--- ray/src/rt/dielectric.c	1996/07/11 15:14:05	2.12
+++ ray/src/rt/dielectric.c	2004/09/09 06:46:07	2.19
@@ -1,25 +1,25 @@
-/* Copyright (c) 1986 Regents of the University of California */
-
 #ifndef lint
-static char SCCSid[] = "$SunId$ LBL";
+static const char	RCSid[] = "$Id: dielectric.c,v 2.19 2004/09/09 06:46:07 greg Exp $";
 #endif
-
 /*
  *  dielectric.c - shading function for transparent materials.
- *
- *     9/6/85
  */
 
-#include  "ray.h"
+#include "copyright.h"
 
+#include  "ray.h"
 #include  "otypes.h"
+#include  "rtotypes.h"
 
 #ifdef  DISPERSE
 #include  "source.h"
-static  disperse();
-static int  lambda();
+static int disperse(OBJREC *m,RAY *r,FVECT vt,double tr,COLOR cet,COLOR abt);
+static int lambda(OBJREC  *m, FVECT  v2, FVECT  dv, FVECT  lr);
 #endif
 
+static double mylog(double  x);
+
+
 /*
  *     Explicit calculations for Fresnel's equation are performed,
  *  but only one square root computation is necessary.
@@ -50,13 +50,11 @@ 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 */
 
-
 static double
-mylog(x)		/* special log for extinction coefficients */
-double  x;
+mylog(		/* special log for extinction coefficients */
+	double  x
+)
 {
 	if (x < 1e-40)
 		return(-100.);
@@ -66,14 +64,19 @@ double  x;
 }
 
 
-m_dielectric(m, r)	/* color a ray which hit a dielectric interface */
-OBJREC  *m;
-register RAY  *r;
+extern int
+m_dielectric(	/* color a ray which hit a dielectric interface */
+	OBJREC  *m,
+	register RAY  *r
+)
 {
 	double  cos1, cos2, nratio;
 	COLOR  ctrans;
 	COLOR  talb;
-	double  mabsorp;
+	int  hastexture;
+	double  transdist, transtest=0;
+	double  mirdist, mirtest=0;
+	int	flatsurface;
 	double  refl, trans;
 	FVECT  dnorm;
 	double  d1, d2;
@@ -85,7 +88,14 @@ 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;
+	}
+	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;
@@ -93,6 +103,7 @@ 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];
@@ -128,14 +139,6 @@ register RAY  *r;
 			r->gecc = 0.;
 		}
 	}
-						/* 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 */
 
@@ -159,13 +162,23 @@ register RAY  *r;
 		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
@@ -181,24 +194,44 @@ register RAY  *r;
 				rayvalue(&p);
 				scalecolor(p.rcol, trans);
 				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;
+				}
 			}
 		}
 	}
 		
 	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);
+						/* 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);
 }
@@ -206,13 +239,15 @@ register RAY  *r;
 
 #ifdef  DISPERSE
 
-static
-disperse(m, r, vt, tr, cet, abt)  /* check light sources for dispersion */
-OBJREC  *m;
-RAY  *r;
-FVECT  vt;
-double  tr;
-COLOR  cet, abt;
+static int
+disperse(  /* check light sources for dispersion */
+	OBJREC  *m,
+	RAY  *r,
+	FVECT  vt,
+	double  tr,
+	COLOR  cet,
+	COLOR  abt
+)
 {
 	RAY  sray, *entray;
 	FVECT  v1, v2, n1, n2;
@@ -343,9 +378,12 @@ COLOR  cet, abt;
 
 
 static int
-lambda(m, v2, dv, lr)			/* compute lambda for material */
-register OBJREC  *m;
-FVECT  v2, dv, lr;
+lambda(			/* compute lambda for material */
+	register OBJREC  *m,
+	FVECT  v2,
+	FVECT  dv,
+	FVECT  lr
+)
 {
 	FVECT  lrXdv, v2Xlr;
 	double  dtmp, denom;