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/* Copyright (c) 1991 Regents of the University of California */ |
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|
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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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/* |
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* Routines to compute "ambient" values using Monte Carlo |
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*/ |
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|
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#include "ray.h" |
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|
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#include "ambient.h" |
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|
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#include "random.h" |
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|
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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 k; /* error contribution for this division */ |
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int n; /* number of subsamples */ |
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} AMBSAMP; /* ambient division sample */ |
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|
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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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|
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extern double sin(), cos(), sqrt(); |
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|
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|
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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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|
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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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|
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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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|
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|
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static double |
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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[4]; |
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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 k; |
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|
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if (rayorigin(&ar, r, AMBIENT, 0.5) < 0) |
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return(0.0); |
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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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hlist[3] = 0; |
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zd = sqrt((dp->t+urand(ilhash(hlist,4)+dp->n))/h->nt); |
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hlist[3] = 1; |
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phi = 2.0*PI * (dp->p+urand(ilhash(hlist,4)+dp->n))/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 (k = 0; k < 3; k++) |
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ar.rdir[k] = xd*h->ux[k] + |
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yd*h->uy[k] + |
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zd*h->uz[k]; |
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dimlist[ndims++] = dp->t*h->np + dp->p + 38813; |
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rayvalue(&ar); |
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ndims--; |
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addcolor(dp->v, ar.rcol); |
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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(ar.rot); |
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} |
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|
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|
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double |
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doambient(acol, r, pg, dg) /* compute ambient component */ |
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COLOR acol; |
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RAY *r; |
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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); |
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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 * r->rweight + 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->n = 0; |
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if ((d = divsample(dp, &hemi, r)) == 0.0) |
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goto oopsy; |
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if (d < FHUGE) |
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arad += 1.0 / d; |
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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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} |
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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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dp = div + ndivs; /* skim excess */ |
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for (i = ndivs; i > ns; i--) { |
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dp--; |
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addcolor(acol, dp->v); |
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} |
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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 ((d = divsample(&dnew, &hemi)) == 0.0) |
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goto oopsy; |
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if (d < FHUGE) |
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arad += 1.0 / d; |
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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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/* extract darkest */ |
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if (i <= ndivs) { |
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dp = div + i-1; |
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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->n = 1; |
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} |
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addcolor(acol, dp->v); |
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} |
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} |
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if (pg != NULL || dg != NULL) /* reorder */ |
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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 (pg != NULL) |
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posgradient(pg, div, &hemi); |
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if (dg != NULL) |
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dirgradient(dg, div, &hemi); |
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if (div != NULL) |
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free((char *)div); |
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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 (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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arad /= sqrt(r->rweight); |
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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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return(0.0); |
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} |
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|
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|
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inithemi(hp, r) /* 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 k; |
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/* set number of divisions */ |
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hp->nt = sqrt(ambdiv * r->rweight * 0.5) + 0.5; |
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hp->np = 2 * hp->nt; |
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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 (k = 0; k < 3; k++) |
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if (hp->uz[k] < 0.6 && hp->uz[k] > -0.6) |
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break; |
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if (k >= 3) |
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error(CONSISTENCY, "bad ray direction in inithemi"); |
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hp->uy[k] = 1.0; |
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fcross(hp->ux, hp->uz, hp->uy); |
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normalize(hp->ux); |
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fcross(hp->uy, hp->ux, hp->uz); |
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} |
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|
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|
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comperrs(da, hp) /* compute initial error estimates */ |
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AMBSAMP *da; |
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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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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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} |
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if (j == hp->np-1) { /* 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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|
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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; |
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AMBHEMI *hp; |
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{ |
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gv[0] = 0.0; gv[1] = 0.0; gv[2] = 0.0; |
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} |
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|
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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; |
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AMBHEMI *hp; |
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{ |
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gv[0] = 0.0; gv[1] = 0.0; gv[2] = 0.0; |
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} |
