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root/radiance/ray/src/rt/m_brdf.c
Revision: 2.14
Committed: Wed Nov 22 09:27:53 1995 UTC (28 years, 5 months ago) by greg
Content type: text/plain
Branch: MAIN
Changes since 2.13: +20 -5 lines
Log Message:
fixed problem with back side normal computation for ambient()

File Contents

# User Rev Content
1 greg 1.7 /* Copyright (c) 1991 Regents of the University of California */
2 greg 1.1
3     #ifndef lint
4     static char SCCSid[] = "$SunId$ LBL";
5     #endif
6    
7     /*
8     * Shading for materials with arbitrary BRDF's
9     */
10    
11     #include "ray.h"
12    
13     #include "data.h"
14    
15     #include "otypes.h"
16    
17 greg 2.2 #include "func.h"
18    
19 greg 2.11 extern int backvis; /* back faces visible? */
20    
21 greg 1.1 /*
22     * Arguments to this material include the color and specularity.
23     * String arguments include the reflection function and files.
24     * The BRDF is currently used just for the specular component to light
25     * sources. Reflectance values or data coordinates are functions
26 greg 2.7 * of the direction to the light source. (Data modification functions
27     * are passed the source direction as args 2-4.)
28 greg 1.1 * We orient the surface towards the incoming ray, so a single
29     * surface can be used to represent an infinitely thin object.
30     *
31     * Arguments for MAT_PFUNC and MAT_MFUNC are:
32 greg 1.4 * 2+ func funcfile transform
33 greg 1.1 * 0
34 greg 1.4 * 4+ red grn blu specularity A5 ..
35 greg 1.1 *
36     * Arguments for MAT_PDATA and MAT_MDATA are:
37 greg 1.4 * 4+ func datafile funcfile v0 .. transform
38 greg 1.1 * 0
39 greg 1.4 * 4+ red grn blu specularity A5 ..
40 greg 1.5 *
41     * Arguments for MAT_TFUNC are:
42     * 2+ func funcfile transform
43     * 0
44     * 4+ red grn blu rspec trans tspec A7 ..
45     *
46     * Arguments for MAT_TDATA are:
47     * 4+ func datafile funcfile v0 .. transform
48     * 0
49     * 4+ red grn blu rspec trans tspec A7 ..
50     *
51     * Arguments for the more general MAT_BRTDF are:
52     * 10+ rrefl grefl brefl
53     * rtrns gtrns btrns
54     * rbrtd gbrtd bbrtd
55     * funcfile transform
56     * 0
57 greg 2.6 * 9+ rdf gdf bdf
58     * rdb gdb bdb
59     * rdt gdt bdt A10 ..
60 greg 1.5 *
61     * In addition to the normal variables available to functions,
62     * we define the following:
63     * NxP, NyP, NzP - perturbed surface normal
64     * RdotP - perturbed ray dot product
65 greg 2.6 * CrP, CgP, CbP - perturbed material color (or pattern)
66 greg 1.1 */
67    
68     typedef struct {
69     OBJREC *mp; /* material pointer */
70     RAY *pr; /* intersected ray */
71 greg 1.5 DATARRAY *dp; /* data array for PDATA, MDATA or TDATA */
72 greg 2.6 COLOR mcolor; /* material (or pattern) color */
73     COLOR rdiff; /* diffuse reflection */
74     COLOR tdiff; /* diffuse transmission */
75     double rspec; /* specular reflectance (1 for BRDTF) */
76     double trans; /* transmissivity (.5 for BRDTF) */
77     double tspec; /* specular transmittance (1 for BRDTF) */
78 greg 1.1 FVECT pnorm; /* perturbed surface normal */
79     double pdot; /* perturbed dot product */
80     } BRDFDAT; /* BRDF material data */
81    
82    
83     dirbrdf(cval, np, ldir, omega) /* compute source contribution */
84     COLOR cval; /* returned coefficient */
85     register BRDFDAT *np; /* material data */
86     FVECT ldir; /* light source direction */
87     double omega; /* light source size */
88     {
89     double ldot;
90     double dtmp;
91     COLOR ctmp;
92 greg 1.4 FVECT ldx;
93 greg 2.12 static double vldx[5], pt[MAXDIM];
94 greg 1.5 register char **sa;
95 greg 1.1 register int i;
96 greg 2.12 #define lddx (vldx+1)
97 greg 1.1
98     setcolor(cval, 0.0, 0.0, 0.0);
99    
100     ldot = DOT(np->pnorm, ldir);
101    
102 greg 1.5 if (ldot <= FTINY && ldot >= -FTINY)
103     return; /* too close to grazing */
104 greg 2.6
105 greg 1.5 if (ldot < 0.0 ? np->trans <= FTINY : np->trans >= 1.0-FTINY)
106 greg 1.1 return; /* wrong side */
107    
108 greg 2.6 if (ldot > 0.0) {
109 greg 1.1 /*
110     * Compute and add diffuse reflected component to returned
111     * color. The diffuse reflected component will always be
112     * modified by the color of the material.
113     */
114 greg 2.6 copycolor(ctmp, np->rdiff);
115     dtmp = ldot * omega / PI;
116 greg 1.1 scalecolor(ctmp, dtmp);
117     addcolor(cval, ctmp);
118 greg 2.6 } else {
119 greg 1.1 /*
120 greg 1.5 * Diffuse transmitted component.
121 greg 1.1 */
122 greg 2.6 copycolor(ctmp, np->tdiff);
123     dtmp = -ldot * omega / PI;
124 greg 1.5 scalecolor(ctmp, dtmp);
125     addcolor(cval, ctmp);
126 greg 1.1 }
127 greg 1.5 if (ldot > 0.0 ? np->rspec <= FTINY : np->tspec <= FTINY)
128     return; /* no specular component */
129     /* set up function */
130 greg 1.10 setbrdfunc(np);
131 greg 1.5 sa = np->mp->oargs.sarg;
132     errno = 0;
133     /* transform light vector */
134     multv3(ldx, ldir, funcxf.xfm);
135     for (i = 0; i < 3; i++)
136 greg 2.3 lddx[i] = ldx[i]/funcxf.sca;
137 greg 2.12 lddx[3] = omega;
138 greg 1.5 /* compute BRTDF */
139     if (np->mp->otype == MAT_BRTDF) {
140 greg 2.6 if (sa[6][0] == '0') /* special case */
141     colval(ctmp,RED) = 0.0;
142     else
143 greg 2.12 colval(ctmp,RED) = funvalue(sa[6], 4, lddx);
144 greg 1.7 if (!strcmp(sa[7],sa[6]))
145 greg 1.5 colval(ctmp,GRN) = colval(ctmp,RED);
146     else
147 greg 2.12 colval(ctmp,GRN) = funvalue(sa[7], 4, lddx);
148 greg 1.7 if (!strcmp(sa[8],sa[6]))
149 greg 1.5 colval(ctmp,BLU) = colval(ctmp,RED);
150 greg 1.7 else if (!strcmp(sa[8],sa[7]))
151 greg 1.5 colval(ctmp,BLU) = colval(ctmp,GRN);
152     else
153 greg 2.12 colval(ctmp,BLU) = funvalue(sa[8], 4, lddx);
154 greg 1.5 dtmp = bright(ctmp);
155     } else if (np->dp == NULL) {
156 greg 2.12 dtmp = funvalue(sa[0], 4, lddx);
157 greg 1.5 setcolor(ctmp, dtmp, dtmp, dtmp);
158     } else {
159     for (i = 0; i < np->dp->nd; i++)
160 greg 2.12 pt[i] = funvalue(sa[3+i], 4, lddx);
161 greg 2.7 vldx[0] = datavalue(np->dp, pt);
162 greg 2.12 dtmp = funvalue(sa[0], 5, vldx);
163 greg 1.5 setcolor(ctmp, dtmp, dtmp, dtmp);
164     }
165 greg 2.2 if (errno) {
166     objerror(np->mp, WARNING, "compute error");
167     return;
168     }
169 greg 1.5 if (dtmp <= FTINY)
170     return;
171     if (ldot > 0.0) {
172     /*
173     * Compute reflected non-diffuse component.
174     */
175 greg 2.6 if (np->mp->otype == MAT_MFUNC | np->mp->otype == MAT_MDATA)
176 greg 1.6 multcolor(ctmp, np->mcolor);
177     dtmp = ldot * omega * np->rspec;
178 greg 1.5 scalecolor(ctmp, dtmp);
179     addcolor(cval, ctmp);
180     } else {
181     /*
182     * Compute transmitted non-diffuse component.
183     */
184 greg 2.6 if (np->mp->otype == MAT_TFUNC | np->mp->otype == MAT_TDATA)
185 greg 1.6 multcolor(ctmp, np->mcolor);
186 greg 1.5 dtmp = -ldot * omega * np->tspec;
187     scalecolor(ctmp, dtmp);
188     addcolor(cval, ctmp);
189     }
190 greg 2.12 #undef lddx
191 greg 1.1 }
192    
193    
194 greg 2.13 m_brdf(m, r) /* color a ray which hit a BRDTfunc material */
195 greg 1.1 register OBJREC *m;
196     register RAY *r;
197     {
198     BRDFDAT nd;
199 greg 2.6 RAY sr;
200 greg 1.7 double transtest, transdist;
201 greg 2.6 int hasrefl, hastrans;
202 greg 1.1 COLOR ctmp;
203 greg 2.14 FVECT vtmp;
204 greg 2.6 register MFUNC *mf;
205 greg 1.1 register int i;
206 greg 1.5 /* check arguments */
207 greg 2.6 if (m->oargs.nsargs < 10 | m->oargs.nfargs < 9)
208     objerror(m, USER, "bad # arguments");
209     nd.mp = m;
210     nd.pr = r;
211     /* dummy values */
212     nd.rspec = nd.tspec = 1.0;
213     nd.trans = 0.5;
214     /* diffuse reflectance */
215     if (r->rod > 0.0)
216     setcolor(nd.rdiff, m->oargs.farg[0],
217     m->oargs.farg[1],
218     m->oargs.farg[2]);
219     else
220     setcolor(nd.rdiff, m->oargs.farg[3],
221     m->oargs.farg[4],
222     m->oargs.farg[5]);
223     /* diffuse transmittance */
224     setcolor(nd.tdiff, m->oargs.farg[6],
225     m->oargs.farg[7],
226     m->oargs.farg[8]);
227     /* get modifiers */
228     raytexture(r, m->omod);
229     nd.pdot = raynormal(nd.pnorm, r); /* perturb normal */
230     if (r->rod < 0.0) { /* orient perturbed values */
231     nd.pdot = -nd.pdot;
232     for (i = 0; i < 3; i++) {
233     nd.pnorm[i] = -nd.pnorm[i];
234     r->pert[i] = -r->pert[i];
235     }
236 greg 1.5 }
237 greg 2.6 copycolor(nd.mcolor, r->pcol); /* get pattern color */
238     multcolor(nd.rdiff, nd.mcolor); /* modify diffuse values */
239     multcolor(nd.tdiff, nd.mcolor);
240     hasrefl = bright(nd.rdiff) > FTINY;
241     hastrans = bright(nd.tdiff) > FTINY;
242     /* load cal file */
243     nd.dp = NULL;
244     mf = getfunc(m, 9, 0x3f, 0);
245     /* compute transmitted ray */
246     setbrdfunc(&nd);
247     transtest = 0;
248 greg 2.8 transdist = r->rot;
249 greg 2.6 errno = 0;
250     setcolor(ctmp, evalue(mf->ep[3]),
251     evalue(mf->ep[4]),
252     evalue(mf->ep[5]));
253     if (errno)
254     objerror(m, WARNING, "compute error");
255     else if (rayorigin(&sr, r, TRANS, bright(ctmp)) == 0) {
256     if (!(r->crtype & SHADOW) &&
257     DOT(r->pert,r->pert) > FTINY*FTINY) {
258     for (i = 0; i < 3; i++) /* perturb direction */
259     sr.rdir[i] = r->rdir[i] - .75*r->pert[i];
260     if (normalize(sr.rdir) == 0.0) {
261     objerror(m, WARNING, "illegal perturbation");
262     VCOPY(sr.rdir, r->rdir);
263     }
264     } else {
265     VCOPY(sr.rdir, r->rdir);
266     transtest = 2;
267     }
268     rayvalue(&sr);
269     multcolor(sr.rcol, ctmp);
270     addcolor(r->rcol, sr.rcol);
271     transtest *= bright(sr.rcol);
272     transdist = r->rot + sr.rt;
273     }
274     if (r->crtype & SHADOW) /* the rest is shadow */
275 greg 2.10 return(1);
276 greg 2.6 /* compute reflected ray */
277     setbrdfunc(&nd);
278     errno = 0;
279     setcolor(ctmp, evalue(mf->ep[0]),
280     evalue(mf->ep[1]),
281     evalue(mf->ep[2]));
282     if (errno)
283     objerror(m, WARNING, "compute error");
284     else if (rayorigin(&sr, r, REFLECTED, bright(ctmp)) == 0) {
285     for (i = 0; i < 3; i++)
286     sr.rdir[i] = r->rdir[i] + 2.0*nd.pdot*nd.pnorm[i];
287     rayvalue(&sr);
288     multcolor(sr.rcol, ctmp);
289     addcolor(r->rcol, sr.rcol);
290     }
291     /* compute ambient */
292     if (hasrefl) {
293 greg 2.14 if (nd.pdot < 0.0) {
294 greg 2.6 flipsurface(r);
295 greg 2.14 vtmp[0] = -nd.pnorm[0];
296     vtmp[1] = -nd.pnorm[1];
297     vtmp[2] = -nd.pnorm[2];
298     } else
299     VCOPY(vtmp, nd.pnorm);
300     ambient(ctmp, r, vtmp);
301 greg 2.6 multcolor(ctmp, nd.rdiff);
302     addcolor(r->rcol, ctmp); /* add to returned color */
303     if (nd.pdot < 0.0)
304     flipsurface(r);
305     }
306     if (hastrans) { /* from other side */
307 greg 2.14 if (nd.pdot > 0.0) {
308 greg 2.6 flipsurface(r);
309 greg 2.14 vtmp[0] = -nd.pnorm[0];
310     vtmp[1] = -nd.pnorm[1];
311     vtmp[2] = -nd.pnorm[2];
312     } else
313     VCOPY(vtmp, nd.pnorm);
314     ambient(ctmp, r, vtmp);
315 greg 2.6 multcolor(ctmp, nd.tdiff);
316     addcolor(r->rcol, ctmp);
317     if (nd.pdot > 0.0)
318     flipsurface(r);
319     }
320     if (hasrefl | hastrans || m->oargs.sarg[6][0] != '0')
321     direct(r, dirbrdf, &nd); /* add direct component */
322     /* check distance */
323     if (transtest > bright(r->rcol))
324     r->rt = transdist;
325 greg 2.10
326     return(1);
327 greg 2.6 }
328    
329    
330    
331     m_brdf2(m, r) /* color a ray which hit a BRDF material */
332     register OBJREC *m;
333     register RAY *r;
334     {
335     BRDFDAT nd;
336     COLOR ctmp;
337 greg 2.14 FVECT vtmp;
338 greg 2.6 double dtmp;
339     /* always a shadow */
340     if (r->crtype & SHADOW)
341 greg 2.10 return(1);
342 greg 2.6 /* check arguments */
343     if (m->oargs.nsargs < (hasdata(m->otype)?4:2) | m->oargs.nfargs <
344     (m->otype==MAT_TFUNC|m->otype==MAT_TDATA?6:4))
345 greg 1.1 objerror(m, USER, "bad # arguments");
346     nd.mp = m;
347     nd.pr = r;
348 greg 2.6 /* get material color */
349     setcolor(nd.mcolor, m->oargs.farg[0],
350     m->oargs.farg[1],
351     m->oargs.farg[2]);
352 greg 1.5 /* get specular component */
353     nd.rspec = m->oargs.farg[3];
354 greg 2.6 /* compute transmittance */
355     if (m->otype == MAT_TFUNC | m->otype == MAT_TDATA) {
356 greg 1.5 nd.trans = m->oargs.farg[4]*(1.0 - nd.rspec);
357     nd.tspec = nd.trans * m->oargs.farg[5];
358 greg 2.6 dtmp = nd.trans - nd.tspec;
359     setcolor(nd.tdiff, dtmp, dtmp, dtmp);
360     } else {
361     nd.tspec = nd.trans = 0.0;
362     setcolor(nd.tdiff, 0.0, 0.0, 0.0);
363     }
364     /* compute reflectance */
365     dtmp = 1.0 - nd.trans - nd.rspec;
366     setcolor(nd.rdiff, dtmp, dtmp, dtmp);
367 greg 2.11 /* check for back side */
368     if (r->rod < 0.0) {
369     if (!backvis && m->otype != MAT_TFUNC
370     && m->otype != MAT_TDATA) {
371     raytrans(r);
372     return(1);
373     }
374     flipsurface(r); /* reorient if backvis */
375     }
376 greg 1.5 /* get modifiers */
377     raytexture(r, m->omod);
378     nd.pdot = raynormal(nd.pnorm, r); /* perturb normal */
379     multcolor(nd.mcolor, r->pcol); /* modify material color */
380 greg 2.6 multcolor(nd.rdiff, nd.mcolor);
381     multcolor(nd.tdiff, nd.mcolor);
382 greg 1.1 /* load auxiliary files */
383 greg 2.2 if (hasdata(m->otype)) {
384 greg 1.1 nd.dp = getdata(m->oargs.sarg[1]);
385 greg 2.6 getfunc(m, 2, 0, 0);
386 greg 1.1 } else {
387     nd.dp = NULL;
388 greg 2.6 getfunc(m, 1, 0, 0);
389 greg 1.1 }
390     /* compute ambient */
391 greg 2.6 if (nd.trans < 1.0-FTINY) {
392 greg 2.13 ambient(ctmp, r, nd.pnorm);
393 greg 2.6 scalecolor(ctmp, 1.0-nd.trans);
394 greg 1.1 multcolor(ctmp, nd.mcolor); /* modified by material color */
395     addcolor(r->rcol, ctmp); /* add to returned color */
396 greg 1.5 }
397 greg 2.6 if (nd.trans > FTINY) { /* from other side */
398 greg 1.5 flipsurface(r);
399 greg 2.14 vtmp[0] = -nd.pnorm[0];
400     vtmp[1] = -nd.pnorm[1];
401     vtmp[2] = -nd.pnorm[2];
402     ambient(ctmp, r, vtmp);
403 greg 2.6 scalecolor(ctmp, nd.trans);
404 greg 1.5 multcolor(ctmp, nd.mcolor);
405     addcolor(r->rcol, ctmp);
406     flipsurface(r);
407 greg 1.1 }
408     /* add direct component */
409     direct(r, dirbrdf, &nd);
410 greg 2.10
411     return(1);
412 greg 1.10 }
413    
414    
415     setbrdfunc(np) /* set up brdf function and variables */
416     register BRDFDAT *np;
417     {
418     FVECT vec;
419    
420     if (setfunc(np->mp, np->pr) == 0)
421     return(0); /* it's OK, setfunc says we're done */
422     /* else (re)assign special variables */
423     multv3(vec, np->pnorm, funcxf.xfm);
424     varset("NxP", '=', vec[0]/funcxf.sca);
425     varset("NyP", '=', vec[1]/funcxf.sca);
426     varset("NzP", '=', vec[2]/funcxf.sca);
427 greg 1.11 varset("RdotP", '=', np->pdot <= -1.0 ? -1.0 :
428     np->pdot >= 1.0 ? 1.0 : np->pdot);
429 greg 1.10 varset("CrP", '=', colval(np->mcolor,RED));
430     varset("CgP", '=', colval(np->mcolor,GRN));
431     varset("CbP", '=', colval(np->mcolor,BLU));
432     return(1);
433 greg 1.1 }