--- ray/src/rt/source.c	1991/06/14 14:58:49	1.32
+++ ray/src/rt/source.c	1995/12/09 11:30:19	2.20
@@ -1,4 +1,4 @@
-/* Copyright (c) 1990 Regents of the University of California */
+/* Copyright (c) 1995 Regents of the University of California */
 
 #ifndef lint
 static char SCCSid[] = "$SunId$ LBL";
@@ -14,38 +14,49 @@ static char SCCSid[] = "$SunId$ LBL";
 
 #include  "octree.h"
 
-#include  "source.h"
-
 #include  "otypes.h"
 
-#include  "cone.h"
+#include  "source.h"
 
-#include  "face.h"
-
 #include  "random.h"
 
+extern double  ssampdist;		/* scatter sampling distance */
 
-extern double  dstrsrc;			/* source distribution amount */
-extern double  shadthresh;		/* relative shadow threshold */
-extern double  shadcert;		/* shadow testing certainty */
+/*
+ * Structures used by direct()
+ */
 
-SRCREC  *source = NULL;			/* our list of sources */
-int  nsources = 0;			/* the number of sources */
+typedef struct {
+	int  sno;		/* source number */
+	FVECT  dir;		/* source direction */
+	COLOR  coef;		/* material coefficient */
+	COLOR  val;		/* contribution */
+}  CONTRIB;		/* direct contribution */
 
+typedef struct {
+	int  sndx;		/* source index (to CONTRIB array) */
+	float  brt;		/* brightness (for comparison) */
+}  CNTPTR;		/* contribution pointer */
+
 static CONTRIB  *srccnt;		/* source contributions in direct() */
 static CNTPTR  *cntord;			/* source ordering in direct() */
+static int  maxcntr = 0;		/* size of contribution arrays */
 
 
 marksources()			/* find and mark source objects */
 {
+	int  foundsource = 0;
+	int  i;
 	register OBJREC  *o, *m;
-	register int  i;
-
+	register int  ns;
+					/* initialize dispatch table */
+	initstypes();
+					/* find direct sources */
 	for (i = 0; i < nobjects; i++) {
 	
 		o = objptr(i);
 
-		if (o->omod == OVOID)
+		if (!issurface(o->otype) || o->omod == OVOID)
 			continue;
 
 		m = objptr(o->omod);
@@ -61,205 +72,129 @@ marksources()			/* find and mark source objects */
 				o->otype != OBJ_SOURCE &&
 				m->oargs.farg[3] <= FTINY)
 			continue;			/* don't bother */
+		if (m->oargs.farg[0] <= FTINY && m->oargs.farg[1] <= FTINY &&
+				m->oargs.farg[2] <= FTINY)
+			continue;			/* don't bother */
 
-		if (source == NULL)
-			source = (SRCREC *)malloc(sizeof(SRCREC));
-		else
-			source = (SRCREC *)realloc((char *)source,
-					(unsigned)(nsources+1)*sizeof(SRCREC));
-		if (source == NULL)
+		if (sfun[o->otype].of == NULL ||
+				sfun[o->otype].of->setsrc == NULL)
+			objerror(o, USER, "illegal material");
+
+		if ((ns = newsource()) < 0)
 			goto memerr;
 
-		newsource(&source[nsources], o);
+		setsource(&source[ns], o);
 
 		if (m->otype == MAT_GLOW) {
-			source[nsources].sflags |= SPROX;
-			source[nsources].sl.prox = m->oargs.farg[3];
-			if (o->otype == OBJ_SOURCE)
-				source[nsources].sflags |= SSKIP;
+			source[ns].sflags |= SPROX;
+			source[ns].sl.prox = m->oargs.farg[3];
+			if (source[ns].sflags & SDISTANT)
+				source[ns].sflags |= SSKIP;
 		} else if (m->otype == MAT_SPOT) {
-			source[nsources].sflags |= SSPOT;
-			source[nsources].sl.s = makespot(m);
+			source[ns].sflags |= SSPOT;
+			if ((source[ns].sl.s = makespot(m)) == NULL)
+				goto memerr;
+			if (source[ns].sflags & SFLAT &&
+				!checkspot(source[ns].sl.s,source[ns].snorm)) {
+				objerror(o, WARNING,
+					"invalid spotlight direction");
+				source[ns].sflags |= SSKIP;
+			}
 		}
-		nsources++;
+		if (!(source[ns].sflags & SSKIP))
+			foundsource++;
 	}
-	if (nsources <= 0) {
+	if (!foundsource) {
 		error(WARNING, "no light sources found");
 		return;
 	}
-	srccnt = (CONTRIB *)malloc(nsources*sizeof(CONTRIB));
-	cntord = (CNTPTR *)malloc(nsources*sizeof(CNTPTR));
-	if (srccnt != NULL && cntord != NULL)
-		return;
-	/* fall through */
+	markvirtuals();			/* find and add virtual sources */
+				/* allocate our contribution arrays */
+	maxcntr = nsources + MAXSPART;	/* start with this many */
+	srccnt = (CONTRIB *)malloc(maxcntr*sizeof(CONTRIB));
+	cntord = (CNTPTR *)malloc(maxcntr*sizeof(CNTPTR));
+	if (srccnt == NULL | cntord == NULL)
+		goto memerr;
+	return;
 memerr:
 	error(SYSTEM, "out of memory in marksources");
 }
 
 
-newsource(src, so)			/* add a source to the array */
-register SRCREC  *src;
-register OBJREC  *so;
-{
-	double  cos(), tan(), sqrt();
-	double  theta;
-	FACE  *f;
-	CONE  *co;
-	int  j;
-	register int  i;
-	
-	src->sflags = 0;
-	src->aimsuccess = 2*AIMREQT-1;		/* bitch on second failure */
-	src->nhits = 1; src->ntests = 2;	/* start probability = 1/2 */
-	src->so = so;
-
-	switch (so->otype) {
-	case OBJ_SOURCE:
-		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));
-		break;
-	case OBJ_SPHERE:
-		VCOPY(src->sloc, so->oargs.farg);
-		src->ss = so->oargs.farg[3];
-		src->ss2 = PI * src->ss * src->ss;
-		break;
-	case OBJ_FACE:
-						/* 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] /= f->nv;
-		}
-		if (!inface(src->sloc, f))
-			objerror(so, USER, "cannot hit center");
-		src->ss = sqrt(f->area / PI);
-		src->ss2 = f->area;
-		break;
-	case OBJ_RING:
-						/* 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->ss = CO_R1(co);
-		src->ss2 = PI * src->ss * src->ss;
-		break;
-	default:
-		objerror(so, USER, "illegal material");
-	}
-}
-
-
-SPOT *
-makespot(m)			/* make a spotlight */
-register OBJREC  *m;
-{
-	extern double  cos();
-	register SPOT  *ns;
-
-	if ((ns = (SPOT *)malloc(sizeof(SPOT))) == NULL)
-		error(SYSTEM, "out of memory in makespot");
-	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
-srcray(sr, r, sn)		/* send a ray to a source, return domega */
+srcray(sr, r, si)		/* send a ray to a source, return domega */
 register RAY  *sr;		/* returned source ray */
 RAY  *r;			/* ray which hit object */
-register int  sn;		/* source number */
+SRCINDEX  *si;			/* source sample index */
 {
-	register double  *norm = NULL;	/* plane normal */
-	double  ddot;			/* (distance times) cosine */
-	FVECT  vd;
-	double  d;
-	register int  i;
+    double  d;				/* distance to source */
+    register SRCREC  *srcp;
 
-	if (source[sn].sflags & SSKIP)
-		return(0.0);			/* skip this source */
+    rayorigin(sr, r, SHADOW, 1.0);		/* ignore limits */
 
-	rayorigin(sr, r, SHADOW, 1.0);		/* ignore limits */
-
-	sr->rsrc = sn;				/* remember source */
-						/* get source direction */
-	if (source[sn].sflags & SDISTANT)
-						/* constant direction */
-		VCOPY(sr->rdir, source[sn].sloc);
-	else {					/* compute direction */
-		for (i = 0; i < 3; i++)
-			sr->rdir[i] = source[sn].sloc[i] - sr->rorg[i];
-
-		if (source[sn].so->otype == OBJ_FACE)
- 			norm = getface(source[sn].so)->norm;
-		else if (source[sn].so->otype == OBJ_RING)
-			norm = getcone(source[sn].so,0)->ad;
-
-		if (norm != NULL && (ddot = -DOT(sr->rdir, norm)) <= FTINY)
-			return(0.0);		/* behind surface! */
+    while ((d = nextssamp(sr, si)) != 0.0) {
+	sr->rsrc = si->sn;			/* remember source */
+	srcp = source + si->sn;
+	if (srcp->sflags & SDISTANT) {
+		if (srcp->sflags & SSPOT && spotout(sr, srcp->sl.s))
+			continue;
+		return(1);		/* sample OK */
 	}
-	if (dstrsrc > FTINY) {
-					/* distribute source direction */
-		dimlist[ndims++] = sn;
-		for (i = 0; i < 3; i++) {
-			dimlist[ndims] = i + 8831;
-			vd[i] = dstrsrc * source[sn].ss *
-		(1.0 - 2.0*urand(ilhash(dimlist,ndims+1)+samplendx));
-		}
-		ndims--;
-		if (norm != NULL) {		/* project offset */
-			d = DOT(vd, norm);
-			for (i = 0; i < 3; i++)
-				vd[i] -= d * norm[i];
-		}
-		for (i = 0; i < 3; i++)		/* offset source direction */
-			sr->rdir[i] += vd[i];
+				/* local source */
+						/* check proximity */
+	if (srcp->sflags & SPROX && d > srcp->sl.prox)
+		continue;
+						/* check angle */
+	if (srcp->sflags & SSPOT) {
+		if (spotout(sr, srcp->sl.s))
+			continue;
+					/* adjust solid angle */
+		si->dom *= d*d;
+		d += srcp->sl.s->flen;
+		si->dom /= d*d;
+	}
+	return(1);			/* sample OK */
+    }
+    return(0);			/* no more samples */
+}
 
-	} else if (source[sn].sflags & SDISTANT)
-						/* already normalized */
-		return(source[sn].ss2);
 
-	if ((d = normalize(sr->rdir)) == 0.0)
-						/* at source! */
-		return(0.0);
-	
-	if (source[sn].sflags & SDISTANT)
-						/* domega constant */
-		return(source[sn].ss2);
+srcvalue(r)			/* punch ray to source and compute value */
+register RAY  *r;
+{
+	register SRCREC  *sp;
 
-						/* check proximity */
-	if (source[sn].sflags & SPROX &&
-			d > source[sn].sl.prox)
-		return(0.0);
-						/* compute dot product */
-	if (norm != NULL)
-		ddot /= d;
-	else
-		ddot = 1.0;
-						/* check angle */
-	if (source[sn].sflags & SSPOT) {
-		if (source[sn].sl.s->siz < 2.0*PI *
-				(1.0 + DOT(source[sn].sl.s->aim,sr->rdir)))
-			return(0.0);
-		d += source[sn].sl.s->flen;	/* adjust length */
+	sp = &source[r->rsrc];
+	if (sp->sflags & SVIRTUAL) {	/* virtual source */
+					/* check intersection */
+		if (!(*ofun[sp->so->otype].funp)(sp->so, r))
+			return;
+		if (!rayshade(r, r->ro->omod))	/* compute contribution */
+			goto nomat;
+		rayparticipate(r);
+		return;
 	}
-						/* compute domega */
-	return(ddot*source[sn].ss2/(d*d));
+					/* compute intersection */
+	if (sp->sflags & SDISTANT ? sourcehit(r) :
+			(*ofun[sp->so->otype].funp)(sp->so, r)) {
+		if (sp->sa.success >= 0)
+			sp->sa.success++;
+		if (!rayshade(r, r->ro->omod))	/* compute contribution */
+			goto nomat;
+		rayparticipate(r);
+		return;
+	}
+					/* we missed our mark! */
+	if (sp->sa.success < 0)
+		return;			/* bitched already */
+	sp->sa.success -= AIMREQT;
+	if (sp->sa.success >= 0)
+		return;			/* leniency */
+	sprintf(errmsg, "aiming failure for light source \"%s\"",
+			sp->so->oname);
+	error(WARNING, errmsg);		/* issue warning */
+	return;
+nomat:
+	objerror(r->ro, USER, "material not found");
 }
 
 
@@ -275,7 +210,7 @@ register RAY  *r;
 		first = 0; last = nsources-1;
 	}
 	for (i = first; i <= last; i++)
-		if (source[i].sflags & SDISTANT)
+		if ((source[i].sflags & (SDISTANT|SVIRTUAL)) == SDISTANT)
 			/*
 			 * Check to see if ray is within
 			 * solid angle of source.
@@ -315,8 +250,10 @@ RAY  *r;			/* ray that hit surface */
 int  (*f)();			/* direct component coefficient function */
 char  *p;			/* data for f */
 {
-	extern double  pow();
+	extern int  (*trace)();
 	register int  sn;
+	register CONTRIB  *scp;
+	SRCINDEX  si;
 	int  nshadcheck, ncnts;
 	int  nhits;
 	double  prob, ourthresh, hwt;
@@ -324,54 +261,41 @@ char  *p;			/* data for f */
 			/* NOTE: srccnt and cntord global so no recursion */
 	if (nsources <= 0)
 		return;		/* no sources?! */
-						/* compute number to check */
-	nshadcheck = pow((double)nsources, shadcert) + .5;
-						/* modify threshold */
-	ourthresh = shadthresh / r->rweight;
 						/* potential contributions */
-	for (sn = 0; sn < nsources; sn++) {
-		cntord[sn].sno = sn;
-		cntord[sn].brt = 0.0;
-						/* get source ray */
-		if ((srccnt[sn].dom = srcray(&sr, r, sn)) == 0.0)
-			continue;
-		VCOPY(srccnt[sn].dir, sr.rdir);
+	initsrcindex(&si);
+	for (sn = 0; srcray(&sr, r, &si); sn++) {
+		if (sn >= maxcntr) {
+			maxcntr = sn + MAXSPART;
+			srccnt = (CONTRIB *)realloc((char *)srccnt,
+					maxcntr*sizeof(CONTRIB));
+			cntord = (CNTPTR *)realloc((char *)cntord,
+					maxcntr*sizeof(CNTPTR));
+			if (srccnt == NULL | cntord == NULL)
+				error(SYSTEM, "out of memory in direct");
+		}
+		cntord[sn].sndx = sn;
+		scp = srccnt + sn;
+		scp->sno = sr.rsrc;
 						/* compute coefficient */
-		(*f)(srccnt[sn].val, p, srccnt[sn].dir, srccnt[sn].dom);
-		cntord[sn].brt = bright(srccnt[sn].val);
+		(*f)(scp->coef, p, sr.rdir, si.dom);
+		cntord[sn].brt = bright(scp->coef);
 		if (cntord[sn].brt <= 0.0)
 			continue;
-						/* compute intersection */
-		if (source[sn].sflags & SDISTANT ?
-				sourcehit(&sr) :
-				(*ofun[source[sn].so->otype].funp)
-				(source[sn].so, &sr)) {
-			if (source[sn].aimsuccess >= 0)
-				source[sn].aimsuccess++;
-		} else {
-			cntord[sn].brt = 0.0;
-			if (source[sn].aimsuccess < 0)
-				continue;	/* bitched already */
-			source[sn].aimsuccess -= AIMREQT;
-			if (source[sn].aimsuccess >= 0)
-				continue;	/* leniency */
-			sprintf(errmsg,
-				"aiming failure for light source \"%s\"",
-					source[sn].so->oname);
-			error(WARNING, errmsg);
-			continue;
-		}
-						/* compute contribution */
-		raycont(&sr);
-		multcolor(srccnt[sn].val, sr.rcol);
-		cntord[sn].brt = bright(srccnt[sn].val);
+		VCOPY(scp->dir, sr.rdir);
+						/* compute potential */
+		sr.revf = srcvalue;
+		rayvalue(&sr);
+		copycolor(scp->val, sr.rcol);
+		multcolor(scp->val, scp->coef);
+		cntord[sn].brt = bright(scp->val);
 	}
 						/* sort contributions */
-	qsort(cntord, nsources, sizeof(CNTPTR), cntcmp);
+	qsort(cntord, sn, sizeof(CNTPTR), cntcmp);
 	{					/* find last */
 		register int  l, m;
 
-		sn = 0; ncnts = l = nsources;
+		ncnts = l = sn;
+		sn = 0;
 		while ((m = (sn + ncnts) >> 1) != l) {
 			if (cntord[m].brt > 0.0)
 				sn = m;
@@ -380,98 +304,258 @@ char  *p;			/* data for f */
 			l = m;
 		}
 	}
+	if (ncnts == 0)
+		return;		/* no contributions! */
                                                 /* accumulate tail */
         for (sn = ncnts-1; sn > 0; sn--)
                 cntord[sn-1].brt += cntord[sn].brt;
+						/* compute number to check */
+	nshadcheck = pow((double)ncnts, shadcert) + .5;
+						/* modify threshold */
+	ourthresh = shadthresh / r->rweight;
 						/* test for shadows */
-	nhits = 0;
-	for (sn = 0; sn < ncnts; sn++) {
+	for (nhits = 0, hwt = 0.0, sn = 0; sn < ncnts;
+			hwt += (double)source[scp->sno].nhits /
+				(double)source[scp->sno].ntests,
+			sn++) {
 						/* check threshold */
 		if ((sn+nshadcheck>=ncnts ? cntord[sn].brt :
 				cntord[sn].brt-cntord[sn+nshadcheck].brt)
 				< ourthresh*bright(r->rcol))
 			break;
-						/* get statistics */
-		source[cntord[sn].sno].ntests++;
+		scp = srccnt + cntord[sn].sndx;
 						/* test for hit */
 		rayorigin(&sr, r, SHADOW, 1.0);
-		VCOPY(sr.rdir, srccnt[cntord[sn].sno].dir);
-		sr.rsrc = cntord[sn].sno;
+		VCOPY(sr.rdir, scp->dir);
+		sr.rsrc = scp->sno;
+		source[scp->sno].ntests++;	/* keep statistics */
 		if (localhit(&sr, &thescene) &&
-				sr.ro != source[cntord[sn].sno].so) {
-						/* check for transmission */
-			raycont(&sr);
+				( sr.ro != source[scp->sno].so ||
+				source[scp->sno].sflags & SFOLLOW )) {
+						/* follow entire path */
+			if (!raycont(&sr))
+				objerror(sr.ro, USER, "material not found");
+			rayparticipate(&sr);
+			if (trace != NULL)
+				(*trace)(&sr);	/* trace execution */
 			if (bright(sr.rcol) <= FTINY)
 				continue;	/* missed! */
-			(*f)(srccnt[cntord[sn].sno].val, p,
-					srccnt[cntord[sn].sno].dir,
-					srccnt[cntord[sn].sno].dom);
-			multcolor(srccnt[cntord[sn].sno].val, sr.rcol);
+			copycolor(scp->val, sr.rcol);
+			multcolor(scp->val, scp->coef);
 		}
 						/* add contribution if hit */
-		addcolor(r->rcol, srccnt[cntord[sn].sno].val);
+		addcolor(r->rcol, scp->val);
 		nhits++;
-		source[cntord[sn].sno].nhits++;
+		source[scp->sno].nhits++;
 	}
-					/* surface hit rate */
-	if (sn > 0)
-		hwt = (double)nhits / (double)sn;
+					/* source hit rate */
+	if (hwt > FTINY)
+		hwt = (double)nhits / hwt;
 	else
 		hwt = 0.5;
 #ifdef DEBUG
-	sprintf(errmsg, "%d tested, %d untested, %f hit rate\n",
+	sprintf(errmsg, "%d tested, %d untested, %f conditional hit rate\n",
 			sn, ncnts-sn, hwt);
 	eputs(errmsg);
 #endif
 					/* add in untested sources */
 	for ( ; sn < ncnts; sn++) {
-		prob = hwt * (double)source[cntord[sn].sno].nhits /
-				(double)source[cntord[sn].sno].ntests;
-		scalecolor(srccnt[cntord[sn].sno].val, prob);
-		addcolor(r->rcol, srccnt[cntord[sn].sno].val);
+		scp = srccnt + cntord[sn].sndx;
+		prob = hwt * (double)source[scp->sno].nhits /
+				(double)source[scp->sno].ntests;
+		if (prob > 1.0)
+			prob = 1.0;
+		scalecolor(scp->val, prob);
+		addcolor(r->rcol, scp->val);
 	}
 }
 
 
-#define  wrongsource(m, r)	(m->otype!=MAT_ILLUM && \
-				r->rsrc>=0 && \
-				source[r->rsrc].so!=r->ro)
+srcscatter(r)			/* compute source scattering into ray */
+register RAY  *r;
+{
+	int  oldsampndx;
+	int  nsamps;
+	RAY  sr;
+	SRCINDEX  si;
+	double  t, lastt, d;
+	COLOR  cumval, ctmp;
+	int  i, j;
 
-#define  badambient(m, r)	((r->crtype&(AMBIENT|SHADOW))==AMBIENT && \
-				!(r->rtype&REFLECTED) && 	/* hack! */\
-				!(m->otype==MAT_GLOW&&r->rot>m->oargs.farg[3]))
+	if (r->slights == NULL || r->slights[0] == 0 || r->gecc >= 1.-FTINY)
+		return;
+	if (ssampdist <= FTINY || (nsamps = r->rot/ssampdist + .5) < 1)
+		nsamps = 1;
+	oldsampndx = samplendx;
+	samplendx = random()&0x7fff;		/* randomize */
+	initsrcindex(&si);
+	for (i = r->slights[0]; i > 0; i--) {	/* for each source */
+		setcolor(cumval, 0., 0., 0.);
+		lastt = r->rot;
+		for (j = nsamps; j-- > 0; ) {	/* for each sample position */
+			samplendx++;
+			t = r->rot * (j+frandom())/nsamps;
+			sr.rorg[0] = r->rorg[0] + r->rdir[0]*t;
+			sr.rorg[1] = r->rorg[1] + r->rdir[1]*t;
+			sr.rorg[2] = r->rorg[2] + r->rdir[2]*t;
+			sr.rmax = 0.;
+						/* sample ray to this source */
+			if (si.sp >= si.np-1 || !srcray(&sr, NULL, &si) ||
+					sr.rsrc != r->slights[i]) {
+				si.sn = r->slights[i]-1;	/* reset */
+				si.np = 0;
+				if (!srcray(&sr, NULL, &si) ||
+						sr.rsrc != r->slights[i])
+					continue;		/* no path */
+			}
+			copycolor(sr.cext, r->cext);
+			sr.albedo = r->albedo;
+			sr.gecc = r->gecc;
+			rayvalue(&sr);			/* eval. source ray */
+			if (bright(sr.rcol) <= FTINY)
+				continue;
+							/* compute fall-off */
+			d = lastt - t;
+			setcolor(ctmp,	1.-d*colval(r->cext,RED),
+					1.-d*colval(r->cext,GRN),
+					1.-d*colval(r->cext,BLU));
+			multcolor(cumval, ctmp);
+			lastt = t;
+			if (r->gecc <= FTINY)		/* compute P(theta) */
+				d = 1.;
+			else {
+				d = DOT(r->rdir, sr.rdir);
+				d = sqrt(1. + r->gecc*r->gecc - 2.*r->gecc*d);
+				d = (1. - r->gecc*r->gecc) / (d*d*d);
+			}
+							/* other factors */
+			d *= si.dom * r->albedo * r->rot / (4.*PI*nsamps);
+			multcolor(sr.rcol, r->cext);
+			scalecolor(sr.rcol, d);
+			addcolor(cumval, sr.rcol);
+		}
+						/* final fall-off */
+		setcolor(ctmp,	1.-lastt*colval(r->cext,RED),
+				1.-lastt*colval(r->cext,GRN),
+				1.-lastt*colval(r->cext,BLU));
+		multcolor(cumval, ctmp);
+		addcolor(r->rcol, cumval);	/* sum into ray result */
+	}
+	samplendx = oldsampndx;
+}
 
+
+/****************************************************************
+ * The following macros were separated from the m_light() routine
+ * because they are very nasty and difficult to understand.
+ */
+
+/* illumblock *
+ *
+ * We cannot allow an illum to pass to another illum, because that
+ * would almost certainly constitute overcounting.
+ * However, we do allow an illum to pass to another illum
+ * that is actually going to relay to a virtual light source.
+ * We also prevent an illum from passing to a glow; this provides a
+ * convenient mechanism for defining detailed light source
+ * geometry behind (or inside) an effective radiator.
+ */
+
+static int weaksrcmod(obj) int obj;	/* efficiency booster function */
+{register OBJREC *o = objptr(obj);
+return(o->otype==MAT_ILLUM|o->otype==MAT_GLOW);}
+
+#define  illumblock(m, r)	(!(source[r->rsrc].sflags&SVIRTUAL) && \
+				r->rod > 0.0 && \
+				weaksrcmod(source[r->rsrc].so->omod))
+
+/* wrongsource *
+ *
+ * This source is the wrong source (ie. overcounted) if we are
+ * aimed to a different source than the one we hit and the one
+ * we hit is not an illum that should be passed.
+ */
+
+#define  wrongsource(m, r)	(r->rsrc>=0 && source[r->rsrc].so!=r->ro && \
+				(m->otype!=MAT_ILLUM || illumblock(m,r)))
+
+/* distglow *
+ *
+ * A distant glow is an object that sometimes acts as a light source,
+ * but is too far away from the test point to be one in this case.
+ * (Glows with negative radii should NEVER participate in illumination.)
+ */
+
+#define  distglow(m, r, d)	(m->otype==MAT_GLOW && \
+				m->oargs.farg[3] >= -FTINY && \
+				d > m->oargs.farg[3])
+
+/* badcomponent *
+ *
+ * We must avoid counting light sources in the ambient calculation,
+ * since the direct component is handled separately.  Therefore, any
+ * ambient ray which hits an active light source must be discarded.
+ * The same is true for stray specular samples, since the specular
+ * contribution from light sources is calculated separately.
+ */
+
+#define  badcomponent(m, r)	(r->crtype&(AMBIENT|SPECULAR) && \
+				!(r->crtype&SHADOW || r->rod < 0.0 || \
+		/* not 100% correct */	distglow(m, r, r->rot)))
+
+/* passillum *
+ *
+ * An illum passes to another material type when we didn't hit it
+ * on purpose (as part of a direct calculation), or it is relaying
+ * a virtual light source.
+ */
+
 #define  passillum(m, r)	(m->otype==MAT_ILLUM && \
-				!(r->rsrc>=0&&source[r->rsrc].so==r->ro))
+				(r->rsrc<0 || source[r->rsrc].so!=r->ro || \
+				source[r->rsrc].sflags&SVIRTUAL))
 
+/* srcignore *
+ *
+ * The -dv flag is normally on for sources to be visible.
+ */
 
+#define  srcignore(m, r)	!(directvis || r->crtype&SHADOW || \
+				distglow(m, r, raydist(r,PRIMARY)))
+
+
 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;
+	if (badcomponent(m, r))
+		return(1);
+	if (wrongsource(m, r))
+		return(1);
 						/* 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 {
+		if (m->oargs.nsargs && strcmp(m->oargs.sarg[0], VOIDID))
+			return(rayshade(r, modifier(m->oargs.sarg[0])));
+		raytrans(r);
+		return(1);
+	}
+					/* otherwise treat as source */
 						/* check for behind */
-		if (r->rod < 0.0)
-			return;
+	if (r->rod < 0.0)
+		return(1);
+						/* check for invisibility */
+	if (srcignore(m, r))
+		return(1);
+						/* check for outside spot */
+	if (m->otype==MAT_SPOT && spotout(r, makespot(m)))
+		return(1);
 						/* get distribution pattern */
-		raytexture(r, m->omod);
+	raytexture(r, m->omod);
 						/* get source color */
-		setcolor(r->rcol, m->oargs.farg[0],
-				  m->oargs.farg[1],
-				  m->oargs.farg[2]);
+	setcolor(r->rcol, m->oargs.farg[0],
+			  m->oargs.farg[1],
+			  m->oargs.farg[2]);
 						/* modify value */
-		multcolor(r->rcol, r->pcol);
-	}
+	multcolor(r->rcol, r->pcol);
+	return(1);
 }