--- ray/src/rt/source.c	1995/11/07 12:40:32	2.18
+++ ray/src/rt/source.c	1998/08/10 18:37:56	2.28
@@ -1,7 +1,7 @@
-/* Copyright (c) 1995 Regents of the University of California */
+/* Copyright (c) 1998 Silicon Graphics, Inc. */
 
 #ifndef lint
-static char SCCSid[] = "$SunId$ LBL";
+static char SCCSid[] = "$SunId$ SGI";
 #endif
 
 /*
@@ -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()
  */
@@ -166,6 +174,7 @@ register RAY  *r;
 			return;
 		if (!rayshade(r, r->ro->omod))	/* compute contribution */
 			goto nomat;
+		rayparticipate(r);
 		return;
 	}
 					/* compute intersection */
@@ -175,6 +184,7 @@ register RAY  *r;
 			sp->sa.success++;
 		if (!rayshade(r, r->ro->omod))	/* compute contribution */
 			goto nomat;
+		rayparticipate(r);
 		return;
 	}
 					/* we missed our mark! */
@@ -217,6 +227,7 @@ register RAY  *r;
 			}
 
 	if (r->ro != NULL) {
+		r->robj = objndx(r->ro);
 		for (i = 0; i < 3; i++)
 			r->ron[i] = -r->rdir[i];
 		r->rod = 1.0;
@@ -327,8 +338,8 @@ char  *p;			/* data for f */
 				( sr.ro != source[scp->sno].so ||
 				source[scp->sno].sflags & SFOLLOW )) {
 						/* follow entire path */
-			if (!raycont(&sr))
-				objerror(sr.ro, USER, "material not found");
+			raycont(&sr);
+			rayparticipate(&sr);
 			if (trace != NULL)
 				(*trace)(&sr);	/* trace execution */
 			if (bright(sr.rcol) <= FTINY)
@@ -364,6 +375,79 @@ char  *p;			/* data for f */
 }
 
 
+srcscatter(r)			/* compute source scattering into ray */
+register RAY  *r;
+{
+	int  oldsampndx;
+	int  nsamps;
+	RAY  sr;
+	SRCINDEX  si;
+	double  t, d;
+	double  re, ge, be;
+	COLOR  cvext;
+	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 */
+		for (j = 0; j < nsamps; j++) {	/* for each sample position */
+			samplendx++;
+			t = r->rot * (j+frandom())/nsamps;
+							/* extinction */
+			re = t*colval(r->cext,RED);
+			ge = t*colval(r->cext,GRN);
+			be = t*colval(r->cext,BLU);
+			setcolor(cvext,	re > 92. ? 0. : exp(-re),
+					ge > 92. ? 0. : exp(-ge),
+					be > 92. ? 0. : exp(-be));
+			if (intens(cvext) <= FTINY)
+				break;			/* too far away */
+			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;
+			sr.slights = r->slights;
+			rayvalue(&sr);			/* eval. source ray */
+			if (bright(sr.rcol) <= FTINY)
+				continue;
+			if (r->gecc <= FTINY)		/* compute P(theta) */
+				d = 1.;
+			else {
+				d = DOT(r->rdir, sr.rdir);
+				d = 1. + r->gecc*r->gecc - 2.*r->gecc*d;
+				d = (1. - r->gecc*r->gecc) / (d*sqrt(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);
+			multcolor(sr.rcol, cvext);
+			addcolor(r->rcol, sr.rcol);	/* add it in */
+		}
+	}
+	samplendx = oldsampndx;
+}
+
+
 /****************************************************************
  * The following macros were separated from the m_light() routine
  * because they are very nasty and difficult to understand.
@@ -454,7 +538,7 @@ register RAY  *r;
 						/* 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])));
+			return(rayshade(r,lastmod(objndx(m),m->oargs.sarg[0])));
 		raytrans(r);
 		return(1);
 	}