--- ray/src/rt/dielectric.c	1995/12/05 11:46:00	2.8
+++ ray/src/rt/dielectric.c	2003/02/25 02:47:22	2.16
@@ -1,15 +1,12 @@
-/* Copyright (c) 1986 Regents of the University of California */
-
 #ifndef lint
-static char SCCSid[] = "$SunId$ LBL";
+static const char	RCSid[] = "$Id: dielectric.c,v 2.16 2003/02/25 02:47:22 greg Exp $";
 #endif
-
 /*
  *  dielectric.c - shading function for transparent materials.
- *
- *     9/6/85
  */
 
+#include "copyright.h"
+
 #include  "ray.h"
 
 #include  "otypes.h"
@@ -51,13 +48,26 @@ static int  lambda();
 #define  MINCOS		0.997		/* minimum dot product for dispersion */
 
 
-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;
-	double  mabsorp;
+	COLOR  ctrans;
+	COLOR  talb;
+	int  hastexture;
 	double  refl, trans;
 	FVECT  dnorm;
 	double  d1, d2;
@@ -69,7 +79,12 @@ register RAY  *r;
 
 	raytexture(r, m->omod);			/* get modifiers */
 
-	cos1 = raynormal(dnorm, r);		/* cosine of theta1 */
+	if (hastexture = DOT(r->pert,r->pert) > FTINY*FTINY)
+		cos1 = raynormal(dnorm, r);	/* perturb normal */
+	else {
+		VCOPY(dnorm, r->ron);
+		cos1 = r->rod;
+	}
 						/* index of refraction */
 	if (m->otype == MAT_DIELECTRIC)
 		nratio = m->oargs.farg[3] + m->oargs.farg[4]/MLAMBDA;
@@ -77,24 +92,42 @@ register RAY  *r;
 		nratio = m->oargs.farg[3] / m->oargs.farg[7];
 	
 	if (cos1 < 0.0) {			/* inside */
+		hastexture = -hastexture;
 		cos1 = -cos1;
 		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));
-		multcolor(mcolor, r->pcol);	/* modify */
+		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);
 
 	d2 = 1.0 - nratio*nratio*(1.0 - cos1*cos1);	/* compute cos theta2 */
 
@@ -115,25 +148,38 @@ 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) {
+		trans *= nratio*nratio;		/* solid angle ratio */
 
+		if (rayorigin(&p, r, REFRACTED, trans) == 0) {
+
 						/* compute refracted ray */
 			d1 = nratio*cos1 - cos2;
 			for (i = 0; i < 3; i++)
 				p.rdir[i] = nratio*r->rdir[i] + d1*dnorm[i];
-
+						/* accidental reflection? */
+			if (hastexture &&
+				DOT(p.rdir,r->ron)*hastexture >= -FTINY) {
+				d1 *= (double)hastexture;
+				for (i = 0; i < 3; i++)	/* ignore texture */
+					p.rdir[i] = nratio*r->rdir[i] +
+							d1*r->ron[i];
+				normalize(p.rdir);	/* not exact */
+			}
 #ifdef  DISPERSE
 			if (m->otype != MAT_DIELECTRIC
 					|| r->rod > 0.0
 					|| 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);
 				scalecolor(p.rcol, trans);
 				addcolor(r->rcol, p.rcol);
@@ -144,20 +190,22 @@ register RAY  *r;
 	}
 		
 	if (!(r->crtype & SHADOW) &&
-			rayorigin(&p, r, REFLECTED, mabsorp*refl) == 0) {
+			rayorigin(&p, r, REFLECTED, refl) == 0) {
 
 					/* compute reflected ray */
 		for (i = 0; i < 3; i++)
 			p.rdir[i] = r->rdir[i] + 2.0*cos1*dnorm[i];
+					/* accidental penetration? */
+		if (hastexture && DOT(p.rdir,r->ron)*hastexture <= FTINY)
+			for (i = 0; i < 3; i++)		/* ignore texture */
+				p.rdir[i] = r->rdir[i] + 2.0*r->rod*r->ron[i];
 
 		rayvalue(&p);			/* reflected ray value */
 
 		scalecolor(p.rcol, refl);	/* color contribution */
 		addcolor(r->rcol, p.rcol);
 	}
-
-	multcolor(r->rcol, mcolor);		/* multiply by transmittance */
-
+				/* rayvalue() computes absorption */
 	return(1);
 }
 
@@ -165,11 +213,12 @@ register RAY  *r;
 #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;
@@ -255,6 +304,8 @@ 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 */