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root/radiance/ray/src/rt/ambcomp.c
Revision: 2.96
Committed: Fri Nov 15 20:47:42 2024 UTC (6 months, 1 week ago) by greg
Content type: text/plain
Branch: MAIN
Changes since 2.95: +5 -1 lines
Log Message:
feat(rpict): Experimental source skipping option with -DSSKIPOPT compile flag

File Contents

# Content
1 #ifndef lint
2 static const char RCSid[] = "$Id: ambcomp.c,v 2.95 2024/04/19 01:52:50 greg Exp $";
3 #endif
4 /*
5 * Routines to compute "ambient" values using Monte Carlo
6 *
7 * Hessian calculations based on "Practical Hessian-Based Error Control
8 * for Irradiance Caching" by Schwarzhaupt, Wann Jensen, & Jarosz
9 * from ACM SIGGRAPH Asia 2012 conference proceedings.
10 *
11 * Added book-keeping optimization to avoid calculations that would
12 * cancel due to traversal both directions on edges that are adjacent
13 * to same-valued triangles. This cuts about half of Hessian math.
14 *
15 * Declarations of external symbols in ambient.h
16 */
17
18 #include "copyright.h"
19
20 #include "ray.h"
21 #include "ambient.h"
22 #include "random.h"
23
24 #ifndef MINADIV
25 #define MINADIV 7 /* minimum # divisions in each dimension */
26 #endif
27
28 typedef struct {
29 FVECT p; /* intersection point */
30 float d; /* reciprocal distance */
31 SCOLOR v; /* hemisphere sample value */
32 } AMBSAMP; /* sample value */
33
34 typedef struct {
35 RAY *rp; /* originating ray sample */
36 int ns; /* number of samples per axis */
37 int sampOK; /* acquired full sample set? */
38 int atyp; /* RAMBIENT or TAMBIENT */
39 SCOLOR acoef; /* division contribution coefficient */
40 SCOLOR acol; /* accumulated color */
41 FVECT onrm; /* oriented unperturbed surface normal */
42 FVECT ux, uy; /* tangent axis unit vectors */
43 AMBSAMP sa[1]; /* sample array (extends struct) */
44 } AMBHEMI; /* ambient sample hemisphere */
45
46 #define AI(h,i,j) ((i)*(h)->ns + (j))
47 #define ambsam(h,i,j) (h)->sa[AI(h,i,j)]
48
49 typedef struct {
50 FVECT r_i, r_i1, e_i, rcp, rI2_eJ2;
51 double I1, I2;
52 } FFTRI; /* vectors and coefficients for Hessian calculation */
53
54
55 static int
56 ambcollision( /* proposed direciton collides? */
57 AMBHEMI *hp,
58 int i,
59 int j,
60 FVECT dv
61 )
62 {
63 double cos_thresh;
64 int ii, jj;
65 /* min. spacing = 1/4th division */
66 cos_thresh = (PI/4.)/(double)hp->ns;
67 cos_thresh = 1. - .5*cos_thresh*cos_thresh;
68 /* check existing neighbors */
69 for (ii = i-1; ii <= i+1; ii++) {
70 if (ii < 0) continue;
71 if (ii >= hp->ns) break;
72 for (jj = j-1; jj <= j+1; jj++) {
73 AMBSAMP *ap;
74 FVECT avec;
75 double dprod;
76 if (jj < 0) continue;
77 if (jj >= hp->ns) break;
78 if ((ii==i) & (jj==j)) continue;
79 ap = &ambsam(hp,ii,jj);
80 if (ap->d <= .5/FHUGE)
81 continue; /* no one home */
82 VSUB(avec, ap->p, hp->rp->rop);
83 dprod = DOT(avec, dv);
84 if (dprod >= cos_thresh*VLEN(avec))
85 return(1); /* collision */
86 }
87 }
88 return(0); /* nothing to worry about */
89 }
90
91
92 static int
93 ambsample( /* initial ambient division sample */
94 AMBHEMI *hp,
95 int i,
96 int j,
97 int n
98 )
99 {
100 AMBSAMP *ap = &ambsam(hp,i,j);
101 RAY ar;
102 int hlist[3], ii;
103 double ss[2];
104 RREAL spt[2];
105 double zd;
106 /* generate hemispherical sample */
107 /* ambient coefficient for weight */
108 if (ambacc > FTINY)
109 setscolor(ar.rcoef, AVGREFL, AVGREFL, AVGREFL);
110 else
111 copyscolor(ar.rcoef, hp->acoef);
112 if (rayorigin(&ar, hp->atyp, hp->rp, ar.rcoef) < 0)
113 return(0);
114 if (ambacc > FTINY) {
115 #ifdef SSKIPOPT
116 ar.rsrc = -1; /* protect cache from source opt. */
117 ar.scorr = 1.f;
118 #endif
119 smultscolor(ar.rcoef, hp->acoef);
120 scalescolor(ar.rcoef, 1./AVGREFL);
121 }
122 hlist[0] = hp->rp->rno;
123 hlist[1] = AI(hp,i,j);
124 hlist[2] = samplendx;
125 multisamp(ss, 2, urand(ilhash(hlist,3)+n));
126 resample:
127 square2disk(spt, (j+ss[1])/hp->ns, (i+ss[0])/hp->ns);
128 zd = sqrt(1. - spt[0]*spt[0] - spt[1]*spt[1]);
129 for (ii = 3; ii--; )
130 ar.rdir[ii] = spt[0]*hp->ux[ii] +
131 spt[1]*hp->uy[ii] +
132 zd*hp->onrm[ii];
133 checknorm(ar.rdir);
134 /* avoid coincident samples */
135 if (!n && hp->ns >= 4 && ambcollision(hp, i, j, ar.rdir)) {
136 ss[0] = frandom(); ss[1] = frandom();
137 goto resample; /* reject this sample */
138 }
139 dimlist[ndims++] = AI(hp,i,j) + 90171;
140 rayvalue(&ar); /* evaluate ray */
141 ndims--;
142 zd = raydistance(&ar);
143 if (zd <= FTINY)
144 return(0); /* should never happen */
145 smultscolor(ar.rcol, ar.rcoef); /* apply coefficient */
146 if (zd*ap->d < 1.0) /* new/closer distance? */
147 ap->d = 1.0/zd;
148 if (!n) { /* record first vertex & value */
149 if (zd > 10.0*thescene.cusize + 1000.)
150 zd = 10.0*thescene.cusize + 1000.;
151 VSUM(ap->p, ar.rorg, ar.rdir, zd);
152 copyscolor(ap->v, ar.rcol);
153 } else { /* else update recorded value */
154 sopscolor(hp->acol, -=, ap->v);
155 zd = 1.0/(double)(n+1);
156 scalescolor(ar.rcol, zd);
157 zd *= (double)n;
158 scalescolor(ap->v, zd);
159 saddscolor(ap->v, ar.rcol);
160 }
161 saddscolor(hp->acol, ap->v); /* add to our sum */
162 return(1);
163 }
164
165
166 /* Estimate variance based on ambient division differences */
167 static float *
168 getambdiffs(AMBHEMI *hp)
169 {
170 const double normf = 1./(pbright(hp->acoef) + FTINY);
171 float *earr = (float *)calloc(2*hp->ns*hp->ns, sizeof(float));
172 float *ep;
173 AMBSAMP *ap;
174 double b, b1, d2;
175 int i, j;
176
177 if (earr == NULL) /* out of memory? */
178 return(NULL);
179 /* sum squared neighbor diffs */
180 ap = hp->sa;
181 ep = earr + hp->ns*hp->ns; /* original estimates to scratch */
182 for (i = 0; i < hp->ns; i++)
183 for (j = 0; j < hp->ns; j++, ap++, ep++) {
184 b = pbright(ap[0].v);
185 if (i) { /* from above */
186 b1 = pbright(ap[-hp->ns].v);
187 d2 = b - b1;
188 d2 *= d2*normf/(b + b1 + FTINY);
189 ep[0] += d2;
190 ep[-hp->ns] += d2;
191 }
192 if (!j) continue;
193 /* from behind */
194 b1 = pbright(ap[-1].v);
195 d2 = b - b1;
196 d2 *= d2*normf/(b + b1 + FTINY);
197 ep[0] += d2;
198 ep[-1] += d2;
199 if (!i) continue;
200 /* diagonal */
201 b1 = pbright(ap[-hp->ns-1].v);
202 d2 = b - b1;
203 d2 *= d2*normf/(b + b1 + FTINY);
204 ep[0] += d2;
205 ep[-hp->ns-1] += d2;
206 }
207 /* correct for number of neighbors */
208 ep = earr + hp->ns*hp->ns;
209 ep[0] *= 6./3.;
210 ep[hp->ns-1] *= 6./3.;
211 ep[(hp->ns-1)*hp->ns] *= 6./3.;
212 ep[(hp->ns-1)*hp->ns + hp->ns-1] *= 6./3.;
213 for (i = 1; i < hp->ns-1; i++) {
214 ep[i*hp->ns] *= 6./5.;
215 ep[i*hp->ns + hp->ns-1] *= 6./5.;
216 }
217 for (j = 1; j < hp->ns-1; j++) {
218 ep[j] *= 6./5.;
219 ep[(hp->ns-1)*hp->ns + j] *= 6./5.;
220 }
221 /* blur final map to reduce bias */
222 for (i = 0; i < hp->ns-1; i++) {
223 float *ep2;
224 ep = earr + i*hp->ns;
225 ep2 = ep + hp->ns*hp->ns;
226 for (j = 0; j < hp->ns-1; j++, ep++, ep2++) {
227 ep[0] += .5*ep2[0] + .125*(ep2[1] + ep2[hp->ns]);
228 ep[1] += .125*ep2[0];
229 ep[hp->ns] += .125*ep2[0];
230 }
231 }
232 return(earr);
233 }
234
235
236 /* Perform super-sampling on hemisphere (introduces bias) */
237 static void
238 ambsupersamp(AMBHEMI *hp, int cnt)
239 {
240 float *earr = getambdiffs(hp);
241 double e2rem = 0;
242 float *ep;
243 int i, j, n, nss;
244
245 if (earr == NULL) /* just skip calc. if no memory */
246 return;
247 /* accumulate estimated variances */
248 for (ep = earr + hp->ns*hp->ns; ep > earr; )
249 e2rem += *--ep;
250 ep = earr; /* perform super-sampling */
251 for (i = 0; i < hp->ns; i++)
252 for (j = 0; j < hp->ns; j++) {
253 if (e2rem <= FTINY)
254 goto done; /* nothing left to do */
255 nss = *ep/e2rem*cnt + frandom();
256 for (n = 1; n <= nss && ambsample(hp,i,j,n); n++)
257 if (!--cnt) goto done;
258 e2rem -= *ep++; /* update remainder */
259 }
260 done:
261 free(earr);
262 }
263
264
265 static AMBHEMI *
266 samp_hemi( /* sample indirect hemisphere */
267 SCOLOR rcol,
268 RAY *r,
269 double wt
270 )
271 {
272 int backside = (wt < 0);
273 AMBHEMI *hp;
274 double d;
275 int n, i, j;
276 /* insignificance check */
277 d = sintens(rcol);
278 if (d <= FTINY)
279 return(NULL);
280 /* set number of divisions */
281 if (backside) wt = -wt;
282 if (ambacc <= FTINY &&
283 wt > (d *= 0.8*r->rweight/(ambdiv*minweight + 1e-20)))
284 wt = d; /* avoid ray termination */
285 n = sqrt(ambdiv * wt) + 0.5;
286 i = 1 + (MINADIV-1)*(ambacc > FTINY);
287 if (n < i) /* use minimum number of samples? */
288 n = i;
289 /* allocate sampling array */
290 hp = (AMBHEMI *)malloc(sizeof(AMBHEMI) + sizeof(AMBSAMP)*(n*n - 1));
291 if (hp == NULL)
292 error(SYSTEM, "out of memory in samp_hemi");
293
294 if (backside) {
295 hp->atyp = TAMBIENT;
296 hp->onrm[0] = -r->ron[0];
297 hp->onrm[1] = -r->ron[1];
298 hp->onrm[2] = -r->ron[2];
299 } else {
300 hp->atyp = RAMBIENT;
301 VCOPY(hp->onrm, r->ron);
302 }
303 hp->rp = r;
304 hp->ns = n;
305 scolorblack(hp->acol);
306 memset(hp->sa, 0, sizeof(AMBSAMP)*n*n);
307 hp->sampOK = 0;
308 /* assign coefficient */
309 copyscolor(hp->acoef, rcol);
310 d = 1.0/(n*n);
311 scalescolor(hp->acoef, d);
312 /* make tangent plane axes */
313 if (!getperpendicular(hp->ux, hp->onrm, 1))
314 error(CONSISTENCY, "bad ray direction in samp_hemi");
315 VCROSS(hp->uy, hp->onrm, hp->ux);
316 /* sample divisions */
317 for (i = hp->ns; i--; )
318 for (j = hp->ns; j--; )
319 hp->sampOK += ambsample(hp, i, j, 0);
320 copyscolor(rcol, hp->acol);
321 if (!hp->sampOK) { /* utter failure? */
322 free(hp);
323 return(NULL);
324 }
325 if (hp->sampOK < hp->ns*hp->ns) {
326 hp->sampOK *= -1; /* soft failure */
327 return(hp);
328 }
329 if (hp->sampOK <= MINADIV*MINADIV)
330 return(hp); /* don't bother super-sampling */
331 n = ambssamp*wt + 0.5;
332 if (n >= 4*hp->ns) { /* perform super-sampling? */
333 ambsupersamp(hp, n);
334 copyscolor(rcol, hp->acol);
335 }
336 return(hp); /* all is well */
337 }
338
339
340 /* Return brightness of farthest ambient sample */
341 static double
342 back_ambval(AMBHEMI *hp, const int n1, const int n2, const int n3)
343 {
344 if (hp->sa[n1].d <= hp->sa[n2].d) {
345 if (hp->sa[n1].d <= hp->sa[n3].d)
346 return(hp->sa[n1].v[0]);
347 return(hp->sa[n3].v[0]);
348 }
349 if (hp->sa[n2].d <= hp->sa[n3].d)
350 return(hp->sa[n2].v[0]);
351 return(hp->sa[n3].v[0]);
352 }
353
354
355 /* Compute vectors and coefficients for Hessian/gradient calcs */
356 static void
357 comp_fftri(FFTRI *ftp, AMBHEMI *hp, const int n0, const int n1)
358 {
359 double rdot_cp, dot_e, dot_er, rdot_r, rdot_r1, J2;
360 int ii;
361
362 VSUB(ftp->r_i, hp->sa[n0].p, hp->rp->rop);
363 VSUB(ftp->r_i1, hp->sa[n1].p, hp->rp->rop);
364 VSUB(ftp->e_i, hp->sa[n1].p, hp->sa[n0].p);
365 VCROSS(ftp->rcp, ftp->r_i, ftp->r_i1);
366 rdot_cp = 1.0/DOT(ftp->rcp,ftp->rcp);
367 dot_e = DOT(ftp->e_i,ftp->e_i);
368 dot_er = DOT(ftp->e_i, ftp->r_i);
369 rdot_r = 1.0/DOT(ftp->r_i,ftp->r_i);
370 rdot_r1 = 1.0/DOT(ftp->r_i1,ftp->r_i1);
371 ftp->I1 = acos( DOT(ftp->r_i, ftp->r_i1) * sqrt(rdot_r*rdot_r1) ) *
372 sqrt( rdot_cp );
373 ftp->I2 = ( DOT(ftp->e_i, ftp->r_i1)*rdot_r1 - dot_er*rdot_r +
374 dot_e*ftp->I1 )*0.5*rdot_cp;
375 J2 = ( 0.5*(rdot_r - rdot_r1) - dot_er*ftp->I2 ) / dot_e;
376 for (ii = 3; ii--; )
377 ftp->rI2_eJ2[ii] = ftp->I2*ftp->r_i[ii] + J2*ftp->e_i[ii];
378 }
379
380
381 /* Compose 3x3 matrix from two vectors */
382 static void
383 compose_matrix(FVECT mat[3], FVECT va, FVECT vb)
384 {
385 mat[0][0] = 2.0*va[0]*vb[0];
386 mat[1][1] = 2.0*va[1]*vb[1];
387 mat[2][2] = 2.0*va[2]*vb[2];
388 mat[0][1] = mat[1][0] = va[0]*vb[1] + va[1]*vb[0];
389 mat[0][2] = mat[2][0] = va[0]*vb[2] + va[2]*vb[0];
390 mat[1][2] = mat[2][1] = va[1]*vb[2] + va[2]*vb[1];
391 }
392
393
394 /* Compute partial 3x3 Hessian matrix for edge */
395 static void
396 comp_hessian(FVECT hess[3], FFTRI *ftp, FVECT nrm)
397 {
398 FVECT ncp;
399 FVECT m1[3], m2[3], m3[3], m4[3];
400 double d1, d2, d3, d4;
401 double I3, J3, K3;
402 int i, j;
403 /* compute intermediate coefficients */
404 d1 = 1.0/DOT(ftp->r_i,ftp->r_i);
405 d2 = 1.0/DOT(ftp->r_i1,ftp->r_i1);
406 d3 = 1.0/DOT(ftp->e_i,ftp->e_i);
407 d4 = DOT(ftp->e_i, ftp->r_i);
408 I3 = ( DOT(ftp->e_i, ftp->r_i1)*d2*d2 - d4*d1*d1 + 3.0/d3*ftp->I2 )
409 / ( 4.0*DOT(ftp->rcp,ftp->rcp) );
410 J3 = 0.25*d3*(d1*d1 - d2*d2) - d4*d3*I3;
411 K3 = d3*(ftp->I2 - I3/d1 - 2.0*d4*J3);
412 /* intermediate matrices */
413 VCROSS(ncp, nrm, ftp->e_i);
414 compose_matrix(m1, ncp, ftp->rI2_eJ2);
415 compose_matrix(m2, ftp->r_i, ftp->r_i);
416 compose_matrix(m3, ftp->e_i, ftp->e_i);
417 compose_matrix(m4, ftp->r_i, ftp->e_i);
418 d1 = DOT(nrm, ftp->rcp);
419 d2 = -d1*ftp->I2;
420 d1 *= 2.0;
421 for (i = 3; i--; ) /* final matrix sum */
422 for (j = 3; j--; ) {
423 hess[i][j] = m1[i][j] + d1*( I3*m2[i][j] + K3*m3[i][j] +
424 2.0*J3*m4[i][j] );
425 hess[i][j] += d2*(i==j);
426 hess[i][j] *= -1.0/PI;
427 }
428 }
429
430
431 /* Reverse hessian calculation result for edge in other direction */
432 static void
433 rev_hessian(FVECT hess[3])
434 {
435 int i;
436
437 for (i = 3; i--; ) {
438 hess[i][0] = -hess[i][0];
439 hess[i][1] = -hess[i][1];
440 hess[i][2] = -hess[i][2];
441 }
442 }
443
444
445 /* Add to radiometric Hessian from the given triangle */
446 static void
447 add2hessian(FVECT hess[3], FVECT ehess1[3],
448 FVECT ehess2[3], FVECT ehess3[3], double v)
449 {
450 int i, j;
451
452 for (i = 3; i--; )
453 for (j = 3; j--; )
454 hess[i][j] += v*( ehess1[i][j] + ehess2[i][j] + ehess3[i][j] );
455 }
456
457
458 /* Compute partial displacement form factor gradient for edge */
459 static void
460 comp_gradient(FVECT grad, FFTRI *ftp, FVECT nrm)
461 {
462 FVECT ncp;
463 double f1;
464 int i;
465
466 f1 = 2.0*DOT(nrm, ftp->rcp);
467 VCROSS(ncp, nrm, ftp->e_i);
468 for (i = 3; i--; )
469 grad[i] = (0.5/PI)*( ftp->I1*ncp[i] + f1*ftp->rI2_eJ2[i] );
470 }
471
472
473 /* Reverse gradient calculation result for edge in other direction */
474 static void
475 rev_gradient(FVECT grad)
476 {
477 grad[0] = -grad[0];
478 grad[1] = -grad[1];
479 grad[2] = -grad[2];
480 }
481
482
483 /* Add to displacement gradient from the given triangle */
484 static void
485 add2gradient(FVECT grad, FVECT egrad1, FVECT egrad2, FVECT egrad3, double v)
486 {
487 int i;
488
489 for (i = 3; i--; )
490 grad[i] += v*( egrad1[i] + egrad2[i] + egrad3[i] );
491 }
492
493
494 /* Compute anisotropic radii and eigenvector directions */
495 static void
496 eigenvectors(FVECT uv[2], float ra[2], FVECT hessian[3])
497 {
498 double hess2[2][2];
499 FVECT a, b;
500 double evalue[2], slope1, xmag1;
501 int i;
502 /* project Hessian to sample plane */
503 for (i = 3; i--; ) {
504 a[i] = DOT(hessian[i], uv[0]);
505 b[i] = DOT(hessian[i], uv[1]);
506 }
507 hess2[0][0] = DOT(uv[0], a);
508 hess2[0][1] = DOT(uv[0], b);
509 hess2[1][0] = DOT(uv[1], a);
510 hess2[1][1] = DOT(uv[1], b);
511 /* compute eigenvalue(s) */
512 i = quadratic(evalue, 1.0, -hess2[0][0]-hess2[1][1],
513 hess2[0][0]*hess2[1][1]-hess2[0][1]*hess2[1][0]);
514 if (i == 1) /* double-root (circle) */
515 evalue[1] = evalue[0];
516 if (!i || ((evalue[0] = fabs(evalue[0])) <= FTINY*FTINY) |
517 ((evalue[1] = fabs(evalue[1])) <= FTINY*FTINY) ) {
518 ra[0] = ra[1] = maxarad;
519 return;
520 }
521 if (evalue[0] > evalue[1]) {
522 ra[0] = sqrt(sqrt(4.0/evalue[0]));
523 ra[1] = sqrt(sqrt(4.0/evalue[1]));
524 slope1 = evalue[1];
525 } else {
526 ra[0] = sqrt(sqrt(4.0/evalue[1]));
527 ra[1] = sqrt(sqrt(4.0/evalue[0]));
528 slope1 = evalue[0];
529 }
530 /* compute unit eigenvectors */
531 if (fabs(hess2[0][1]) <= FTINY)
532 return; /* uv OK as is */
533 slope1 = (slope1 - hess2[0][0]) / hess2[0][1];
534 xmag1 = sqrt(1.0/(1.0 + slope1*slope1));
535 for (i = 3; i--; ) {
536 b[i] = xmag1*uv[0][i] + slope1*xmag1*uv[1][i];
537 a[i] = slope1*xmag1*uv[0][i] - xmag1*uv[1][i];
538 }
539 VCOPY(uv[0], a);
540 VCOPY(uv[1], b);
541 }
542
543
544 static void
545 ambHessian( /* anisotropic radii & pos. gradient */
546 AMBHEMI *hp,
547 FVECT uv[2], /* returned */
548 float ra[2], /* returned (optional) */
549 float pg[2] /* returned (optional) */
550 )
551 {
552 static char memerrmsg[] = "out of memory in ambHessian()";
553 FVECT (*hessrow)[3] = NULL;
554 FVECT *gradrow = NULL;
555 FVECT hessian[3];
556 FVECT gradient;
557 FFTRI fftr;
558 int i, j;
559 /* be sure to assign unit vectors */
560 VCOPY(uv[0], hp->ux);
561 VCOPY(uv[1], hp->uy);
562 /* clock-wise vertex traversal from sample POV */
563 if (ra != NULL) { /* initialize Hessian row buffer */
564 hessrow = (FVECT (*)[3])malloc(sizeof(FVECT)*3*(hp->ns-1));
565 if (hessrow == NULL)
566 error(SYSTEM, memerrmsg);
567 memset(hessian, 0, sizeof(hessian));
568 } else if (pg == NULL) /* bogus call? */
569 return;
570 if (pg != NULL) { /* initialize form factor row buffer */
571 gradrow = (FVECT *)malloc(sizeof(FVECT)*(hp->ns-1));
572 if (gradrow == NULL)
573 error(SYSTEM, memerrmsg);
574 memset(gradient, 0, sizeof(gradient));
575 }
576 /* compute first row of edges */
577 for (j = 0; j < hp->ns-1; j++) {
578 comp_fftri(&fftr, hp, AI(hp,0,j), AI(hp,0,j+1));
579 if (hessrow != NULL)
580 comp_hessian(hessrow[j], &fftr, hp->onrm);
581 if (gradrow != NULL)
582 comp_gradient(gradrow[j], &fftr, hp->onrm);
583 }
584 /* sum each row of triangles */
585 for (i = 0; i < hp->ns-1; i++) {
586 FVECT hesscol[3]; /* compute first vertical edge */
587 FVECT gradcol;
588 comp_fftri(&fftr, hp, AI(hp,i,0), AI(hp,i+1,0));
589 if (hessrow != NULL)
590 comp_hessian(hesscol, &fftr, hp->onrm);
591 if (gradrow != NULL)
592 comp_gradient(gradcol, &fftr, hp->onrm);
593 for (j = 0; j < hp->ns-1; j++) {
594 FVECT hessdia[3]; /* compute triangle contributions */
595 FVECT graddia;
596 double backg;
597 backg = back_ambval(hp, AI(hp,i,j),
598 AI(hp,i,j+1), AI(hp,i+1,j));
599 /* diagonal (inner) edge */
600 comp_fftri(&fftr, hp, AI(hp,i,j+1), AI(hp,i+1,j));
601 if (hessrow != NULL) {
602 comp_hessian(hessdia, &fftr, hp->onrm);
603 rev_hessian(hesscol);
604 add2hessian(hessian, hessrow[j], hessdia, hesscol, backg);
605 }
606 if (gradrow != NULL) {
607 comp_gradient(graddia, &fftr, hp->onrm);
608 rev_gradient(gradcol);
609 add2gradient(gradient, gradrow[j], graddia, gradcol, backg);
610 }
611 /* initialize edge in next row */
612 comp_fftri(&fftr, hp, AI(hp,i+1,j+1), AI(hp,i+1,j));
613 if (hessrow != NULL)
614 comp_hessian(hessrow[j], &fftr, hp->onrm);
615 if (gradrow != NULL)
616 comp_gradient(gradrow[j], &fftr, hp->onrm);
617 /* new column edge & paired triangle */
618 backg = back_ambval(hp, AI(hp,i+1,j+1),
619 AI(hp,i+1,j), AI(hp,i,j+1));
620 comp_fftri(&fftr, hp, AI(hp,i,j+1), AI(hp,i+1,j+1));
621 if (hessrow != NULL) {
622 comp_hessian(hesscol, &fftr, hp->onrm);
623 rev_hessian(hessdia);
624 add2hessian(hessian, hessrow[j], hessdia, hesscol, backg);
625 if (i < hp->ns-2)
626 rev_hessian(hessrow[j]);
627 }
628 if (gradrow != NULL) {
629 comp_gradient(gradcol, &fftr, hp->onrm);
630 rev_gradient(graddia);
631 add2gradient(gradient, gradrow[j], graddia, gradcol, backg);
632 if (i < hp->ns-2)
633 rev_gradient(gradrow[j]);
634 }
635 }
636 }
637 /* release row buffers */
638 if (hessrow != NULL) free(hessrow);
639 if (gradrow != NULL) free(gradrow);
640
641 if (ra != NULL) /* extract eigenvectors & radii */
642 eigenvectors(uv, ra, hessian);
643 if (pg != NULL) { /* tangential position gradient */
644 pg[0] = DOT(gradient, uv[0]);
645 pg[1] = DOT(gradient, uv[1]);
646 }
647 }
648
649
650 /* Compute direction gradient from a hemispherical sampling */
651 static void
652 ambdirgrad(AMBHEMI *hp, FVECT uv[2], float dg[2])
653 {
654 AMBSAMP *ap;
655 double dgsum[2];
656 int n;
657 FVECT vd;
658 double gfact;
659
660 dgsum[0] = dgsum[1] = 0.0; /* sum values times -tan(theta) */
661 for (ap = hp->sa, n = hp->ns*hp->ns; n--; ap++) {
662 /* use vector for azimuth + 90deg */
663 VSUB(vd, ap->p, hp->rp->rop);
664 /* brightness over cosine factor */
665 gfact = ap->v[0] / DOT(hp->onrm, vd);
666 /* sine = proj_radius/vd_length */
667 dgsum[0] -= DOT(uv[1], vd) * gfact;
668 dgsum[1] += DOT(uv[0], vd) * gfact;
669 }
670 dg[0] = dgsum[0] / (hp->ns*hp->ns);
671 dg[1] = dgsum[1] / (hp->ns*hp->ns);
672 }
673
674
675 /* Compute potential light leak direction flags for cache value */
676 static uint32
677 ambcorral(AMBHEMI *hp, FVECT uv[2], const double r0, const double r1)
678 {
679 const double max_d = 1.0/(minarad*ambacc + 0.001);
680 const double ang_res = 0.5*PI/hp->ns;
681 const double ang_step = ang_res/((int)(16/PI*ang_res) + 1.01);
682 double avg_d = 0;
683 uint32 flgs = 0;
684 FVECT vec;
685 double u, v;
686 double ang, a1;
687 int i, j;
688 /* don't bother for a few samples */
689 if (hp->ns < 8)
690 return(0);
691 /* check distances overhead */
692 for (i = hp->ns*3/4; i-- > hp->ns>>2; )
693 for (j = hp->ns*3/4; j-- > hp->ns>>2; )
694 avg_d += ambsam(hp,i,j).d;
695 avg_d *= 4.0/(hp->ns*hp->ns);
696 if (avg_d*r0 >= 1.0) /* ceiling too low for corral? */
697 return(0);
698 if (avg_d >= max_d) /* insurance */
699 return(0);
700 /* else circle around perimeter */
701 for (i = 0; i < hp->ns; i++)
702 for (j = 0; j < hp->ns; j += !i|(i==hp->ns-1) ? 1 : hp->ns-1) {
703 AMBSAMP *ap = &ambsam(hp,i,j);
704 if ((ap->d <= FTINY) | (ap->d >= max_d))
705 continue; /* too far or too near */
706 VSUB(vec, ap->p, hp->rp->rop);
707 u = DOT(vec, uv[0]);
708 v = DOT(vec, uv[1]);
709 if ((r0*r0*u*u + r1*r1*v*v) * ap->d*ap->d <= u*u + v*v)
710 continue; /* occluder outside ellipse */
711 ang = atan2a(v, u); /* else set direction flags */
712 for (a1 = ang-ang_res; a1 <= ang+ang_res; a1 += ang_step)
713 flgs |= 1L<<(int)(16/PI*(a1 + 2.*PI*(a1 < 0)));
714 }
715 return(flgs);
716 }
717
718
719 int
720 doambient( /* compute ambient component */
721 SCOLOR rcol, /* input/output color */
722 RAY *r,
723 double wt, /* negative for back side */
724 FVECT uv[2], /* returned (optional) */
725 float ra[2], /* returned (optional) */
726 float pg[2], /* returned (optional) */
727 float dg[2], /* returned (optional) */
728 uint32 *crlp /* returned (optional) */
729 )
730 {
731 AMBHEMI *hp = samp_hemi(rcol, r, wt);
732 FVECT my_uv[2];
733 double d, K;
734 AMBSAMP *ap;
735 int i;
736 /* clear return values */
737 if (uv != NULL)
738 memset(uv, 0, sizeof(FVECT)*2);
739 if (ra != NULL)
740 ra[0] = ra[1] = 0.0;
741 if (pg != NULL)
742 pg[0] = pg[1] = 0.0;
743 if (dg != NULL)
744 dg[0] = dg[1] = 0.0;
745 if (crlp != NULL)
746 *crlp = 0;
747 if (hp == NULL) /* sampling falure? */
748 return(0);
749
750 if ((ra == NULL) & (pg == NULL) & (dg == NULL) ||
751 (hp->sampOK < 0) | (hp->ns < MINADIV)) {
752 free(hp); /* Hessian not requested/possible */
753 return(-1); /* value-only return value */
754 }
755 if ((d = scolor_mean(rcol)) > FTINY) {
756 d = 0.99*(hp->ns*hp->ns)/d; /* normalize avg. values */
757 K = 0.01;
758 } else { /* or fall back on geometric Hessian */
759 K = 1.0;
760 pg = NULL;
761 dg = NULL;
762 crlp = NULL;
763 }
764 ap = hp->sa; /* single channel from here on... */
765 for (i = hp->ns*hp->ns; i--; ap++)
766 ap->v[0] = scolor_mean(ap->v)*d + K;
767
768 if (uv == NULL) /* make sure we have axis pointers */
769 uv = my_uv;
770 /* compute radii & pos. gradient */
771 ambHessian(hp, uv, ra, pg);
772
773 if (dg != NULL) /* compute direction gradient */
774 ambdirgrad(hp, uv, dg);
775
776 if (ra != NULL) { /* scale/clamp radii */
777 if (pg != NULL) {
778 if (ra[0]*(d = fabs(pg[0])) > 1.0)
779 ra[0] = 1.0/d;
780 if (ra[1]*(d = fabs(pg[1])) > 1.0)
781 ra[1] = 1.0/d;
782 if (ra[0] > ra[1])
783 ra[0] = ra[1];
784 }
785 if (ra[0] < minarad) {
786 ra[0] = minarad;
787 if (ra[1] < minarad)
788 ra[1] = minarad;
789 }
790 ra[0] *= d = 1.0/sqrt(fabs(wt));
791 if ((ra[1] *= d) > 2.0*ra[0])
792 ra[1] = 2.0*ra[0];
793 if (ra[1] > maxarad) {
794 ra[1] = maxarad;
795 if (ra[0] > maxarad)
796 ra[0] = maxarad;
797 }
798 /* flag encroached directions */
799 if (crlp != NULL) /* XXX doesn't update with changes to ambacc */
800 *crlp = ambcorral(hp, uv, ra[0]*ambacc, ra[1]*ambacc);
801 if (pg != NULL) { /* cap gradient if necessary */
802 d = pg[0]*pg[0]*ra[0]*ra[0] + pg[1]*pg[1]*ra[1]*ra[1];
803 if (d > 1.0) {
804 d = 1.0/sqrt(d);
805 pg[0] *= d;
806 pg[1] *= d;
807 }
808 }
809 }
810 free(hp); /* clean up and return */
811 return(1);
812 }