src/rt/srcsamp.c

#ifndef lint
static const char       RCSid[] = "$Id: srcsamp.c,v 2.18 2011/12/28 18:39:36 greg Exp $";
#endif
/*
 * Source sampling routines
 *
 *  External symbols declared in source.h
 */

#include "copyright.h"

#include  "ray.h"

#include  "source.h"

#include  "random.h"


static int
srcskip(                        /* pre-emptive test for out-of-range glow */
        SRCREC  *sp,
        FVECT  orig
)
{
        if (sp->sflags & SSKIP)
                return(1);

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

        return(dist2(orig, 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(source+si->sn, r->rorg))
                        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:	2.19
Committed:	Tue Jul 15 23:44:53 2014 UTC (9 years, 9 months ago) by greg
Content type:	text/plain
Branch:	MAIN
CVS Tags:	rad5R2, rad4R2P2, rad5R0, rad5R1, rad4R2, rad4R2P1
Changes since 2.18:	+2 -2 lines
Log Message:	Fixed potential type conflict
#	User	Rev	Content
1	greg	1.1	#ifndef lint
2	greg	2.19	static const char RCSid[] = "$Id: srcsamp.c,v 2.18 2011/12/28 18:39:36 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	2.18	static int
20			srcskip( /* pre-emptive test for out-of-range glow */
21			SRCREC *sp,
22			FVECT orig
23			)
24			{
25			if (sp->sflags & SSKIP)
26			return(1);
27	greg	2.5
28	greg	2.18	if ((sp->sflags & (SPROX\|SDISTANT)) != SPROX)
29			return(0);
30
31			return(dist2(orig, sp->sloc) >
32			(sp->sl.prox + sp->srad)*(sp->sl.prox + sp->srad));
33			}
34	greg	2.5
35	greg	1.1	double
36	greg	2.18	nextssamp( /* compute sample for source, rtn. distance */
37			RAY r, / origin is read, direction is set */
38			SRCINDEX si / source index (modified to current) */\
39			)
40	greg	1.1	{
41			int cent[3], size[3], parr[2];
42	greg	2.16	SRCREC *srcp;
43	greg	2.19	double vpos[3];
44	greg	1.1	double d;
45	greg	2.18	int i;
46	greg	2.2	nextsample:
47	greg	1.1	while (++si->sp >= si->np) { /* get next sample */
48			if (++si->sn >= nsources)
49			return(0.0); /* no more */
50	greg	2.18	if (srcskip(source+si->sn, r->rorg))
51	greg	1.7	si->np = 0;
52			else if (srcsizerat <= FTINY)
53	greg	1.4	nopart(si, r);
54	greg	1.1	else {
55			for (i = si->sn; source[i].sflags & SVIRTUAL;
56			i = source[i].sa.sv.sn)
57			; /* partition source */
58	greg	1.4	(*sfun[source[i].so->otype].of->partit)(si, r);
59	greg	1.1	}
60			si->sp = -1;
61			}
62			/* get partition */
63			cent[0] = cent[1] = cent[2] = 0;
64			size[0] = size[1] = size[2] = MAXSPART;
65			parr[0] = 0; parr[1] = si->sp;
66			if (!skipparts(cent, size, parr, si->spt))
67			error(CONSISTENCY, "bad source partition in nextssamp");
68			/* compute sample */
69	greg	2.16	srcp = source + si->sn;
70	greg	1.1	if (dstrsrc > FTINY) { /* jitter sample */
71			dimlist[ndims] = si->sn + 8831;
72			dimlist[ndims+1] = si->sp + 3109;
73			d = urand(ilhash(dimlist,ndims+2)+samplendx);
74	greg	2.16	if (srcp->sflags & SFLAT) {
75	greg	1.1	multisamp(vpos, 2, d);
76	greg	2.12	vpos[SW] = 0.5;
77	greg	1.1	} else
78			multisamp(vpos, 3, d);
79			for (i = 0; i < 3; i++)
80			vpos[i] = dstrsrc * (1. - 2.vpos[i])
81	greg	2.17	(double)size[i]*(1.0/MAXSPART);
82	greg	1.1	} else
83			vpos[0] = vpos[1] = vpos[2] = 0.0;
84
85	greg	2.17	VSUM(vpos, vpos, cent, 1.0/MAXSPART);
86	greg	2.12	/* avoid circular aiming failures */
87	greg	2.16	if ((srcp->sflags & SCIR) && (si->np > 1 \|\| dstrsrc > 0.7)) {
88	greg	2.12	FVECT trim;
89	greg	2.16	if (srcp->sflags & (SFLAT\|SDISTANT)) {
90	greg	2.12	d = 1.12837917; /* correct setflatss() */
91			trim[SU] = dsqrt(1.0 - 0.5vpos[SV]*vpos[SV]);
92			trim[SV] = dsqrt(1.0 - 0.5vpos[SU]*vpos[SU]);
93			trim[SW] = 0.0;
94			} else {
95			trim[SW] = trim[SU] = vpos[SU]*vpos[SU];
96			d = vpos[SV]*vpos[SV];
97			if (d > trim[SW]) trim[SW] = d;
98			trim[SU] += d;
99			d = vpos[SW]*vpos[SW];
100			if (d > trim[SW]) trim[SW] = d;
101			trim[SU] += d;
102	greg	2.15	if (trim[SU] > FTINY*FTINY) {
103			d = 1.0/0.7236; /* correct sphsetsrc() */
104			trim[SW] = trim[SV] = trim[SU] =
105			d*sqrt(trim[SW]/trim[SU]);
106			} else
107			trim[SW] = trim[SV] = trim[SU] = 0.0;
108	greg	2.12	}
109			for (i = 0; i < 3; i++)
110			vpos[i] *= trim[i];
111			}
112	greg	1.1	/* compute direction */
113			for (i = 0; i < 3; i++)
114	greg	2.16	r->rdir[i] = srcp->sloc[i] +
115			vpos[SU]*srcp->ss[SU][i] +
116			vpos[SV]*srcp->ss[SV][i] +
117			vpos[SW]*srcp->ss[SW][i];
118	greg	1.1
119	greg	2.16	if (!(srcp->sflags & SDISTANT))
120	greg	2.17	VSUB(r->rdir, r->rdir, r->rorg);
121	greg	1.1	/* compute distance */
122	greg	1.4	if ((d = normalize(r->rdir)) == 0.0)
123	greg	2.2	goto nextsample; /* at source! */
124	greg	1.1
125			/* compute sample size */
126	greg	2.16	if (srcp->sflags & SFLAT) {
127	greg	2.6	si->dom = sflatform(si->sn, r->rdir);
128	greg	2.17	si->dom = size[SU]size[SV]*(1.0/MAXSPART/MAXSPART);
129	greg	2.16	} else if (srcp->sflags & SCYL) {
130	greg	2.6	si->dom = scylform(si->sn, r->rdir);
131	greg	2.17	si->dom = size[SU](1.0/MAXSPART);
132	greg	1.1	} else {
133	greg	2.17	si->dom = size[SU]size[SV](double)size[SW] *
134			(1.0/MAXSPART/MAXSPART/MAXSPART) ;
135	greg	1.1	}
136	greg	2.16	if (srcp->sflags & SDISTANT) {
137			si->dom *= srcp->ss2;
138	greg	1.1	return(FHUGE);
139	greg	2.6	}
140	greg	2.3	if (si->dom <= 1e-4)
141	greg	2.2	goto nextsample; /* behind source? */
142	greg	2.16	si->dom = srcp->ss2/(dd);
143	greg	1.1	return(d); /* sample OK, return distance */
144			}
145
146
147	greg	2.7	int
148	greg	2.18	skipparts( /* skip to requested partition */
149			int ct[3],
150			int sz[3], /* center and size of partition (returned) */
151			int pp[2], /* current index, number to skip (modified) */
152			unsigned char pt / partition array */
153			)
154	greg	1.1	{
155	greg	2.18	int p;
156	greg	1.1	/* check this partition */
157			p = spart(pt, pp[0]);
158			pp[0]++;
159	schorsch	2.10	if (p == S0) { /* leaf partition */
160	greg	1.1	if (pp[1]) {
161			pp[1]--;
162			return(0); /* not there yet */
163			} else
164			return(1); /* we've arrived */
165	schorsch	2.10	}
166	greg	1.1	/* else check lower */
167			sz[p] >>= 1;
168			ct[p] -= sz[p];
169			if (skipparts(ct, sz, pp, pt))
170			return(1); /* return hit */
171			/* else check upper */
172			ct[p] += sz[p] << 1;
173			if (skipparts(ct, sz, pp, pt))
174			return(1); /* return hit */
175			/* else return to starting position */
176			ct[p] -= sz[p];
177			sz[p] <<= 1;
178			return(0); /* return miss */
179			}
180
181
182	greg	2.7	void
183	greg	2.18	nopart( /* single source partition */
184			SRCINDEX *si,
185			RAY *r
186			)
187	greg	1.1	{
188			clrpart(si->spt);
189			setpart(si->spt, 0, S0);
190			si->np = 1;
191			}
192
193
194			static int
195	greg	2.18	cyl_partit( /* slice a cylinder */
196			FVECT ro,
197			unsigned char *pt,
198			int *pi,
199			int mp,
200			FVECT cent,
201			FVECT axis,
202			double d2
203			)
204	greg	1.1	{
205			FVECT newct, newax;
206			int npl, npu;
207
208			if (mp < 2 \|\| dist2(ro, cent) >= d2) { /* hit limit? */
209			setpart(pt, *pi, S0);
210			(*pi)++;
211			return(1);
212			}
213			/* subdivide */
214			setpart(pt, *pi, SU);
215			(*pi)++;
216			newax[0] = .5*axis[0];
217			newax[1] = .5*axis[1];
218			newax[2] = .5*axis[2];
219			d2 *= 0.25;
220			/* lower half */
221			newct[0] = cent[0] - newax[0];
222			newct[1] = cent[1] - newax[1];
223			newct[2] = cent[2] - newax[2];
224	greg	1.2	npl = cyl_partit(ro, pt, pi, mp/2, newct, newax, d2);
225	greg	1.1	/* upper half */
226			newct[0] = cent[0] + newax[0];
227			newct[1] = cent[1] + newax[1];
228			newct[2] = cent[2] + newax[2];
229	greg	1.2	npu = cyl_partit(ro, pt, pi, mp/2, newct, newax, d2);
230	greg	1.1	/* return total */
231			return(npl + npu);
232			}
233
234
235	greg	2.7	void
236	greg	2.18	cylpart( /* partition a cylinder */
237			SRCINDEX *si,
238			RAY *r
239			)
240	greg	1.1	{
241	greg	2.18	double dist2, safedist2, dist2cent, rad2;
242	greg	1.5	FVECT v;
243	greg	2.18	SRCREC *sp;
244	greg	1.1	int pi;
245	greg	2.18	/* first check point location */
246	greg	1.5	clrpart(si->spt);
247	greg	2.18	sp = source + si->sn;
248			rad2 = 1.365 * DOT(sp->ss[SV],sp->ss[SV]);
249			v[0] = r->rorg[0] - sp->sloc[0];
250			v[1] = r->rorg[1] - sp->sloc[1];
251			v[2] = r->rorg[2] - sp->sloc[2];
252			dist2 = DOT(v,sp->ss[SU]);
253			safedist2 = DOT(sp->ss[SU],sp->ss[SU]);
254			dist2 *= dist2 / safedist2;
255			dist2cent = DOT(v,v);
256			dist2 = dist2cent - dist2;
257			if (dist2 <= rad2) { /* point inside extended cylinder */
258	greg	1.5	si->np = 0;
259			return;
260			}
261	greg	2.18	safedist2 = 4.r->rweightr->rweight/(srcsizeratsrcsizerat);
262			if (dist2 <= 4.rad2 \|\| / point too close to subdivide */
263			dist2cent >= safedist2) { /* or too far */
264			setpart(si->spt, 0, S0);
265			si->np = 1;
266			return;
267			}
268	greg	1.1	pi = 0;
269	greg	2.18	si->np = cyl_partit(r->rorg, si->spt, &pi, MAXSPART,
270			sp->sloc, sp->ss[SU], safedist2);
271	greg	1.1	}
272
273
274			static int
275	greg	2.18	flt_partit( /* partition flatty */
276			FVECT ro,
277			unsigned char *pt,
278			int *pi,
279			int mp,
280			FVECT cent,
281			FVECT u,
282			FVECT v,
283			double du2,
284			double dv2
285			)
286	greg	1.1	{
287			double d2;
288			FVECT newct, newax;
289			int npl, npu;
290
291			if (mp < 2 \|\| ((d2 = dist2(ro, cent)) >= du2
292			&& d2 >= dv2)) { /* hit limit? */
293			setpart(pt, *pi, S0);
294			(*pi)++;
295			return(1);
296			}
297			if (du2 > dv2) { /* subdivide in U */
298			setpart(pt, *pi, SU);
299			(*pi)++;
300			newax[0] = .5*u[0];
301			newax[1] = .5*u[1];
302			newax[2] = .5*u[2];
303			u = newax;
304			du2 *= 0.25;
305			} else { /* subdivide in V */
306			setpart(pt, *pi, SV);
307			(*pi)++;
308			newax[0] = .5*v[0];
309			newax[1] = .5*v[1];
310			newax[2] = .5*v[2];
311			v = newax;
312			dv2 *= 0.25;
313			}
314			/* lower half */
315			newct[0] = cent[0] - newax[0];
316			newct[1] = cent[1] - newax[1];
317			newct[2] = cent[2] - newax[2];
318	greg	1.2	npl = flt_partit(ro, pt, pi, mp/2, newct, u, v, du2, dv2);
319	greg	1.1	/* upper half */
320			newct[0] = cent[0] + newax[0];
321			newct[1] = cent[1] + newax[1];
322			newct[2] = cent[2] + newax[2];
323	greg	1.2	npu = flt_partit(ro, pt, pi, mp/2, newct, u, v, du2, dv2);
324	greg	1.1	/* return total */
325			return(npl + npu);
326			}
327
328
329	greg	2.18	void
330			flatpart( /* partition a flat source */
331			SRCINDEX *si,
332			RAY *r
333			)
334			{
335			RREAL *vp;
336			FVECT v;
337			double du2, dv2;
338			int pi;
339
340			clrpart(si->spt);
341			vp = source[si->sn].sloc;
342			v[0] = r->rorg[0] - vp[0];
343			v[1] = r->rorg[1] - vp[1];
344			v[2] = r->rorg[2] - vp[2];
345			vp = source[si->sn].snorm;
346			if (DOT(v,vp) <= 0.) { /* behind source */
347			si->np = 0;
348			return;
349			}
350			dv2 = 2.*r->rweight/srcsizerat;
351			dv2 *= dv2;
352			vp = source[si->sn].ss[SU];
353			du2 = dv2 * DOT(vp,vp);
354			vp = source[si->sn].ss[SV];
355			dv2 *= DOT(vp,vp);
356			pi = 0;
357			si->np = flt_partit(r->rorg, si->spt, &pi, MAXSPART,
358			source[si->sn].sloc,
359			source[si->sn].ss[SU], source[si->sn].ss[SV], du2, dv2);
360			}
361
362
363	greg	1.1	double
364	greg	2.18	scylform( /* compute cosine for cylinder's projection */
365			int sn,
366			FVECT dir /* assume normalized */
367			)
368	greg	1.1	{
369	greg	2.18	RREAL *dv;
370	greg	1.1	double d;
371
372			dv = source[sn].ss[SU];
373			d = DOT(dir, dv);
374			d *= d / DOT(dv,dv);
375			return(sqrt(1. - d));
376			}