--- ray/src/rt/raytrace.c	1996/03/21 15:33:05	2.24
+++ ray/src/rt/raytrace.c	1998/08/06 10:30:38	2.32
@@ -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
 
 /*
@@ -27,7 +27,7 @@ extern int  do_irrad;			/* compute irradiance? */
 extern COLOR  ambval;			/* ambient value */
 
 extern COLOR  cextinction;		/* global extinction coefficient */
-extern double  salbedo;			/* global scattering albedo */
+extern COLOR  salbedo;			/* global scattering albedo */
 extern double  seccg;			/* global scattering eccentricity */
 extern double  ssampdist;		/* scatter sampling distance */
 
@@ -54,6 +54,8 @@ register RAY  *r, *ro;
 int  rt;
 double  rw;
 {
+	double	re;
+
 	if ((r->parent = ro) == NULL) {		/* primary ray */
 		r->rlvl = 0;
 		r->rweight = rw;
@@ -62,7 +64,7 @@ double  rw;
 		r->clipset = NULL;
 		r->revf = raytrace;
 		copycolor(r->cext, cextinction);
-		r->albedo = salbedo;
+		copycolor(r->albedo, salbedo);
 		r->gecc = seccg;
 		r->slights = NULL;
 	} else {				/* spawned ray */
@@ -79,12 +81,18 @@ double  rw;
 		}
 		r->revf = ro->revf;
 		copycolor(r->cext, ro->cext);
-		r->albedo = ro->albedo;
+		copycolor(r->albedo, ro->albedo);
 		r->gecc = ro->gecc;
 		r->slights = ro->slights;
-		r->rweight = ro->rweight * rw;
 		r->crtype = ro->crtype | (r->rtype = rt);
 		VCOPY(r->rorg, ro->rop);
+		r->rweight = ro->rweight * rw;
+						/* estimate absorption */
+		re = colval(ro->cext,RED) < colval(ro->cext,GRN) ?
+				colval(ro->cext,RED) : colval(ro->cext,GRN);
+		if (colval(ro->cext,BLU) < re) re = colval(ro->cext,BLU);
+		if (re > 0.)
+			r->rweight *= exp(-re*ro->rot);
 	}
 	rayclear(r);
 	return(r->rlvl <= maxdepth && r->rweight >= minweight ? 0 : -1);
@@ -96,12 +104,12 @@ register RAY  *r;
 {
 	r->rno = raynum++;
 	r->newcset = r->clipset;
+	r->robj = OVOID;
 	r->ro = NULL;
-	r->rot = FHUGE;
+	r->rt = r->rot = FHUGE;
 	r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
 	setcolor(r->pcol, 1.0, 1.0, 1.0);
 	setcolor(r->rcol, 0.0, 0.0, 0.0);
-	r->rt = 0.0;
 }
 
 
@@ -189,29 +197,28 @@ rayparticipate(r)			/* compute ray medium participatio
 register RAY  *r;
 {
 	COLOR	ce, ca;
-	double	dist;
 	double	re, ge, be;
 
 	if (intens(r->cext) <= 1./FHUGE)
 		return;				/* no medium */
-	if ((dist = r->rot) >= FHUGE)
-		dist = 2.*thescene.cusize;	/* what to use for infinity? */
-	if (r->crtype & SHADOW)
-		dist *= 1. - salbedo;		/* no scattering for sources */
-	if (dist <= FTINY)
-		return;				/* no effective ray travel */
-	re = dist*colval(r->cext,RED);
-	ge = dist*colval(r->cext,GRN);
-	be = dist*colval(r->cext,BLU);
-	setcolor(ce,	re>92. ? 0. : exp(-re),
-			ge>92. ? 0. : exp(-ge),
-			be>92. ? 0. : exp(-be));
+	re = r->rot*colval(r->cext,RED);
+	ge = r->rot*colval(r->cext,GRN);
+	be = r->rot*colval(r->cext,BLU);
+	if (r->crtype & SHADOW) {		/* no scattering for sources */
+		re *= 1. - colval(r->albedo,RED);
+		ge *= 1. - colval(r->albedo,GRN);
+		be *= 1. - colval(r->albedo,BLU);
+	}
+	setcolor(ce,	re<=0. ? 1. : re>92. ? 0. : exp(-re),
+			ge<=0. ? 1. : ge>92. ? 0. : exp(-ge),
+			be<=0. ? 1. : be>92. ? 0. : exp(-be));
 	multcolor(r->rcol, ce);			/* path absorption */
-	if (r->albedo <= FTINY || r->crtype & SHADOW)
+	if (r->crtype & SHADOW || intens(r->albedo) <= FTINY)
 		return;				/* no scattering */
-	setcolor(ca,	salbedo*colval(ambval,RED)*(1.-colval(ce,RED)),
-			salbedo*colval(ambval,GRN)*(1.-colval(ce,GRN)),
-			salbedo*colval(ambval,BLU)*(1.-colval(ce,BLU)));
+	setcolor(ca,
+		colval(r->albedo,RED)*colval(ambval,RED)*(1.-colval(ce,RED)),
+		colval(r->albedo,GRN)*colval(ambval,GRN)*(1.-colval(ce,GRN)),
+		colval(r->albedo,BLU)*colval(ambval,BLU)*(1.-colval(ce,BLU)));
 	addcolor(r->rcol, ca);			/* ambient in scattering */
 	srcscatter(r);				/* source in scattering */
 }
@@ -270,9 +277,9 @@ double  coef;
 		backmat = rayshade(&br, back);
 					/* check for transparency */
 	if (backmat ^ foremat)
-		if (backmat)
+		if (!foremat && coef > FTINY)
 			raytrans(&fr);
-		else
+		else if (!backmat && coef < 1.0-FTINY)
 			raytrans(&br);
 					/* mix perturbations */
 	for (i = 0; i < 3; i++)
@@ -555,7 +562,8 @@ OBJECT  *cxs;
 	checkset(oset, cxs);			/* eliminate double-checking */
 	for (i = oset[0]; i > 0; i--) {
 		o = objptr(oset[i]);
-		(*ofun[o->otype].funp)(o, r);
+		if ((*ofun[o->otype].funp)(o, r))
+			r->robj = oset[i];
 	}
 	if (r->ro == NULL)
 		return(0);			/* no scores yet */