src/rt/srcsamp.c

/* Copyright (c) 1991 Regents of the University of California */

#ifndef lint
static char SCCSid[] = "$SunId$ LBL";
#endif

/*
 * Source sampling routines
 */

#include  "ray.h"

#include  "source.h"

#include  "random.h"


double
nextssamp(r, si)                /* compute sample for source, rtn. distance */
register RAY  *r;               /* origin is read, direction is set */
register SRCINDEX  *si;         /* source index (modified to current) */
{
        int  cent[3], size[3], parr[2];
        FVECT  vpos;
        double  d;
        register int  i;
nextsample:
        while (++si->sp >= si->np) {    /* get next sample */
                if (++si->sn >= nsources)
                        return(0.0);    /* no more */
                if (source[si->sn].sflags & SSKIP)
                        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 */
        if (dstrsrc > FTINY) {                  /* jitter sample */
                dimlist[ndims] = si->sn + 8831;
                dimlist[ndims+1] = si->sp + 3109;
                d = urand(ilhash(dimlist,ndims+2)+samplendx);
                if (source[si->sn].sflags & SFLAT) {
                        multisamp(vpos, 2, d);
                        vpos[2] = 0.5;
                } else
                        multisamp(vpos, 3, d);
                for (i = 0; i < 3; i++)
                        vpos[i] = dstrsrc * (1. - 2.*vpos[i]) *
                                        (double)size[i]/MAXSPART;
        } else
                vpos[0] = vpos[1] = vpos[2] = 0.0;

        for (i = 0; i < 3; i++)
                vpos[i] += (double)cent[i]/MAXSPART;
                                        /* compute direction */
        for (i = 0; i < 3; i++)
                r->rdir[i] = source[si->sn].sloc[i] +
                                vpos[SU]*source[si->sn].ss[SU][i] +
                                vpos[SV]*source[si->sn].ss[SV][i] +
                                vpos[SW]*source[si->sn].ss[SW][i];

        if (!(source[si->sn].sflags & SDISTANT))
                for (i = 0; i < 3; i++)
                        r->rdir[i] -= r->rorg[i];
                                        /* compute distance */
        if ((d = normalize(r->rdir)) == 0.0)
                goto nextsample;                /* at source! */

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


skipparts(ct, sz, pp, pt)               /* skip to requested partition */
int  ct[3], sz[3];              /* center and size of partition (returned) */
register int  pp[2];            /* current index, number to skip (modified) */
unsigned char  *pt;             /* partition array */
{
        register 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 */
}


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


cylpart(si, r)                  /* partition a cylinder */
SRCINDEX  *si;
register RAY  *r;
{
        double  dist2, safedist2, dist2cent, rad2;
        FVECT  v;
        register 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
cyl_partit(ro, pt, pi, mp, cent, axis, d2)      /* slice a cylinder */
FVECT  ro;
unsigned char  *pt;
register int  *pi;
int  mp;
FVECT  cent, 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);
}


flatpart(si, r)                         /* partition a flat source */
register SRCINDEX  *si;
register RAY  *r;
{
        register FLOAT  *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) <= FTINY) {       /* 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);
}


static int
flt_partit(ro, pt, pi, mp, cent, u, v, du2, dv2)        /* partition flatty */
FVECT  ro;
unsigned char  *pt;
register int  *pi;
int  mp;
FVECT  cent, u, v;
double  du2, 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);
}


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

        dv = source[sn].ss[SU];
        d = DOT(dir, dv);
        d *= d / DOT(dv,dv);
        return(sqrt(1. - d));
}
Revision:	2.2
Committed:	Mon Nov 25 09:52:49 1991 UTC (33 years, 11 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 2.1:	+4 -2 lines
Log Message:	fixed small bug yielding inappropriate samples for flat sources
#	User	Rev	Content
1	greg	1.1	/* Copyright (c) 1991 Regents of the University of California */
2
3			#ifndef lint
4			static char SCCSid[] = "$SunId$ LBL";
5			#endif
6
7			/*
8			* Source sampling routines
9			*/
10
11	greg	1.4	#include "ray.h"
12	greg	1.1
13			#include "source.h"
14
15			#include "random.h"
16
17
18			double
19	greg	1.4	nextssamp(r, si) /* compute sample for source, rtn. distance */
20			register RAY r; / origin is read, direction is set */
21	greg	1.1	register SRCINDEX si; / source index (modified to current) */
22			{
23			int cent[3], size[3], parr[2];
24			FVECT vpos;
25			double d;
26			register int i;
27	greg	2.2	nextsample:
28	greg	1.1	while (++si->sp >= si->np) { /* get next sample */
29			if (++si->sn >= nsources)
30			return(0.0); /* no more */
31	greg	1.7	if (source[si->sn].sflags & SSKIP)
32			si->np = 0;
33			else if (srcsizerat <= FTINY)
34	greg	1.4	nopart(si, r);
35	greg	1.1	else {
36			for (i = si->sn; source[i].sflags & SVIRTUAL;
37			i = source[i].sa.sv.sn)
38			; /* partition source */
39	greg	1.4	(*sfun[source[i].so->otype].of->partit)(si, r);
40	greg	1.1	}
41			si->sp = -1;
42			}
43			/* get partition */
44			cent[0] = cent[1] = cent[2] = 0;
45			size[0] = size[1] = size[2] = MAXSPART;
46			parr[0] = 0; parr[1] = si->sp;
47			if (!skipparts(cent, size, parr, si->spt))
48			error(CONSISTENCY, "bad source partition in nextssamp");
49			/* compute sample */
50			if (dstrsrc > FTINY) { /* jitter sample */
51			dimlist[ndims] = si->sn + 8831;
52			dimlist[ndims+1] = si->sp + 3109;
53			d = urand(ilhash(dimlist,ndims+2)+samplendx);
54			if (source[si->sn].sflags & SFLAT) {
55			multisamp(vpos, 2, d);
56			vpos[2] = 0.5;
57			} else
58			multisamp(vpos, 3, d);
59			for (i = 0; i < 3; i++)
60			vpos[i] = dstrsrc * (1. - 2.vpos[i])
61			(double)size[i]/MAXSPART;
62			} else
63			vpos[0] = vpos[1] = vpos[2] = 0.0;
64
65			for (i = 0; i < 3; i++)
66			vpos[i] += (double)cent[i]/MAXSPART;
67			/* compute direction */
68			for (i = 0; i < 3; i++)
69	greg	1.4	r->rdir[i] = source[si->sn].sloc[i] +
70	greg	1.1	vpos[SU]*source[si->sn].ss[SU][i] +
71			vpos[SV]*source[si->sn].ss[SV][i] +
72			vpos[SW]*source[si->sn].ss[SW][i];
73
74			if (!(source[si->sn].sflags & SDISTANT))
75			for (i = 0; i < 3; i++)
76	greg	1.4	r->rdir[i] -= r->rorg[i];
77	greg	1.1	/* compute distance */
78	greg	1.4	if ((d = normalize(r->rdir)) == 0.0)
79	greg	2.2	goto nextsample; /* at source! */
80	greg	1.1
81			/* compute sample size */
82			si->dom = source[si->sn].ss2;
83			if (source[si->sn].sflags & SFLAT) {
84	greg	1.4	si->dom *= sflatform(si->sn, r->rdir);
85	greg	1.1	si->dom = (double)(size[SU]size[SV])/(MAXSPART*MAXSPART);
86			} else if (source[si->sn].sflags & SCYL) {
87	greg	1.4	si->dom *= scylform(si->sn, r->rdir);
88	greg	1.1	si->dom *= (double)size[SU]/MAXSPART;
89			} else {
90			si->dom = (double)(size[SU]size[SV]*size[SW]) /
91			(MAXSPARTMAXSPARTMAXSPART) ;
92			}
93			if (source[si->sn].sflags & SDISTANT)
94			return(FHUGE);
95	greg	2.2	if (si->dom <= FTINY)
96			goto nextsample; /* behind source? */
97	greg	1.1	si->dom /= d*d;
98			return(d); /* sample OK, return distance */
99			}
100
101
102			skipparts(ct, sz, pp, pt) /* skip to requested partition */
103			int ct[3], sz[3]; /* center and size of partition (returned) */
104			register int pp[2]; /* current index, number to skip (modified) */
105			unsigned char pt; / partition array */
106			{
107			register int p;
108			/* check this partition */
109			p = spart(pt, pp[0]);
110			pp[0]++;
111			if (p == S0) /* leaf partition */
112			if (pp[1]) {
113			pp[1]--;
114			return(0); /* not there yet */
115			} else
116			return(1); /* we've arrived */
117			/* else check lower */
118			sz[p] >>= 1;
119			ct[p] -= sz[p];
120			if (skipparts(ct, sz, pp, pt))
121			return(1); /* return hit */
122			/* else check upper */
123			ct[p] += sz[p] << 1;
124			if (skipparts(ct, sz, pp, pt))
125			return(1); /* return hit */
126			/* else return to starting position */
127			ct[p] -= sz[p];
128			sz[p] <<= 1;
129			return(0); /* return miss */
130			}
131
132
133	greg	1.4	nopart(si, r) /* single source partition */
134	greg	1.1	register SRCINDEX *si;
135	greg	1.4	RAY *r;
136	greg	1.1	{
137			clrpart(si->spt);
138			setpart(si->spt, 0, S0);
139			si->np = 1;
140			}
141
142
143	greg	1.4	cylpart(si, r) /* partition a cylinder */
144	greg	1.1	SRCINDEX *si;
145	greg	1.4	register RAY *r;
146	greg	1.1	{
147			double dist2, safedist2, dist2cent, rad2;
148			FVECT v;
149			register SRCREC *sp;
150			int pi;
151			/* first check point location */
152			clrpart(si->spt);
153	greg	1.4	sp = source + si->sn;
154	greg	1.3	rad2 = 1.365 * DOT(sp->ss[SV],sp->ss[SV]);
155	greg	1.4	v[0] = r->rorg[0] - sp->sloc[0];
156			v[1] = r->rorg[1] - sp->sloc[1];
157			v[2] = r->rorg[2] - sp->sloc[2];
158	greg	1.1	dist2 = DOT(v,sp->ss[SU]);
159			safedist2 = DOT(sp->ss[SU],sp->ss[SU]);
160			dist2 *= dist2 / safedist2;
161			dist2cent = DOT(v,v);
162			dist2 = dist2cent - dist2;
163			if (dist2 <= rad2) { /* point inside extended cylinder */
164			si->np = 0;
165			return;
166			}
167	greg	1.4	safedist2 = 4.r->rweightr->rweight/(srcsizeratsrcsizerat);
168	greg	1.5	if (dist2 <= 4.rad2 \|\| / point too close to subdivide */
169			dist2cent >= safedist2) { /* or too far */
170	greg	1.1	setpart(si->spt, 0, S0);
171			si->np = 1;
172			return;
173			}
174			pi = 0;
175	greg	1.4	si->np = cyl_partit(r->rorg, si->spt, &pi, MAXSPART,
176	greg	1.1	sp->sloc, sp->ss[SU], safedist2);
177			}
178
179
180			static int
181			cyl_partit(ro, pt, pi, mp, cent, axis, d2) /* slice a cylinder */
182			FVECT ro;
183			unsigned char *pt;
184			register int *pi;
185			int mp;
186			FVECT cent, axis;
187			double d2;
188			{
189			FVECT newct, newax;
190			int npl, npu;
191
192			if (mp < 2 \|\| dist2(ro, cent) >= d2) { /* hit limit? */
193			setpart(pt, *pi, S0);
194			(*pi)++;
195			return(1);
196			}
197			/* subdivide */
198			setpart(pt, *pi, SU);
199			(*pi)++;
200			newax[0] = .5*axis[0];
201			newax[1] = .5*axis[1];
202			newax[2] = .5*axis[2];
203			d2 *= 0.25;
204			/* lower half */
205			newct[0] = cent[0] - newax[0];
206			newct[1] = cent[1] - newax[1];
207			newct[2] = cent[2] - newax[2];
208	greg	1.2	npl = cyl_partit(ro, pt, pi, mp/2, newct, newax, d2);
209	greg	1.1	/* upper half */
210			newct[0] = cent[0] + newax[0];
211			newct[1] = cent[1] + newax[1];
212			newct[2] = cent[2] + newax[2];
213	greg	1.2	npu = cyl_partit(ro, pt, pi, mp/2, newct, newax, d2);
214	greg	1.1	/* return total */
215			return(npl + npu);
216			}
217
218
219	greg	1.4	flatpart(si, r) /* partition a flat source */
220	greg	1.1	register SRCINDEX *si;
221	greg	1.5	register RAY *r;
222	greg	1.1	{
223	greg	1.6	register FLOAT *vp;
224	greg	1.5	FVECT v;
225	greg	1.1	double du2, dv2;
226			int pi;
227
228	greg	1.5	clrpart(si->spt);
229			vp = source[si->sn].sloc;
230			v[0] = r->rorg[0] - vp[0];
231			v[1] = r->rorg[1] - vp[1];
232			v[2] = r->rorg[2] - vp[2];
233			vp = source[si->sn].snorm;
234			if (DOT(v,vp) <= FTINY) { /* behind source */
235			si->np = 0;
236			return;
237			}
238	greg	1.4	dv2 = 2.*r->rweight/srcsizerat;
239			dv2 *= dv2;
240	greg	1.1	vp = source[si->sn].ss[SU];
241	greg	1.4	du2 = dv2 * DOT(vp,vp);
242	greg	1.1	vp = source[si->sn].ss[SV];
243	greg	1.4	dv2 *= DOT(vp,vp);
244	greg	1.1	pi = 0;
245	greg	1.4	si->np = flt_partit(r->rorg, si->spt, &pi, MAXSPART,
246			source[si->sn].sloc,
247	greg	1.1	source[si->sn].ss[SU], source[si->sn].ss[SV], du2, dv2);
248			}
249
250
251			static int
252			flt_partit(ro, pt, pi, mp, cent, u, v, du2, dv2) /* partition flatty */
253			FVECT ro;
254			unsigned char *pt;
255			register int *pi;
256			int mp;
257			FVECT cent, u, v;
258			double du2, dv2;
259			{
260			double d2;
261			FVECT newct, newax;
262			int npl, npu;
263
264			if (mp < 2 \|\| ((d2 = dist2(ro, cent)) >= du2
265			&& d2 >= dv2)) { /* hit limit? */
266			setpart(pt, *pi, S0);
267			(*pi)++;
268			return(1);
269			}
270			if (du2 > dv2) { /* subdivide in U */
271			setpart(pt, *pi, SU);
272			(*pi)++;
273			newax[0] = .5*u[0];
274			newax[1] = .5*u[1];
275			newax[2] = .5*u[2];
276			u = newax;
277			du2 *= 0.25;
278			} else { /* subdivide in V */
279			setpart(pt, *pi, SV);
280			(*pi)++;
281			newax[0] = .5*v[0];
282			newax[1] = .5*v[1];
283			newax[2] = .5*v[2];
284			v = newax;
285			dv2 *= 0.25;
286			}
287			/* lower half */
288			newct[0] = cent[0] - newax[0];
289			newct[1] = cent[1] - newax[1];
290			newct[2] = cent[2] - newax[2];
291	greg	1.2	npl = flt_partit(ro, pt, pi, mp/2, newct, u, v, du2, dv2);
292	greg	1.1	/* upper half */
293			newct[0] = cent[0] + newax[0];
294			newct[1] = cent[1] + newax[1];
295			newct[2] = cent[2] + newax[2];
296	greg	1.2	npu = flt_partit(ro, pt, pi, mp/2, newct, u, v, du2, dv2);
297	greg	1.1	/* return total */
298			return(npl + npu);
299			}
300
301
302			double
303			scylform(sn, dir) /* compute cosine for cylinder's projection */
304			int sn;
305			register FVECT dir; /* assume normalized */
306			{
307	greg	1.6	register FLOAT *dv;
308	greg	1.1	double d;
309
310			dv = source[sn].ss[SU];
311			d = DOT(dir, dv);
312			d *= d / DOT(dv,dv);
313			return(sqrt(1. - d));
314			}