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 lightradius, float projectdistance, int visiblevolume)
  40 {
  41         int i, *e, *n, *out, tris;
  42         float *v0, *v1, *v2, temp[3], f;
  43         if (projectdistance < 0.1)
  44         {
  45                 Con_Printf("R_Shadow_Volume: projectdistance %f\n");
  46                 return;
  47         }
  48 // terminology:
  49 //
  50 // frontface:
  51 // a triangle facing the light source
  52 //
  53 // backface:
  54 // a triangle not facing the light source
  55 //
  56 // shadow volume:
  57 // an extrusion of the backfaces, beginning at the original geometry and
  58 // ending further from the light source than the original geometry
  59 // (presumably at least as far as the light's radius, if the light has a
  60 // radius at all), capped at both front and back to avoid any problems
  61 //
  62 // description:
  63 // draws the shadow volumes of the model.
  64 // requirements:
  65 // vertex loations must already be in vertex before use.
  66 // vertex must have capacity for numverts * 2.
  67
  68         // make sure trianglefacinglight is big enough for this volume
  69         if (maxtrianglefacinglight < numtris)
  70         {
  71                 maxtrianglefacinglight = numtris;
  72                 if (trianglefacinglight)
  73                         Mem_Free(trianglefacinglight);
  74                 trianglefacinglight = Mem_Alloc(r_shadow_mempool, maxtrianglefacinglight);
  75         }
  76
  77         // make sure shadowelements is big enough for this volume
  78         if (maxshadowelements < numtris * 24)
  79         {
  80                 maxshadowelements = numtris * 24;
  81                 if (shadowelements)
  82                         Mem_Free(shadowelements);
  83                 shadowelements = Mem_Alloc(r_shadow_mempool, maxshadowelements * sizeof(int));
  84         }
  85
  86         // make projected vertices
  87         // by clever use of elements we'll construct the whole shadow from
  88         // the unprojected vertices and these projected vertices
  89         for (i = 0, v0 = vertex, v1 = vertex + numverts * 4;i < numverts;i++, v0 += 4, v1 += 4)
  90         {
  91                 VectorSubtract(v0, relativelightorigin, temp);
  92 #if 0
  93                 f = lightradius / sqrt(DotProduct(temp,temp));
  94                 if (f < 1)
  95                         f = 1;
  96                 VectorMA(relativelightorigin, f, temp, v1);
  97 #else
  98                 f = projectdistance / sqrt(DotProduct(temp,temp));
  99                 VectorMA(v0, f, temp, v1);
 100 #endif
 101         }
 102
 103         // check which triangles are facing the light
 104         for (i = 0, e = elements;i < numtris;i++, e += 3)
 105         {
 106                 // calculate triangle facing flag
 107                 v0 = vertex + e[0] * 4;
 108                 v1 = vertex + e[1] * 4;
 109                 v2 = vertex + e[2] * 4;
 110                 // we do not need to normalize the surface normal because both sides
 111                 // of the comparison use it, therefore they are both multiplied the
 112                 // same amount...  furthermore the subtract can be done on the
 113                 // vectors, saving a little bit of math in the dotproducts
 114 #if 1
 115                 // fast version
 116                 // subtracts v1 from v0 and v2, combined into a crossproduct,
 117                 // combined with a dotproduct of the light location relative to the
 118                 // first point of the triangle (any point works, since the triangle
 119                 // is obviously flat), and finally a comparison to determine if the
 120                 // light is infront of the triangle (the goal of this statement)
 121                 trianglefacinglight[i] =
 122                    (relativelightorigin[0] - v0[0]) * ((v0[1] - v1[1]) * (v2[2] - v1[2]) - (v0[2] - v1[2]) * (v2[1] - v1[1]))
 123                  + (relativelightorigin[1] - v0[1]) * ((v0[2] - v1[2]) * (v2[0] - v1[0]) - (v0[0] - v1[0]) * (v2[2] - v1[2]))
 124                  + (relativelightorigin[2] - v0[2]) * ((v0[0] - v1[0]) * (v2[1] - v1[1]) - (v0[1] - v1[1]) * (v2[0] - v1[0])) > 0;
 125 #else
 126                 // readable version
 127                 {
 128                 float dir0[3], dir1[3];
 129
 130                 // calculate two mostly perpendicular edge directions
 131                 VectorSubtract(v0, v1, dir0);
 132                 VectorSubtract(v2, v1, dir1);
 133
 134                 // we have two edge directions, we can calculate a third vector from
 135                 // them, which is the direction of the surface normal (it's magnitude
 136                 // is not 1 however)
 137                 CrossProduct(dir0, dir1, temp);
 138
 139                 // this is entirely unnecessary, but kept for clarity
 140                 //VectorNormalize(temp);
 141
 142                 // compare distance of light along normal, with distance of any point
 143                 // of the triangle along the same normal (the triangle is planar,
 144                 // I.E. flat, so all points give the same answer)
 145                 // the normal is not normalized because it is used on both sides of
 146                 // the comparison, so it's magnitude does not matter
 147                 trianglefacinglight[i] = DotProduct(relativelightorigin, temp) >= DotProduct(v0, temp);
 148 #endif
 149         }
 150
 151         // output triangle elements
 152         out = shadowelements;
 153         tris = 0;
 154
 155         // check each backface for bordering frontfaces,
 156         // and cast shadow polygons from those edges,
 157         // also create front and back caps for shadow volume
 158         for (i = 0, e = elements, n = neighbors;i < numtris;i++, e += 3, n += 3)
 159         {
 160                 if (!trianglefacinglight[i])
 161                 {
 162                         // triangle is backface and therefore casts shadow,
 163                         // output front and back caps for shadow volume
 164 #if 1
 165                         // front cap (with flipped winding order)
 166                         out[0] = e[0];
 167                         out[1] = e[2];
 168                         out[2] = e[1];
 169                         // rear cap
 170                         out[3] = e[0] + numverts;
 171                         out[4] = e[1] + numverts;
 172                         out[5] = e[2] + numverts;
 173                         out += 6;
 174                         tris += 2;
 175 #else
 176                         // rear cap
 177                         out[0] = e[0] + numverts;
 178                         out[1] = e[1] + numverts;
 179                         out[2] = e[2] + numverts;
 180                         out += 3;
 181                         tris += 1;
 182 #endif
 183                         // check the edges
 184                         if (n[0] < 0 || trianglefacinglight[n[0]])
 185                         {
 186                                 out[0] = e[0];
 187                                 out[1] = e[1];
 188                                 out[2] = e[1] + numverts;
 189                                 out[3] = e[0];
 190                                 out[4] = e[1] + numverts;
 191                                 out[5] = e[0] + numverts;
 192                                 out += 6;
 193                                 tris += 2;
 194                         }
 195                         if (n[1] < 0 || trianglefacinglight[n[1]])
 196                         {
 197                                 out[0] = e[1];
 198                                 out[1] = e[2];
 199                                 out[2] = e[2] + numverts;
 200                                 out[3] = e[1];
 201                                 out[4] = e[2] + numverts;
 202                                 out[5] = e[1] + numverts;
 203                                 out += 6;
 204                                 tris += 2;
 205                         }
 206                         if (n[2] < 0 || trianglefacinglight[n[2]])
 207                         {
 208                                 out[0] = e[2];
 209                                 out[1] = e[0];
 210                                 out[2] = e[0] + numverts;
 211                                 out[3] = e[2];
 212                                 out[4] = e[0] + numverts;
 213                                 out[5] = e[2] + numverts;
 214                                 out += 6;
 215                                 tris += 2;
 216                         }
 217                 }
 218         }
 219         // draw the volume
 220         if (visiblevolume)
 221         {
 222                 //qglDisable(GL_CULL_FACE);
 223                 R_Mesh_Draw(numverts * 2, tris, shadowelements);
 224                 //qglEnable(GL_CULL_FACE);
 225         }
 226         else
 227         {
 228                 qglColorMask(0,0,0,0);
 229                 qglDepthMask(0);
 230                 qglEnable(GL_STENCIL_TEST);
 231
 232                 // increment stencil if backface is behind depthbuffer
 233                 qglCullFace(GL_BACK); // quake is backwards, this culls front faces
 234                 qglStencilOp(GL_KEEP, GL_INCR, GL_KEEP);
 235                 R_Mesh_Draw(numverts * 2, tris, shadowelements);
 236                 // decrement stencil if frontface is infront of depthbuffer
 237                 qglCullFace(GL_FRONT); // quake is backwards, this culls back faces
 238                 qglStencilOp(GL_KEEP, GL_DECR, GL_KEEP);
 239                 R_Mesh_Draw(numverts * 2, tris, shadowelements);
 240
 241                 // restore to normal quake rendering
 242                 qglDisable(GL_STENCIL_TEST);
 243                 qglStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
 244                 qglDepthMask(1);
 245                 qglColorMask(1,1,1,1);
 246         }
 247 }
 248
 249 void R_Shadow_VertexLight(int numverts, float *vertex, float *normals, vec3_t relativelightorigin, float lightradius2, float lightdistbias, float lightsubtract, float *lightcolor)
 250 {
 251         int i;
 252         float *n, *v, *c, f, dist, temp[3];
 253         // calculate vertex colors
 254         for (i = 0, v = vertex, c = varray_color, n = normals;i < numverts;i++, v += 4, c += 4, n += 3)
 255         {
 256                 VectorSubtract(relativelightorigin, v, temp);
 257                 c[0] = 0;
 258                 c[1] = 0;
 259                 c[2] = 0;
 260                 c[3] = 1;
 261                 f = DotProduct(n, temp);
 262                 if (f > 0)
 263                 {
 264                         dist = DotProduct(temp, temp);
 265                         if (dist < lightradius2)
 266                         {
 267                                 f = ((1.0f / (dist + lightdistbias)) - lightsubtract) * (f / sqrt(dist));
 268                                 c[0] = f * lightcolor[0];
 269                                 c[1] = f * lightcolor[1];
 270                                 c[2] = f * lightcolor[2];
 271                         }
 272                 }
 273         }
 274 }
 275
 276 void R_Shadow_RenderLightThroughStencil(int numverts, int numtris, int *elements, vec3_t relativelightorigin, float *normals)
 277 {
 278         // only draw light where this geometry was already rendered AND the
 279         // stencil is 0 (non-zero means shadow)
 280         qglDepthFunc(GL_EQUAL);
 281         qglEnable(GL_STENCIL_TEST);
 282         qglStencilFunc(GL_EQUAL, 0, 0xFF);
 283         R_Mesh_Draw(numverts, numtris, elements);
 284         qglDisable(GL_STENCIL_TEST);
 285         qglDepthFunc(GL_LEQUAL);
 286 }
 287
 288 void R_Shadow_ClearStencil(void)
 289 {
 290         qglClearStencil(0);
 291         qglClear(GL_STENCIL_BUFFER_BIT);
 292 }