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root/radiance/ray/src/rt/aniso.c
Revision: 2.52
Committed: Wed Oct 26 03:44:56 2011 UTC (12 years, 6 months ago) by greg
Content type: text/plain
Branch: MAIN
CVS Tags: rad4R1
Changes since 2.51: +4 -5 lines
Log Message:
Fixed underestimation of reflection in non-metals below -st threshold

File Contents

# Content
1 #ifndef lint
2 static const char RCSid[] = "$Id: aniso.c,v 2.51 2011/02/18 00:40:25 greg Exp $";
3 #endif
4 /*
5 * Shading functions for anisotropic materials.
6 */
7
8 #include "copyright.h"
9
10 #include "ray.h"
11 #include "ambient.h"
12 #include "otypes.h"
13 #include "rtotypes.h"
14 #include "source.h"
15 #include "func.h"
16 #include "random.h"
17
18 #ifndef MAXITER
19 #define MAXITER 10 /* maximum # specular ray attempts */
20 #endif
21
22 /*
23 * This routine implements the anisotropic Gaussian
24 * model described by Ward in Siggraph `92 article.
25 * We orient the surface towards the incoming ray, so a single
26 * surface can be used to represent an infinitely thin object.
27 *
28 * Arguments for MAT_PLASTIC2 and MAT_METAL2 are:
29 * 4+ ux uy uz funcfile [transform...]
30 * 0
31 * 6 red grn blu specular-frac. u-facet-slope v-facet-slope
32 *
33 * Real arguments for MAT_TRANS2 are:
34 * 8 red grn blu rspec u-rough v-rough trans tspec
35 */
36
37 /* specularity flags */
38 #define SP_REFL 01 /* has reflected specular component */
39 #define SP_TRAN 02 /* has transmitted specular */
40 #define SP_FLAT 04 /* reflecting surface is flat */
41 #define SP_RBLT 010 /* reflection below sample threshold */
42 #define SP_TBLT 020 /* transmission below threshold */
43 #define SP_BADU 040 /* bad u direction calculation */
44
45 typedef struct {
46 OBJREC *mp; /* material pointer */
47 RAY *rp; /* ray pointer */
48 short specfl; /* specularity flags, defined above */
49 COLOR mcolor; /* color of this material */
50 COLOR scolor; /* color of specular component */
51 FVECT vrefl; /* vector in reflected direction */
52 FVECT prdir; /* vector in transmitted direction */
53 FVECT u, v; /* u and v vectors orienting anisotropy */
54 double u_alpha; /* u roughness */
55 double v_alpha; /* v roughness */
56 double rdiff, rspec; /* reflected specular, diffuse */
57 double trans; /* transmissivity */
58 double tdiff, tspec; /* transmitted specular, diffuse */
59 FVECT pnorm; /* perturbed surface normal */
60 double pdot; /* perturbed dot product */
61 } ANISODAT; /* anisotropic material data */
62
63 static srcdirf_t diraniso;
64 static void getacoords(RAY *r, ANISODAT *np);
65 static void agaussamp(RAY *r, ANISODAT *np);
66
67
68 static void
69 diraniso( /* compute source contribution */
70 COLOR cval, /* returned coefficient */
71 void *nnp, /* material data */
72 FVECT ldir, /* light source direction */
73 double omega /* light source size */
74 )
75 {
76 register ANISODAT *np = nnp;
77 double ldot;
78 double dtmp, dtmp1, dtmp2;
79 FVECT h;
80 double au2, av2;
81 COLOR ctmp;
82
83 setcolor(cval, 0.0, 0.0, 0.0);
84
85 ldot = DOT(np->pnorm, ldir);
86
87 if (ldot < 0.0 ? np->trans <= FTINY : np->trans >= 1.0-FTINY)
88 return; /* wrong side */
89
90 if (ldot > FTINY && np->rdiff > FTINY) {
91 /*
92 * Compute and add diffuse reflected component to returned
93 * color. The diffuse reflected component will always be
94 * modified by the color of the material.
95 */
96 copycolor(ctmp, np->mcolor);
97 dtmp = ldot * omega * np->rdiff * (1.0/PI);
98 scalecolor(ctmp, dtmp);
99 addcolor(cval, ctmp);
100 }
101 if (ldot > FTINY && (np->specfl&(SP_REFL|SP_BADU)) == SP_REFL) {
102 /*
103 * Compute specular reflection coefficient using
104 * anisotropic Gaussian distribution model.
105 */
106 /* add source width if flat */
107 if (np->specfl & SP_FLAT)
108 au2 = av2 = omega * (0.25/PI);
109 else
110 au2 = av2 = 0.0;
111 au2 += np->u_alpha*np->u_alpha;
112 av2 += np->v_alpha*np->v_alpha;
113 /* half vector */
114 h[0] = ldir[0] - np->rp->rdir[0];
115 h[1] = ldir[1] - np->rp->rdir[1];
116 h[2] = ldir[2] - np->rp->rdir[2];
117 /* ellipse */
118 dtmp1 = DOT(np->u, h);
119 dtmp1 *= dtmp1 / au2;
120 dtmp2 = DOT(np->v, h);
121 dtmp2 *= dtmp2 / av2;
122 /* new W-G-M-D model */
123 dtmp = DOT(np->pnorm, h);
124 dtmp *= dtmp;
125 dtmp1 = (dtmp1 + dtmp2) / dtmp;
126 dtmp = exp(-dtmp1) * DOT(h,h) /
127 (PI * dtmp*dtmp * sqrt(au2*av2));
128 /* worth using? */
129 if (dtmp > FTINY) {
130 copycolor(ctmp, np->scolor);
131 dtmp *= ldot * omega;
132 scalecolor(ctmp, dtmp);
133 addcolor(cval, ctmp);
134 }
135 }
136 if (ldot < -FTINY && np->tdiff > FTINY) {
137 /*
138 * Compute diffuse transmission.
139 */
140 copycolor(ctmp, np->mcolor);
141 dtmp = -ldot * omega * np->tdiff * (1.0/PI);
142 scalecolor(ctmp, dtmp);
143 addcolor(cval, ctmp);
144 }
145 if (ldot < -FTINY && (np->specfl&(SP_TRAN|SP_BADU)) == SP_TRAN) {
146 /*
147 * Compute specular transmission. Specular transmission
148 * is always modified by material color.
149 */
150 /* roughness + source */
151 au2 = av2 = omega * (1.0/PI);
152 au2 += np->u_alpha*np->u_alpha;
153 av2 += np->v_alpha*np->v_alpha;
154 /* "half vector" */
155 h[0] = ldir[0] - np->prdir[0];
156 h[1] = ldir[1] - np->prdir[1];
157 h[2] = ldir[2] - np->prdir[2];
158 dtmp = DOT(h,h);
159 if (dtmp > FTINY*FTINY) {
160 dtmp1 = DOT(h,np->pnorm);
161 dtmp = 1.0 - dtmp1*dtmp1/dtmp;
162 if (dtmp > FTINY*FTINY) {
163 dtmp1 = DOT(h,np->u);
164 dtmp1 *= dtmp1 / au2;
165 dtmp2 = DOT(h,np->v);
166 dtmp2 *= dtmp2 / av2;
167 dtmp = (dtmp1 + dtmp2) / dtmp;
168 }
169 } else
170 dtmp = 0.0;
171 /* Gaussian */
172 dtmp = exp(-dtmp) * (1.0/PI) * sqrt(-ldot/(np->pdot*au2*av2));
173 /* worth using? */
174 if (dtmp > FTINY) {
175 copycolor(ctmp, np->mcolor);
176 dtmp *= np->tspec * omega;
177 scalecolor(ctmp, dtmp);
178 addcolor(cval, ctmp);
179 }
180 }
181 }
182
183
184 extern int
185 m_aniso( /* shade ray that hit something anisotropic */
186 register OBJREC *m,
187 register RAY *r
188 )
189 {
190 ANISODAT nd;
191 COLOR ctmp;
192 register int i;
193 /* easy shadow test */
194 if (r->crtype & SHADOW)
195 return(1);
196
197 if (m->oargs.nfargs != (m->otype == MAT_TRANS2 ? 8 : 6))
198 objerror(m, USER, "bad number of real arguments");
199 /* check for back side */
200 if (r->rod < 0.0) {
201 if (!backvis && m->otype != MAT_TRANS2) {
202 raytrans(r);
203 return(1);
204 }
205 raytexture(r, m->omod);
206 flipsurface(r); /* reorient if backvis */
207 } else
208 raytexture(r, m->omod);
209 /* get material color */
210 nd.mp = m;
211 nd.rp = r;
212 setcolor(nd.mcolor, m->oargs.farg[0],
213 m->oargs.farg[1],
214 m->oargs.farg[2]);
215 /* get roughness */
216 nd.specfl = 0;
217 nd.u_alpha = m->oargs.farg[4];
218 nd.v_alpha = m->oargs.farg[5];
219 if (nd.u_alpha <= FTINY || nd.v_alpha <= FTINY)
220 objerror(m, USER, "roughness too small");
221
222 nd.pdot = raynormal(nd.pnorm, r); /* perturb normal */
223 if (nd.pdot < .001)
224 nd.pdot = .001; /* non-zero for diraniso() */
225 multcolor(nd.mcolor, r->pcol); /* modify material color */
226 /* get specular component */
227 if ((nd.rspec = m->oargs.farg[3]) > FTINY) {
228 nd.specfl |= SP_REFL;
229 /* compute specular color */
230 if (m->otype == MAT_METAL2)
231 copycolor(nd.scolor, nd.mcolor);
232 else
233 setcolor(nd.scolor, 1.0, 1.0, 1.0);
234 scalecolor(nd.scolor, nd.rspec);
235 /* check threshold */
236 if (specthresh >= nd.rspec-FTINY)
237 nd.specfl |= SP_RBLT;
238 /* compute refl. direction */
239 VSUM(nd.vrefl, r->rdir, nd.pnorm, 2.0*nd.pdot);
240 if (DOT(nd.vrefl, r->ron) <= FTINY) /* penetration? */
241 VSUM(nd.vrefl, r->rdir, r->ron, 2.0*r->rod);
242 }
243 /* compute transmission */
244 if (m->otype == MAT_TRANS2) {
245 nd.trans = m->oargs.farg[6]*(1.0 - nd.rspec);
246 nd.tspec = nd.trans * m->oargs.farg[7];
247 nd.tdiff = nd.trans - nd.tspec;
248 if (nd.tspec > FTINY) {
249 nd.specfl |= SP_TRAN;
250 /* check threshold */
251 if (specthresh >= nd.tspec-FTINY)
252 nd.specfl |= SP_TBLT;
253 if (DOT(r->pert,r->pert) <= FTINY*FTINY) {
254 VCOPY(nd.prdir, r->rdir);
255 } else {
256 for (i = 0; i < 3; i++) /* perturb */
257 nd.prdir[i] = r->rdir[i] - r->pert[i];
258 if (DOT(nd.prdir, r->ron) < -FTINY)
259 normalize(nd.prdir); /* OK */
260 else
261 VCOPY(nd.prdir, r->rdir);
262 }
263 }
264 } else
265 nd.tdiff = nd.tspec = nd.trans = 0.0;
266
267 /* diffuse reflection */
268 nd.rdiff = 1.0 - nd.trans - nd.rspec;
269
270 if (r->ro != NULL && isflat(r->ro->otype))
271 nd.specfl |= SP_FLAT;
272
273 getacoords(r, &nd); /* set up coordinates */
274
275 if (nd.specfl & (SP_REFL|SP_TRAN) && !(nd.specfl & SP_BADU))
276 agaussamp(r, &nd);
277
278 if (nd.rdiff > FTINY) { /* ambient from this side */
279 copycolor(ctmp, nd.mcolor); /* modified by material color */
280 scalecolor(ctmp, nd.rdiff);
281 if (nd.specfl & SP_RBLT) /* add in specular as well? */
282 addcolor(ctmp, nd.scolor);
283 multambient(ctmp, r, nd.pnorm);
284 addcolor(r->rcol, ctmp); /* add to returned color */
285 }
286 if (nd.tdiff > FTINY) { /* ambient from other side */
287 FVECT bnorm;
288
289 flipsurface(r);
290 bnorm[0] = -nd.pnorm[0];
291 bnorm[1] = -nd.pnorm[1];
292 bnorm[2] = -nd.pnorm[2];
293 copycolor(ctmp, nd.mcolor); /* modified by color */
294 if (nd.specfl & SP_TBLT)
295 scalecolor(ctmp, nd.trans);
296 else
297 scalecolor(ctmp, nd.tdiff);
298 multambient(ctmp, r, bnorm);
299 addcolor(r->rcol, ctmp);
300 flipsurface(r);
301 }
302 /* add direct component */
303 direct(r, diraniso, &nd);
304
305 return(1);
306 }
307
308
309 static void
310 getacoords( /* set up coordinate system */
311 RAY *r,
312 register ANISODAT *np
313 )
314 {
315 register MFUNC *mf;
316 register int i;
317
318 mf = getfunc(np->mp, 3, 0x7, 1);
319 setfunc(np->mp, r);
320 errno = 0;
321 for (i = 0; i < 3; i++)
322 np->u[i] = evalue(mf->ep[i]);
323 if (errno == EDOM || errno == ERANGE) {
324 objerror(np->mp, WARNING, "compute error");
325 np->specfl |= SP_BADU;
326 return;
327 }
328 if (mf->f != &unitxf)
329 multv3(np->u, np->u, mf->f->xfm);
330 fcross(np->v, np->pnorm, np->u);
331 if (normalize(np->v) == 0.0) {
332 objerror(np->mp, WARNING, "illegal orientation vector");
333 np->specfl |= SP_BADU;
334 return;
335 }
336 fcross(np->u, np->v, np->pnorm);
337 }
338
339
340 static void
341 agaussamp( /* sample anisotropic Gaussian specular */
342 RAY *r,
343 register ANISODAT *np
344 )
345 {
346 RAY sr;
347 FVECT h;
348 double rv[2];
349 double d, sinp, cosp;
350 COLOR scol;
351 int maxiter, ntrials, nstarget, nstaken;
352 register int i;
353 /* compute reflection */
354 if ((np->specfl & (SP_REFL|SP_RBLT)) == SP_REFL &&
355 rayorigin(&sr, SPECULAR, r, np->scolor) == 0) {
356 nstarget = 1;
357 if (specjitter > 1.5) { /* multiple samples? */
358 nstarget = specjitter*r->rweight + .5;
359 if (sr.rweight <= minweight*nstarget)
360 nstarget = sr.rweight/minweight;
361 if (nstarget > 1) {
362 d = 1./nstarget;
363 scalecolor(sr.rcoef, d);
364 sr.rweight *= d;
365 } else
366 nstarget = 1;
367 }
368 setcolor(scol, 0., 0., 0.);
369 dimlist[ndims++] = (int)(size_t)np->mp;
370 maxiter = MAXITER*nstarget;
371 for (nstaken = ntrials = 0; nstaken < nstarget &&
372 ntrials < maxiter; ntrials++) {
373 if (ntrials)
374 d = frandom();
375 else
376 d = urand(ilhash(dimlist,ndims)+samplendx);
377 multisamp(rv, 2, d);
378 d = 2.0*PI * rv[0];
379 cosp = tcos(d) * np->u_alpha;
380 sinp = tsin(d) * np->v_alpha;
381 d = 1./sqrt(cosp*cosp + sinp*sinp);
382 cosp *= d;
383 sinp *= d;
384 if ((0. <= specjitter) & (specjitter < 1.))
385 rv[1] = 1.0 - specjitter*rv[1];
386 if (rv[1] <= FTINY)
387 d = 1.0;
388 else
389 d = sqrt(-log(rv[1]) /
390 (cosp*cosp/(np->u_alpha*np->u_alpha) +
391 sinp*sinp/(np->v_alpha*np->v_alpha)));
392 for (i = 0; i < 3; i++)
393 h[i] = np->pnorm[i] +
394 d*(cosp*np->u[i] + sinp*np->v[i]);
395 d = -2.0 * DOT(h, r->rdir) / (1.0 + d*d);
396 VSUM(sr.rdir, r->rdir, h, d);
397 /* sample rejection test */
398 if ((d = DOT(sr.rdir, r->ron)) <= FTINY)
399 continue;
400 checknorm(sr.rdir);
401 if (nstarget > 1) { /* W-G-M-D adjustment */
402 if (nstaken) rayclear(&sr);
403 rayvalue(&sr);
404 d = 2./(1. + r->rod/d);
405 scalecolor(sr.rcol, d);
406 addcolor(scol, sr.rcol);
407 } else {
408 rayvalue(&sr);
409 multcolor(sr.rcol, sr.rcoef);
410 addcolor(r->rcol, sr.rcol);
411 }
412 ++nstaken;
413 }
414 if (nstarget > 1) { /* final W-G-M-D weighting */
415 multcolor(scol, sr.rcoef);
416 d = (double)nstarget/ntrials;
417 scalecolor(scol, d);
418 addcolor(r->rcol, scol);
419 }
420 ndims--;
421 }
422 /* compute transmission */
423 copycolor(sr.rcoef, np->mcolor); /* modify by material color */
424 scalecolor(sr.rcoef, np->tspec);
425 if ((np->specfl & (SP_TRAN|SP_TBLT)) == SP_TRAN &&
426 rayorigin(&sr, SPECULAR, r, sr.rcoef) == 0) {
427 nstarget = 1;
428 if (specjitter > 1.5) { /* multiple samples? */
429 nstarget = specjitter*r->rweight + .5;
430 if (sr.rweight <= minweight*nstarget)
431 nstarget = sr.rweight/minweight;
432 if (nstarget > 1) {
433 d = 1./nstarget;
434 scalecolor(sr.rcoef, d);
435 sr.rweight *= d;
436 } else
437 nstarget = 1;
438 }
439 dimlist[ndims++] = (int)(size_t)np->mp;
440 maxiter = MAXITER*nstarget;
441 for (nstaken = ntrials = 0; nstaken < nstarget &&
442 ntrials < maxiter; ntrials++) {
443 if (ntrials)
444 d = frandom();
445 else
446 d = urand(ilhash(dimlist,ndims)+1823+samplendx);
447 multisamp(rv, 2, d);
448 d = 2.0*PI * rv[0];
449 cosp = tcos(d) * np->u_alpha;
450 sinp = tsin(d) * np->v_alpha;
451 d = 1./sqrt(cosp*cosp + sinp*sinp);
452 cosp *= d;
453 sinp *= d;
454 if ((0. <= specjitter) & (specjitter < 1.))
455 rv[1] = 1.0 - specjitter*rv[1];
456 if (rv[1] <= FTINY)
457 d = 1.0;
458 else
459 d = sqrt(-log(rv[1]) /
460 (cosp*cosp/(np->u_alpha*np->u_alpha) +
461 sinp*sinp/(np->v_alpha*np->v_alpha)));
462 for (i = 0; i < 3; i++)
463 sr.rdir[i] = np->prdir[i] +
464 d*(cosp*np->u[i] + sinp*np->v[i]);
465 if (DOT(sr.rdir, r->ron) >= -FTINY)
466 continue;
467 normalize(sr.rdir); /* OK, normalize */
468 if (nstaken) /* multi-sampling */
469 rayclear(&sr);
470 rayvalue(&sr);
471 multcolor(sr.rcol, sr.rcoef);
472 addcolor(r->rcol, sr.rcol);
473 ++nstaken;
474 }
475 ndims--;
476 }
477 }