src/rt/virtuals.c

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

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

/*
 * Routines for simulating virtual light sources
 *      Thus far, we only support planar mirrors.
 */

#include  "ray.h"

#include  "octree.h"

#include  "otypes.h"

#include  "source.h"

#include  "random.h"

#define  MINSAMPLES     3               /* minimum number of pretest samples */
#define  STESTMAX       30              /* maximum seeks per sample */


double  getdisk();

static OBJECT  *vobject;                /* virtual source objects */
static int  nvobjects = 0;              /* number of virtual source objects */


markvirtuals()                  /* find and mark virtual sources */
{
        register OBJREC  *o;
        register int  i;
                                        /* check number of direct relays */
        if (directrelay <= 0)
                return;
                                        /* find virtual source objects */
        for (i = 0; i < nobjects; i++) {
                o = objptr(i);
                if (!issurface(o->otype) || o->omod == OVOID)
                        continue;
                if (!isvlight(objptr(o->omod)->otype))
                        continue;
                if (sfun[o->otype].of == NULL ||
                                sfun[o->otype].of->getpleq == NULL)
                        objerror(o, USER, "illegal material");
                if (nvobjects == 0)
                        vobject = (OBJECT *)malloc(sizeof(OBJECT));
                else
                        vobject = (OBJECT *)realloc((char *)vobject,
                                (unsigned)(nvobjects+1)*sizeof(OBJECT));
                if (vobject == NULL)
                        error(SYSTEM, "out of memory in addvirtuals");
                vobject[nvobjects++] = i;
        }
        if (nvobjects == 0)
                return;
#ifdef DEBUG
        fprintf(stderr, "found %d virtual source objects\n", nvobjects);
#endif
                                        /* append virtual sources */
        for (i = nsources; i-- > 0; )
                addvirtuals(i, directrelay);
                                        /* done with our object list */
        free((char *)vobject);
        nvobjects = 0;
}


addvirtuals(sn, nr)             /* add virtuals associated with source */
int  sn;
int  nr;
{
        register int  i;
                                /* check relay limit first */
        if (nr <= 0)
                return;
        if (source[sn].sflags & SSKIP)
                return;
                                /* check each virtual object for projection */
        for (i = 0; i < nvobjects; i++)
                                        /* vproject() calls us recursively */
                vproject(objptr(vobject[i]), sn, nr-1);
}


vproject(o, sn, n)              /* create projected source(s) if they exist */
OBJREC  *o;
int  sn;
int  n;
{
        register int  i;
        register VSMATERIAL  *vsmat;
        MAT4  proj;
        int  ns;

        if (o == source[sn].so) /* objects cannot project themselves */
                return;
                                /* get virtual source material */
        vsmat = sfun[objptr(o->omod)->otype].mf;
                                /* project virtual sources */
        for (i = 0; i < vsmat->nproj; i++)
                if ((*vsmat->vproj)(proj, o, &source[sn], i))
                        if ((ns = makevsrc(o, sn, proj)) >= 0) {
#ifdef DEBUG
                                virtverb(ns, stderr);
#endif
                                addvirtuals(ns, n);
                        }
}


int
makevsrc(op, sn, pm)            /* make virtual source if reasonable */
OBJREC  *op;
register int  sn;
MAT4  pm;
{
        FVECT  nsloc, nsnorm, ocent, v;
        double  maxrad2, d;
        int  nsflags;
        SPOT  theirspot, ourspot;
        register int  i;

        nsflags = source[sn].sflags | (SVIRTUAL|SSPOT|SFOLLOW);
                                        /* get object center and max. radius */
        maxrad2 = getdisk(ocent, op, sn);
        if (maxrad2 <= FTINY)                   /* too small? */
                return(-1);
                                        /* get location and spot */
        if (source[sn].sflags & SDISTANT) {             /* distant source */
                if (source[sn].sflags & SPROX)
                        return(-1);             /* should never get here! */
                multv3(nsloc, source[sn].sloc, pm);
                VCOPY(ourspot.aim, ocent);
                ourspot.siz = PI*maxrad2;
                ourspot.flen = 0.;
                if (source[sn].sflags & SSPOT) {
                        copystruct(&theirspot, source[sn].sl.s);
                        multp3(theirspot.aim, source[sn].sl.s->aim, pm);
                        d = ourspot.siz;
                        if (!commonbeam(&ourspot, &theirspot, nsloc))
                                return(-1);     /* no overlap */
                        if (ourspot.siz < d-FTINY) {    /* it shrunk */
                                d = beamdisk(v, op, &ourspot, nsloc);
                                if (d <= FTINY)
                                        return(-1);
                                if (d < maxrad2) {
                                        maxrad2 = d;
                                        VCOPY(ocent, v);
                                }
                        }
                }
        } else {                                /* local source */
                multp3(nsloc, source[sn].sloc, pm);
                for (i = 0; i < 3; i++)
                        ourspot.aim[i] = ocent[i] - nsloc[i];
                if ((d = normalize(ourspot.aim)) == 0.)
                        return(-1);             /* at source!! */
                if (source[sn].sflags & SPROX && d > source[sn].sl.prox)
                        return(-1);             /* too far away */
                ourspot.flen = 0.;
                if (d*d > maxrad2)
                        ourspot.siz = 2.*PI*(1. - sqrt(1.-maxrad2/(d*d)));
                else
                        nsflags &= ~SSPOT;
                if (source[sn].sflags & SSPOT) {
                        copystruct(&theirspot, source[sn].sl.s);
                        multv3(theirspot.aim, source[sn].sl.s->aim, pm);
                        if (nsflags & SSPOT) {
                                ourspot.flen = theirspot.flen;
                                d = ourspot.siz;
                                if (!commonspot(&ourspot, &theirspot, nsloc))
                                        return(-1);     /* no overlap */
                        } else {
                                nsflags |= SSPOT;
                                copystruct(&ourspot, &theirspot);
                                d = 2.*ourspot.siz;
                        }
                        if (ourspot.siz < d-FTINY) {    /* it shrunk */
                                d = spotdisk(v, op, &ourspot, nsloc);
                                if (d <= FTINY)
                                        return(-1);
                                if (d < maxrad2) {
                                        maxrad2 = d;
                                        VCOPY(ocent, v);
                                }
                        }
                }
                if (source[sn].sflags & SFLAT) {        /* behind source? */
                        multv3(nsnorm, source[sn].snorm, pm);
                        if (!checkspot(&ourspot, nsnorm))
                                return(-1);
                }
        }
                                        /* pretest visibility */
        nsflags = vstestvis(nsflags, op, ocent, maxrad2, sn);
        if (nsflags & SSKIP)
                return(-1);     /* obstructed */
                                        /* it all checks out, so make it */
        if ((i = newsource()) < 0)
                goto memerr;
        source[i].sflags = nsflags;
        VCOPY(source[i].sloc, nsloc);
        if (nsflags & SFLAT)
                VCOPY(source[i].snorm, nsnorm);
        source[i].ss = source[sn].ss; source[i].ss2 = source[sn].ss2;
        if (nsflags & SSPOT) {
                if ((source[i].sl.s = (SPOT *)malloc(sizeof(SPOT))) == NULL)
                        goto memerr;
                copystruct(source[i].sl.s, &ourspot);
        }
        if (nsflags & SPROX)
                source[i].sl.prox = source[sn].sl.prox;
        source[i].sa.svnext = sn;
        source[i].so = op;
        return(i);
memerr:
        error(SYSTEM, "out of memory in makevsrc");
}


double
getdisk(oc, op, sn)             /* get visible object disk */
FVECT  oc;
OBJREC  *op;
register int  sn;
{
        double  rad2, roffs, offs, d, rd, rdoto;
        FVECT  rnrm, nrm;
                                /* first, use object getdisk function */
        rad2 = getmaxdisk(oc, op);
        if (!(source[sn].sflags & SVIRTUAL))
                return(rad2);           /* all done for normal source */
                                /* check for correct side of relay surface */
        roffs = getplaneq(rnrm, source[sn].so);
        rd = DOT(rnrm, source[sn].sloc);        /* source projection */
        if (!(source[sn].sflags & SDISTANT))
                rd -= roffs;
        d = DOT(rnrm, oc) - roffs;      /* disk distance to relay plane */
        if ((d > 0.) ^ (rd > 0.))
                return(rad2);           /* OK if opposite sides */
        if (d*d >= rad2)
                return(0.);             /* no relay is possible */
                                /* we need a closer look */
        offs = getplaneq(nrm, op);
        rdoto = DOT(rnrm, nrm);
        if (d*d >= rad2*(1.-rdoto*rdoto))
                return(0.);             /* disk entirely on projection side */
                                /* should shrink disk but I'm lazy */
        return(rad2);
}


int
vstestvis(f, o, oc, or2, sn)            /* pretest source visibility */
int  f;                 /* virtual source flags */
OBJREC  *o;             /* relay object */
FVECT  oc;              /* relay object center */
double  or2;            /* relay object radius squared */
register int  sn;       /* target source number */
{
        RAY  sr;
        FVECT  onorm;
        FVECT  offsdir;
        double  or, d;
        int  infront;
        int  ssn;
        int  nhit, nok;
        register int  i, n;
                                /* return if pretesting disabled */
        if (vspretest <= 0)
                return(f);
                                /* get surface normal */
        getplaneq(onorm, o);
                                /* set number of rays to sample */
        if (source[sn].sflags & SDISTANT) {
                n = (2./3.*PI*PI)*or2/(thescene.cusize*thescene.cusize)*
                                vspretest + .5;
                infront = DOT(onorm, source[sn].sloc) > 0.;
        } else {
                for (i = 0; i < 3; i++)
                        offsdir[i] = source[sn].sloc[i] - oc[i];
                n = or2/DOT(offsdir,offsdir)*vspretest + .5;
                infront = DOT(onorm, offsdir) > 0.;
        }
        if (n < MINSAMPLES) n = MINSAMPLES;
#ifdef DEBUG
        fprintf(stderr, "pretesting source %d in object %s with %d rays\n",
                        sn, o->oname, n);
#endif
                                /* sample */
        or = sqrt(or2);
        ssn = STESTMAX*n;
        nhit = nok = 0;
        while (n-- > 0) {
                                        /* get sample point */
                do {
                        if (--ssn < 0) {
#ifdef DEBUG
                                fprintf(stderr, "\ttoo hard to hit\n");
#endif
                                return(f);      /* too small a target! */
                        }
                        for (i = 0; i < 3; i++)
                                offsdir[i] = or*(1. -
                                                2.*urand(931*i+5827+ssn));
                        for (i = 0; i < 3; i++)
                                sr.rorg[i] = oc[i] + offsdir[i];
                        d = DOT(offsdir,onorm);
                        if (infront)
                                for (i = 0; i < 3; i++) {
                                        sr.rorg[i] -= (d-.0001)*onorm[i];
                                        sr.rdir[i] = -onorm[i];
                                }
                        else
                                for (i = 0; i < 3; i++) {
                                        sr.rorg[i] -= (d+.0001)*onorm[i];
                                        sr.rdir[i] = onorm[i];
                                }
                        rayorigin(&sr, NULL, PRIMARY, 1.0);
                } while (!(*ofun[o->otype].funp)(o, &sr));
                                        /* check against source */
                samplendx++;
                if (srcray(&sr, NULL, sn) == 0.)
                        continue;
                sr.revf = srcvalue;
                rayvalue(&sr);
                if (bright(sr.rcol) <= FTINY)
                        continue;
                nok++;
                                        /* check against obstructions */
                srcray(&sr, NULL, sn);
                rayvalue(&sr);
                if (bright(sr.rcol) > FTINY)
                        nhit++;
                if (nhit > 0 && nhit < nok) {
#ifdef DEBUG
                        fprintf(stderr, "\tpartially occluded\n");
#endif
                        return(f);              /* need to shadow test */
                }
        }
        if (nhit == 0) {
#ifdef DEBUG
                fprintf(stderr, "\t0%% hit rate\n");
#endif
                return(f | SSKIP);      /* 0% hit rate:  totally occluded */
        }
#ifdef DEBUG
        fprintf(stderr, "\t100%% hit rate\n");
#endif
        return(f & ~SFOLLOW);           /* 100% hit rate:  no occlusion */
}
        

#ifdef DEBUG
virtverb(sn, fp)        /* print verbose description of virtual source */
register int  sn;
FILE  *fp;
{
        register int  i;

        fprintf(fp, "%s virtual source %d in %s %s\n",
                        source[sn].sflags & SDISTANT ? "distant" : "local",
                        sn, ofun[source[sn].so->otype].funame,
                        source[sn].so->oname);
        fprintf(fp, "\tat (%f,%f,%f)\n",
                source[sn].sloc[0], source[sn].sloc[1], source[sn].sloc[2]);
        fprintf(fp, "\tlinked to source %d (%s)\n",
                source[sn].sa.svnext, source[source[sn].sa.svnext].so->oname);
        if (source[sn].sflags & SFOLLOW)
                fprintf(fp, "\talways followed\n");
        else
                fprintf(fp, "\tnever followed\n");
        if (!(source[sn].sflags & SSPOT))
                return;
        fprintf(fp, "\twith spot aim (%f,%f,%f) and size %f\n",
                        source[sn].sl.s->aim[0], source[sn].sl.s->aim[1],
                        source[sn].sl.s->aim[2], source[sn].sl.s->siz);
}
#endif
Revision:	1.14
Committed:	Wed Jun 26 11:54:43 1991 UTC (34 years, 4 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 1.13:	+19 -8 lines
Log Message:	fixed bug in solid angle determination for local 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			* Routines for simulating virtual light sources
9			* Thus far, we only support planar mirrors.
10			*/
11
12			#include "ray.h"
13
14	greg	1.7	#include "octree.h"
15
16	greg	1.3	#include "otypes.h"
17
18	greg	1.1	#include "source.h"
19
20	greg	1.7	#include "random.h"
21	greg	1.1
22	greg	1.13	#define MINSAMPLES 3 /* minimum number of pretest samples */
23			#define STESTMAX 30 /* maximum seeks per sample */
24	greg	1.1
25	greg	1.13
26	greg	1.7	double getdisk();
27
28	greg	1.1	static OBJECT vobject; / virtual source objects */
29			static int nvobjects = 0; /* number of virtual source objects */
30
31
32			markvirtuals() /* find and mark virtual sources */
33			{
34			register OBJREC *o;
35			register int i;
36			/* check number of direct relays */
37			if (directrelay <= 0)
38			return;
39			/* find virtual source objects */
40			for (i = 0; i < nobjects; i++) {
41			o = objptr(i);
42	greg	1.3	if (!issurface(o->otype) \|\| o->omod == OVOID)
43	greg	1.1	continue;
44			if (!isvlight(objptr(o->omod)->otype))
45			continue;
46	greg	1.3	if (sfun[o->otype].of == NULL \|\|
47			sfun[o->otype].of->getpleq == NULL)
48			objerror(o, USER, "illegal material");
49	greg	1.1	if (nvobjects == 0)
50			vobject = (OBJECT *)malloc(sizeof(OBJECT));
51			else
52			vobject = (OBJECT )realloc((char )vobject,
53			(unsigned)(nvobjects+1)*sizeof(OBJECT));
54			if (vobject == NULL)
55			error(SYSTEM, "out of memory in addvirtuals");
56			vobject[nvobjects++] = i;
57			}
58			if (nvobjects == 0)
59			return;
60	greg	1.4	#ifdef DEBUG
61			fprintf(stderr, "found %d virtual source objects\n", nvobjects);
62			#endif
63	greg	1.1	/* append virtual sources */
64			for (i = nsources; i-- > 0; )
65	greg	1.7	addvirtuals(i, directrelay);
66	greg	1.1	/* done with our object list */
67			free((char *)vobject);
68			nvobjects = 0;
69			}
70
71
72	greg	1.4	addvirtuals(sn, nr) /* add virtuals associated with source */
73			int sn;
74	greg	1.1	int nr;
75			{
76			register int i;
77			/* check relay limit first */
78			if (nr <= 0)
79			return;
80	greg	1.7	if (source[sn].sflags & SSKIP)
81			return;
82	greg	1.1	/* check each virtual object for projection */
83			for (i = 0; i < nvobjects; i++)
84	greg	1.3	/* vproject() calls us recursively */
85	greg	1.4	vproject(objptr(vobject[i]), sn, nr-1);
86	greg	1.1	}
87
88
89	greg	1.4	vproject(o, sn, n) /* create projected source(s) if they exist */
90	greg	1.3	OBJREC *o;
91	greg	1.4	int sn;
92	greg	1.3	int n;
93			{
94			register int i;
95			register VSMATERIAL *vsmat;
96			MAT4 proj;
97	greg	1.4	int ns;
98
99			if (o == source[sn].so) /* objects cannot project themselves */
100			return;
101	greg	1.3	/* get virtual source material */
102			vsmat = sfun[objptr(o->omod)->otype].mf;
103			/* project virtual sources */
104			for (i = 0; i < vsmat->nproj; i++)
105	greg	1.4	if ((*vsmat->vproj)(proj, o, &source[sn], i))
106			if ((ns = makevsrc(o, sn, proj)) >= 0) {
107			#ifdef DEBUG
108	greg	1.6	virtverb(ns, stderr);
109	greg	1.4	#endif
110	greg	1.3	addvirtuals(ns, n);
111	greg	1.4	}
112	greg	1.3	}
113
114
115	greg	1.4	int
116			makevsrc(op, sn, pm) /* make virtual source if reasonable */
117	greg	1.1	OBJREC *op;
118	greg	1.4	register int sn;
119	greg	1.1	MAT4 pm;
120			{
121	greg	1.9	FVECT nsloc, nsnorm, ocent, v;
122			double maxrad2, d;
123	greg	1.3	int nsflags;
124	greg	1.1	SPOT theirspot, ourspot;
125			register int i;
126	greg	1.3
127	greg	1.6	nsflags = source[sn].sflags \| (SVIRTUAL\|SSPOT\|SFOLLOW);
128	greg	1.1	/* get object center and max. radius */
129	greg	1.6	maxrad2 = getdisk(ocent, op, sn);
130			if (maxrad2 <= FTINY) /* too small? */
131			return(-1);
132	greg	1.1	/* get location and spot */
133	greg	1.4	if (source[sn].sflags & SDISTANT) { /* distant source */
134			if (source[sn].sflags & SPROX)
135	greg	1.5	return(-1); /* should never get here! */
136	greg	1.4	multv3(nsloc, source[sn].sloc, pm);
137	greg	1.6	VCOPY(ourspot.aim, ocent);
138			ourspot.siz = PI*maxrad2;
139			ourspot.flen = 0.;
140	greg	1.4	if (source[sn].sflags & SSPOT) {
141			copystruct(&theirspot, source[sn].sl.s);
142			multp3(theirspot.aim, source[sn].sl.s->aim, pm);
143	greg	1.9	d = ourspot.siz;
144	greg	1.6	if (!commonbeam(&ourspot, &theirspot, nsloc))
145	greg	1.9	return(-1); /* no overlap */
146			if (ourspot.siz < d-FTINY) { /* it shrunk */
147			d = beamdisk(v, op, &ourspot, nsloc);
148			if (d <= FTINY)
149			return(-1);
150			if (d < maxrad2) {
151			maxrad2 = d;
152			VCOPY(ocent, v);
153			}
154			}
155	greg	1.1	}
156			} else { /* local source */
157	greg	1.4	multp3(nsloc, source[sn].sloc, pm);
158	greg	1.6	for (i = 0; i < 3; i++)
159			ourspot.aim[i] = ocent[i] - nsloc[i];
160	greg	1.9	if ((d = normalize(ourspot.aim)) == 0.)
161	greg	1.6	return(-1); /* at source!! */
162	greg	1.9	if (source[sn].sflags & SPROX && d > source[sn].sl.prox)
163	greg	1.6	return(-1); /* too far away */
164			ourspot.flen = 0.;
165	greg	1.14	if (d*d > maxrad2)
166			ourspot.siz = 2.PI(1. - sqrt(1.-maxrad2/(d*d)));
167			else
168			nsflags &= ~SSPOT;
169	greg	1.4	if (source[sn].sflags & SSPOT) {
170			copystruct(&theirspot, source[sn].sl.s);
171			multv3(theirspot.aim, source[sn].sl.s->aim, pm);
172	greg	1.14	if (nsflags & SSPOT) {
173			ourspot.flen = theirspot.flen;
174			d = ourspot.siz;
175			if (!commonspot(&ourspot, &theirspot, nsloc))
176			return(-1); /* no overlap */
177			} else {
178			nsflags \|= SSPOT;
179			copystruct(&ourspot, &theirspot);
180			d = 2.*ourspot.siz;
181			}
182	greg	1.9	if (ourspot.siz < d-FTINY) { /* it shrunk */
183			d = spotdisk(v, op, &ourspot, nsloc);
184			if (d <= FTINY)
185			return(-1);
186			if (d < maxrad2) {
187			maxrad2 = d;
188			VCOPY(ocent, v);
189			}
190			}
191	greg	1.1	}
192	greg	1.4	if (source[sn].sflags & SFLAT) { /* behind source? */
193			multv3(nsnorm, source[sn].snorm, pm);
194	greg	1.12	if (!checkspot(&ourspot, nsnorm))
195	greg	1.5	return(-1);
196	greg	1.1	}
197			}
198	greg	1.7	/* pretest visibility */
199			nsflags = vstestvis(nsflags, op, ocent, maxrad2, sn);
200			if (nsflags & SSKIP)
201			return(-1); /* obstructed */
202			/* it all checks out, so make it */
203	greg	1.6	if ((i = newsource()) < 0)
204	greg	1.1	goto memerr;
205	greg	1.6	source[i].sflags = nsflags;
206			VCOPY(source[i].sloc, nsloc);
207	greg	1.3	if (nsflags & SFLAT)
208	greg	1.6	VCOPY(source[i].snorm, nsnorm);
209			source[i].ss = source[sn].ss; source[i].ss2 = source[sn].ss2;
210	greg	1.14	if (nsflags & SSPOT) {
211			if ((source[i].sl.s = (SPOT *)malloc(sizeof(SPOT))) == NULL)
212			goto memerr;
213			copystruct(source[i].sl.s, &ourspot);
214			}
215	greg	1.3	if (nsflags & SPROX)
216	greg	1.6	source[i].sl.prox = source[sn].sl.prox;
217			source[i].sa.svnext = sn;
218			source[i].so = op;
219			return(i);
220	greg	1.1	memerr:
221			error(SYSTEM, "out of memory in makevsrc");
222			}
223
224
225	greg	1.6	double
226			getdisk(oc, op, sn) /* get visible object disk */
227			FVECT oc;
228			OBJREC *op;
229			register int sn;
230			{
231			double rad2, roffs, offs, d, rd, rdoto;
232			FVECT rnrm, nrm;
233			/* first, use object getdisk function */
234	greg	1.9	rad2 = getmaxdisk(oc, op);
235	greg	1.6	if (!(source[sn].sflags & SVIRTUAL))
236			return(rad2); /* all done for normal source */
237			/* check for correct side of relay surface */
238	greg	1.9	roffs = getplaneq(rnrm, source[sn].so);
239	greg	1.6	rd = DOT(rnrm, source[sn].sloc); /* source projection */
240			if (!(source[sn].sflags & SDISTANT))
241			rd -= roffs;
242			d = DOT(rnrm, oc) - roffs; /* disk distance to relay plane */
243			if ((d > 0.) ^ (rd > 0.))
244			return(rad2); /* OK if opposite sides */
245			if (d*d >= rad2)
246	greg	1.9	return(0.); /* no relay is possible */
247	greg	1.6	/* we need a closer look */
248	greg	1.9	offs = getplaneq(nrm, op);
249	greg	1.6	rdoto = DOT(rnrm, nrm);
250			if (dd >= rad2(1.-rdoto*rdoto))
251			return(0.); /* disk entirely on projection side */
252			/* should shrink disk but I'm lazy */
253			return(rad2);
254			}
255
256
257	greg	1.7	int
258			vstestvis(f, o, oc, or2, sn) /* pretest source visibility */
259			int f; /* virtual source flags */
260			OBJREC o; / relay object */
261			FVECT oc; /* relay object center */
262			double or2; /* relay object radius squared */
263			register int sn; /* target source number */
264	greg	1.1	{
265	greg	1.7	RAY sr;
266			FVECT onorm;
267			FVECT offsdir;
268			double or, d;
269	greg	1.8	int infront;
270			int ssn;
271	greg	1.11	int nhit, nok;
272	greg	1.7	register int i, n;
273			/* return if pretesting disabled */
274			if (vspretest <= 0)
275			return(f);
276			/* get surface normal */
277	greg	1.9	getplaneq(onorm, o);
278	greg	1.7	/* set number of rays to sample */
279	greg	1.8	if (source[sn].sflags & SDISTANT) {
280	greg	1.7	n = (2./3.PIPI)or2/(thescene.cusizethescene.cusize)*
281			vspretest + .5;
282	greg	1.8	infront = DOT(onorm, source[sn].sloc) > 0.;
283			} else {
284			for (i = 0; i < 3; i++)
285			offsdir[i] = source[sn].sloc[i] - oc[i];
286	greg	1.9	n = or2/DOT(offsdir,offsdir)*vspretest + .5;
287	greg	1.8	infront = DOT(onorm, offsdir) > 0.;
288			}
289	greg	1.13	if (n < MINSAMPLES) n = MINSAMPLES;
290	greg	1.9	#ifdef DEBUG
291			fprintf(stderr, "pretesting source %d in object %s with %d rays\n",
292			sn, o->oname, n);
293			#endif
294	greg	1.7	/* sample */
295	greg	1.8	or = sqrt(or2);
296	greg	1.13	ssn = STESTMAX*n;
297	greg	1.11	nhit = nok = 0;
298	greg	1.7	while (n-- > 0) {
299	greg	1.8	/* get sample point */
300			do {
301	greg	1.9	if (--ssn < 0) {
302			#ifdef DEBUG
303			fprintf(stderr, "\ttoo hard to hit\n");
304			#endif
305	greg	1.8	return(f); /* too small a target! */
306	greg	1.9	}
307	greg	1.8	for (i = 0; i < 3; i++)
308			offsdir[i] = or*(1. -
309			2.urand(931i+5827+ssn));
310			for (i = 0; i < 3; i++)
311			sr.rorg[i] = oc[i] + offsdir[i];
312			d = DOT(offsdir,onorm);
313			if (infront)
314			for (i = 0; i < 3; i++) {
315			sr.rorg[i] -= (d-.0001)*onorm[i];
316			sr.rdir[i] = -onorm[i];
317			}
318			else
319			for (i = 0; i < 3; i++) {
320			sr.rorg[i] -= (d+.0001)*onorm[i];
321			sr.rdir[i] = onorm[i];
322			}
323			rayorigin(&sr, NULL, PRIMARY, 1.0);
324			} while (!(*ofun[o->otype].funp)(o, &sr));
325			/* check against source */
326	greg	1.7	samplendx++;
327	greg	1.9	if (srcray(&sr, NULL, sn) == 0.)
328	greg	1.7	continue;
329			sr.revf = srcvalue;
330			rayvalue(&sr);
331			if (bright(sr.rcol) <= FTINY)
332			continue;
333	greg	1.11	nok++;
334	greg	1.7	/* check against obstructions */
335			srcray(&sr, NULL, sn);
336			rayvalue(&sr);
337	greg	1.11	if (bright(sr.rcol) > FTINY)
338			nhit++;
339			if (nhit > 0 && nhit < nok) {
340	greg	1.9	#ifdef DEBUG
341	greg	1.11	fprintf(stderr, "\tpartially occluded\n");
342	greg	1.9	#endif
343	greg	1.11	return(f); /* need to shadow test */
344			}
345	greg	1.1	}
346	greg	1.9	if (nhit == 0) {
347			#ifdef DEBUG
348			fprintf(stderr, "\t0%% hit rate\n");
349			#endif
350	greg	1.7	return(f \| SSKIP); /* 0% hit rate: totally occluded */
351	greg	1.9	}
352			#ifdef DEBUG
353			fprintf(stderr, "\t100%% hit rate\n");
354			#endif
355			return(f & ~SFOLLOW); /* 100% hit rate: no occlusion */
356	greg	1.1	}
357	greg	1.7
358	greg	1.4
359			#ifdef DEBUG
360	greg	1.6	virtverb(sn, fp) /* print verbose description of virtual source */
361			register int sn;
362	greg	1.4	FILE *fp;
363			{
364			register int i;
365
366			fprintf(fp, "%s virtual source %d in %s %s\n",
367	greg	1.6	source[sn].sflags & SDISTANT ? "distant" : "local",
368			sn, ofun[source[sn].so->otype].funame,
369			source[sn].so->oname);
370	greg	1.4	fprintf(fp, "\tat (%f,%f,%f)\n",
371	greg	1.6	source[sn].sloc[0], source[sn].sloc[1], source[sn].sloc[2]);
372	greg	1.4	fprintf(fp, "\tlinked to source %d (%s)\n",
373	greg	1.6	source[sn].sa.svnext, source[source[sn].sa.svnext].so->oname);
374			if (source[sn].sflags & SFOLLOW)
375	greg	1.4	fprintf(fp, "\talways followed\n");
376			else
377			fprintf(fp, "\tnever followed\n");
378	greg	1.6	if (!(source[sn].sflags & SSPOT))
379	greg	1.4	return;
380			fprintf(fp, "\twith spot aim (%f,%f,%f) and size %f\n",
381	greg	1.6	source[sn].sl.s->aim[0], source[sn].sl.s->aim[1],
382			source[sn].sl.s->aim[2], source[sn].sl.s->siz);
383	greg	1.4	}
384			#endif