--- ray/src/rt/raytrace.c	2005/04/19 01:15:06	2.49
+++ ray/src/rt/raytrace.c	2005/08/22 21:54:41	2.56
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char RCSid[] = "$Id: raytrace.c,v 2.49 2005/04/19 01:15:06 greg Exp $";
+static const char RCSid[] = "$Id: raytrace.c,v 2.56 2005/08/22 21:54:41 greg Exp $";
 #endif
 /*
  *  raytrace.c - routines for tracing and shading rays.
@@ -13,6 +13,7 @@ static const char RCSid[] = "$Id: raytrace.c,v 2.49 20
 #include  "source.h"
 #include  "otypes.h"
 #include  "otspecial.h"
+#include  "random.h"
 
 #define  MAXCSET	((MAXSET+1)*2-1)	/* maximum check set size */
 
@@ -58,6 +59,7 @@ rayorigin(		/* start new ray from old one */
 		r->crtype = r->rtype = rt;
 		r->rsrc = -1;
 		r->clipset = NULL;
+		r->revf = raytrace;
 		copycolor(r->cext, cextinction);
 		copycolor(r->albedo, salbedo);
 		r->gecc = seccg;
@@ -78,6 +80,7 @@ rayorigin(		/* start new ray from old one */
 			r->clipset = ro->newcset;
 			r->rmax = ro->rmax <= FTINY ? 0.0 : ro->rmax - ro->rot;
 		}
+		r->revf = ro->revf;
 		copycolor(r->cext, ro->cext);
 		copycolor(r->albedo, ro->albedo);
 		r->gecc = ro->gecc;
@@ -90,11 +93,32 @@ rayorigin(		/* start new ray from old one */
 				colval(ro->cext,RED) : colval(ro->cext,GRN);
 		if (colval(ro->cext,BLU) < re) re = colval(ro->cext,BLU);
 		re *= ro->rot;
-		if (re > .1)
-			r->rweight *= exp(-re);
+		if (re > 0.1)
+			if (re > 92.)
+				r->rweight = 0.0;
+			else
+				r->rweight *= exp(-re);
 	}
 	rayclear(r);
-	return(r->rlvl <= maxdepth && r->rweight >= minweight ? 0 : -1);
+	if (r->rweight <= 0.0)			/* check for expiration */
+		return(-1);
+	if (r->crtype & SHADOW)			/* shadow commitment */
+		return(0);
+	if (maxdepth <= 0 && rc != NULL) {	/* Russian roulette */
+		if (minweight <= 0.0)
+			error(USER, "zero ray weight in Russian roulette");
+		if (maxdepth < 0 && r->rlvl > -maxdepth)
+			return(-1);		/* upper reflection limit */
+		if (r->rweight >= minweight)
+			return(0);
+		if (frandom() > r->rweight/minweight)
+			return(-1);
+		rw = minweight/r->rweight;	/* promote survivor */
+		scalecolor(r->rcoef, rw);
+		r->rweight = minweight;
+		return(0);
+	}
+	return(r->rlvl <= abs(maxdepth) && r->rweight >= minweight ? 0 : -1);
 }
 
 
@@ -118,7 +142,7 @@ rayclear(			/* clear a ray for (re)evaluation */
 
 
 extern void
-rayvalue(			/* trace a ray and compute its value */
+raytrace(			/* trace a ray and compute its value */
 	RAY  *r
 )
 {
@@ -277,12 +301,16 @@ raymixture(		/* mix modifiers */
 	foremat = backmat = 0;
 					/* foreground */
 	fr = *r;
-	if (coef > FTINY)
+	if (coef > FTINY) {
+		scalecolor(fr.rcoef, coef);
 		foremat = rayshade(&fr, fore);
+	}
 					/* background */
 	br = *r;
-	if (coef < 1.0-FTINY)
+	if (coef < 1.0-FTINY) {
+		scalecolor(br.rcoef, 1.0-coef);
 		backmat = rayshade(&br, back);
+	}
 					/* check for transparency */
 	if (backmat ^ foremat) {
 		if (backmat && coef > FTINY)
@@ -329,29 +357,27 @@ raydist(		/* compute (cumulative) ray distance */
 
 extern void
 raycontrib(		/* compute (cumulative) ray contribution */
-	COLOR  rc,
+	double  rc[3],
 	const RAY  *r,
 	int  flags
 )
 {
-	COLOR	eext, ext1;
-	
-	setcolor(eext, 0., 0., 0.);
-	setcolor(rc, 1., 1., 1.);
+	double	eext[3];
+	int	i;
 
+	eext[0] = eext[1] = eext[2] = 0.;
+	rc[0] = rc[1] = rc[2] = 1.;
+
 	while (r != NULL && r->crtype&flags) {
-		multcolor(rc, r->rcoef);
-		copycolor(ext1, r->cext);
-		scalecolor(ext1, r->rot);
-		addcolor(eext, ext1);
+		for (i = 3; i--; ) {
+			rc[i] *= colval(r->rcoef,i);
+			eext[i] += r->rot * colval(r->cext,i);
+		}
 		r = r->parent;
 	}
-	if (intens(eext) > FTINY) {
-		setcolor(ext1,	exp(-colval(eext,RED)),
-				exp(-colval(eext,GRN)),
-				exp(-colval(eext,BLU)));
-		multcolor(rc, ext1);
-	}
+	for (i = 3; i--; )
+		rc[i] *= (eext[i] <= FTINY) ? 1. :
+				(eext[i] > 92.) ? 0. : exp(-eext[i]);
 }