--- ray/src/rt/source.c	1991/11/12 17:08:57	2.1
+++ ray/src/rt/source.c	1996/04/17 14:02:18	2.24
@@ -1,4 +1,4 @@
-/* Copyright (c) 1991 Regents of the University of California */
+/* Copyright (c) 1995 Regents of the University of California */
 
 #ifndef lint
 static char SCCSid[] = "$SunId$ LBL";
@@ -18,6 +18,14 @@ static char SCCSid[] = "$SunId$ LBL";
 
 #include  "source.h"
 
+#include  "random.h"
+
+extern double  ssampdist;		/* scatter sampling distance */
+
+#ifndef MAXSSAMP
+#define MAXSSAMP	16		/* maximum samples per ray */
+#endif
+
 /*
  * Structures used by direct()
  */
@@ -41,6 +49,7 @@ static int  maxcntr = 0;		/* size of contribution arra
 
 marksources()			/* find and mark source objects */
 {
+	int  foundsource = 0;
 	int  i;
 	register OBJREC  *o, *m;
 	register int  ns;
@@ -67,6 +76,9 @@ 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 (sfun[o->otype].of == NULL ||
 				sfun[o->otype].of->setsrc == NULL)
@@ -80,7 +92,7 @@ marksources()			/* find and mark source objects */
 		if (m->otype == MAT_GLOW) {
 			source[ns].sflags |= SPROX;
 			source[ns].sl.prox = m->oargs.farg[3];
-			if (o->otype == OBJ_SOURCE)
+			if (source[ns].sflags & SDISTANT)
 				source[ns].sflags |= SSKIP;
 		} else if (m->otype == MAT_SPOT) {
 			source[ns].sflags |= SSPOT;
@@ -93,8 +105,10 @@ marksources()			/* find and mark source objects */
 				source[ns].sflags |= SSKIP;
 			}
 		}
+		if (!(source[ns].sflags & SSKIP))
+			foundsource++;
 	}
-	if (nsources <= 0) {
+	if (!foundsource) {
 		error(WARNING, "no light sources found");
 		return;
 	}
@@ -117,9 +131,7 @@ RAY  *r;			/* ray which hit object */
 SRCINDEX  *si;			/* source sample index */
 {
     double  d;				/* distance to source */
-    FVECT  vd;
     register SRCREC  *srcp;
-    register int  i;
 
     rayorigin(sr, r, SHADOW, 1.0);		/* ignore limits */
 
@@ -127,16 +139,8 @@ SRCINDEX  *si;			/* source sample index */
 	sr->rsrc = si->sn;			/* remember source */
 	srcp = source + si->sn;
 	if (srcp->sflags & SDISTANT) {
-		if (srcp->sflags & SSPOT) {	/* check location */
-			for (i = 0; i < 3; i++)
-			    vd[i] = srcp->sl.s->aim[i] - sr->rorg[i];
-			d = DOT(sr->rdir,vd);
-			if (d <= FTINY)
-				continue;
-			d = DOT(vd,vd) - d*d;
-			if (PI*d > srcp->sl.s->siz)
-				continue;
-		}
+		if (srcp->sflags & SSPOT && spotout(sr, srcp->sl.s))
+			continue;
 		return(1);		/* sample OK */
 	}
 				/* local source */
@@ -145,8 +149,7 @@ SRCINDEX  *si;			/* source sample index */
 		continue;
 						/* check angle */
 	if (srcp->sflags & SSPOT) {
-		if (srcp->sl.s->siz < 2.0*PI *
-				(1.0 + DOT(srcp->sl.s->aim,sr->rdir)))
+		if (spotout(sr, srcp->sl.s))
 			continue;
 					/* adjust solid angle */
 		si->dom *= d*d;
@@ -160,7 +163,7 @@ SRCINDEX  *si;			/* source sample index */
 
 
 srcvalue(r)			/* punch ray to source and compute value */
-RAY  *r;
+register RAY  *r;
 {
 	register SRCREC  *sp;
 
@@ -169,7 +172,9 @@ RAY  *r;
 					/* check intersection */
 		if (!(*ofun[sp->so->otype].funp)(sp->so, r))
 			return;
-		raycont(r);		/* compute contribution */
+		if (!rayshade(r, r->ro->omod))	/* compute contribution */
+			goto nomat;
+		rayparticipate(r);
 		return;
 	}
 					/* compute intersection */
@@ -177,9 +182,12 @@ RAY  *r;
 			(*ofun[sp->so->otype].funp)(sp->so, r)) {
 		if (sp->sa.success >= 0)
 			sp->sa.success++;
-		raycont(r);		/* compute contribution */
+		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;
@@ -188,9 +196,47 @@ RAY  *r;
 	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");
 }
 
 
+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|SVIRTUAL)) == 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);
+}
+
+
 static int
 cntcmp(sc1, sc2)			/* contribution compare (descending) */
 register CNTPTR  *sc1, *sc2;
@@ -209,8 +255,8 @@ int  (*f)();			/* direct component coefficient functio
 char  *p;			/* data for f */
 {
 	extern int  (*trace)();
-	extern double  pow();
 	register int  sn;
+	register CONTRIB  *scp;
 	SRCINDEX  si;
 	int  nshadcheck, ncnts;
 	int  nhits;
@@ -232,19 +278,20 @@ char  *p;			/* data for f */
 				error(SYSTEM, "out of memory in direct");
 		}
 		cntord[sn].sndx = sn;
-		srccnt[sn].sno = sr.rsrc;
+		scp = srccnt + sn;
+		scp->sno = sr.rsrc;
 						/* compute coefficient */
-		(*f)(srccnt[sn].coef, p, sr.rdir, si.dom);
-		cntord[sn].brt = bright(srccnt[sn].coef);
+		(*f)(scp->coef, p, sr.rdir, si.dom);
+		cntord[sn].brt = bright(scp->coef);
 		if (cntord[sn].brt <= 0.0)
 			continue;
-		VCOPY(srccnt[sn].dir, sr.rdir);
+		VCOPY(scp->dir, sr.rdir);
 						/* compute potential */
 		sr.revf = srcvalue;
 		rayvalue(&sr);
-		copycolor(srccnt[sn].val, sr.rcol);
-		multcolor(srccnt[sn].val, srccnt[sn].coef);
-		cntord[sn].brt = bright(srccnt[sn].val);
+		copycolor(scp->val, sr.rcol);
+		multcolor(scp->val, scp->coef);
+		cntord[sn].brt = bright(scp->val);
 	}
 						/* sort contributions */
 	qsort(cntord, sn, sizeof(CNTPTR), cntcmp);
@@ -261,6 +308,8 @@ 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;
@@ -269,52 +318,249 @@ char  *p;			/* data for f */
 						/* 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;
+		scp = srccnt + cntord[sn].sndx;
 						/* test for hit */
 		rayorigin(&sr, r, SHADOW, 1.0);
-		VCOPY(sr.rdir, srccnt[cntord[sn].sndx].dir);
-		sr.rsrc = srccnt[cntord[sn].sndx].sno;
-		source[sr.rsrc].ntests++;	/* keep statistics */
+		VCOPY(sr.rdir, scp->dir);
+		sr.rsrc = scp->sno;
+		source[scp->sno].ntests++;	/* keep statistics */
 		if (localhit(&sr, &thescene) &&
-				( sr.ro != source[sr.rsrc].so ||
-				source[sr.rsrc].sflags & SFOLLOW )) {
+				( sr.ro != source[scp->sno].so ||
+				source[scp->sno].sflags & SFOLLOW )) {
 						/* follow entire path */
 			raycont(&sr);
+			rayparticipate(&sr);
 			if (trace != NULL)
 				(*trace)(&sr);	/* trace execution */
 			if (bright(sr.rcol) <= FTINY)
 				continue;	/* missed! */
-			copycolor(srccnt[cntord[sn].sndx].val, sr.rcol);
-			multcolor(srccnt[cntord[sn].sndx].val,
-					srccnt[cntord[sn].sndx].coef);
+			copycolor(scp->val, sr.rcol);
+			multcolor(scp->val, scp->coef);
 		}
 						/* add contribution if hit */
-		addcolor(r->rcol, srccnt[cntord[sn].sndx].val);
+		addcolor(r->rcol, scp->val);
 		nhits++;
-		source[sr.rsrc].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++) {
-		sr.rsrc = srccnt[cntord[sn].sndx].sno;
-		prob = hwt * (double)source[sr.rsrc].nhits /
-				(double)source[sr.rsrc].ntests;
-		scalecolor(srccnt[cntord[sn].sndx].val, prob);
-		addcolor(r->rcol, srccnt[cntord[sn].sndx].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);
 	}
+}
+
+
+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;
+
+	if (r->slights == NULL || r->slights[0] == 0
+			|| r->gecc >= 1.-FTINY || r->rot >= FHUGE)
+		return;
+	if (ssampdist <= FTINY || (nsamps = r->rot/ssampdist + .5) < 1)
+		nsamps = 1;
+#if MAXSSAMP
+	else if (nsamps > MAXSSAMP)
+		nsamps = MAXSSAMP;
+#endif
+	oldsampndx = samplendx;
+	samplendx = random()&0x7fff;		/* randomize */
+	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.;
+			initsrcindex(&si);	/* sample ray to this source */
+			si.sn = r->slights[i];
+			nopart(&si, &sr);
+			if (!srcray(&sr, NULL, &si) ||
+					sr.rsrc != r->slights[i])
+				continue;		/* no path */
+			copycolor(sr.cext, r->cext);
+			copycolor(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->rot / (4.*PI*nsamps);
+			multcolor(sr.rcol, r->cext);
+			multcolor(sr.rcol, r->albedo);
+			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 || \
+				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 (badcomponent(m, r))
+		return(1);
+	if (wrongsource(m, r))
+		return(1);
+						/* check for passed illum */
+	if (passillum(m, r)) {
+		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(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);
+						/* 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);
+	return(1);
 }