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#ifndef lint |
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static const char RCSid[] = "$Id$"; |
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#endif |
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/* |
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* Routines for computing ray intersections with meshes. |
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* |
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* Intersection with a triangle mesh is based on Segura and Feito's |
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* WSCG 2001 paper, "Algorithms to Test Ray-Triangle Intersection, |
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* Comparative Study." This method avoids additional storage |
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* requirements, floating divides, and allows some savings by |
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* caching ray-edge comparisons that are otherwise repeated locally |
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* in typical mesh geometries. (This is our own optimization.) |
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* |
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* The code herein is quite similar to that in o_instance.c, the |
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* chief differences being the custom triangle intersection routines |
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* and the fact that an "OBJECT" in the mesh octree is not an index |
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* into the Radiance OBJREC list, but a mesh triangle index. We still |
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* utilize the standard octree traversal code by setting the hitf |
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* function pointer in the RAY struct to our custom mesh_hit() call. |
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*/ |
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|
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#include "copyright.h" |
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|
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#include "ray.h" |
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|
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#include "mesh.h" |
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|
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#include "tmesh.h" |
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|
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|
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#define EDGE_CACHE_SIZ 251 /* length of mesh edge cache */ |
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|
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#define curmi (edge_cache.mi) |
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#define curmsh (curmi->msh) |
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|
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|
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/* Cache of signed volumes for this ray and this mesh */ |
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struct EdgeCache { |
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OBJREC *o; /* mesh object */ |
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MESHINST *mi; /* current mesh instance */ |
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struct EdgeSide { |
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int4 v1i, v2i; /* vertex indices (lowest first) */ |
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short signum; /* signed volume */ |
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} cache[EDGE_CACHE_SIZ]; |
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} edge_cache; |
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|
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|
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static void |
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prep_edge_cache(o) /* get instance and clear edge cache */ |
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OBJREC *o; |
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{ |
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/* get mesh instance */ |
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edge_cache.mi = getmeshinst(edge_cache.o = o, IO_ALL); |
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/* clear edge cache */ |
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bzero((void *)edge_cache.cache, sizeof(edge_cache.cache)); |
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} |
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|
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|
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static int |
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signed_volume(r, v1, v2) /* get signed volume for ray and edge */ |
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register RAY *r; |
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int4 v1, v2; |
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{ |
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int reversed = 0; |
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register struct EdgeSide *ecp; |
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|
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if (v1 > v2) { |
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int4 t = v2; v2 = v1; v1 = t; |
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reversed = 1; |
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} |
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ecp = &edge_cache.cache[((v2<<11 ^ v1) & 0x7fffffff) % EDGE_CACHE_SIZ]; |
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if (ecp->v1i != v1 || ecp->v2i != v2) { |
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MESHVERT tv1, tv2; /* compute signed volume */ |
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FVECT v2d; |
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double vol; |
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if (!getmeshvert(&tv1, edge_cache.mi->msh, v1, MT_V) || |
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!getmeshvert(&tv2, edge_cache.mi->msh, v2, MT_V)) |
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objerror(edge_cache.o, INTERNAL, |
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"missing mesh vertex in signed_volume"); |
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VSUB(v2d, tv2.v, r->rorg); |
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vol = (tv1.v[0] - r->rorg[0]) * |
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(v2d[1]*r->rdir[2] - v2d[2]*r->rdir[1]); |
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vol += (tv1.v[1] - r->rorg[1]) * |
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(v2d[2]*r->rdir[0] - v2d[0]*r->rdir[2]); |
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vol += (tv1.v[2] - r->rorg[2]) * |
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(v2d[0]*r->rdir[1] - v2d[1]*r->rdir[0]); |
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if (vol > .0) |
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ecp->signum = 1; |
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else if (vol < .0) |
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ecp->signum = -1; |
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else |
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ecp->signum = 0; |
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ecp->v1i = v1; |
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ecp->v2i = v2; |
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} |
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return(reversed ? -ecp->signum : ecp->signum); |
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} |
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|
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|
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static void |
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mesh_hit(oset, r) /* intersect ray with mesh triangle(s) */ |
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OBJECT *oset; |
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RAY *r; |
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{ |
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int4 tvi[3]; |
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int sv1, sv2, sv3; |
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MESHVERT tv[3]; |
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FVECT va, vb, nrm; |
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double d; |
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int i; |
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/* check each triangle */ |
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for (i = oset[0]; i > 0; i--) { |
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if (!getmeshtrivid(tvi, curmsh, oset[i])) |
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objerror(edge_cache.o, INTERNAL, |
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"missing triangle vertices in mesh_hit"); |
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sv1 = signed_volume(r, tvi[0], tvi[1]); |
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sv2 = signed_volume(r, tvi[1], tvi[2]); |
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sv3 = signed_volume(r, tvi[2], tvi[0]); |
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if (sv1 != sv2 || sv2 != sv3) /* compare volume signs */ |
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if (sv1 && sv2 && sv3) |
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continue; |
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/* compute intersection */ |
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getmeshvert(&tv[0], curmsh, tvi[0], MT_V); |
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getmeshvert(&tv[1], curmsh, tvi[1], MT_V); |
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getmeshvert(&tv[2], curmsh, tvi[2], MT_V); |
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VSUB(va, tv[0].v, tv[2].v); |
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VSUB(vb, tv[1].v, tv[0].v); |
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VCROSS(nrm, va, vb); |
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d = DOT(r->rdir, nrm); |
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if (d == 0.0) |
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continue; /* ray is tangent */ |
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VSUB(va, tv[0].v, r->rorg); |
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d = DOT(va, nrm) / d; |
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if (d <= FTINY || d >= r->rot) |
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continue; /* not good enough */ |
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r->robj = oset[i]; /* else record hit */ |
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r->ro = edge_cache.o; |
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r->rot = d; |
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VSUM(r->rop, r->rorg, r->rdir, d); |
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VCOPY(r->ron, nrm); |
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/* normalize(r->ron) called & r->rod set in o_mesh() */ |
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} |
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} |
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|
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|
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int |
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o_mesh(o, r) /* compute ray intersection with a mesh */ |
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OBJREC *o; |
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register RAY *r; |
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{ |
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RAY rcont; |
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int flags; |
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MESHVERT tv[3]; |
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FLOAT wt[3]; |
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int i; |
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/* get the mesh instance */ |
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prep_edge_cache(o); |
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/* copy and transform ray */ |
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copystruct(&rcont, r); |
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multp3(rcont.rorg, r->rorg, curmi->x.b.xfm); |
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multv3(rcont.rdir, r->rdir, curmi->x.b.xfm); |
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for (i = 0; i < 3; i++) |
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rcont.rdir[i] /= curmi->x.b.sca; |
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rcont.rmax *= curmi->x.b.sca; |
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/* clear and trace ray */ |
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rayclear(&rcont); |
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rcont.hitf = mesh_hit; |
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if (!localhit(&rcont, &curmi->msh->mcube)) |
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return(0); /* missed */ |
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if (rcont.rot * curmi->x.f.sca >= r->rot) |
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return(0); /* not close enough */ |
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|
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r->robj = objndx(o); /* record new hit */ |
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r->ro = o; |
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/* transform ray back */ |
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r->rot = rcont.rot * curmi->x.f.sca; |
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multp3(r->rop, rcont.rop, curmi->x.f.xfm); |
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multv3(r->ron, rcont.ron, curmi->x.f.xfm); |
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normalize(r->ron); |
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r->rod = -DOT(r->rdir, r->ron); |
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/* compute barycentric weights */ |
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flags = getmeshtri(tv, curmsh, rcont.robj, MT_ALL); |
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if (!(flags & MT_V)) |
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objerror(o, INTERNAL, "missing mesh vertices in o_mesh"); |
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if (flags & (MT_N|MT_UV)) |
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if (get_baryc(wt, rcont.rop, tv[0].v, tv[1].v, tv[2].v) < 0) { |
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objerror(o, WARNING, "bad triangle in o_mesh"); |
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flags &= ~(MT_N|MT_UV); |
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} |
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if (flags & MT_N) { /* interpolate normal */ |
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for (i = 0; i < 3; i++) |
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rcont.pert[i] = wt[0]*tv[0].n[i] + |
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wt[1]*tv[1].n[i] + |
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wt[2]*tv[2].n[i]; |
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multv3(r->pert, rcont.pert, curmi->x.f.xfm); |
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if (normalize(r->pert) != 0.0) |
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for (i = 0; i < 3; i++) |
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r->pert[i] -= r->ron[i]; |
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} else |
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r->pert[0] = r->pert[1] = r->pert[2] = .0; |
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|
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if (flags & MT_UV) /* interpolate uv coordinates */ |
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for (i = 0; i < 2; i++) |
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r->uv[i] = wt[0]*tv[0].uv[i] + |
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wt[1]*tv[1].uv[i] + |
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wt[2]*tv[2].uv[i]; |
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else |
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r->uv[0] = r->uv[1] = .0; |
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|
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/* return hit */ |
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return(1); |
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} |
