--- ray/src/rt/dielectric.c	1993/11/18 09:43:00	2.6
+++ ray/src/rt/dielectric.c	1996/07/11 15:14:05	2.12
@@ -50,13 +50,29 @@ static int  lambda();
 
 #define  MINCOS		0.997		/* minimum dot product for dispersion */
 
+extern COLOR  cextinction;		/* global coefficient of extinction */
+extern COLOR  salbedo;			/* global scattering albedo */
 
-m_dielectric(m, r)	/* color a ray which hit something transparent */
+
+static double
+mylog(x)		/* special log for extinction coefficients */
+double  x;
+{
+	if (x < 1e-40)
+		return(-100.);
+	if (x >= 1.)
+		return(0.);
+	return(log(x));
+}
+
+
+m_dielectric(m, r)	/* color a ray which hit a dielectric interface */
 OBJREC  *m;
 register RAY  *r;
 {
 	double  cos1, cos2, nratio;
-	COLOR  mcolor;
+	COLOR  ctrans;
+	COLOR  talb;
 	double  mabsorp;
 	double  refl, trans;
 	FVECT  dnorm;
@@ -81,19 +97,45 @@ register RAY  *r;
 		dnorm[0] = -dnorm[0];
 		dnorm[1] = -dnorm[1];
 		dnorm[2] = -dnorm[2];
-		setcolor(mcolor, pow(m->oargs.farg[0], r->rot),
-				 pow(m->oargs.farg[1], r->rot),
-				 pow(m->oargs.farg[2], r->rot));
+		setcolor(r->cext, -mylog(m->oargs.farg[0]*colval(r->pcol,RED)),
+				 -mylog(m->oargs.farg[1]*colval(r->pcol,GRN)),
+				 -mylog(m->oargs.farg[2]*colval(r->pcol,BLU)));
+		setcolor(r->albedo, 0., 0., 0.);
+		r->gecc = 0.;
+		if (m->otype == MAT_INTERFACE) {
+			setcolor(ctrans,
+				-mylog(m->oargs.farg[4]*colval(r->pcol,RED)),
+				-mylog(m->oargs.farg[5]*colval(r->pcol,GRN)),
+				-mylog(m->oargs.farg[6]*colval(r->pcol,BLU)));
+			setcolor(talb, 0., 0., 0.);
+		} else {
+			copycolor(ctrans, cextinction);
+			copycolor(talb, salbedo);
+		}
 	} else {				/* outside */
 		nratio = 1.0 / nratio;
-		if (m->otype == MAT_INTERFACE)
-			setcolor(mcolor, pow(m->oargs.farg[4], r->rot),
-					 pow(m->oargs.farg[5], r->rot),
-					 pow(m->oargs.farg[6], r->rot));
-		else
-			setcolor(mcolor, 1.0, 1.0, 1.0);
+
+		setcolor(ctrans, -mylog(m->oargs.farg[0]*colval(r->pcol,RED)),
+				 -mylog(m->oargs.farg[1]*colval(r->pcol,GRN)),
+				 -mylog(m->oargs.farg[2]*colval(r->pcol,BLU)));
+		setcolor(talb, 0., 0., 0.);
+		if (m->otype == MAT_INTERFACE) {
+			setcolor(r->cext,
+				-mylog(m->oargs.farg[4]*colval(r->pcol,RED)),
+				-mylog(m->oargs.farg[5]*colval(r->pcol,GRN)),
+				-mylog(m->oargs.farg[6]*colval(r->pcol,BLU)));
+			setcolor(r->albedo, 0., 0., 0.);
+			r->gecc = 0.;
+		}
 	}
-	mabsorp = bright(mcolor);
+						/* estimate absorption */
+	mabsorp = colval(r->cext,RED) < colval(r->cext,GRN) ?
+			colval(r->cext,RED) : colval(r->cext,GRN);
+	if (colval(r->cext,BLU) < mabsorp) mabsorp = colval(r->cext,BLU);
+	if (mabsorp > 0.)
+		mabsorp = exp(-mabsorp*r->rot);		/* conservative */
+	else
+		mabsorp = 1.0;
 
 	d2 = 1.0 - nratio*nratio*(1.0 - cos1*cos1);	/* compute cos theta2 */
 
@@ -114,7 +156,7 @@ register RAY  *r;
 		d1 = (d1 - d2) / (d1 + d2);
 		refl += d1 * d1;
 
-		refl /= 2.0;
+		refl *= 0.5;
 		trans = 1.0 - refl;
 
 		if (rayorigin(&p, r, REFRACTED, mabsorp*trans) == 0) {
@@ -130,11 +172,13 @@ register RAY  *r;
 					|| r->crtype & SHADOW
 					|| !directvis
 					|| m->oargs.farg[4] == 0.0
-					|| !disperse(m, r, p.rdir, trans))
+					|| !disperse(m, r, p.rdir,
+							trans, ctrans, talb))
 #endif
 			{
+				copycolor(p.cext, ctrans);
+				copycolor(p.albedo, talb);
 				rayvalue(&p);
-				multcolor(mcolor, r->pcol);	/* modify */
 				scalecolor(p.rcol, trans);
 				addcolor(r->rcol, p.rcol);
 				if (nratio >= 1.0-FTINY && nratio <= 1.0+FTINY)
@@ -155,19 +199,20 @@ register RAY  *r;
 		scalecolor(p.rcol, refl);	/* color contribution */
 		addcolor(r->rcol, p.rcol);
 	}
-
-	multcolor(r->rcol, mcolor);		/* multiply by transmittance */
+				/* rayvalue() computes absorption */
+	return(1);
 }
 
 
 #ifdef  DISPERSE
 
 static
-disperse(m, r, vt, tr)		/* check light sources for dispersion */
+disperse(m, r, vt, tr, cet, abt)  /* check light sources for dispersion */
 OBJREC  *m;
 RAY  *r;
 FVECT  vt;
 double  tr;
+COLOR  cet, abt;
 {
 	RAY  sray, *entray;
 	FVECT  v1, v2, n1, n2;
@@ -253,6 +298,8 @@ double  tr;
 		if (l1 > MAXLAMBDA || l1 < MINLAMBDA)	/* not visible */
 			continue;
 						/* trace source ray */
+		copycolor(sray.cext, cet);
+		copycolor(sray.albedo, abt);
 		normalize(sray.rdir);
 		rayvalue(&sray);
 		if (bright(sray.rcol) <= FTINY)	/* missed it */