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#ifndef lint
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static const char RCSid[] = "$Id: srcsamp.c,v 2.24 2024/12/25 17:40:27 greg Exp $";
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#endif
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/*
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* Source sampling routines
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*
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* External symbols declared in source.h
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*/
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#include "copyright.h"
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#include "ray.h"
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#include "source.h"
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#include "random.h"
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int
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srcskip( /* pre-emptive test for source to skip */
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int sn,
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RAY *r
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)
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{
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SRCREC *sp = source + sn;
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if (sp->sflags & SSKIP)
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return(1);
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if ((sp->sflags & (SPROX|SDISTANT)) == SPROX)
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return(dist2(r->rorg, sp->sloc) >
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(sp->sl.prox + sp->srad)*(sp->sl.prox + sp->srad));
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return(0);
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}
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double
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nextssamp( /* compute sample for source, rtn. distance */
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RAY *r, /* origin is read, direction is set */
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SRCINDEX *si /* source index (modified to current) */
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)
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{
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int cent[3], size[3], parr[2];
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SRCREC *srcp;
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double vpos[3];
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double d;
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int i;
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nextsample:
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while (++si->sp >= si->np) { /* get next sample */
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if (++si->sn >= nsources)
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return(0.0); /* no more */
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if (srcskip(si->sn, r))
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si->np = 0;
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else if (srcsizerat <= FTINY)
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nopart(si, r);
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else {
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for (i = si->sn; source[i].sflags & SVIRTUAL;
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i = source[i].sa.sv.sn)
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; /* partition source */
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(*sfun[source[i].so->otype].of->partit)(si, r);
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}
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si->sp = -1;
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}
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/* get partition */
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cent[0] = cent[1] = cent[2] = 0;
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size[0] = size[1] = size[2] = MAXSPART;
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parr[0] = 0; parr[1] = si->sp;
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if (!skipparts(cent, size, parr, si->spt))
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error(CONSISTENCY, "bad source partition in nextssamp");
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/* compute sample */
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srcp = source + si->sn;
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if (dstrsrc > FTINY) { /* jitter sample */
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dimlist[ndims] = si->sn + 8831;
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dimlist[ndims+1] = si->sp + 3109;
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d = urand(ilhash(dimlist,ndims+2)+samplendx);
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if (srcp->sflags & SFLAT) {
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multisamp(vpos, 2, d);
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vpos[SW] = 0.5;
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} else
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multisamp(vpos, 3, d);
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for (i = 0; i < 3; i++)
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vpos[i] = dstrsrc * (1. - 2.*vpos[i]) *
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(double)size[i]*(1.0/MAXSPART);
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} else
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vpos[0] = vpos[1] = vpos[2] = 0.0;
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VSUM(vpos, vpos, cent, 1.0/MAXSPART);
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/* avoid circular aiming failures */
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if ((srcp->sflags & SCIR) && (si->np > 1) | (dstrsrc > 0.7)) {
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FVECT trim;
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if (srcp->sflags & (SFLAT|SDISTANT)) {
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d = 1.12837917; /* correct setflatss() */
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trim[SU] = d*sqrt(1.0 - 0.5*vpos[SV]*vpos[SV]);
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trim[SV] = d*sqrt(1.0 - 0.5*vpos[SU]*vpos[SU]);
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trim[SW] = 0.0;
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} else {
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trim[SW] = trim[SU] = vpos[SU]*vpos[SU];
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d = vpos[SV]*vpos[SV];
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if (d > trim[SW]) trim[SW] = d;
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trim[SU] += d;
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d = vpos[SW]*vpos[SW];
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if (d > trim[SW]) trim[SW] = d;
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trim[SU] += d;
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if (trim[SU] > FTINY*FTINY) {
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d = 1.0/0.7236; /* correct sphsetsrc() */
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trim[SW] = trim[SV] = trim[SU] =
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d*sqrt(trim[SW]/trim[SU]);
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} else
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trim[SW] = trim[SV] = trim[SU] = 0.0;
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}
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for (i = 0; i < 3; i++)
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vpos[i] *= trim[i];
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}
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/* compute direction */
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for (i = 0; i < 3; i++)
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r->rdir[i] = srcp->sloc[i] +
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vpos[SU]*srcp->ss[SU][i] +
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vpos[SV]*srcp->ss[SV][i] +
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vpos[SW]*srcp->ss[SW][i];
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if (!(srcp->sflags & SDISTANT))
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VSUB(r->rdir, r->rdir, r->rorg);
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/* compute distance */
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if ((d = normalize(r->rdir)) == 0.0)
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goto nextsample; /* at source! */
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/* compute sample size */
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if (srcp->sflags & SFLAT) {
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si->dom = sflatform(si->sn, r->rdir);
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si->dom *= size[SU]*size[SV]*(1.0/MAXSPART/MAXSPART);
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} else if (srcp->sflags & SCYL) {
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si->dom = scylform(si->sn, r->rdir);
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si->dom *= size[SU]*(1.0/MAXSPART);
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} else {
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si->dom = size[SU]*size[SV]*(double)size[SW] *
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(1.0/MAXSPART/MAXSPART/MAXSPART) ;
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}
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if (srcp->sflags & SDISTANT) {
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si->dom *= srcp->ss2;
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return(FHUGE);
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}
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if (si->dom <= 1e-4)
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goto nextsample; /* behind source? */
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si->dom *= srcp->ss2/(d*d);
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return(d); /* sample OK, return distance */
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}
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int
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skipparts( /* skip to requested partition */
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int ct[3],
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int sz[3], /* center and size of partition (returned) */
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int pp[2], /* current index, number to skip (modified) */
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unsigned char *pt /* partition array */
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)
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{
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int p;
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/* check this partition */
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p = spart(pt, pp[0]);
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pp[0]++;
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if (p == S0) { /* leaf partition */
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if (pp[1]) {
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pp[1]--;
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return(0); /* not there yet */
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} else
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return(1); /* we've arrived */
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}
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/* else check lower */
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sz[p] >>= 1;
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ct[p] -= sz[p];
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if (skipparts(ct, sz, pp, pt))
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return(1); /* return hit */
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/* else check upper */
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ct[p] += sz[p] << 1;
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if (skipparts(ct, sz, pp, pt))
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return(1); /* return hit */
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/* else return to starting position */
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ct[p] -= sz[p];
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sz[p] <<= 1;
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return(0); /* return miss */
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}
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void
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nopart( /* single source partition */
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SRCINDEX *si,
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RAY *r
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)
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{
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clrpart(si->spt);
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setpart(si->spt, 0, S0);
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si->np = 1;
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}
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static int
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cyl_partit( /* slice a cylinder */
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FVECT ro,
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unsigned char *pt,
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int *pi,
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int mp,
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FVECT cent,
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FVECT axis,
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double d2
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)
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{
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FVECT newct, newax;
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int npl, npu;
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if (mp < 2 || dist2(ro, cent) >= d2) { /* hit limit? */
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setpart(pt, *pi, S0);
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(*pi)++;
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return(1);
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}
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/* subdivide */
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setpart(pt, *pi, SU);
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(*pi)++;
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newax[0] = .5*axis[0];
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newax[1] = .5*axis[1];
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newax[2] = .5*axis[2];
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d2 *= 0.25;
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/* lower half */
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newct[0] = cent[0] - newax[0];
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newct[1] = cent[1] - newax[1];
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newct[2] = cent[2] - newax[2];
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npl = cyl_partit(ro, pt, pi, mp/2, newct, newax, d2);
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/* upper half */
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newct[0] = cent[0] + newax[0];
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newct[1] = cent[1] + newax[1];
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newct[2] = cent[2] + newax[2];
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npu = cyl_partit(ro, pt, pi, mp/2, newct, newax, d2);
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/* return total */
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return(npl + npu);
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}
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void
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cylpart( /* partition a cylinder */
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SRCINDEX *si,
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RAY *r
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)
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{
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double dist2, safedist2, dist2cent, rad2;
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FVECT v;
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SRCREC *sp;
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int pi;
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/* first check point location */
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clrpart(si->spt);
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sp = source + si->sn;
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rad2 = 1.365 * DOT(sp->ss[SV],sp->ss[SV]);
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v[0] = r->rorg[0] - sp->sloc[0];
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v[1] = r->rorg[1] - sp->sloc[1];
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v[2] = r->rorg[2] - sp->sloc[2];
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dist2 = DOT(v,sp->ss[SU]);
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safedist2 = DOT(sp->ss[SU],sp->ss[SU]);
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dist2 *= dist2 / safedist2;
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dist2cent = DOT(v,v);
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dist2 = dist2cent - dist2;
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if (dist2 <= rad2) { /* point inside extended cylinder */
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si->np = 0;
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return;
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}
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safedist2 *= 4.*r->rweight*r->rweight/(srcsizerat*srcsizerat);
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if (dist2 <= 4.*rad2 || /* point too close to subdivide */
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dist2cent >= safedist2) { /* or too far */
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setpart(si->spt, 0, S0);
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si->np = 1;
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return;
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}
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pi = 0;
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si->np = cyl_partit(r->rorg, si->spt, &pi, MAXSPART,
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sp->sloc, sp->ss[SU], safedist2);
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}
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static int
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flt_partit( /* partition flatty */
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FVECT ro,
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unsigned char *pt,
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int *pi,
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int mp,
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FVECT cent,
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FVECT u,
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FVECT v,
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double du2,
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double dv2
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)
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{
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double d2;
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FVECT newct, newax;
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int npl, npu;
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if (mp < 2 || ((d2 = dist2(ro, cent)) >= du2
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&& d2 >= dv2)) { /* hit limit? */
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setpart(pt, *pi, S0);
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(*pi)++;
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return(1);
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}
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if (du2 > dv2) { /* subdivide in U */
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setpart(pt, *pi, SU);
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(*pi)++;
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newax[0] = .5*u[0];
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newax[1] = .5*u[1];
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newax[2] = .5*u[2];
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u = newax;
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du2 *= 0.25;
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} else { /* subdivide in V */
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setpart(pt, *pi, SV);
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(*pi)++;
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newax[0] = .5*v[0];
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newax[1] = .5*v[1];
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newax[2] = .5*v[2];
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v = newax;
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dv2 *= 0.25;
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}
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/* lower half */
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newct[0] = cent[0] - newax[0];
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newct[1] = cent[1] - newax[1];
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newct[2] = cent[2] - newax[2];
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npl = flt_partit(ro, pt, pi, mp/2, newct, u, v, du2, dv2);
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/* upper half */
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newct[0] = cent[0] + newax[0];
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newct[1] = cent[1] + newax[1];
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newct[2] = cent[2] + newax[2];
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npu = flt_partit(ro, pt, pi, mp/2, newct, u, v, du2, dv2);
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/* return total */
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return(npl + npu);
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}
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void
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flatpart( /* partition a flat source */
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SRCINDEX *si,
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RAY *r
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)
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{
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RREAL *vp;
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FVECT v;
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double du2, dv2;
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int pi;
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clrpart(si->spt);
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vp = source[si->sn].sloc;
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v[0] = r->rorg[0] - vp[0];
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v[1] = r->rorg[1] - vp[1];
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v[2] = r->rorg[2] - vp[2];
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vp = source[si->sn].snorm;
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if (DOT(v,vp) <= 0.) { /* behind source */
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si->np = 0;
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return;
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}
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dv2 = 2.*r->rweight/srcsizerat;
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dv2 *= dv2;
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vp = source[si->sn].ss[SU];
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du2 = dv2 * DOT(vp,vp);
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vp = source[si->sn].ss[SV];
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dv2 *= DOT(vp,vp);
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pi = 0;
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si->np = flt_partit(r->rorg, si->spt, &pi, MAXSPART,
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source[si->sn].sloc,
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source[si->sn].ss[SU], source[si->sn].ss[SV], du2, dv2);
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}
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double
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scylform( /* compute cosine for cylinder's projection */
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| 365 |
int sn,
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| 366 |
FVECT dir /* assume normalized */
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| 367 |
)
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| 368 |
{
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| 369 |
RREAL *dv;
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| 370 |
double d;
|
| 371 |
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dv = source[sn].ss[SU];
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d = DOT(dir, dv);
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| 374 |
d *= d / DOT(dv,dv);
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| 375 |
return(sqrt(1. - d));
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| 376 |
}
|
