--- ray/src/rt/glass.c	1992/05/20 10:24:26	2.2
+++ ray/src/rt/glass.c	2004/03/30 16:13:01	2.15
@@ -1,16 +1,15 @@
-/* Copyright (c) 1991 Regents of the University of California */
-
 #ifndef lint
-static char SCCSid[] = "$SunId$ LBL";
+static const char RCSid[] = "$Id: glass.c,v 2.15 2004/03/30 16:13:01 schorsch Exp $";
 #endif
-
 /*
  *  glass.c - simpler shading function for thin glass surfaces.
- *
- *     11/14/86
  */
 
+#include "copyright.h"
+
 #include  "ray.h"
+#include  "otypes.h"
+#include  "rtotypes.h"
 
 /*
  *  This definition of glass provides for a quick calculation
@@ -24,14 +23,14 @@ static char SCCSid[] = "$SunId$ LBL";
  *	modifier glass id
  *	0
  *	0
- *	3 red grn blu
+ *	3+ red grn blu [refractive_index]
  *
  *  The color is used for the transmission at normal incidence.
- *  To compute transmission (tn) from transmissivity (Tn) use:
+ *  To compute transmissivity (tn) from transmittance (Tn) use:
  *
  *	tn = (sqrt(.8402528435+.0072522239*Tn*Tn)-.9166530661)/.0036261119/Tn
  *
- *  The transmission of standard 88% transmissivity glass is 0.96.
+ *  The transmissivity of standard 88% transmittance glass is 0.96.
  *  A refractive index other than the default can be used by giving
  *  it as the fourth real argument.  The above formula no longer applies.
  *
@@ -42,18 +41,21 @@ static char SCCSid[] = "$SunId$ LBL";
 #define  RINDEX		1.52		/* refractive index of glass */
 
 
-m_glass(m, r)		/* color a ray which hit a thin glass surface */
-OBJREC  *m;
-register RAY  *r;
+extern int
+m_glass(		/* color a ray which hit a thin glass surface */
+	OBJREC  *m,
+	register RAY  *r
+)
 {
-	double  sqrt(), pow();
 	COLOR  mcolor;
 	double  pdot;
 	FVECT  pnorm;
 	double  rindex, cos2;
 	COLOR  trans, refl;
+	int  hastexture;
 	double  d, r1e, r1m;
 	double  transtest, transdist;
+	double  mirtest, mirdist;
 	RAY  p;
 	register int  i;
 						/* check arguments */
@@ -66,12 +68,19 @@ register RAY  *r;
 
 	setcolor(mcolor, m->oargs.farg[0], m->oargs.farg[1], m->oargs.farg[2]);
 
-	if (r->rod < 0.0)			/* reorient if necessary */
-		flipsurface(r);
-	transtest = 0;
 						/* get modifiers */
 	raytexture(r, m->omod);
-	pdot = raynormal(pnorm, r);
+	if (r->rod < 0.0)			/* reorient if necessary */
+		flipsurface(r);
+	mirtest = transtest = 0;
+	mirdist = transdist = r->rot;
+						/* perturb normal */
+	if ( (hastexture = (DOT(r->pert,r->pert) > FTINY*FTINY)) ) {
+		pdot = raynormal(pnorm, r);
+	} else {
+		VCOPY(pnorm, r->ron);
+		pdot = r->rod;
+	}
 						/* angular transmission */
 	cos2 = sqrt( (1.0-1.0/(rindex*rindex)) +
 		     pdot*pdot/(rindex*rindex) );
@@ -92,12 +101,14 @@ register RAY  *r;
 	}
 						/* transmitted ray */
 	if (rayorigin(&p, r, TRANS, bright(trans)) == 0) {
-		if (!(r->crtype & SHADOW) &&
-				DOT(r->pert,r->pert) > FTINY*FTINY) {
+		if (!(r->crtype & SHADOW) && hastexture) {
 			for (i = 0; i < 3; i++)		/* perturb direction */
 				p.rdir[i] = r->rdir[i] +
 						2.*(1.-rindex)*r->pert[i];
-			normalize(p.rdir);
+			if (normalize(p.rdir) == 0.0) {
+				objerror(m, WARNING, "bad perturbation");
+				VCOPY(p.rdir, r->rdir);
+			}
 		} else {
 			VCOPY(p.rdir, r->rdir);
 			transtest = 2;
@@ -110,8 +121,10 @@ register RAY  *r;
 		transdist = r->rot + p.rt;
 	}
 
-	if (r->crtype & SHADOW)			/* skip reflected ray */
-		return;
+	if (r->crtype & SHADOW) {		/* skip reflected ray */
+		r->rt = transdist;
+		return(1);
+	}
 						/* compute reflectance */
 	for (i = 0; i < 3; i++) {
 		d = colval(mcolor, i);
@@ -126,7 +139,16 @@ register RAY  *r;
 		rayvalue(&p);
 		multcolor(p.rcol, refl);
 		addcolor(r->rcol, p.rcol);
+		if (!hastexture && r->ro != NULL && isflat(r->ro->otype)) {
+			mirtest = 2.0*bright(p.rcol);
+			mirdist = r->rot + p.rt;
+		}
 	}
-	if (transtest > bright(r->rcol))
+                                        /* check distance */
+	d = bright(r->rcol);
+	if (transtest > d)
 		r->rt = transdist;
+	else if (mirtest > d)
+		r->rt = mirdist;
+	return(1);
 }