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root/radiance/ray/src/rt/ashikhmin.c
Revision: 2.3
Committed: Wed Aug 7 05:10:09 2013 UTC (10 years, 7 months ago) by greg
Content type: text/plain
Branch: MAIN
CVS Tags: rad4R2P2, rad4R2, rad4R2P1
Changes since 2.2: +1 -2 lines
Log Message:
Eliminated a number of minor warnings (all innocuous)

File Contents

# Content
1 #ifndef lint
2 static const char RCSid[] = "$Id: ashikhmin.c,v 2.2 2012/07/29 21:56:16 greg Exp $";
3 #endif
4 /*
5 * Shading functions for Ashikhmin-Shirley 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 * Ashikhmin-Shirley model
24 *
25 * Arguments for MAT_ASHIKHMIN are:
26 * 4+ ux uy uz funcfile [transform...]
27 * 0
28 * 8 dred dgrn dblu sred sgrn sblu u-power v-power
29 */
30
31 /* specularity flags */
32 #define SPA_REFL 01 /* has reflected specular component */
33 #define SPA_FLAT 02 /* reflecting surface is flat */
34 #define SPA_RBLT 010 /* reflection below sample threshold */
35 #define SPA_BADU 020 /* bad u direction calculation */
36
37 typedef struct {
38 OBJREC *mp; /* material pointer */
39 RAY *rp; /* ray pointer */
40 short specfl; /* specularity flags, defined above */
41 COLOR mcolor; /* color of this material */
42 COLOR scolor; /* color of specular component */
43 FVECT u, v; /* u and v vectors orienting anisotropy */
44 double u_power; /* u power */
45 double v_power; /* v power */
46 FVECT pnorm; /* perturbed surface normal */
47 double pdot; /* perturbed dot product */
48 } ASHIKDAT; /* anisotropic material data */
49
50 static void getacoords_as(ASHIKDAT *np);
51 static void ashiksamp(ASHIKDAT *np);
52
53 #undef MAX
54 #define MAX(a,b) ((a)>(b) ? (a) : (b))
55
56
57 static double
58 schlick_fres(double dprod)
59 {
60 double pf = 1. - dprod;
61
62 return(pf*pf*pf*pf*pf);
63 }
64
65
66 static void
67 dirashik( /* compute source contribution */
68 COLOR cval, /* returned coefficient */
69 void *nnp, /* material data */
70 FVECT ldir, /* light source direction */
71 double omega /* light source size */
72 )
73 {
74 ASHIKDAT *np = nnp;
75 double ldot;
76 double dtmp, dtmp1, dtmp2;
77 FVECT h;
78 COLOR ctmp;
79
80 setcolor(cval, 0.0, 0.0, 0.0);
81
82 ldot = DOT(np->pnorm, ldir);
83
84 if (ldot < 0.0)
85 return; /* wrong side */
86
87 /*
88 * Compute and add diffuse reflected component to returned
89 * color.
90 */
91 copycolor(ctmp, np->mcolor);
92 dtmp = ldot * omega * (1.0/PI) * (1. - schlick_fres(ldot));
93 scalecolor(ctmp, dtmp);
94 addcolor(cval, ctmp);
95
96 if ((np->specfl & (SPA_REFL|SPA_BADU)) != SPA_REFL)
97 return;
98 /*
99 * Compute specular reflection coefficient
100 */
101 /* half vector */
102 VSUB(h, ldir, np->rp->rdir);
103 normalize(h);
104 /* ellipse */
105 dtmp1 = DOT(np->u, h);
106 dtmp1 *= dtmp1 * np->u_power;
107 dtmp2 = DOT(np->v, h);
108 dtmp2 *= dtmp2 * np->v_power;
109 /* Ashikhmin-Shirley model*/
110 dtmp = DOT(np->pnorm, h);
111 dtmp = pow(dtmp, (dtmp1+dtmp2)/(1.-dtmp*dtmp));
112 dtmp *= sqrt((np->u_power+1.)*(np->v_power+1.));
113 dtmp /= 8.*PI * DOT(ldir,h) * MAX(ldot,np->pdot);
114 /* worth using? */
115 if (dtmp > FTINY) {
116 copycolor(ctmp, np->scolor);
117 dtmp *= ldot * omega;
118 scalecolor(ctmp, dtmp);
119 addcolor(cval, ctmp);
120 }
121 }
122
123
124 int
125 m_ashikhmin( /* shade ray that hit something anisotropic */
126 OBJREC *m,
127 RAY *r
128 )
129 {
130 ASHIKDAT nd;
131 COLOR ctmp;
132 double fres;
133 int i;
134 /* easy shadow test */
135 if (r->crtype & SHADOW)
136 return(1);
137
138 if (m->oargs.nfargs != 8)
139 objerror(m, USER, "bad number of real arguments");
140 /* check for back side */
141 if (r->rod < 0.0) {
142 if (!backvis) {
143 raytrans(r);
144 return(1);
145 }
146 raytexture(r, m->omod);
147 flipsurface(r); /* reorient if backvis */
148 } else
149 raytexture(r, m->omod);
150 /* get material color */
151 nd.mp = m;
152 nd.rp = r;
153 setcolor(nd.mcolor, m->oargs.farg[0],
154 m->oargs.farg[1],
155 m->oargs.farg[2]);
156 setcolor(nd.scolor, m->oargs.farg[3],
157 m->oargs.farg[4],
158 m->oargs.farg[5]);
159 /* get specular power */
160 nd.specfl = 0;
161 nd.u_power = m->oargs.farg[6];
162 nd.v_power = m->oargs.farg[7];
163
164 nd.pdot = raynormal(nd.pnorm, r); /* perturb normal */
165 if (nd.pdot < .001)
166 nd.pdot = .001; /* non-zero for dirashik() */
167 multcolor(nd.mcolor, r->pcol); /* modify diffuse color */
168
169 if (bright(nd.scolor) > FTINY) { /* adjust specular color */
170 nd.specfl |= SPA_REFL;
171 /* check threshold */
172 if (specthresh >= bright(nd.scolor)-FTINY)
173 nd.specfl |= SPA_RBLT;
174 fres = schlick_fres(nd.pdot); /* Schick's Fresnel approx */
175 for (i = 0; i < 3; i++)
176 colval(nd.scolor,i) += (1.-colval(nd.scolor,i))*fres;
177 }
178 if (r->ro != NULL && isflat(r->ro->otype))
179 nd.specfl |= SPA_FLAT;
180 /* set up coordinates */
181 getacoords_as(&nd);
182 /* specular sampling? */
183 if ((nd.specfl & (SPA_REFL|SPA_RBLT)) == SPA_REFL)
184 ashiksamp(&nd);
185 /* diffuse interreflection */
186 if (bright(nd.mcolor) > FTINY) {
187 copycolor(ctmp, nd.mcolor); /* modified by material color */
188 if (nd.specfl & SPA_RBLT) /* add in specular as well? */
189 addcolor(ctmp, nd.scolor);
190 multambient(ctmp, r, nd.pnorm);
191 addcolor(r->rcol, ctmp); /* add to returned color */
192 }
193 direct(r, dirashik, &nd); /* add direct component */
194
195 return(1);
196 }
197
198
199 static void
200 getacoords_as( /* set up coordinate system */
201 ASHIKDAT *np
202 )
203 {
204 MFUNC *mf;
205 int i;
206
207 mf = getfunc(np->mp, 3, 0x7, 1);
208 setfunc(np->mp, np->rp);
209 errno = 0;
210 for (i = 0; i < 3; i++)
211 np->u[i] = evalue(mf->ep[i]);
212 if ((errno == EDOM) | (errno == ERANGE)) {
213 objerror(np->mp, WARNING, "compute error");
214 np->specfl |= SPA_BADU;
215 return;
216 }
217 if (mf->fxp != &unitxf)
218 multv3(np->u, np->u, mf->fxp->xfm);
219 fcross(np->v, np->pnorm, np->u);
220 if (normalize(np->v) == 0.0) {
221 objerror(np->mp, WARNING, "illegal orientation vector");
222 np->specfl |= SPA_BADU;
223 return;
224 }
225 fcross(np->u, np->v, np->pnorm);
226 }
227
228
229 static void
230 ashiksamp( /* sample anisotropic Ashikhmin-Shirley specular */
231 ASHIKDAT *np
232 )
233 {
234 RAY sr;
235 FVECT h;
236 double rv[2], dtmp;
237 double cosph, sinph, costh, sinth;
238 int maxiter, ntrials, nstarget, nstaken;
239 int i;
240
241 if (np->specfl & SPA_BADU ||
242 rayorigin(&sr, SPECULAR, np->rp, np->scolor) < 0)
243 return;
244
245 nstarget = 1;
246 if (specjitter > 1.5) { /* multiple samples? */
247 nstarget = specjitter*np->rp->rweight + .5;
248 if (sr.rweight <= minweight*nstarget)
249 nstarget = sr.rweight/minweight;
250 if (nstarget > 1) {
251 dtmp = 1./nstarget;
252 scalecolor(sr.rcoef, dtmp);
253 sr.rweight *= dtmp;
254 } else
255 nstarget = 1;
256 }
257 dimlist[ndims++] = (int)(size_t)np->mp;
258 maxiter = MAXITER*nstarget;
259 for (nstaken = ntrials = 0; nstaken < nstarget &&
260 ntrials < maxiter; ntrials++) {
261 if (ntrials)
262 dtmp = frandom();
263 else
264 dtmp = urand(ilhash(dimlist,ndims)+647+samplendx);
265 multisamp(rv, 2, dtmp);
266 dtmp = 2.*PI * rv[0];
267 cosph = sqrt(np->v_power + 1.) * tcos(dtmp);
268 sinph = sqrt(np->u_power + 1.) * tsin(dtmp);
269 dtmp = 1./sqrt(cosph*cosph + sinph*sinph);
270 cosph *= dtmp;
271 sinph *= dtmp;
272 costh = pow(rv[1], 1./(np->u_power*cosph*cosph+np->v_power*sinph*sinph+1.));
273 if (costh <= FTINY)
274 continue;
275 sinth = sqrt(1. - costh*costh);
276 for (i = 0; i < 3; i++)
277 h[i] = cosph*sinth*np->u[i] + sinph*sinth*np->v[i] + costh*np->pnorm[i];
278
279 if (nstaken)
280 rayclear(&sr);
281 dtmp = -2.*DOT(h, np->rp->rdir);
282 VSUM(sr.rdir, np->rp->rdir, h, dtmp);
283 /* sample rejection test */
284 if (DOT(sr.rdir, np->rp->ron) <= FTINY)
285 continue;
286 checknorm(sr.rdir);
287 rayvalue(&sr);
288 multcolor(sr.rcol, sr.rcoef);
289 addcolor(np->rp->rcol, sr.rcol);
290 ++nstaken;
291 }
292 ndims--;
293 }