src/rt/srcsupp.c

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

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

/*
 *  Support routines for source objects and materials
 */

#include  "ray.h"

#include  "otypes.h"

#include  "source.h"

#include  "cone.h"

#include  "face.h"


SRCREC  *source = NULL;                 /* our list of sources */
int  nsources = 0;                      /* the number of sources */

SRCFUNC  sfun[NUMOTYPE];                /* source dispatch table */


initstypes()                    /* initialize source dispatch table */
{
        extern VSMATERIAL  mirror_vs;
        extern int  fsetsrc(), ssetsrc(), sphsetsrc(), rsetsrc();
        extern double  fgetplaneq(), rgetplaneq();
        extern double  fgetmaxdisk(), rgetmaxdisk();
        static SOBJECT  fsobj = {fsetsrc, fgetplaneq, fgetmaxdisk};
        static SOBJECT  ssobj = {ssetsrc};
        static SOBJECT  sphsobj = {sphsetsrc};
        static SOBJECT  rsobj = {rsetsrc, rgetplaneq, rgetmaxdisk};

        sfun[MAT_MIRROR].mf = &mirror_vs;
        sfun[OBJ_FACE].of = &fsobj;
        sfun[OBJ_SOURCE].of = &ssobj;
        sfun[OBJ_SPHERE].of = &sphsobj;
        sfun[OBJ_RING].of = &rsobj;
}


int
newsource()                     /* allocate new source in our array */
{
        if (nsources == 0)
                source = (SRCREC *)malloc(sizeof(SRCREC));
        else
                source = (SRCREC *)realloc((char *)source,
                                (unsigned)(nsources+1)*sizeof(SRCREC));
        if (source == NULL)
                return(-1);
        source[nsources].sflags = 0;
        source[nsources].nhits = 1;
        source[nsources].ntests = 2;    /* initial hit probability = 1/2 */
        return(nsources++);
}


fsetsrc(src, so)                        /* set a face as a source */
register SRCREC  *src;
OBJREC  *so;
{
        register FACE  *f;
        register int  i, j;
        
        src->sa.success = 2*AIMREQT-1;          /* bitch on second failure */
        src->so = so;
                                                /* get the face */
        f = getface(so);
                                                /* find the center */
        for (j = 0; j < 3; j++) {
                src->sloc[j] = 0.0;
                for (i = 0; i < f->nv; i++)
                        src->sloc[j] += VERTEX(f,i)[j];
                src->sloc[j] /= (double)f->nv;
        }
        if (!inface(src->sloc, f))
                objerror(so, USER, "cannot hit center");
        src->sflags |= SFLAT;
        VCOPY(src->snorm, f->norm);
        src->ss = sqrt(f->area / PI);
        src->ss2 = f->area;
}


ssetsrc(src, so)                        /* set a source as a source */
register SRCREC  *src;
register OBJREC  *so;
{
        double  theta;
        
        src->sa.success = 2*AIMREQT-1;          /* bitch on second failure */
        src->so = so;
        if (so->oargs.nfargs != 4)
                objerror(so, USER, "bad arguments");
        src->sflags |= SDISTANT;
        VCOPY(src->sloc, so->oargs.farg);
        if (normalize(src->sloc) == 0.0)
                objerror(so, USER, "zero direction");
        theta = PI/180.0/2.0 * so->oargs.farg[3];
        if (theta <= FTINY)
                objerror(so, USER, "zero size");
        src->ss = theta >= PI/4 ? 1.0 : tan(theta);
        src->ss2 = 2.0*PI * (1.0 - cos(theta));
}


sphsetsrc(src, so)                      /* set a sphere as a source */
register SRCREC  *src;
register OBJREC  *so;
{
        src->sa.success = 2*AIMREQT-1;          /* bitch on second failure */
        src->so = so;
        if (so->oargs.nfargs != 4)
                objerror(so, USER, "bad # arguments");
        if (so->oargs.farg[3] <= FTINY)
                objerror(so, USER, "illegal radius");
        VCOPY(src->sloc, so->oargs.farg);
        src->ss = so->oargs.farg[3];
        src->ss2 = PI * src->ss * src->ss;
}


rsetsrc(src, so)                        /* set a ring (disk) as a source */
register SRCREC  *src;
OBJREC  *so;
{
        register CONE  *co;
        
        src->sa.success = 2*AIMREQT-1;          /* bitch on second failure */
        src->so = so;
                                                /* get the ring */
        co = getcone(so, 0);
        VCOPY(src->sloc, CO_P0(co));
        if (CO_R0(co) > 0.0)
                objerror(so, USER, "cannot hit center");
        src->sflags |= SFLAT;
        VCOPY(src->snorm, co->ad);
        src->ss = CO_R1(co);
        src->ss2 = PI * src->ss * src->ss;
}


SPOT *
makespot(m)                     /* make a spotlight */
register OBJREC  *m;
{
        register SPOT  *ns;

        if ((ns = (SPOT *)malloc(sizeof(SPOT))) == NULL)
                return(NULL);
        ns->siz = 2.0*PI * (1.0 - cos(PI/180.0/2.0 * m->oargs.farg[3]));
        VCOPY(ns->aim, m->oargs.farg+4);
        if ((ns->flen = normalize(ns->aim)) == 0.0)
                objerror(m, USER, "zero focus vector");
        return(ns);
}


double
fgetmaxdisk(ocent, op)          /* get center and squared radius of face */
FVECT  ocent;
OBJREC  *op;
{
        double  maxrad2;
        double  d2;
        register int  i, j;
        register FACE  *f;
        
        f = getface(op);
        for (i = 0; i < 3; i++) {
                ocent[i] = 0.;
                for (j = 0; j < f->nv; j++)
                        ocent[i] += VERTEX(f,j)[i];
                ocent[i] /= (double)f->nv;
        }
        if (f->area == 0.)
                return(0.);
        maxrad2 = 0.;
        for (j = 0; j < f->nv; j++) {
                d2 = dist2(VERTEX(f,j), ocent);
                if (d2 > maxrad2)
                        maxrad2 = d2;
        }
        return(maxrad2);
}


double
rgetmaxdisk(ocent, op)          /* get center and squared radius of ring */
FVECT  ocent;
OBJREC  *op;
{
        register CONE  *co;
        
        co = getcone(op, 0);
        VCOPY(ocent, CO_P0(co));
        return(CO_R1(co)*CO_R1(co));
}


double
fgetplaneq(nvec, op)                    /* get plane equation for face */
FVECT  nvec;
OBJREC  *op;
{
        register FACE  *fo;

        fo = getface(op);
        VCOPY(nvec, fo->norm);
        return(fo->offset);
}


double
rgetplaneq(nvec, op)                    /* get plane equation for ring */
FVECT  nvec;
OBJREC  *op;
{
        register CONE  *co;

        co = getcone(op, 0);
        VCOPY(nvec, co->ad);
        return(DOT(nvec, CO_P0(co)));
}


commonspot(sp1, sp2, org)       /* set sp1 to intersection of sp1 and sp2 */
register SPOT  *sp1, *sp2;
FVECT  org;
{
        FVECT  cent;
        double  rad2, cos1, cos2;

        cos1 = 1. - sp1->siz/(2.*PI);
        cos2 = 1. - sp2->siz/(2.*PI);
        if (sp2->siz >= 2.*PI-FTINY)            /* BIG, just check overlap */
                return(DOT(sp1->aim,sp2->aim) >= cos1*cos2 -
                                        sqrt((1.-cos1*cos1)*(1.-cos2*cos2)));
                                /* compute and check disks */
        rad2 = intercircle(cent, sp1->aim, sp2->aim,
                        1./(cos1*cos1) - 1.,  1./(cos2*cos2) - 1.);
        if (rad2 <= FTINY || normalize(cent) == 0.)
                return(0);
        VCOPY(sp1->aim, cent);
        sp1->siz = 2.*PI*(1. - 1./sqrt(1.+rad2));
        return(1);
}


commonbeam(sp1, sp2, dir)       /* set sp1 to intersection of sp1 and sp2 */
register SPOT  *sp1, *sp2;
FVECT  dir;
{
        FVECT  cent, c1, c2;
        double  rad2, d;
        register int  i;
                                        /* move centers to common plane */
        d = DOT(sp1->aim, dir);
        for (i = 0; i < 3; i++)
                c1[i] = sp1->aim[i] - d*dir[i];
        d = DOT(sp2->aim, dir);
        for (i = 0; i < 3; i++)
                c2[i] = sp2->aim[i] - d*dir[i];
                                        /* compute overlap */
        rad2 = intercircle(cent, c1, c2, sp1->siz/PI, sp2->siz/PI);
        if (rad2 <= FTINY)
                return(0);
        VCOPY(sp1->aim, cent);
        sp1->siz = PI*rad2;
        return(1);
}


checkspot(sp, nrm)              /* check spotlight for behind source */
register SPOT  *sp;     /* spotlight */
FVECT  nrm;             /* source surface normal */
{
        double  d, d1;

        d = DOT(sp->aim, nrm);
        if (d > FTINY)                  /* center in front? */
                return(0);
                                        /* else check horizon */
        d1 = 1. - sp->siz/(2.*PI);
        return(1.-FTINY-d*d > d1*d1);
}


double
intercircle(cc, c1, c2, r1s, r2s)       /* intersect two circles */
FVECT  cc;                      /* midpoint (return value) */
FVECT  c1, c2;                  /* circle centers */
double  r1s, r2s;               /* radii squared */
{
        double  a2, d2, l;
        FVECT  disp;
        register int  i;

        for (i = 0; i < 3; i++)
                disp[i] = c2[i] - c1[i];
        d2 = DOT(disp,disp);
                                        /* circle within overlap? */
        if (r1s < r2s) {
                if (r2s >= r1s + d2) {
                        VCOPY(cc, c1);
                        return(r1s);
                }
        } else {
                if (r1s >= r2s + d2) {
                        VCOPY(cc, c2);
                        return(r2s);
                }
        }
        a2 = .25*(2.*(r1s+r2s) - d2 - (r2s-r1s)*(r2s-r1s)/d2);
                                        /* no overlap? */
        if (a2 <= 0.)
                return(0.);
                                        /* overlap, compute center */
        l = sqrt((r1s - a2)/d2);
        for (i = 0; i < 3; i++)
                cc[i] = c1[i] + l*disp[i];
        return(a2);
}


sourcehit(r)                    /* check to see if ray hit distant source */
register RAY  *r;
{
        int  first, last;
        register int  i;

        if (r->rsrc >= 0) {             /* check only one if aimed */
                first = last = r->rsrc;
        } else {                        /* otherwise check all */
                first = 0; last = nsources-1;
        }
        for (i = first; i <= last; i++)
                if (source[i].sflags & SDISTANT)
                        /*
                         * Check to see if ray is within
                         * solid angle of source.
                         */
                        if (2.0*PI * (1.0 - DOT(source[i].sloc,r->rdir))
                                        <= source[i].ss2) {
                                r->ro = source[i].so;
                                if (!(source[i].sflags & SSKIP))
                                        break;
                        }

        if (r->ro != NULL) {
                for (i = 0; i < 3; i++)
                        r->ron[i] = -r->rdir[i];
                r->rod = 1.0;
                r->rox = NULL;
                return(1);
        }
        return(0);
}


#define  wrongsource(m, r)      (m->otype!=MAT_ILLUM && \
                                r->rsrc>=0 && \
                                source[r->rsrc].so!=r->ro)

#define  badambient(m, r)       ((r->crtype&(AMBIENT|SHADOW))==AMBIENT && \
                                !(m->otype==MAT_GLOW&&r->rot>m->oargs.farg[3]))

#define  passillum(m, r)        (m->otype==MAT_ILLUM && \
                                !(r->rsrc>=0&&source[r->rsrc].so==r->ro))


m_light(m, r)                   /* ray hit a light source */
register OBJREC  *m;
register RAY  *r;
{
                                                /* check for over-counting */
        if (wrongsource(m, r) || badambient(m, r))
                return;
                                                /* check for passed illum */
        if (passillum(m, r)) {

                if (m->oargs.nsargs < 1 || !strcmp(m->oargs.sarg[0], VOIDID))
                        raytrans(r);
                else
                        rayshade(r, modifier(m->oargs.sarg[0]));

                                                /* otherwise treat as source */
        } else {
                                                /* check for behind */
                if (r->rod < 0.0)
                        return;
                                                /* get distribution pattern */
                raytexture(r, m->omod);
                                                /* get source color */
                setcolor(r->rcol, m->oargs.farg[0],
                                  m->oargs.farg[1],
                                  m->oargs.farg[2]);
                                                /* modify value */
                multcolor(r->rcol, r->pcol);
        }
}
Revision:	1.4
Committed:	Fri Jun 21 16:44:01 1991 UTC (32 years, 10 months ago) by greg
Content type:	text/plain
Branch:	MAIN
Changes since 1.3:	+99 -1 lines
Log Message:	moved some routines here from virtuals.c
#	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			* Support routines for source objects and materials
9			*/
10
11			#include "ray.h"
12
13			#include "otypes.h"
14
15			#include "source.h"
16
17			#include "cone.h"
18
19			#include "face.h"
20
21
22			SRCREC source = NULL; / our list of sources */
23			int nsources = 0; /* the number of sources */
24
25			SRCFUNC sfun[NUMOTYPE]; /* source dispatch table */
26
27
28			initstypes() /* initialize source dispatch table */
29			{
30			extern VSMATERIAL mirror_vs;
31			extern int fsetsrc(), ssetsrc(), sphsetsrc(), rsetsrc();
32			extern double fgetplaneq(), rgetplaneq();
33			extern double fgetmaxdisk(), rgetmaxdisk();
34			static SOBJECT fsobj = {fsetsrc, fgetplaneq, fgetmaxdisk};
35			static SOBJECT ssobj = {ssetsrc};
36			static SOBJECT sphsobj = {sphsetsrc};
37			static SOBJECT rsobj = {rsetsrc, rgetplaneq, rgetmaxdisk};
38
39			sfun[MAT_MIRROR].mf = &mirror_vs;
40			sfun[OBJ_FACE].of = &fsobj;
41			sfun[OBJ_SOURCE].of = &ssobj;
42			sfun[OBJ_SPHERE].of = &sphsobj;
43			sfun[OBJ_RING].of = &rsobj;
44			}
45
46
47	greg	1.2	int
48	greg	1.1	newsource() /* allocate new source in our array */
49			{
50			if (nsources == 0)
51			source = (SRCREC *)malloc(sizeof(SRCREC));
52			else
53			source = (SRCREC )realloc((char )source,
54			(unsigned)(nsources+1)*sizeof(SRCREC));
55			if (source == NULL)
56	greg	1.2	return(-1);
57	greg	1.1	source[nsources].sflags = 0;
58			source[nsources].nhits = 1;
59			source[nsources].ntests = 2; /* initial hit probability = 1/2 */
60	greg	1.2	return(nsources++);
61	greg	1.1	}
62
63
64			fsetsrc(src, so) /* set a face as a source */
65			register SRCREC *src;
66			OBJREC *so;
67			{
68			register FACE *f;
69			register int i, j;
70
71			src->sa.success = 2AIMREQT-1; / bitch on second failure */
72			src->so = so;
73			/* get the face */
74			f = getface(so);
75			/* find the center */
76			for (j = 0; j < 3; j++) {
77			src->sloc[j] = 0.0;
78			for (i = 0; i < f->nv; i++)
79			src->sloc[j] += VERTEX(f,i)[j];
80			src->sloc[j] /= (double)f->nv;
81			}
82			if (!inface(src->sloc, f))
83			objerror(so, USER, "cannot hit center");
84			src->sflags \|= SFLAT;
85			VCOPY(src->snorm, f->norm);
86			src->ss = sqrt(f->area / PI);
87			src->ss2 = f->area;
88			}
89
90
91			ssetsrc(src, so) /* set a source as a source */
92			register SRCREC *src;
93			register OBJREC *so;
94			{
95			double theta;
96
97			src->sa.success = 2AIMREQT-1; / bitch on second failure */
98			src->so = so;
99			if (so->oargs.nfargs != 4)
100			objerror(so, USER, "bad arguments");
101			src->sflags \|= SDISTANT;
102			VCOPY(src->sloc, so->oargs.farg);
103			if (normalize(src->sloc) == 0.0)
104			objerror(so, USER, "zero direction");
105			theta = PI/180.0/2.0 * so->oargs.farg[3];
106			if (theta <= FTINY)
107			objerror(so, USER, "zero size");
108			src->ss = theta >= PI/4 ? 1.0 : tan(theta);
109			src->ss2 = 2.0PI (1.0 - cos(theta));
110			}
111
112
113			sphsetsrc(src, so) /* set a sphere as a source */
114			register SRCREC *src;
115			register OBJREC *so;
116			{
117			src->sa.success = 2AIMREQT-1; / bitch on second failure */
118			src->so = so;
119			if (so->oargs.nfargs != 4)
120			objerror(so, USER, "bad # arguments");
121			if (so->oargs.farg[3] <= FTINY)
122			objerror(so, USER, "illegal radius");
123			VCOPY(src->sloc, so->oargs.farg);
124			src->ss = so->oargs.farg[3];
125			src->ss2 = PI * src->ss * src->ss;
126			}
127
128
129			rsetsrc(src, so) /* set a ring (disk) as a source */
130			register SRCREC *src;
131			OBJREC *so;
132			{
133			register CONE *co;
134
135			src->sa.success = 2AIMREQT-1; / bitch on second failure */
136			src->so = so;
137			/* get the ring */
138			co = getcone(so, 0);
139			VCOPY(src->sloc, CO_P0(co));
140			if (CO_R0(co) > 0.0)
141			objerror(so, USER, "cannot hit center");
142			src->sflags \|= SFLAT;
143			VCOPY(src->snorm, co->ad);
144			src->ss = CO_R1(co);
145			src->ss2 = PI * src->ss * src->ss;
146			}
147
148
149			SPOT *
150			makespot(m) /* make a spotlight */
151			register OBJREC *m;
152			{
153			register SPOT *ns;
154
155			if ((ns = (SPOT *)malloc(sizeof(SPOT))) == NULL)
156			return(NULL);
157			ns->siz = 2.0PI (1.0 - cos(PI/180.0/2.0 * m->oargs.farg[3]));
158			VCOPY(ns->aim, m->oargs.farg+4);
159			if ((ns->flen = normalize(ns->aim)) == 0.0)
160			objerror(m, USER, "zero focus vector");
161			return(ns);
162			}
163
164
165			double
166			fgetmaxdisk(ocent, op) /* get center and squared radius of face */
167			FVECT ocent;
168			OBJREC *op;
169			{
170			double maxrad2;
171			double d2;
172			register int i, j;
173			register FACE *f;
174
175			f = getface(op);
176			for (i = 0; i < 3; i++) {
177			ocent[i] = 0.;
178			for (j = 0; j < f->nv; j++)
179			ocent[i] += VERTEX(f,j)[i];
180			ocent[i] /= (double)f->nv;
181			}
182	greg	1.3	if (f->area == 0.)
183			return(0.);
184	greg	1.1	maxrad2 = 0.;
185			for (j = 0; j < f->nv; j++) {
186			d2 = dist2(VERTEX(f,j), ocent);
187			if (d2 > maxrad2)
188			maxrad2 = d2;
189			}
190			return(maxrad2);
191			}
192
193
194			double
195			rgetmaxdisk(ocent, op) /* get center and squared radius of ring */
196			FVECT ocent;
197			OBJREC *op;
198			{
199			register CONE *co;
200
201			co = getcone(op, 0);
202			VCOPY(ocent, CO_P0(co));
203			return(CO_R1(co)*CO_R1(co));
204			}
205
206
207			double
208			fgetplaneq(nvec, op) /* get plane equation for face */
209			FVECT nvec;
210			OBJREC *op;
211			{
212			register FACE *fo;
213
214			fo = getface(op);
215			VCOPY(nvec, fo->norm);
216			return(fo->offset);
217			}
218
219
220			double
221			rgetplaneq(nvec, op) /* get plane equation for ring */
222			FVECT nvec;
223			OBJREC *op;
224			{
225			register CONE *co;
226
227			co = getcone(op, 0);
228			VCOPY(nvec, co->ad);
229			return(DOT(nvec, CO_P0(co)));
230	greg	1.4	}
231
232
233			commonspot(sp1, sp2, org) /* set sp1 to intersection of sp1 and sp2 */
234			register SPOT sp1, sp2;
235			FVECT org;
236			{
237			FVECT cent;
238			double rad2, cos1, cos2;
239
240			cos1 = 1. - sp1->siz/(2.*PI);
241			cos2 = 1. - sp2->siz/(2.*PI);
242			if (sp2->siz >= 2.PI-FTINY) / BIG, just check overlap */
243			return(DOT(sp1->aim,sp2->aim) >= cos1*cos2 -
244			sqrt((1.-cos1cos1)(1.-cos2*cos2)));
245			/* compute and check disks */
246			rad2 = intercircle(cent, sp1->aim, sp2->aim,
247			1./(cos1cos1) - 1., 1./(cos2cos2) - 1.);
248			if (rad2 <= FTINY \|\| normalize(cent) == 0.)
249			return(0);
250			VCOPY(sp1->aim, cent);
251			sp1->siz = 2.PI(1. - 1./sqrt(1.+rad2));
252			return(1);
253			}
254
255
256			commonbeam(sp1, sp2, dir) /* set sp1 to intersection of sp1 and sp2 */
257			register SPOT sp1, sp2;
258			FVECT dir;
259			{
260			FVECT cent, c1, c2;
261			double rad2, d;
262			register int i;
263			/* move centers to common plane */
264			d = DOT(sp1->aim, dir);
265			for (i = 0; i < 3; i++)
266			c1[i] = sp1->aim[i] - d*dir[i];
267			d = DOT(sp2->aim, dir);
268			for (i = 0; i < 3; i++)
269			c2[i] = sp2->aim[i] - d*dir[i];
270			/* compute overlap */
271			rad2 = intercircle(cent, c1, c2, sp1->siz/PI, sp2->siz/PI);
272			if (rad2 <= FTINY)
273			return(0);
274			VCOPY(sp1->aim, cent);
275			sp1->siz = PI*rad2;
276			return(1);
277			}
278
279
280			checkspot(sp, nrm) /* check spotlight for behind source */
281			register SPOT sp; / spotlight */
282			FVECT nrm; /* source surface normal */
283			{
284			double d, d1;
285
286			d = DOT(sp->aim, nrm);
287			if (d > FTINY) /* center in front? */
288			return(0);
289			/* else check horizon */
290			d1 = 1. - sp->siz/(2.*PI);
291			return(1.-FTINY-dd > d1d1);
292			}
293
294
295			double
296			intercircle(cc, c1, c2, r1s, r2s) /* intersect two circles */
297			FVECT cc; /* midpoint (return value) */
298			FVECT c1, c2; /* circle centers */
299			double r1s, r2s; /* radii squared */
300			{
301			double a2, d2, l;
302			FVECT disp;
303			register int i;
304
305			for (i = 0; i < 3; i++)
306			disp[i] = c2[i] - c1[i];
307			d2 = DOT(disp,disp);
308			/* circle within overlap? */
309			if (r1s < r2s) {
310			if (r2s >= r1s + d2) {
311			VCOPY(cc, c1);
312			return(r1s);
313			}
314			} else {
315			if (r1s >= r2s + d2) {
316			VCOPY(cc, c2);
317			return(r2s);
318			}
319			}
320			a2 = .25(2.(r1s+r2s) - d2 - (r2s-r1s)*(r2s-r1s)/d2);
321			/* no overlap? */
322			if (a2 <= 0.)
323			return(0.);
324			/* overlap, compute center */
325			l = sqrt((r1s - a2)/d2);
326			for (i = 0; i < 3; i++)
327			cc[i] = c1[i] + l*disp[i];
328			return(a2);
329	greg	1.1	}
330
331
332			sourcehit(r) /* check to see if ray hit distant source */
333			register RAY *r;
334			{
335			int first, last;
336			register int i;
337
338			if (r->rsrc >= 0) { /* check only one if aimed */
339			first = last = r->rsrc;
340			} else { /* otherwise check all */
341			first = 0; last = nsources-1;
342			}
343			for (i = first; i <= last; i++)
344			if (source[i].sflags & SDISTANT)
345			/*
346			* Check to see if ray is within
347			* solid angle of source.
348			*/
349			if (2.0PI (1.0 - DOT(source[i].sloc,r->rdir))
350			<= source[i].ss2) {
351			r->ro = source[i].so;
352			if (!(source[i].sflags & SSKIP))
353			break;
354			}
355
356			if (r->ro != NULL) {
357			for (i = 0; i < 3; i++)
358			r->ron[i] = -r->rdir[i];
359			r->rod = 1.0;
360			r->rox = NULL;
361			return(1);
362			}
363			return(0);
364			}
365
366
367			#define wrongsource(m, r) (m->otype!=MAT_ILLUM && \
368			r->rsrc>=0 && \
369			source[r->rsrc].so!=r->ro)
370
371			#define badambient(m, r) ((r->crtype&(AMBIENT\|SHADOW))==AMBIENT && \
372			!(m->otype==MAT_GLOW&&r->rot>m->oargs.farg[3]))
373
374			#define passillum(m, r) (m->otype==MAT_ILLUM && \
375			!(r->rsrc>=0&&source[r->rsrc].so==r->ro))
376
377
378			m_light(m, r) /* ray hit a light source */
379			register OBJREC *m;
380			register RAY *r;
381			{
382			/* check for over-counting */
383			if (wrongsource(m, r) \|\| badambient(m, r))
384			return;
385			/* check for passed illum */
386			if (passillum(m, r)) {
387
388			if (m->oargs.nsargs < 1 \|\| !strcmp(m->oargs.sarg[0], VOIDID))
389			raytrans(r);
390			else
391			rayshade(r, modifier(m->oargs.sarg[0]));
392
393			/* otherwise treat as source */
394			} else {
395			/* check for behind */
396			if (r->rod < 0.0)
397			return;
398			/* get distribution pattern */
399			raytexture(r, m->omod);
400			/* get source color */
401			setcolor(r->rcol, m->oargs.farg[0],
402			m->oargs.farg[1],
403			m->oargs.farg[2]);
404			/* modify value */
405			multcolor(r->rcol, r->pcol);
406			}
407			}