Classifies whether or not a polygon is behind,in front, or straddles a plane
| 276 | |
| 277 | // Classifies whether or not a polygon is behind,in front, or straddles a plane |
| 278 | int ClassifyPolygon(bspplane *plane, bsppolygon *poly) { |
| 279 | int numfront, numback, numon; |
| 280 | int i; |
| 281 | int nv = poly->nv; |
| 282 | |
| 283 | ASSERT(nv >= 3); |
| 284 | |
| 285 | numfront = numback = numon = 0; |
| 286 | |
| 287 | for (i = 0; i < nv; i++) { |
| 288 | int fate; |
| 289 | vector *vec = &poly->verts[i]; |
| 290 | |
| 291 | fate = ClassifyVector(plane, vec); |
| 292 | |
| 293 | switch (fate) { |
| 294 | case BSP_IN_FRONT: |
| 295 | numfront++; |
| 296 | break; |
| 297 | case BSP_BEHIND: |
| 298 | numback++; |
| 299 | break; |
| 300 | case BSP_ON_PLANE: |
| 301 | numfront++; |
| 302 | numback++; |
| 303 | numon++; |
| 304 | break; |
| 305 | } |
| 306 | } |
| 307 | |
| 308 | if (numon == nv) { |
| 309 | return BSP_COINCIDENT; |
| 310 | } else if (numfront == nv) { |
| 311 | return BSP_IN_FRONT; |
| 312 | } else if (numback == nv) { |
| 313 | return BSP_BEHIND; |
| 314 | } |
| 315 | |
| 316 | // The polygon straddles the plane |
| 317 | return BSP_SPANNING; |
| 318 | } |
| 319 | |
| 320 | // Tries to split a polygon across a plane |
| 321 | int SplitPolygon(bspplane *plane, bsppolygon *testpoly, bsppolygon **frontpoly, bsppolygon **backpoly) { |
no test coverage detected