex(points[0], points[1], points[2], 0, 0, 0, 0.25, 0, 1);
 317                 Debug_PolygonVertex(points[0 + (i + 1) * 3], points[1 + (i + 1) * 3], points[2 + (i + 1) * 3], 0, 0, 0, 0.25, 0, 1);
 318                 Debug_PolygonVertex(points[0 + (i + 2) * 3], points[1 + (i + 2) * 3], points[2 + (i + 2) * 3], 0, 0, 0, 0.25, 0, 1);
 319                 Debug_PolygonEnd();
 320         }
 321 #endif
 322         nodenum = 0;
 323         i = SVBSP_AddPolygonNode(b, &nodenum, -1, numpoints, points, insertoccluder, fragmentcallback, fragmentcallback_pointer1, fragmentcallback_number1);
 324         if (insertoccluder)
 325         {
 326                 if (i & 2)
 327                         b->stat_occluders_accepted++;
 328                 else
 329                         b->stat_occluders_rejected++;
 330         }
 331         else
 332         {
 333                 if (i & 2)
 334                         b->stat_queries_accepted++;
 335                 else
 336                         b->stat_queries_rejected++;
 337         }
 338         return i;
 339 }
 340