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#ifndef lint |
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static const char RCSid[] = "$Id: srcsamp.c,v 2.8 2003/02/25 02:47:23 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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|
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#include "copyright.h" |
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|
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#include "ray.h" |
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|
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#include "source.h" |
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|
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#include "random.h" |
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|
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|
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static int cyl_partit(), flt_partit(); |
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|
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|
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double |
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nextssamp(r, si) /* compute sample for source, rtn. distance */ |
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register RAY *r; /* origin is read, direction is set */ |
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register SRCINDEX *si; /* source index (modified to current) */ |
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{ |
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int cent[3], size[3], parr[2]; |
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FVECT vpos; |
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double d; |
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register 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 (source[si->sn].sflags & SSKIP) |
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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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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 (source[si->sn].sflags & SFLAT) { |
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multisamp(vpos, 2, d); |
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vpos[2] = 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]/MAXSPART; |
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} else |
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vpos[0] = vpos[1] = vpos[2] = 0.0; |
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|
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for (i = 0; i < 3; i++) |
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vpos[i] += (double)cent[i]/MAXSPART; |
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/* compute direction */ |
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for (i = 0; i < 3; i++) |
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r->rdir[i] = source[si->sn].sloc[i] + |
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vpos[SU]*source[si->sn].ss[SU][i] + |
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vpos[SV]*source[si->sn].ss[SV][i] + |
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vpos[SW]*source[si->sn].ss[SW][i]; |
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|
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if (!(source[si->sn].sflags & SDISTANT)) |
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for (i = 0; i < 3; i++) |
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r->rdir[i] -= r->rorg[i]; |
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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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|
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/* compute sample size */ |
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if (source[si->sn].sflags & SFLAT) { |
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si->dom = sflatform(si->sn, r->rdir); |
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si->dom *= size[SU]*size[SV]/(MAXSPART*(double)MAXSPART); |
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} else if (source[si->sn].sflags & SCYL) { |
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si->dom = scylform(si->sn, r->rdir); |
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si->dom *= size[SU]/(double)MAXSPART; |
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} else { |
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si->dom = size[SU]*size[SV]*(double)size[SW] / |
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(MAXSPART*MAXSPART*(double)MAXSPART) ; |
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} |
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if (source[si->sn].sflags & SDISTANT) { |
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si->dom *= source[si->sn].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 *= source[si->sn].ss2/(d*d); |
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return(d); /* sample OK, return distance */ |
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} |
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|
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|
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int |
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skipparts(ct, sz, pp, pt) /* skip to requested partition */ |
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int ct[3], sz[3]; /* center and size of partition (returned) */ |
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register 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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register 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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/* 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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|
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|
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void |
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nopart(si, r) /* single source partition */ |
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register SRCINDEX *si; |
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RAY *r; |
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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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|
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|
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void |
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cylpart(si, r) /* partition a cylinder */ |
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SRCINDEX *si; |
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register RAY *r; |
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{ |
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double dist2, safedist2, dist2cent, rad2; |
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FVECT v; |
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register 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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|
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|
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static int |
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cyl_partit(ro, pt, pi, mp, cent, axis, d2) /* slice a cylinder */ |
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FVECT ro; |
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unsigned char *pt; |
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register int *pi; |
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int mp; |
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FVECT cent, axis; |
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double d2; |
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{ |
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FVECT newct, newax; |
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int npl, npu; |
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|
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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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|
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|
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void |
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flatpart(si, r) /* partition a flat source */ |
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register SRCINDEX *si; |
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register RAY *r; |
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{ |
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register 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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|
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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) <= FTINY) { /* 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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|
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|
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static int |
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flt_partit(ro, pt, pi, mp, cent, u, v, du2, dv2) /* partition flatty */ |
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FVECT ro; |
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unsigned char *pt; |
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register int *pi; |
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int mp; |
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FVECT cent, u, v; |
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double du2, dv2; |
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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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|
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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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|
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|
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double |
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scylform(sn, dir) /* compute cosine for cylinder's projection */ |
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int sn; |
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register FVECT dir; /* assume normalized */ |
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{ |
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register RREAL *dv; |
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double d; |
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|
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dv = source[sn].ss[SU]; |
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d = DOT(dir, dv); |
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d *= d / DOT(dv,dv); |
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return(sqrt(1. - d)); |
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} |
