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/* Copyright (c) 1991 Regents of the University of California */
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#ifndef lint
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static char SCCSid[] = "$SunId$ LBL";
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#endif
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/*
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* Routines to compute "ambient" values using Monte Carlo
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*/
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#include "ray.h"
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#include "ambient.h"
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#include "random.h"
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typedef struct {
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short t, p; /* theta, phi indices */
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COLOR v; /* value sum */
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float r; /* 1/distance sum */
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float k; /* variance for this division */
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int n; /* number of subsamples */
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} AMBSAMP; /* ambient sample division */
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typedef struct {
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FVECT ux, uy, uz; /* x, y and z axis directions */
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short nt, np; /* number of theta and phi directions */
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} AMBHEMI; /* ambient sample hemisphere */
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extern double sin(), cos(), sqrt();
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static int
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ambcmp(d1, d2) /* decreasing order */
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AMBSAMP *d1, *d2;
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{
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if (d1->k < d2->k)
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return(1);
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if (d1->k > d2->k)
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return(-1);
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return(0);
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}
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static int
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ambnorm(d1, d2) /* standard order */
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AMBSAMP *d1, *d2;
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{
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register int c;
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if (c = d1->t - d2->t)
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return(c);
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return(d1->p - d2->p);
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}
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divsample(dp, h, r) /* sample a division */
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register AMBSAMP *dp;
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AMBHEMI *h;
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RAY *r;
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{
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RAY ar;
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int hlist[3];
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double spt[2];
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double xd, yd, zd;
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double b2;
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double phi;
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register int i;
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if (rayorigin(&ar, r, AMBIENT, AVGREFL) < 0)
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return(-1);
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hlist[0] = r->rno;
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hlist[1] = dp->t;
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hlist[2] = dp->p;
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multisamp(spt, 2, urand(ilhash(hlist,3)+dp->n));
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zd = sqrt((dp->t + spt[0])/h->nt);
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phi = 2.0*PI * (dp->p + spt[1])/h->np;
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xd = cos(phi) * zd;
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yd = sin(phi) * zd;
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zd = sqrt(1.0 - zd*zd);
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for (i = 0; i < 3; i++)
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ar.rdir[i] = xd*h->ux[i] +
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yd*h->uy[i] +
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zd*h->uz[i];
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dimlist[ndims++] = dp->t*h->np + dp->p + 90171;
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rayvalue(&ar);
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ndims--;
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addcolor(dp->v, ar.rcol);
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if (ar.rt > FTINY && ar.rt < FHUGE)
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dp->r += 1.0/ar.rt;
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/* (re)initialize error */
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if (dp->n++) {
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b2 = bright(dp->v)/dp->n - bright(ar.rcol);
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b2 = b2*b2 + dp->k*((dp->n-1)*(dp->n-1));
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dp->k = b2/(dp->n*dp->n);
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} else
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dp->k = 0.0;
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return(0);
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}
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double
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doambient(acol, r, wt, pg, dg) /* compute ambient component */
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COLOR acol;
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RAY *r;
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double wt;
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FVECT pg, dg;
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{
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double b, d;
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AMBHEMI hemi;
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AMBSAMP *div;
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AMBSAMP dnew;
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register AMBSAMP *dp;
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double arad;
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int ndivs, ns;
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register int i, j;
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/* initialize color */
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setcolor(acol, 0.0, 0.0, 0.0);
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/* initialize hemisphere */
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inithemi(&hemi, r, wt);
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ndivs = hemi.nt * hemi.np;
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if (ndivs == 0)
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return(0.0);
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/* set number of super-samples */
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ns = ambssamp * wt + 0.5;
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if (ns > 0 || pg != NULL || dg != NULL) {
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div = (AMBSAMP *)malloc(ndivs*sizeof(AMBSAMP));
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if (div == NULL)
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error(SYSTEM, "out of memory in doambient");
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} else
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div = NULL;
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/* sample the divisions */
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arad = 0.0;
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if ((dp = div) == NULL)
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dp = &dnew;
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for (i = 0; i < hemi.nt; i++)
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for (j = 0; j < hemi.np; j++) {
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dp->t = i; dp->p = j;
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setcolor(dp->v, 0.0, 0.0, 0.0);
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dp->r = 0.0;
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dp->n = 0;
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if (divsample(dp, &hemi, r) < 0)
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goto oopsy;
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if (div != NULL)
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dp++;
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else {
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addcolor(acol, dp->v);
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arad += dp->r;
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}
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}
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if (ns > 0) { /* perform super-sampling */
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comperrs(div, &hemi); /* compute errors */
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qsort(div, ndivs, sizeof(AMBSAMP), ambcmp); /* sort divs */
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/* super-sample */
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for (i = ns; i > 0; i--) {
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copystruct(&dnew, div);
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if (divsample(&dnew, &hemi, r) < 0)
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goto oopsy;
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/* reinsert */
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dp = div;
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j = ndivs < i ? ndivs : i;
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while (--j > 0 && dnew.k < dp[1].k) {
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copystruct(dp, dp+1);
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dp++;
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}
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copystruct(dp, &dnew);
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}
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if (pg != NULL || dg != NULL) /* restore order */
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qsort(div, ndivs, sizeof(AMBSAMP), ambnorm);
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}
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/* compute returned values */
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if (div != NULL) {
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for (i = ndivs, dp = div; i-- > 0; dp++) {
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arad += dp->r;
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if (dp->n > 1) {
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b = 1.0/dp->n;
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scalecolor(dp->v, b);
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dp->r *= b;
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dp->n = 1;
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}
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addcolor(acol, dp->v);
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}
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b = bright(acol);
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if (b > FTINY) {
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b = ndivs/b;
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if (pg != NULL) {
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posgradient(pg, div, &hemi);
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for (i = 0; i < 3; i++)
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pg[i] *= b;
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}
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if (dg != NULL) {
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dirgradient(dg, div, &hemi);
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for (i = 0; i < 3; i++)
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dg[i] *= b;
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}
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} else {
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if (pg != NULL)
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for (i = 0; i < 3; i++)
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pg[i] = 0.0;
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if (dg != NULL)
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for (i = 0; i < 3; i++)
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dg[i] = 0.0;
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}
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free((char *)div);
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}
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b = 1.0/ndivs;
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scalecolor(acol, b);
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if (arad <= FTINY)
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arad = FHUGE;
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else
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arad = (ndivs+ns)/arad;
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if (pg != NULL) { /* reduce radius if gradient large */
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d = DOT(pg,pg);
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if (d*arad*arad > 1.0)
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arad = 1.0/sqrt(d);
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}
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if (arad > maxarad)
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arad = maxarad;
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else if (arad < minarad)
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arad = minarad;
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return(arad/sqrt(wt));
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oopsy:
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if (div != NULL)
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free((char *)div);
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return(0.0);
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}
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inithemi(hp, r, wt) /* initialize sampling hemisphere */
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register AMBHEMI *hp;
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RAY *r;
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double wt;
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{
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register int i;
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/* set number of divisions */
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if (wt < (.25*PI)/ambdiv+FTINY) {
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hp->nt = hp->np = 0;
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return; /* zero samples */
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}
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hp->nt = sqrt(ambdiv * wt / PI) + 0.5;
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hp->np = PI * hp->nt + 0.5;
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/* make axes */
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VCOPY(hp->uz, r->ron);
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hp->uy[0] = hp->uy[1] = hp->uy[2] = 0.0;
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for (i = 0; i < 3; i++)
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if (hp->uz[i] < 0.6 && hp->uz[i] > -0.6)
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break;
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if (i >= 3)
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error(CONSISTENCY, "bad ray direction in inithemi");
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hp->uy[i] = 1.0;
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fcross(hp->ux, hp->uy, hp->uz);
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normalize(hp->ux);
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fcross(hp->uy, hp->uz, hp->ux);
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}
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comperrs(da, hp) /* compute initial error estimates */
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AMBSAMP *da; /* assumes standard ordering */
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register AMBHEMI *hp;
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{
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double b, b2;
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int i, j;
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register AMBSAMP *dp;
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/* sum differences from neighbors */
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dp = da;
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for (i = 0; i < hp->nt; i++)
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for (j = 0; j < hp->np; j++) {
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#ifdef DEBUG
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if (dp->t != i || dp->p != j)
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error(CONSISTENCY,
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"division order in comperrs");
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#endif
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b = bright(dp[0].v);
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if (i > 0) { /* from above */
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b2 = bright(dp[-hp->np].v) - b;
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b2 *= b2 * 0.25;
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dp[0].k += b2;
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dp[-hp->np].k += b2;
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}
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if (j > 0) { /* from behind */
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b2 = bright(dp[-1].v) - b;
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b2 *= b2 * 0.25;
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dp[0].k += b2;
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dp[-1].k += b2;
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} else { /* around */
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b2 = bright(dp[hp->np-1].v) - b;
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b2 *= b2 * 0.25;
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dp[0].k += b2;
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dp[hp->np-1].k += b2;
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}
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dp++;
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}
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/* divide by number of neighbors */
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dp = da;
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for (j = 0; j < hp->np; j++) /* top row */
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(dp++)->k *= 1.0/3.0;
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if (hp->nt < 2)
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return;
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for (i = 1; i < hp->nt-1; i++) /* central region */
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for (j = 0; j < hp->np; j++)
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(dp++)->k *= 0.25;
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for (j = 0; j < hp->np; j++) /* bottom row */
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(dp++)->k *= 1.0/3.0;
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}
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posgradient(gv, da, hp) /* compute position gradient */
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FVECT gv;
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AMBSAMP *da; /* assumes standard ordering */
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AMBHEMI *hp;
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{
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register int i, j;
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double b, d;
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double mag0, mag1;
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double phi, cosp, sinp, xd, yd;
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register AMBSAMP *dp;
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xd = yd = 0.0;
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for (j = 0; j < hp->np; j++) {
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dp = da + j;
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mag0 = mag1 = 0.0;
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for (i = 0; i < hp->nt; i++) {
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#ifdef DEBUG
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if (dp->t != i || dp->p != j)
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error(CONSISTENCY,
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"division order in posgradient");
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#endif
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b = bright(dp->v);
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if (i > 0) {
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d = dp[-hp->np].r;
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if (dp[0].r > d) d = dp[0].r;
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d *= 1.0 - (double)i/hp->nt; /* cos(t)^2 */
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mag0 += d*(b - bright(dp[-hp->np].v));
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}
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if (j > 0) {
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d = dp[-1].r;
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if (dp[0].r > d) d = dp[0].r;
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mag1 += d*(b - bright(dp[-1].v));
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} else {
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d = dp[hp->np-1].r;
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if (dp[0].r > d) d = dp[0].r;
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mag1 += d*(b - bright(dp[hp->np-1].v));
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}
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dp += hp->np;
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}
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if (hp->nt > 1) {
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mag0 /= (double)hp->np;
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mag1 /= (double)hp->nt;
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}
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phi = 2.0*PI * (double)j/hp->np;
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cosp = cos(phi); sinp = sin(phi);
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xd += mag0*cosp - mag1*sinp;
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yd += mag0*sinp + mag1*cosp;
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}
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for (i = 0; i < 3; i++)
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gv[i] = (xd*hp->ux[i] + yd*hp->uy[i])/PI;
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}
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dirgradient(gv, da, hp) /* compute direction gradient */
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FVECT gv;
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AMBSAMP *da; /* assumes standard ordering */
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AMBHEMI *hp;
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{
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register int i, j;
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double mag;
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double phi, xd, yd;
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register AMBSAMP *dp;
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xd = yd = 0.0;
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for (j = 0; j < hp->np; j++) {
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dp = da + j;
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mag = 0.0;
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for (i = 0; i < hp->nt; i++) {
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#ifdef DEBUG
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if (dp->t != i || dp->p != j)
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error(CONSISTENCY,
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"division order in dirgradient");
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#endif
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mag += sqrt((i+.5)/hp->nt)*bright(dp->v); /* sin(t) */
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dp += hp->np;
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}
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phi = 2.0*PI * (j+.5)/hp->np + PI/2.0;
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xd += mag * cos(phi);
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yd += mag * sin(phi);
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}
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for (i = 0; i < 3; i++)
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gv[i] = (xd*hp->ux[i] + yd*hp->uy[i])*PI/(hp->nt*hp->np);
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}
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