src/rt/srcsamp.c

#ifndef lint
static const char       RCSid[] = "$Id: srcsamp.c,v 2.20 2019/06/11 17:00:59 greg Exp $";
#endif
/*
 * Source sampling routines
 *
 *  External symbols declared in source.h
 */

#include "copyright.h"

#include  "ray.h"

#include  "source.h"

#include  "random.h"


int
srcskip(                        /* pre-emptive test for source to skip */
        int  sn,
        RAY  *r
)
{
        SRCREC  *sp = source + sn;

        if (sp->sflags & SSKIP)
                return(1);

        if ((sp->sflags & (SPROX|SDISTANT)) != SPROX)
                return(0);

        return(dist2(r->rorg, sp->sloc) >
                        (sp->sl.prox + sp->srad)*(sp->sl.prox + sp->srad));
}

double
nextssamp(                      /* compute sample for source, rtn. distance */
        RAY  *r,                /* origin is read, direction is set */
        SRCINDEX  *si           /* source index (modified to current) */
)
{
        int  cent[3], size[3], parr[2];
        SRCREC  *srcp;
        double  vpos[3];
        double  d;
        int  i;
nextsample:
        while (++si->sp >= si->np) {    /* get next sample */
                if (++si->sn >= nsources)
                        return(0.0);    /* no more */
                if (srcskip(si->sn, r))
                        si->np = 0;
                else if (srcsizerat <= FTINY)
                        nopart(si, r);
                else {
                        for (i = si->sn; source[i].sflags & SVIRTUAL;
                                        i = source[i].sa.sv.sn)
                                ;               /* partition source */
                        (*sfun[source[i].so->otype].of->partit)(si, r);
                }
                si->sp = -1;
        }
                                        /* get partition */
        cent[0] = cent[1] = cent[2] = 0;
        size[0] = size[1] = size[2] = MAXSPART;
        parr[0] = 0; parr[1] = si->sp;
        if (!skipparts(cent, size, parr, si->spt))
                error(CONSISTENCY, "bad source partition in nextssamp");
                                        /* compute sample */
        srcp = source + si->sn;
        if (dstrsrc > FTINY) {                  /* jitter sample */
                dimlist[ndims] = si->sn + 8831;
                dimlist[ndims+1] = si->sp + 3109;
                d = urand(ilhash(dimlist,ndims+2)+samplendx);
                if (srcp->sflags & SFLAT) {
                        multisamp(vpos, 2, d);
                        vpos[SW] = 0.5;
                } else
                        multisamp(vpos, 3, d);
                for (i = 0; i < 3; i++)
                        vpos[i] = dstrsrc * (1. - 2.*vpos[i]) *
                                        (double)size[i]*(1.0/MAXSPART);
        } else
                vpos[0] = vpos[1] = vpos[2] = 0.0;

        VSUM(vpos, vpos, cent, 1.0/MAXSPART);
                                        /* avoid circular aiming failures */
        if ((srcp->sflags & SCIR) && (si->np > 1) | (dstrsrc > 0.7)) {
                FVECT   trim;
                if (srcp->sflags & (SFLAT|SDISTANT)) {
                        d = 1.12837917;         /* correct setflatss() */
                        trim[SU] = d*sqrt(1.0 - 0.5*vpos[SV]*vpos[SV]);
                        trim[SV] = d*sqrt(1.0 - 0.5*vpos[SU]*vpos[SU]);
                        trim[SW] = 0.0;
                } else {
                        trim[SW] = trim[SU] = vpos[SU]*vpos[SU];
                        d = vpos[SV]*vpos[SV];
                        if (d > trim[SW]) trim[SW] = d;
                        trim[SU] += d;
                        d = vpos[SW]*vpos[SW];
                        if (d > trim[SW]) trim[SW] = d;
                        trim[SU] += d;
                        if (trim[SU] > FTINY*FTINY) {
                                d = 1.0/0.7236; /* correct sphsetsrc() */
                                trim[SW] = trim[SV] = trim[SU] =
                                                d*sqrt(trim[SW]/trim[SU]);
                        } else
                                trim[SW] = trim[SV] = trim[SU] = 0.0;
                }
                for (i = 0; i < 3; i++)
                        vpos[i] *= trim[i];
        }
                                        /* compute direction */
        for (i = 0; i < 3; i++)
                r->rdir[i] = srcp->sloc[i] +
                                vpos[SU]*srcp->ss[SU][i] +
                                vpos[SV]*srcp->ss[SV][i] +
                                vpos[SW]*srcp->ss[SW][i];

        if (!(srcp->sflags & SDISTANT))
                VSUB(r->rdir, r->rdir, r->rorg);
                                        /* compute distance */
        if ((d = normalize(r->rdir)) == 0.0)
                goto nextsample;                /* at source! */

                                        /* compute sample size */
        if (srcp->sflags & SFLAT) {
                si->dom = sflatform(si->sn, r->rdir);
                si->dom *= size[SU]*size[SV]*(1.0/MAXSPART/MAXSPART);
        } else if (srcp->sflags & SCYL) {
                si->dom = scylform(si->sn, r->rdir);
                si->dom *= size[SU]*(1.0/MAXSPART);
        } else {
                si->dom = size[SU]*size[SV]*(double)size[SW] *
                                (1.0/MAXSPART/MAXSPART/MAXSPART) ;
        }
        if (srcp->sflags & SDISTANT) {
                si->dom *= srcp->ss2;
                return(FHUGE);
        }
        if (si->dom <= 1e-4)
                goto nextsample;                /* behind source? */
        si->dom *= srcp->ss2/(d*d);
        return(d);              /* sample OK, return distance */
}


int
skipparts(                      /* skip to requested partition */
        int  ct[3],
        int  sz[3],             /* center and size of partition (returned) */
        int  pp[2],             /* current index, number to skip (modified) */
        unsigned char  *pt      /* partition array */
)
{
        int  p;
                                        /* check this partition */
        p = spart(pt, pp[0]);
        pp[0]++;
        if (p == S0) {                  /* leaf partition */
                if (pp[1]) {
                        pp[1]--;
                        return(0);      /* not there yet */
                } else
                        return(1);      /* we've arrived */
        }
                                /* else check lower */
        sz[p] >>= 1;
        ct[p] -= sz[p];
        if (skipparts(ct, sz, pp, pt))
                return(1);      /* return hit */
                                /* else check upper */
        ct[p] += sz[p] << 1;
        if (skipparts(ct, sz, pp, pt))
                return(1);      /* return hit */
                                /* else return to starting position */
        ct[p] -= sz[p];
        sz[p] <<= 1;
        return(0);              /* return miss */
}


void
nopart(                         /* single source partition */
        SRCINDEX  *si,
        RAY  *r
)
{
        clrpart(si->spt);
        setpart(si->spt, 0, S0);
        si->np = 1;
}


static int
cyl_partit(                             /* slice a cylinder */
        FVECT  ro,
        unsigned char  *pt,
        int  *pi,
        int  mp,
        FVECT  cent,
        FVECT  axis,
        double  d2
)
{
        FVECT  newct, newax;
        int  npl, npu;

        if (mp < 2 || dist2(ro, cent) >= d2) {  /* hit limit? */
                setpart(pt, *pi, S0);
                (*pi)++;
                return(1);
        }
                                        /* subdivide */
        setpart(pt, *pi, SU);
        (*pi)++;
        newax[0] = .5*axis[0];
        newax[1] = .5*axis[1];
        newax[2] = .5*axis[2];
        d2 *= 0.25;
                                        /* lower half */
        newct[0] = cent[0] - newax[0];
        newct[1] = cent[1] - newax[1];
        newct[2] = cent[2] - newax[2];
        npl = cyl_partit(ro, pt, pi, mp/2, newct, newax, d2);
                                        /* upper half */
        newct[0] = cent[0] + newax[0];
        newct[1] = cent[1] + newax[1];
        newct[2] = cent[2] + newax[2];
        npu = cyl_partit(ro, pt, pi, mp/2, newct, newax, d2);
                                        /* return total */
        return(npl + npu);
}


void
cylpart(                        /* partition a cylinder */
        SRCINDEX  *si,
        RAY  *r
)
{
        double  dist2, safedist2, dist2cent, rad2;
        FVECT  v;
        SRCREC  *sp;
        int  pi;
                                        /* first check point location */
        clrpart(si->spt);
        sp = source + si->sn;
        rad2 = 1.365 * DOT(sp->ss[SV],sp->ss[SV]);
        v[0] = r->rorg[0] - sp->sloc[0];
        v[1] = r->rorg[1] - sp->sloc[1];
        v[2] = r->rorg[2] - sp->sloc[2];
        dist2 = DOT(v,sp->ss[SU]);
        safedist2 = DOT(sp->ss[SU],sp->ss[SU]);
        dist2 *= dist2 / safedist2;
        dist2cent = DOT(v,v);
        dist2 = dist2cent - dist2;
        if (dist2 <= rad2) {            /* point inside extended cylinder */
                si->np = 0;
                return;
        }
        safedist2 *= 4.*r->rweight*r->rweight/(srcsizerat*srcsizerat);
        if (dist2 <= 4.*rad2 ||         /* point too close to subdivide */
                        dist2cent >= safedist2) {       /* or too far */
                setpart(si->spt, 0, S0);
                si->np = 1;
                return;
        }
        pi = 0;
        si->np = cyl_partit(r->rorg, si->spt, &pi, MAXSPART,
                        sp->sloc, sp->ss[SU], safedist2);
}


static int
flt_partit(                             /* partition flatty */
        FVECT  ro,
        unsigned char  *pt,
        int  *pi,
        int  mp,
        FVECT  cent,
        FVECT  u,
        FVECT  v,
        double  du2,
        double  dv2
)
{
        double  d2;
        FVECT  newct, newax;
        int  npl, npu;

        if (mp < 2 || ((d2 = dist2(ro, cent)) >= du2
                        && d2 >= dv2)) {        /* hit limit? */
                setpart(pt, *pi, S0);
                (*pi)++;
                return(1);
        }
        if (du2 > dv2) {                        /* subdivide in U */
                setpart(pt, *pi, SU);
                (*pi)++;
                newax[0] = .5*u[0];
                newax[1] = .5*u[1];
                newax[2] = .5*u[2];
                u = newax;
                du2 *= 0.25;
        } else {                                /* subdivide in V */
                setpart(pt, *pi, SV);
                (*pi)++;
                newax[0] = .5*v[0];
                newax[1] = .5*v[1];
                newax[2] = .5*v[2];
                v = newax;
                dv2 *= 0.25;
        }
                                        /* lower half */
        newct[0] = cent[0] - newax[0];
        newct[1] = cent[1] - newax[1];
        newct[2] = cent[2] - newax[2];
        npl = flt_partit(ro, pt, pi, mp/2, newct, u, v, du2, dv2);
                                        /* upper half */
        newct[0] = cent[0] + newax[0];
        newct[1] = cent[1] + newax[1];
        newct[2] = cent[2] + newax[2];
        npu = flt_partit(ro, pt, pi, mp/2, newct, u, v, du2, dv2);
                                /* return total */
        return(npl + npu);
}


void
flatpart(                               /* partition a flat source */
        SRCINDEX  *si,
        RAY  *r
)
{
        RREAL  *vp;
        FVECT  v;
        double  du2, dv2;
        int  pi;

        clrpart(si->spt);
        vp = source[si->sn].sloc;
        v[0] = r->rorg[0] - vp[0];
        v[1] = r->rorg[1] - vp[1];
        v[2] = r->rorg[2] - vp[2];
        vp = source[si->sn].snorm;
        if (DOT(v,vp) <= 0.) {          /* behind source */
                si->np = 0;
                return;
        }
        dv2 = 2.*r->rweight/srcsizerat;
        dv2 *= dv2;
        vp = source[si->sn].ss[SU];
        du2 = dv2 * DOT(vp,vp);
        vp = source[si->sn].ss[SV];
        dv2 *= DOT(vp,vp);
        pi = 0;
        si->np = flt_partit(r->rorg, si->spt, &pi, MAXSPART,
                source[si->sn].sloc,
                source[si->sn].ss[SU], source[si->sn].ss[SV], du2, dv2);
}


double
scylform(                       /* compute cosine for cylinder's projection */
        int  sn,
        FVECT  dir              /* assume normalized */
)
{
        RREAL  *dv;
        double  d;

        dv = source[sn].ss[SU];
        d = DOT(dir, dv);
        d *= d / DOT(dv,dv);
        return(sqrt(1. - d));
}
Revision:	2.21
Committed:	Sat Nov 9 15:21:32 2024 UTC (5 months, 3 weeks ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.20:	+10 -8 lines
Log Message:	perf: Improved source scatter sampling
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.21	static const char RCSid[] = "$Id: srcsamp.c,v 2.20 2019/06/11 17:00:59 greg Exp $";
3	greg	1.1	#endif
4			/*
5			* Source sampling routines
6	greg	2.7	*
7			* External symbols declared in source.h
8			*/
9
10	greg	2.8	#include "copyright.h"
11	greg	1.1
12	greg	1.4	#include "ray.h"
13	greg	1.1
14			#include "source.h"
15
16			#include "random.h"
17
18
19	greg	2.21	int
20			srcskip( /* pre-emptive test for source to skip */
21			int sn,
22			RAY *r
23	greg	2.18	)
24			{
25	greg	2.21	SRCREC *sp = source + sn;
26
27	greg	2.18	if (sp->sflags & SSKIP)
28			return(1);
29	greg	2.5
30	greg	2.18	if ((sp->sflags & (SPROX\|SDISTANT)) != SPROX)
31			return(0);
32
33	greg	2.21	return(dist2(r->rorg, sp->sloc) >
34	greg	2.18	(sp->sl.prox + sp->srad)*(sp->sl.prox + sp->srad));
35			}
36	greg	2.5
37	greg	1.1	double
38	greg	2.18	nextssamp( /* compute sample for source, rtn. distance */
39			RAY r, / origin is read, direction is set */
40	greg	2.21	SRCINDEX si / source index (modified to current) */
41	greg	2.18	)
42	greg	1.1	{
43			int cent[3], size[3], parr[2];
44	greg	2.16	SRCREC *srcp;
45	greg	2.19	double vpos[3];
46	greg	1.1	double d;
47	greg	2.18	int i;
48	greg	2.2	nextsample:
49	greg	1.1	while (++si->sp >= si->np) { /* get next sample */
50			if (++si->sn >= nsources)
51			return(0.0); /* no more */
52	greg	2.21	if (srcskip(si->sn, r))
53	greg	1.7	si->np = 0;
54			else if (srcsizerat <= FTINY)
55	greg	1.4	nopart(si, r);
56	greg	1.1	else {
57			for (i = si->sn; source[i].sflags & SVIRTUAL;
58			i = source[i].sa.sv.sn)
59			; /* partition source */
60	greg	1.4	(*sfun[source[i].so->otype].of->partit)(si, r);
61	greg	1.1	}
62			si->sp = -1;
63			}
64			/* get partition */
65			cent[0] = cent[1] = cent[2] = 0;
66			size[0] = size[1] = size[2] = MAXSPART;
67			parr[0] = 0; parr[1] = si->sp;
68			if (!skipparts(cent, size, parr, si->spt))
69			error(CONSISTENCY, "bad source partition in nextssamp");
70			/* compute sample */
71	greg	2.16	srcp = source + si->sn;
72	greg	1.1	if (dstrsrc > FTINY) { /* jitter sample */
73			dimlist[ndims] = si->sn + 8831;
74			dimlist[ndims+1] = si->sp + 3109;
75			d = urand(ilhash(dimlist,ndims+2)+samplendx);
76	greg	2.16	if (srcp->sflags & SFLAT) {
77	greg	1.1	multisamp(vpos, 2, d);
78	greg	2.12	vpos[SW] = 0.5;
79	greg	1.1	} else
80			multisamp(vpos, 3, d);
81			for (i = 0; i < 3; i++)
82			vpos[i] = dstrsrc * (1. - 2.vpos[i])
83	greg	2.17	(double)size[i]*(1.0/MAXSPART);
84	greg	1.1	} else
85			vpos[0] = vpos[1] = vpos[2] = 0.0;
86
87	greg	2.17	VSUM(vpos, vpos, cent, 1.0/MAXSPART);
88	greg	2.12	/* avoid circular aiming failures */
89	greg	2.20	if ((srcp->sflags & SCIR) && (si->np > 1) \| (dstrsrc > 0.7)) {
90	greg	2.12	FVECT trim;
91	greg	2.16	if (srcp->sflags & (SFLAT\|SDISTANT)) {
92	greg	2.12	d = 1.12837917; /* correct setflatss() */
93			trim[SU] = dsqrt(1.0 - 0.5vpos[SV]*vpos[SV]);
94			trim[SV] = dsqrt(1.0 - 0.5vpos[SU]*vpos[SU]);
95			trim[SW] = 0.0;
96			} else {
97			trim[SW] = trim[SU] = vpos[SU]*vpos[SU];
98			d = vpos[SV]*vpos[SV];
99			if (d > trim[SW]) trim[SW] = d;
100			trim[SU] += d;
101			d = vpos[SW]*vpos[SW];
102			if (d > trim[SW]) trim[SW] = d;
103			trim[SU] += d;
104	greg	2.15	if (trim[SU] > FTINY*FTINY) {
105			d = 1.0/0.7236; /* correct sphsetsrc() */
106			trim[SW] = trim[SV] = trim[SU] =
107			d*sqrt(trim[SW]/trim[SU]);
108			} else
109			trim[SW] = trim[SV] = trim[SU] = 0.0;
110	greg	2.12	}
111			for (i = 0; i < 3; i++)
112			vpos[i] *= trim[i];
113			}
114	greg	1.1	/* compute direction */
115			for (i = 0; i < 3; i++)
116	greg	2.16	r->rdir[i] = srcp->sloc[i] +
117			vpos[SU]*srcp->ss[SU][i] +
118			vpos[SV]*srcp->ss[SV][i] +
119			vpos[SW]*srcp->ss[SW][i];
120	greg	1.1
121	greg	2.16	if (!(srcp->sflags & SDISTANT))
122	greg	2.17	VSUB(r->rdir, r->rdir, r->rorg);
123	greg	1.1	/* compute distance */
124	greg	1.4	if ((d = normalize(r->rdir)) == 0.0)
125	greg	2.2	goto nextsample; /* at source! */
126	greg	1.1
127			/* compute sample size */
128	greg	2.16	if (srcp->sflags & SFLAT) {
129	greg	2.6	si->dom = sflatform(si->sn, r->rdir);
130	greg	2.17	si->dom = size[SU]size[SV]*(1.0/MAXSPART/MAXSPART);
131	greg	2.16	} else if (srcp->sflags & SCYL) {
132	greg	2.6	si->dom = scylform(si->sn, r->rdir);
133	greg	2.17	si->dom = size[SU](1.0/MAXSPART);
134	greg	1.1	} else {
135	greg	2.17	si->dom = size[SU]size[SV](double)size[SW] *
136			(1.0/MAXSPART/MAXSPART/MAXSPART) ;
137	greg	1.1	}
138	greg	2.16	if (srcp->sflags & SDISTANT) {
139			si->dom *= srcp->ss2;
140	greg	1.1	return(FHUGE);
141	greg	2.6	}
142	greg	2.3	if (si->dom <= 1e-4)
143	greg	2.2	goto nextsample; /* behind source? */
144	greg	2.16	si->dom = srcp->ss2/(dd);
145	greg	1.1	return(d); /* sample OK, return distance */
146			}
147
148
149	greg	2.7	int
150	greg	2.18	skipparts( /* skip to requested partition */
151			int ct[3],
152			int sz[3], /* center and size of partition (returned) */
153			int pp[2], /* current index, number to skip (modified) */
154			unsigned char pt / partition array */
155			)
156	greg	1.1	{
157	greg	2.18	int p;
158	greg	1.1	/* check this partition */
159			p = spart(pt, pp[0]);
160			pp[0]++;
161	schorsch	2.10	if (p == S0) { /* leaf partition */
162	greg	1.1	if (pp[1]) {
163			pp[1]--;
164			return(0); /* not there yet */
165			} else
166			return(1); /* we've arrived */
167	schorsch	2.10	}
168	greg	1.1	/* else check lower */
169			sz[p] >>= 1;
170			ct[p] -= sz[p];
171			if (skipparts(ct, sz, pp, pt))
172			return(1); /* return hit */
173			/* else check upper */
174			ct[p] += sz[p] << 1;
175			if (skipparts(ct, sz, pp, pt))
176			return(1); /* return hit */
177			/* else return to starting position */
178			ct[p] -= sz[p];
179			sz[p] <<= 1;
180			return(0); /* return miss */
181			}
182
183
184	greg	2.7	void
185	greg	2.18	nopart( /* single source partition */
186			SRCINDEX *si,
187			RAY *r
188			)
189	greg	1.1	{
190			clrpart(si->spt);
191			setpart(si->spt, 0, S0);
192			si->np = 1;
193			}
194
195
196			static int
197	greg	2.18	cyl_partit( /* slice a cylinder */
198			FVECT ro,
199			unsigned char *pt,
200			int *pi,
201			int mp,
202			FVECT cent,
203			FVECT axis,
204			double d2
205			)
206	greg	1.1	{
207			FVECT newct, newax;
208			int npl, npu;
209
210			if (mp < 2 \|\| dist2(ro, cent) >= d2) { /* hit limit? */
211			setpart(pt, *pi, S0);
212			(*pi)++;
213			return(1);
214			}
215			/* subdivide */
216			setpart(pt, *pi, SU);
217			(*pi)++;
218			newax[0] = .5*axis[0];
219			newax[1] = .5*axis[1];
220			newax[2] = .5*axis[2];
221			d2 *= 0.25;
222			/* lower half */
223			newct[0] = cent[0] - newax[0];
224			newct[1] = cent[1] - newax[1];
225			newct[2] = cent[2] - newax[2];
226	greg	1.2	npl = cyl_partit(ro, pt, pi, mp/2, newct, newax, d2);
227	greg	1.1	/* upper half */
228			newct[0] = cent[0] + newax[0];
229			newct[1] = cent[1] + newax[1];
230			newct[2] = cent[2] + newax[2];
231	greg	1.2	npu = cyl_partit(ro, pt, pi, mp/2, newct, newax, d2);
232	greg	1.1	/* return total */
233			return(npl + npu);
234			}
235
236
237	greg	2.7	void
238	greg	2.18	cylpart( /* partition a cylinder */
239			SRCINDEX *si,
240			RAY *r
241			)
242	greg	1.1	{
243	greg	2.18	double dist2, safedist2, dist2cent, rad2;
244	greg	1.5	FVECT v;
245	greg	2.18	SRCREC *sp;
246	greg	1.1	int pi;
247	greg	2.18	/* first check point location */
248	greg	1.5	clrpart(si->spt);
249	greg	2.18	sp = source + si->sn;
250			rad2 = 1.365 * DOT(sp->ss[SV],sp->ss[SV]);
251			v[0] = r->rorg[0] - sp->sloc[0];
252			v[1] = r->rorg[1] - sp->sloc[1];
253			v[2] = r->rorg[2] - sp->sloc[2];
254			dist2 = DOT(v,sp->ss[SU]);
255			safedist2 = DOT(sp->ss[SU],sp->ss[SU]);
256			dist2 *= dist2 / safedist2;
257			dist2cent = DOT(v,v);
258			dist2 = dist2cent - dist2;
259			if (dist2 <= rad2) { /* point inside extended cylinder */
260	greg	1.5	si->np = 0;
261			return;
262			}
263	greg	2.18	safedist2 = 4.r->rweightr->rweight/(srcsizeratsrcsizerat);
264			if (dist2 <= 4.rad2 \|\| / point too close to subdivide */
265			dist2cent >= safedist2) { /* or too far */
266			setpart(si->spt, 0, S0);
267			si->np = 1;
268			return;
269			}
270	greg	1.1	pi = 0;
271	greg	2.18	si->np = cyl_partit(r->rorg, si->spt, &pi, MAXSPART,
272			sp->sloc, sp->ss[SU], safedist2);
273	greg	1.1	}
274
275
276			static int
277	greg	2.18	flt_partit( /* partition flatty */
278			FVECT ro,
279			unsigned char *pt,
280			int *pi,
281			int mp,
282			FVECT cent,
283			FVECT u,
284			FVECT v,
285			double du2,
286			double dv2
287			)
288	greg	1.1	{
289			double d2;
290			FVECT newct, newax;
291			int npl, npu;
292
293			if (mp < 2 \|\| ((d2 = dist2(ro, cent)) >= du2
294			&& d2 >= dv2)) { /* hit limit? */
295			setpart(pt, *pi, S0);
296			(*pi)++;
297			return(1);
298			}
299			if (du2 > dv2) { /* subdivide in U */
300			setpart(pt, *pi, SU);
301			(*pi)++;
302			newax[0] = .5*u[0];
303			newax[1] = .5*u[1];
304			newax[2] = .5*u[2];
305			u = newax;
306			du2 *= 0.25;
307			} else { /* subdivide in V */
308			setpart(pt, *pi, SV);
309			(*pi)++;
310			newax[0] = .5*v[0];
311			newax[1] = .5*v[1];
312			newax[2] = .5*v[2];
313			v = newax;
314			dv2 *= 0.25;
315			}
316			/* lower half */
317			newct[0] = cent[0] - newax[0];
318			newct[1] = cent[1] - newax[1];
319			newct[2] = cent[2] - newax[2];
320	greg	1.2	npl = flt_partit(ro, pt, pi, mp/2, newct, u, v, du2, dv2);
321	greg	1.1	/* upper half */
322			newct[0] = cent[0] + newax[0];
323			newct[1] = cent[1] + newax[1];
324			newct[2] = cent[2] + newax[2];
325	greg	1.2	npu = flt_partit(ro, pt, pi, mp/2, newct, u, v, du2, dv2);
326	greg	1.1	/* return total */
327			return(npl + npu);
328			}
329
330
331	greg	2.18	void
332			flatpart( /* partition a flat source */
333			SRCINDEX *si,
334			RAY *r
335			)
336			{
337			RREAL *vp;
338			FVECT v;
339			double du2, dv2;
340			int pi;
341
342			clrpart(si->spt);
343			vp = source[si->sn].sloc;
344			v[0] = r->rorg[0] - vp[0];
345			v[1] = r->rorg[1] - vp[1];
346			v[2] = r->rorg[2] - vp[2];
347			vp = source[si->sn].snorm;
348			if (DOT(v,vp) <= 0.) { /* behind source */
349			si->np = 0;
350			return;
351			}
352			dv2 = 2.*r->rweight/srcsizerat;
353			dv2 *= dv2;
354			vp = source[si->sn].ss[SU];
355			du2 = dv2 * DOT(vp,vp);
356			vp = source[si->sn].ss[SV];
357			dv2 *= DOT(vp,vp);
358			pi = 0;
359			si->np = flt_partit(r->rorg, si->spt, &pi, MAXSPART,
360			source[si->sn].sloc,
361			source[si->sn].ss[SU], source[si->sn].ss[SV], du2, dv2);
362			}
363
364
365	greg	1.1	double
366	greg	2.18	scylform( /* compute cosine for cylinder's projection */
367			int sn,
368			FVECT dir /* assume normalized */
369			)
370	greg	1.1	{
371	greg	2.18	RREAL *dv;
372	greg	1.1	double d;
373
374			dv = source[sn].ss[SU];
375			d = DOT(dir, dv);
376			d *= d / DOT(dv,dv);
377			return(sqrt(1. - d));
378			}