--- ray/src/rt/normal.c	1993/08/24 12:59:28	2.26
+++ ray/src/rt/normal.c	1994/12/21 09:51:49	2.28
@@ -23,6 +23,8 @@ static char SCCSid[] = "$SunId$ LBL";
 extern double  specthresh;		/* specular sampling threshold */
 extern double  specjitter;		/* specular sampling jitter */
 
+extern int  backvis;			/* back faces visible? */
+
 static  gaussamp();
 
 /*
@@ -158,7 +160,7 @@ register RAY  *r;
 	register int  i;
 						/* easy shadow test */
 	if (r->crtype & SHADOW && m->otype != MAT_TRANS)
-		return;
+		return(1);
 
 	if (m->oargs.nfargs != (m->otype == MAT_TRANS ? 7 : 5))
 		objerror(m, USER, "bad number of arguments");
@@ -173,9 +175,14 @@ register RAY  *r;
 	nd.alpha2 = m->oargs.farg[4];
 	if ((nd.alpha2 *= nd.alpha2) <= FTINY)
 		nd.specfl |= SP_PURE;
-						/* reorient if necessary */
-	if (r->rod < 0.0)
-		flipsurface(r);
+						/* check for back side */
+	if (r->rod < 0.0) {
+		if (!backvis && m->otype != MAT_TRANS) {
+			raytrans(r);
+			return(1);
+		}
+		flipsurface(r);			/* reorient if backvis */
+	}
 						/* get modifiers */
 	raytexture(r, m->omod);
 	nd.pdot = raynormal(nd.pnorm, r);	/* perturb normal */
@@ -255,12 +262,12 @@ register RAY  *r;
 		transtest = 0;
 
 	if (r->crtype & SHADOW)			/* the rest is shadow */
-		return;
+		return(1);
 						/* diffuse reflection */
 	nd.rdiff = 1.0 - nd.trans - nd.rspec;
 
 	if (nd.specfl & SP_PURE && nd.rdiff <= FTINY && nd.tdiff <= FTINY)
-		return;				/* 100% pure specular */
+		return(1);			/* 100% pure specular */
 
 	if (r->ro != NULL && (r->ro->otype == OBJ_FACE ||
 			r->ro->otype == OBJ_RING))
@@ -294,6 +301,8 @@ register RAY  *r;
 					/* check distance */
 	if (transtest > bright(r->rcol))
 		r->rt = transdist;
+
+	return(1);
 }