r_shadow.c

   1
   2 #include "quakedef.h"
   3
   4 mempool_t *r_shadow_mempool;
   5
   6 int maxshadowelements;
   7 int *shadowelements;
   8 int maxtrianglefacinglight;
   9 qbyte *trianglefacinglight;
  10
  11 void r_shadow_start(void)
  12 {
  13         // allocate vertex processing arrays
  14         r_shadow_mempool = Mem_AllocPool("R_Shadow");
  15         maxshadowelements = 0;
  16         shadowelements = NULL;
  17         maxtrianglefacinglight = 0;
  18         trianglefacinglight = NULL;
  19 }
  20
  21 void r_shadow_shutdown(void)
  22 {
  23         maxshadowelements = 0;
  24         shadowelements = NULL;
  25         maxtrianglefacinglight = 0;
  26         trianglefacinglight = NULL;
  27         Mem_FreePool(&r_shadow_mempool);
  28 }
  29
  30 void r_shadow_newmap(void)
  31 {
  32 }
  33
  34 void R_Shadow_Init(void)
  35 {
  36         R_RegisterModule("R_Shadow", r_shadow_start, r_shadow_shutdown, r_shadow_newmap);
  37 }
  38
  39 void R_Shadow_Volume(int numverts, int numtris, float *vertex, int *elements, int *neighbors, vec3_t relativelightorigin, float projectdistance, int visiblevolume)
  40 {
  41         int i, *e, *n, *out, tris;
  42         float *v0, *v1, *v2, temp[3], f;
  43 // terminology:
  44 //
  45 // frontface:
  46 // a triangle facing the light source
  47 //
  48 // backface:
  49 // a triangle not facing the light source
  50 //
  51 // shadow volume:
  52 // an extrusion of the backfaces, beginning at the original geometry and
  53 // ending further from the light source than the original geometry
  54 // (presumably at least as far as the light's radius, if the light has a
  55 // radius at all), capped at both front and back to avoid any problems
  56 //
  57 // description:
  58 // draws the shadow volumes of the model.
  59 // requirements:
  60 // vertex loations must already be in vertex before use.
  61 // vertex must have capacity for numverts * 2.
  62
  63         // make sure trianglefacinglight is big enough for this volume
  64         if (maxtrianglefacinglight < numtris)
  65         {
  66                 maxtrianglefacinglight = numtris;
  67                 if (trianglefacinglight)
  68                         Mem_Free(trianglefacinglight);
  69                 trianglefacinglight = Mem_Alloc(r_shadow_mempool, maxtrianglefacinglight);
  70         }
  71
  72         // make sure shadowelements is big enough for this volume
  73         if (maxshadowelements < numtris * 24)
  74         {
  75                 maxshadowelements = numtris * 24;
  76                 if (shadowelements)
  77                         Mem_Free(shadowelements);
  78                 shadowelements = Mem_Alloc(r_shadow_mempool, maxshadowelements * sizeof(int));
  79         }
  80
  81         // make projected vertices
  82         // by clever use of elements we'll construct the whole shadow from
  83         // the unprojected vertices and these projected vertices
  84         for (i = 0, v0 = vertex, v1 = vertex + numverts * 4;i < numverts;i++, v0 += 4, v1 += 4)
  85         {
  86                 VectorSubtract(v0, relativelightorigin, temp);
  87                 f = projectdistance / sqrt(DotProduct(temp,temp));
  88                 VectorMA(v0, f, temp, v1);
  89         }
  90
  91         // check which triangles are facing the light
  92         for (i = 0, e = elements;i < numtris;i++, e += 3)
  93         {
  94                 // calculate triangle facing flag
  95                 v0 = vertex + e[0] * 4;
  96                 v1 = vertex + e[1] * 4;
  97                 v2 = vertex + e[2] * 4;
  98                 // we do not need to normalize the surface normal because both sides
  99                 // of the comparison use it, therefore they are both multiplied the
 100                 // same amount...  furthermore the subtract can be done on the
 101                 // vectors, saving a little bit of math in the dotproducts
 102 #if 1
 103                 // fast version
 104                 // subtracts v1 from v0 and v2, combined into a crossproduct,
 105                 // combined with a dotproduct of the light location relative to the
 106                 // first point of the triangle (any point works, since the triangle
 107                 // is obviously flat), and finally a comparison to determine if the
 108                 // light is infront of the triangle (the goal of this statement)
 109                 trianglefacinglight[i] =
 110                    (relativelightorigin[0] - v0[0]) * ((v0[1] - v1[1]) * (v2[2] - v1[2]) - (v0[2] - v1[2]) * (v2[1] - v1[1]))
 111                  + (relativelightorigin[1] - v0[1]) * ((v0[2] - v1[2]) * (v2[0] - v1[0]) - (v0[0] - v1[0]) * (v2[2] - v1[2]))
 112                  + (relativelightorigin[2] - v0[2]) * ((v0[0] - v1[0]) * (v2[1] - v1[1]) - (v0[1] - v1[1]) * (v2[0] - v1[0])) > 0;
 113 #else
 114                 // readable version
 115                 {
 116                 float dir0[3], dir1[3],
 117
 118                 // calculate two mostly perpendicular edge directions
 119                 VectorSubtract(v0, v1, dir0);
 120                 VectorSubtract(v2, v1, dir1);
 121
 122                 // we have two edge directions, we can calculate a third vector from
 123                 // them, which is the direction of the surface normal (it's magnitude
 124                 // is not 1 however)
 125                 CrossProduct(dir0, dir1, temp);
 126
 127                 // this is entirely unnecessary, but kept for clarity
 128                 //VectorNormalize(temp);
 129
 130                 // compare distance of light along normal, with distance of any point
 131                 // of the triangle along the same normal (the triangle is planar,
 132                 // I.E. flat, so all points give the same answer)
 133                 // the normal is not normalized because it is used on both sides of
 134                 // the comparison, so it's magnitude does not matter
 135                 trianglefacinglight[i] = DotProduct(relativelightorigin, temp) >= DotProduct(v0, temp);
 136                 }
 137 #endif
 138         }
 139
 140         // output triangle elements
 141         out = shadowelements;
 142         tris = 0;
 143
 144         // check each backface for bordering frontfaces,
 145         // and cast shadow polygons from those edges,
 146         // also create front and back caps for shadow volume
 147         for (i = 0, e = elements, n = neighbors;i < numtris;i++, e += 3, n += 3)
 148         {
 149                 if (!trianglefacinglight[i])
 150                 {
 151                         // triangle is backface and therefore casts shadow,
 152                         // output front and back caps for shadow volume
 153                         // front cap (with flipped winding order)
 154                         out[0] = e[0];
 155                         out[1] = e[2];
 156                         out[2] = e[1];
 157                         // rear cap
 158                         out[3] = e[0] + numverts;
 159                         out[4] = e[1] + numverts;
 160                         out[5] = e[2] + numverts;
 161                         out += 6;
 162                         tris += 2;
 163                         // check the edges
 164                         if (n[0] < 0 || trianglefacinglight[n[0]])
 165                         {
 166                                 out[0] = e[0];
 167                                 out[1] = e[1];
 168                                 out[2] = e[1] + numverts;
 169                                 out[3] = e[0];
 170                                 out[4] = e[1] + numverts;
 171                                 out[5] = e[0] + numverts;
 172                                 out += 6;
 173                                 tris += 2;
 174                         }
 175                         if (n[1] < 0 || trianglefacinglight[n[1]])
 176                         {
 177                                 out[0] = e[1];
 178                                 out[1] = e[2];
 179                                 out[2] = e[2] + numverts;
 180                                 out[3] = e[1];
 181                                 out[4] = e[2] + numverts;
 182                                 out[5] = e[1] + numverts;
 183                                 out += 6;
 184                                 tris += 2;
 185                         }
 186                         if (n[2] < 0 || trianglefacinglight[n[2]])
 187                         {
 188                                 out[0] = e[2];
 189                                 out[1] = e[0];
 190                                 out[2] = e[0] + numverts;
 191                                 out[3] = e[2];
 192                                 out[4] = e[0] + numverts;
 193                                 out[5] = e[2] + numverts;
 194                                 out += 6;
 195                                 tris += 2;
 196                         }
 197                 }
 198         }
 199         // draw the volume
 200         if (visiblevolume)
 201         {
 202                 qglDisable(GL_CULL_FACE);
 203                 R_Mesh_Draw(numverts * 2, tris, shadowelements);
 204                 qglEnable(GL_CULL_FACE);
 205         }
 206         else
 207         {
 208                 qglColorMask(0,0,0,0);
 209                 qglEnable(GL_STENCIL_TEST);
 210                 // increment stencil if backface is behind depthbuffer
 211                 qglCullFace(GL_BACK); // quake is backwards, this culls front faces
 212                 qglStencilOp(GL_KEEP, GL_INCR, GL_KEEP);
 213                 R_Mesh_Draw(numverts * 2, tris, shadowelements);
 214                 // decrement stencil if frontface is infront of depthbuffer
 215                 qglCullFace(GL_FRONT); // quake is backwards, this culls back faces
 216                 qglStencilOp(GL_KEEP, GL_DECR, GL_KEEP);
 217                 R_Mesh_Draw(numverts * 2, tris, shadowelements);
 218                 // restore to normal quake rendering
 219                 qglDisable(GL_STENCIL_TEST);
 220                 qglStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
 221                 qglColorMask(1,1,1,1);
 222         }
 223 }
 224
 225 void R_Shadow_VertexLight(int numverts, float *vertex, float *normals, vec3_t relativelightorigin, float lightradius2, float lightdistbias, float lightsubtract, float *lightcolor)
 226 {
 227         int i;
 228         float *n, *v, *c, f, dist, temp[3];
 229         // calculate vertex colors
 230         for (i = 0, v = vertex, c = varray_color, n = normals;i < numverts;i++, v += 4, c += 4, n += 3)
 231         {
 232                 VectorSubtract(relativelightorigin, v, temp);
 233                 c[0] = 0;
 234                 c[1] = 0;
 235                 c[2] = 0;
 236                 c[3] = 1;
 237                 f = DotProduct(n, temp);
 238                 if (f > 0)
 239                 {
 240                         dist = DotProduct(temp, temp);
 241                         if (dist < lightradius2)
 242                         {
 243                                 f = ((1.0f / (dist + lightdistbias)) - lightsubtract) * (f / sqrt(dist));
 244                                 c[0] = f * lightcolor[0];
 245                                 c[1] = f * lightcolor[1];
 246                                 c[2] = f * lightcolor[2];
 247                         }
 248                 }
 249         }
 250 }
 251
 252 void R_Shadow_RenderLightThroughStencil(int numverts, int numtris, int *elements, vec3_t relativelightorigin, float *normals)
 253 {
 254         // only draw light where this geometry was already rendered AND the
 255         // stencil is 0 (non-zero means shadow)
 256         qglDepthFunc(GL_EQUAL);
 257         qglEnable(GL_STENCIL_TEST);
 258         qglStencilFunc(GL_EQUAL, 0, 0xFF);
 259         R_Mesh_Draw(numverts, numtris, elements);
 260         qglDisable(GL_STENCIL_TEST);
 261         qglDepthFunc(GL_LEQUAL);
 262 }
 263
 264 void R_Shadow_ClearStencil(void)
 265 {
 266         qglClearStencil(0);
 267         qglClear(GL_STENCIL_BUFFER_BIT);
 268 }