--- ray/src/rt/m_brdf.c	1995/05/17 17:31:39	2.12
+++ ray/src/rt/m_brdf.c	2003/03/05 16:16:53	2.18
@@ -1,13 +1,12 @@
-/* Copyright (c) 1991 Regents of the University of California */
-
 #ifndef lint
-static char SCCSid[] = "$SunId$ LBL";
+static const char	RCSid[] = "$Id: m_brdf.c,v 2.18 2003/03/05 16:16:53 greg Exp $";
 #endif
-
 /*
  *  Shading for materials with arbitrary BRDF's
  */
 
+#include "copyright.h"
+
 #include  "ray.h"
 
 #include  "data.h"
@@ -16,8 +15,6 @@ static char SCCSid[] = "$SunId$ LBL";
 
 #include  "func.h"
 
-extern int  backvis;			/* back faces visible? */
-
 /*
  *	Arguments to this material include the color and specularity.
  *  String arguments include the reflection function and files.
@@ -80,6 +77,7 @@ typedef struct {
 }  BRDFDAT;		/* BRDF material data */
 
 
+static void
 dirbrdf(cval, np, ldir, omega)		/* compute source contribution */
 COLOR  cval;			/* returned coefficient */
 register BRDFDAT  *np;		/* material data */
@@ -162,7 +160,7 @@ double  omega;			/* light source size */
 		dtmp = funvalue(sa[0], 5, vldx);
 		setcolor(ctmp, dtmp, dtmp, dtmp);
 	}
-	if (errno) {
+	if (errno == EDOM || errno == ERANGE) {
 		objerror(np->mp, WARNING, "compute error");
 		return;
 	}
@@ -191,15 +189,18 @@ double  omega;			/* light source size */
 }
 
 
-m_brdf(m, r)			/* color a ray which hit a BRDTF material */
+int
+m_brdf(m, r)			/* color a ray that hit a BRDTfunc material */
 register OBJREC  *m;
 register RAY  *r;
 {
+	int  hitfront = 1;
 	BRDFDAT  nd;
 	RAY  sr;
 	double  transtest, transdist;
 	int  hasrefl, hastrans;
 	COLOR  ctmp;
+	FVECT  vtmp;
 	register MFUNC  *mf;
 	register int  i;
 						/* check arguments */
@@ -223,7 +224,7 @@ register RAY  *r;
 	setcolor(nd.tdiff, m->oargs.farg[6],
 			m->oargs.farg[7],
 			m->oargs.farg[8]);
-					/* get modifiers */
+						/* get modifiers */
 	raytexture(r, m->omod);
 	nd.pdot = raynormal(nd.pnorm, r);	/* perturb normal */
 	if (r->rod < 0.0) {			/* orient perturbed values */
@@ -232,6 +233,7 @@ register RAY  *r;
 			nd.pnorm[i] = -nd.pnorm[i];
 			r->pert[i] = -r->pert[i];
 		}
+		hitfront = 0;
 	}
 	copycolor(nd.mcolor, r->pcol);		/* get pattern color */
 	multcolor(nd.rdiff, nd.mcolor);		/* modify diffuse values */
@@ -249,7 +251,7 @@ register RAY  *r;
 	setcolor(ctmp, evalue(mf->ep[3]),
 			evalue(mf->ep[4]),
 			evalue(mf->ep[5]));
-	if (errno)
+	if (errno == EDOM || errno == ERANGE)
 		objerror(m, WARNING, "compute error");
 	else if (rayorigin(&sr, r, TRANS, bright(ctmp)) == 0) {
 		if (!(r->crtype & SHADOW) &&
@@ -278,7 +280,7 @@ register RAY  *r;
 	setcolor(ctmp, evalue(mf->ep[0]),
 			evalue(mf->ep[1]),
 			evalue(mf->ep[2]));
-	if (errno)
+	if (errno == EDOM || errno == ERANGE)
 		objerror(m, WARNING, "compute error");
 	else if (rayorigin(&sr, r, REFLECTED, bright(ctmp)) == 0) {
 		for (i = 0; i < 3; i++)
@@ -289,21 +291,24 @@ register RAY  *r;
 	}
 						/* compute ambient */
 	if (hasrefl) {
-		if (nd.pdot < 0.0)
+		if (!hitfront)
 			flipsurface(r);
-		ambient(ctmp, r);
+		ambient(ctmp, r, nd.pnorm);
 		multcolor(ctmp, nd.rdiff);
 		addcolor(r->rcol, ctmp);	/* add to returned color */
-		if (nd.pdot < 0.0)
+		if (!hitfront)
 			flipsurface(r);
 	}
 	if (hastrans) {				/* from other side */
-		if (nd.pdot > 0.0)
+		if (hitfront)
 			flipsurface(r);
-		ambient(ctmp, r);
+		vtmp[0] = -nd.pnorm[0];
+		vtmp[1] = -nd.pnorm[1];
+		vtmp[2] = -nd.pnorm[2];
+		ambient(ctmp, r, vtmp);
 		multcolor(ctmp, nd.tdiff);
 		addcolor(r->rcol, ctmp);
-		if (nd.pdot > 0.0)
+		if (hitfront)
 			flipsurface(r);
 	}
 	if (hasrefl | hastrans || m->oargs.sarg[6][0] != '0')
@@ -317,12 +322,14 @@ register RAY  *r;
 
 
 
-m_brdf2(m, r)			/* color a ray which hit a BRDF material */
+int
+m_brdf2(m, r)			/* color a ray that hit a BRDF material */
 register OBJREC  *m;
 register RAY  *r;
 {
 	BRDFDAT  nd;
 	COLOR  ctmp;
+	FVECT  vtmp;
 	double  dtmp;
 						/* always a shadow */
 	if (r->crtype & SHADOW)
@@ -331,6 +338,18 @@ register RAY  *r;
 	if (m->oargs.nsargs < (hasdata(m->otype)?4:2) | m->oargs.nfargs <
 			(m->otype==MAT_TFUNC|m->otype==MAT_TDATA?6:4))
 		objerror(m, USER, "bad # arguments");
+						/* check for back side */
+	if (r->rod < 0.0) {
+		if (!backvis && m->otype != MAT_TFUNC
+				&& m->otype != MAT_TDATA) {
+			raytrans(r);
+			return(1);
+		}
+		raytexture(r, m->omod);
+		flipsurface(r);			/* reorient if backvis */
+	} else
+		raytexture(r, m->omod);
+
 	nd.mp = m;
 	nd.pr = r;
 						/* get material color */
@@ -352,17 +371,6 @@ register RAY  *r;
 						/* compute reflectance */
 	dtmp = 1.0 - nd.trans - nd.rspec;
 	setcolor(nd.rdiff, dtmp, dtmp, dtmp);
-						/* check for back side */
-	if (r->rod < 0.0) {
-		if (!backvis && m->otype != MAT_TFUNC
-				&& m->otype != MAT_TDATA) {
-			raytrans(r);
-			return(1);
-		}
-		flipsurface(r);			/* reorient if backvis */
-	}
-						/* get modifiers */
-	raytexture(r, m->omod);
 	nd.pdot = raynormal(nd.pnorm, r);	/* perturb normal */
 	multcolor(nd.mcolor, r->pcol);		/* modify material color */
 	multcolor(nd.rdiff, nd.mcolor);
@@ -377,14 +385,17 @@ register RAY  *r;
 	}
 						/* compute ambient */
 	if (nd.trans < 1.0-FTINY) {
-		ambient(ctmp, r);
+		ambient(ctmp, r, nd.pnorm);
 		scalecolor(ctmp, 1.0-nd.trans);
 		multcolor(ctmp, nd.mcolor);	/* modified by material color */
 		addcolor(r->rcol, ctmp);	/* add to returned color */
 	}
 	if (nd.trans > FTINY) {		/* from other side */
 		flipsurface(r);
-		ambient(ctmp, r);
+		vtmp[0] = -nd.pnorm[0];
+		vtmp[1] = -nd.pnorm[1];
+		vtmp[2] = -nd.pnorm[2];
+		ambient(ctmp, r, vtmp);
 		scalecolor(ctmp, nd.trans);
 		multcolor(ctmp, nd.mcolor);
 		addcolor(r->rcol, ctmp);
@@ -397,6 +408,7 @@ register RAY  *r;
 }
 
 
+int
 setbrdfunc(np)			/* set up brdf function and variables */
 register BRDFDAT  *np;
 {