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root/radiance/ray/src/rt/normal.c
Revision: 2.13
Committed: Thu Apr 16 13:31:28 1992 UTC (32 years ago) by greg
Content type: text/plain
Branch: MAIN
Changes since 2.12: +16 -13 lines
Log Message:
fixed bug that caused ambient to be overcounted for polished surf's
changed use of Fresnel correction so it will only affect polished surf's

File Contents

# User Rev Content
1 greg 2.2 /* Copyright (c) 1992 Regents of the University of California */
2 greg 1.1
3     #ifndef lint
4     static char SCCSid[] = "$SunId$ LBL";
5     #endif
6    
7     /*
8     * normal.c - shading function for normal materials.
9     *
10     * 8/19/85
11     * 12/19/85 - added stuff for metals.
12     * 6/26/87 - improved specular model.
13     * 9/28/87 - added model for translucent materials.
14 greg 2.2 * Later changes described in delta comments.
15 greg 1.1 */
16    
17     #include "ray.h"
18    
19     #include "otypes.h"
20    
21 greg 2.2 #include "random.h"
22    
23 greg 2.5 extern double specthresh; /* specular sampling threshold */
24     extern double specjitter; /* specular sampling jitter */
25    
26 greg 1.1 /*
27     * This routine uses portions of the reflection
28     * model described by Cook and Torrance.
29     * The computation of specular components has been simplified by
30     * numerous approximations and ommisions to improve speed.
31     * We orient the surface towards the incoming ray, so a single
32     * surface can be used to represent an infinitely thin object.
33     *
34     * Arguments for MAT_PLASTIC and MAT_METAL are:
35     * red grn blu specular-frac. facet-slope
36     *
37     * Arguments for MAT_TRANS are:
38     * red grn blu rspec rough trans tspec
39     */
40    
41     #define BSPEC(m) (6.0) /* specularity parameter b */
42    
43 greg 2.2 /* specularity flags */
44     #define SP_REFL 01 /* has reflected specular component */
45     #define SP_TRAN 02 /* has transmitted specular */
46 greg 2.11 #define SP_PURE 04 /* purely specular (zero roughness) */
47     #define SP_FLAT 010 /* flat reflecting surface */
48     #define SP_RBLT 020 /* reflection below sample threshold */
49     #define SP_TBLT 040 /* transmission below threshold */
50 greg 1.1
51 greg 1.3 typedef struct {
52     OBJREC *mp; /* material pointer */
53 greg 2.2 short specfl; /* specularity flags, defined above */
54 greg 1.1 COLOR mcolor; /* color of this material */
55     COLOR scolor; /* color of specular component */
56     FVECT vrefl; /* vector in direction of reflected ray */
57 greg 1.14 FVECT prdir; /* vector in transmitted direction */
58 greg 2.2 double alpha2; /* roughness squared */
59 greg 1.1 double rdiff, rspec; /* reflected specular, diffuse */
60     double trans; /* transmissivity */
61     double tdiff, tspec; /* transmitted specular, diffuse */
62     FVECT pnorm; /* perturbed surface normal */
63     double pdot; /* perturbed dot product */
64 greg 1.3 } NORMDAT; /* normal material data */
65    
66    
67     dirnorm(cval, np, ldir, omega) /* compute source contribution */
68     COLOR cval; /* returned coefficient */
69     register NORMDAT *np; /* material data */
70     FVECT ldir; /* light source direction */
71     double omega; /* light source size */
72     {
73 greg 1.1 double ldot;
74 greg 1.3 double dtmp;
75 greg 2.3 int i;
76 greg 1.3 COLOR ctmp;
77    
78     setcolor(cval, 0.0, 0.0, 0.0);
79    
80     ldot = DOT(np->pnorm, ldir);
81    
82     if (ldot < 0.0 ? np->trans <= FTINY : np->trans >= 1.0-FTINY)
83     return; /* wrong side */
84    
85     if (ldot > FTINY && np->rdiff > FTINY) {
86     /*
87 greg 1.4 * Compute and add diffuse reflected component to returned
88     * color. The diffuse reflected component will always be
89     * modified by the color of the material.
90 greg 1.3 */
91     copycolor(ctmp, np->mcolor);
92     dtmp = ldot * omega * np->rdiff / PI;
93     scalecolor(ctmp, dtmp);
94     addcolor(cval, ctmp);
95     }
96 greg 2.2 if (ldot > FTINY && (np->specfl&(SP_REFL|SP_PURE)) == SP_REFL) {
97 greg 1.3 /*
98     * Compute specular reflection coefficient using
99     * gaussian distribution model.
100     */
101 greg 2.3 /* roughness */
102     dtmp = 2.0*np->alpha2;
103     /* + source if flat */
104     if (np->specfl & SP_FLAT)
105     dtmp += omega/(2.0*PI);
106 greg 1.3 /* gaussian */
107     dtmp = exp((DOT(np->vrefl,ldir)-1.)/dtmp)/(2.*PI)/dtmp;
108     /* worth using? */
109     if (dtmp > FTINY) {
110     copycolor(ctmp, np->scolor);
111 greg 1.13 dtmp *= omega / np->pdot;
112 greg 1.3 scalecolor(ctmp, dtmp);
113     addcolor(cval, ctmp);
114     }
115     }
116     if (ldot < -FTINY && np->tdiff > FTINY) {
117     /*
118     * Compute diffuse transmission.
119     */
120     copycolor(ctmp, np->mcolor);
121     dtmp = -ldot * omega * np->tdiff / PI;
122     scalecolor(ctmp, dtmp);
123     addcolor(cval, ctmp);
124     }
125 greg 2.2 if (ldot < -FTINY && (np->specfl&(SP_TRAN|SP_PURE)) == SP_TRAN) {
126 greg 1.3 /*
127 greg 1.4 * Compute specular transmission. Specular transmission
128 greg 1.13 * is always modified by material color.
129 greg 1.3 */
130     /* roughness + source */
131 greg 2.8 dtmp = np->alpha2/2.0 + omega/(2.0*PI);
132 greg 1.3 /* gaussian */
133 greg 1.14 dtmp = exp((DOT(np->prdir,ldir)-1.)/dtmp)/(2.*PI)/dtmp;
134 greg 1.3 /* worth using? */
135     if (dtmp > FTINY) {
136 greg 1.13 copycolor(ctmp, np->mcolor);
137     dtmp *= np->tspec * omega / np->pdot;
138     scalecolor(ctmp, dtmp);
139 greg 1.3 addcolor(cval, ctmp);
140     }
141     }
142     }
143    
144    
145 greg 2.2 m_normal(m, r) /* color a ray that hit something normal */
146 greg 1.3 register OBJREC *m;
147     register RAY *r;
148     {
149     NORMDAT nd;
150 greg 1.9 double transtest, transdist;
151 greg 1.1 double dtmp;
152     COLOR ctmp;
153     register int i;
154     /* easy shadow test */
155     if (r->crtype & SHADOW && m->otype != MAT_TRANS)
156     return;
157 greg 2.2
158     if (m->oargs.nfargs != (m->otype == MAT_TRANS ? 7 : 5))
159     objerror(m, USER, "bad number of arguments");
160 greg 1.3 nd.mp = m;
161 greg 1.1 /* get material color */
162 greg 1.3 setcolor(nd.mcolor, m->oargs.farg[0],
163 greg 1.1 m->oargs.farg[1],
164     m->oargs.farg[2]);
165     /* get roughness */
166 greg 2.2 nd.specfl = 0;
167 greg 1.3 nd.alpha2 = m->oargs.farg[4];
168 greg 2.2 if ((nd.alpha2 *= nd.alpha2) <= FTINY)
169     nd.specfl |= SP_PURE;
170 greg 1.1 /* reorient if necessary */
171     if (r->rod < 0.0)
172     flipsurface(r);
173     /* get modifiers */
174     raytexture(r, m->omod);
175 greg 1.3 nd.pdot = raynormal(nd.pnorm, r); /* perturb normal */
176 greg 1.13 if (nd.pdot < .001)
177     nd.pdot = .001; /* non-zero for dirnorm() */
178 greg 1.3 multcolor(nd.mcolor, r->pcol); /* modify material color */
179 greg 1.9 transtest = 0;
180 greg 1.1 /* get specular component */
181 greg 2.2 if ((nd.rspec = m->oargs.farg[3]) > FTINY) {
182     nd.specfl |= SP_REFL;
183 greg 1.1 /* compute specular color */
184     if (m->otype == MAT_METAL)
185 greg 1.3 copycolor(nd.scolor, nd.mcolor);
186 greg 1.1 else
187 greg 1.3 setcolor(nd.scolor, 1.0, 1.0, 1.0);
188     scalecolor(nd.scolor, nd.rspec);
189 greg 2.13 if (nd.specfl & SP_PURE) { /* improved model */
190     dtmp = exp(-BSPEC(m)*nd.pdot);
191     for (i = 0; i < 3; i++)
192     colval(nd.scolor,i) +=
193     (1.0-colval(nd.scolor,i))*dtmp;
194     nd.rspec += (1.0-nd.rspec)*dtmp;
195     } else if (specthresh > FTINY && /* check threshold */
196     (specthresh >= 1.-FTINY ||
197     specthresh > nd.rspec))
198 greg 2.5 nd.specfl |= SP_RBLT;
199 greg 1.1 /* compute reflected ray */
200     for (i = 0; i < 3; i++)
201 greg 1.3 nd.vrefl[i] = r->rdir[i] + 2.0*nd.pdot*nd.pnorm[i];
202 greg 2.7 if (DOT(nd.vrefl, r->ron) <= FTINY) /* penetration? */
203     for (i = 0; i < 3; i++) /* safety measure */
204     nd.vrefl[i] = r->rdir[i] + 2.*r->rod*r->ron[i];
205 greg 1.1
206 greg 2.2 if (!(r->crtype & SHADOW) && nd.specfl & SP_PURE) {
207 greg 1.3 RAY lr;
208     if (rayorigin(&lr, r, REFLECTED, nd.rspec) == 0) {
209     VCOPY(lr.rdir, nd.vrefl);
210 greg 1.1 rayvalue(&lr);
211 greg 1.3 multcolor(lr.rcol, nd.scolor);
212 greg 1.1 addcolor(r->rcol, lr.rcol);
213     }
214 greg 1.3 }
215 greg 1.1 }
216 greg 1.3 /* compute transmission */
217 greg 1.1 if (m->otype == MAT_TRANS) {
218 greg 1.3 nd.trans = m->oargs.farg[5]*(1.0 - nd.rspec);
219     nd.tspec = nd.trans * m->oargs.farg[6];
220     nd.tdiff = nd.trans - nd.tspec;
221 greg 2.2 if (nd.tspec > FTINY) {
222     nd.specfl |= SP_TRAN;
223 greg 2.5 /* check threshold */
224 greg 2.13 if (!(nd.specfl & SP_PURE) && specthresh > FTINY &&
225     (specthresh >= 1.-FTINY ||
226     specthresh > nd.tspec))
227 greg 2.5 nd.specfl |= SP_TBLT;
228 greg 2.2 if (r->crtype & SHADOW ||
229     DOT(r->pert,r->pert) <= FTINY*FTINY) {
230     VCOPY(nd.prdir, r->rdir);
231     transtest = 2;
232     } else {
233     for (i = 0; i < 3; i++) /* perturb */
234     nd.prdir[i] = r->rdir[i] -
235 greg 2.8 0.5*r->pert[i];
236 greg 2.7 if (DOT(nd.prdir, r->ron) < -FTINY)
237     normalize(nd.prdir); /* OK */
238     else
239     VCOPY(nd.prdir, r->rdir);
240 greg 2.2 }
241 greg 1.14 }
242 greg 1.1 } else
243 greg 1.3 nd.tdiff = nd.tspec = nd.trans = 0.0;
244 greg 1.1 /* transmitted ray */
245 greg 2.2 if ((nd.specfl&(SP_TRAN|SP_PURE)) == (SP_TRAN|SP_PURE)) {
246 greg 1.3 RAY lr;
247     if (rayorigin(&lr, r, TRANS, nd.tspec) == 0) {
248 greg 1.14 VCOPY(lr.rdir, nd.prdir);
249 greg 1.1 rayvalue(&lr);
250 greg 1.3 scalecolor(lr.rcol, nd.tspec);
251 greg 1.8 multcolor(lr.rcol, nd.mcolor); /* modified by color */
252 greg 1.1 addcolor(r->rcol, lr.rcol);
253 greg 1.9 transtest *= bright(lr.rcol);
254     transdist = r->rot + lr.rt;
255 greg 1.1 }
256 greg 2.11 } else
257     transtest = 0;
258 greg 2.2
259 greg 1.1 if (r->crtype & SHADOW) /* the rest is shadow */
260     return;
261     /* diffuse reflection */
262 greg 1.3 nd.rdiff = 1.0 - nd.trans - nd.rspec;
263 greg 1.1
264 greg 2.2 if (nd.specfl & SP_PURE && nd.rdiff <= FTINY && nd.tdiff <= FTINY)
265     return; /* 100% pure specular */
266 greg 2.3
267 greg 2.12 if (r->ro != NULL && (r->ro->otype == OBJ_FACE ||
268     r->ro->otype == OBJ_RING))
269 greg 2.3 nd.specfl |= SP_FLAT;
270 greg 1.1
271 greg 2.2 if (nd.specfl & (SP_REFL|SP_TRAN) && !(nd.specfl & SP_PURE))
272     gaussamp(r, &nd);
273    
274 greg 1.3 if (nd.rdiff > FTINY) { /* ambient from this side */
275 greg 1.2 ambient(ctmp, r);
276 greg 2.5 if (nd.specfl & SP_RBLT)
277     scalecolor(ctmp, 1.0-nd.trans);
278     else
279     scalecolor(ctmp, nd.rdiff);
280 greg 1.3 multcolor(ctmp, nd.mcolor); /* modified by material color */
281 greg 1.2 addcolor(r->rcol, ctmp); /* add to returned color */
282     }
283 greg 1.3 if (nd.tdiff > FTINY) { /* ambient from other side */
284 greg 1.1 flipsurface(r);
285 greg 1.2 ambient(ctmp, r);
286 greg 2.5 if (nd.specfl & SP_TBLT)
287     scalecolor(ctmp, nd.trans);
288     else
289     scalecolor(ctmp, nd.tdiff);
290 greg 1.13 multcolor(ctmp, nd.mcolor); /* modified by color */
291 greg 1.1 addcolor(r->rcol, ctmp);
292     flipsurface(r);
293     }
294 greg 1.3 /* add direct component */
295     direct(r, dirnorm, &nd);
296 greg 1.9 /* check distance */
297     if (transtest > bright(r->rcol))
298     r->rt = transdist;
299 greg 2.2 }
300    
301    
302     static
303     gaussamp(r, np) /* sample gaussian specular */
304     RAY *r;
305     register NORMDAT *np;
306     {
307     RAY sr;
308     FVECT u, v, h;
309     double rv[2];
310     double d, sinp, cosp;
311     register int i;
312 greg 2.13 /* quick test */
313     if ((np->specfl & (SP_REFL|SP_RBLT)) != SP_REFL &&
314     (np->specfl & (SP_TRAN|SP_TBLT)) != SP_TRAN)
315     return;
316 greg 2.2 /* set up sample coordinates */
317     v[0] = v[1] = v[2] = 0.0;
318     for (i = 0; i < 3; i++)
319     if (np->pnorm[i] < 0.6 && np->pnorm[i] > -0.6)
320     break;
321     v[i] = 1.0;
322     fcross(u, v, np->pnorm);
323     normalize(u);
324     fcross(v, np->pnorm, u);
325     /* compute reflection */
326 greg 2.5 if ((np->specfl & (SP_REFL|SP_RBLT)) == SP_REFL &&
327 greg 2.2 rayorigin(&sr, r, SPECULAR, np->rspec) == 0) {
328     dimlist[ndims++] = (int)np->mp;
329 greg 2.7 d = urand(ilhash(dimlist,ndims)+samplendx);
330     multisamp(rv, 2, d);
331     d = 2.0*PI * rv[0];
332     cosp = cos(d);
333     sinp = sin(d);
334     rv[1] = 1.0 - specjitter*rv[1];
335     if (rv[1] <= FTINY)
336     d = 1.0;
337     else
338     d = sqrt( np->alpha2 * -log(rv[1]) );
339     for (i = 0; i < 3; i++)
340     h[i] = np->pnorm[i] + d*(cosp*u[i] + sinp*v[i]);
341     d = -2.0 * DOT(h, r->rdir) / (1.0 + d*d);
342     for (i = 0; i < 3; i++)
343     sr.rdir[i] = r->rdir[i] + d*h[i];
344     if (DOT(sr.rdir, r->ron) <= FTINY)
345     VCOPY(sr.rdir, np->vrefl); /* jitter no good */
346     rayvalue(&sr);
347     multcolor(sr.rcol, np->scolor);
348     addcolor(r->rcol, sr.rcol);
349 greg 2.2 ndims--;
350     }
351     /* compute transmission */
352 greg 2.8 if ((np->specfl & (SP_TRAN|SP_TBLT)) == SP_TRAN &&
353     rayorigin(&sr, r, SPECULAR, np->tspec) == 0) {
354     dimlist[ndims++] = (int)np->mp;
355     d = urand(ilhash(dimlist,ndims)+1823+samplendx);
356     multisamp(rv, 2, d);
357     d = 2.0*PI * rv[0];
358     cosp = cos(d);
359     sinp = sin(d);
360     rv[1] = 1.0 - specjitter*rv[1];
361     if (rv[1] <= FTINY)
362     d = 1.0;
363     else
364     d = sqrt( np->alpha2/4.0 * -log(rv[1]) );
365     for (i = 0; i < 3; i++)
366     sr.rdir[i] = np->prdir[i] + d*(cosp*u[i] + sinp*v[i]);
367     if (DOT(sr.rdir, r->ron) < -FTINY)
368     normalize(sr.rdir); /* OK, normalize */
369     else
370     VCOPY(sr.rdir, np->prdir); /* else no jitter */
371     rayvalue(&sr);
372 greg 2.11 scalecolor(sr.rcol, np->tspec);
373     multcolor(sr.rcol, np->mcolor); /* modified by color */
374 greg 2.8 addcolor(r->rcol, sr.rcol);
375     ndims--;
376     }
377 greg 1.1 }