--- ray/src/rt/dielectric.c	2004/03/30 16:13:01	2.18
+++ ray/src/rt/dielectric.c	2005/04/19 01:15:06	2.20
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char	RCSid[] = "$Id: dielectric.c,v 2.18 2004/03/30 16:13:01 schorsch Exp $";
+static const char	RCSid[] = "$Id: dielectric.c,v 2.20 2005/04/19 01:15:06 greg Exp $";
 #endif
 /*
  *  dielectric.c - shading function for transparent materials.
@@ -74,6 +74,9 @@ m_dielectric(	/* color a ray which hit a dielectric in
 	COLOR  ctrans;
 	COLOR  talb;
 	int  hastexture;
+	double  transdist, transtest=0;
+	double  mirdist, mirtest=0;
+	int	flatsurface;
 	double  refl, trans;
 	FVECT  dnorm;
 	double  d1, d2;
@@ -91,6 +94,8 @@ m_dielectric(	/* color a ray which hit a dielectric in
 		VCOPY(dnorm, r->ron);
 		cos1 = r->rod;
 	}
+	flatsurface = !hastexture && r->ro != NULL && isflat(r->ro->otype);
+
 						/* index of refraction */
 	if (m->otype == MAT_DIELECTRIC)
 		nratio = m->oargs.farg[3] + m->oargs.farg[4]/MLAMBDA;
@@ -159,8 +164,10 @@ m_dielectric(	/* color a ray which hit a dielectric in
 
 		trans *= nratio*nratio;		/* solid angle ratio */
 
-		if (rayorigin(&p, r, REFRACTED, trans) == 0) {
+		setcolor(p.rcoef, trans, trans, trans);
 
+		if (rayorigin(&p, REFRACTED, r, p.rcoef) == 0) {
+
 						/* compute refracted ray */
 			d1 = nratio*cos1 - cos2;
 			for (i = 0; i < 3; i++)
@@ -187,16 +194,22 @@ m_dielectric(	/* color a ray which hit a dielectric in
 				copycolor(p.cext, ctrans);
 				copycolor(p.albedo, talb);
 				rayvalue(&p);
-				scalecolor(p.rcol, trans);
+				multcolor(p.rcol, p.rcoef);
 				addcolor(r->rcol, p.rcol);
-				if (nratio >= 1.0-FTINY && nratio <= 1.0+FTINY)
-					r->rt = r->rot + p.rt;
+						/* virtual distance */
+				if (flatsurface ||
+					(1.-FTINY <= nratio &&
+						nratio <= 1.+FTINY)) {
+					transtest = 2*bright(p.rcol);
+					transdist = r->rot + p.rt;
+				}
 			}
 		}
 	}
-		
+	setcolor(p.rcoef, refl, refl, refl);
+
 	if (!(r->crtype & SHADOW) &&
-			rayorigin(&p, r, REFLECTED, refl) == 0) {
+			rayorigin(&p, REFLECTED, r, p.rcoef) == 0) {
 
 					/* compute reflected ray */
 		for (i = 0; i < 3; i++)
@@ -208,9 +221,20 @@ m_dielectric(	/* color a ray which hit a dielectric in
 
 		rayvalue(&p);			/* reflected ray value */
 
-		scalecolor(p.rcol, refl);	/* color contribution */
+		multcolor(p.rcol, p.rcoef);	/* color contribution */
 		addcolor(r->rcol, p.rcol);
+						/* virtual distance */
+		if (flatsurface) {
+			mirtest = 2*bright(p.rcol);
+			mirdist = r->rot + p.rt;
+		}
 	}
+				/* check distance to return */
+	d1 = bright(r->rcol);
+	if (transtest > d1)
+		r->rt = transdist;
+	else if (mirtest > d1)
+		r->rt = mirdist;
 				/* rayvalue() computes absorption */
 	return(1);
 }
@@ -228,7 +252,8 @@ disperse(  /* check light sources for dispersion */
 	COLOR  abt
 )
 {
-	RAY  sray, *entray;
+	RAY  sray;
+	const RAY  *entray;
 	FVECT  v1, v2, n1, n2;
 	FVECT  dv, v2Xdv;
 	double  v2Xdvv2Xdv;