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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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static const char RCSid[] = "$Id$"; |
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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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* Declarations of external symbols in ambient.h |
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*/ |
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#include "copyright.h" |
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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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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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register int c; |
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if (c = d1->t - d2->t) |
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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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int |
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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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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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xd = tcos(phi) * zd; |
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yd = tsin(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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rayvalue(&ar); |
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ndims--; |
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addcolor(dp->v, ar.rcol); |
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/* use rt to improve gradient calc */ |
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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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dp->n = 0; |
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if (divsample(dp, &hemi, r) < 0) |
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goto oopsy; |
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arad += dp->r; |
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if (div != NULL) |
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dp++; |
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else { |
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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 && arad > FTINY && ndivs/arad < minarad) |
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ns = 0; /* close enough */ |
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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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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 = *(dp+1); |
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dp++; |
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} |
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copystruct(dp, &dnew); |
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*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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arad = 0.0; |
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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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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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free((void *)div); |
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} |
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b = 1.0/ndivs; |
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scalecolor(acol, b); |
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return(arad); |
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oopsy: |
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if (div != NULL) |
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free((char *)div); |
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free((void *)div); |
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return(0.0); |
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} |
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void |
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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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{ |
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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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i = ambacc > FTINY ? 3 : 1; /* minimum number of samples */ |
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if (hp->nt < i) |
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hp->nt = i; |
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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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} |
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void |
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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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void |
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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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} |
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mag0 *= 2.0*PI / hp->np; |
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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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cosp = tcos(phi); sinp = tsin(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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} |
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void |
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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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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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xd += mag * tcos(phi); |
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yd += mag * tsin(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])/(hp->nt*hp->np); |
