--- ray/src/rt/raytrace.c	1997/03/07 16:58:54	2.28
+++ ray/src/rt/raytrace.c	1998/09/15 09:52:39	2.33
@@ -1,7 +1,7 @@
-/* Copyright (c) 1996 Regents of the University of California */
+/* Copyright (c) 1998 Silicon Graphics, Inc. */
 
 #ifndef lint
-static char SCCSid[] = "$SunId$ LBL";
+static char SCCSid[] = "$SunId$ SGI";
 #endif
 
 /*
@@ -44,7 +44,9 @@ OBJREC  Aftplane;			/* aft clipping plane object */
 
 static int  raymove(), checkset(), checkhit();
 
-#define  MAXLOOP	128		/* modifier loop detection */
+#ifndef  MAXLOOP
+#define  MAXLOOP	0		/* modifier loop detection */
+#endif
 
 #define  RAYHIT		(-1)		/* return value for intercepted ray */
 
@@ -54,6 +56,8 @@ register RAY  *r, *ro;
 int  rt;
 double  rw;
 {
+	double	re;
+
 	if ((r->parent = ro) == NULL) {		/* primary ray */
 		r->rlvl = 0;
 		r->rweight = rw;
@@ -82,9 +86,15 @@ double  rw;
 		copycolor(r->albedo, ro->albedo);
 		r->gecc = ro->gecc;
 		r->slights = ro->slights;
-		r->rweight = ro->rweight * rw;
 		r->crtype = ro->crtype | (r->rtype = rt);
 		VCOPY(r->rorg, ro->rop);
+		r->rweight = ro->rweight * rw;
+						/* estimate absorption */
+		re = colval(ro->cext,RED) < colval(ro->cext,GRN) ?
+				colval(ro->cext,RED) : colval(ro->cext,GRN);
+		if (colval(ro->cext,BLU) < re) re = colval(ro->cext,BLU);
+		if (re > 0.)
+			r->rweight *= exp(-re*ro->rot);
 	}
 	rayclear(r);
 	return(r->rlvl <= maxdepth && r->rweight >= minweight ? 0 : -1);
@@ -98,11 +108,10 @@ register RAY  *r;
 	r->newcset = r->clipset;
 	r->robj = OVOID;
 	r->ro = NULL;
-	r->rot = FHUGE;
+	r->rt = r->rot = FHUGE;
 	r->pert[0] = r->pert[1] = r->pert[2] = 0.0;
 	setcolor(r->pcol, 1.0, 1.0, 1.0);
 	setcolor(r->rcol, 0.0, 0.0, 0.0);
-	r->rt = 0.0;
 }
 
 
@@ -153,12 +162,14 @@ rayshade(r, mod)		/* shade ray r with material mod */
 register RAY  *r;
 int  mod;
 {
-	static int  depth = 0;
 	int  gotmat;
 	register OBJREC  *m;
+#if  MAXLOOP
+	static int  depth = 0;
 					/* check for infinite loop */
 	if (depth++ >= MAXLOOP)
 		objerror(r->ro, USER, "possible modifier loop");
+#endif
 	r->rt = r->rot;			/* set effective ray length */
 	for (gotmat = 0; !gotmat && mod != OVOID; mod = m->omod) {
 		m = objptr(mod);
@@ -171,7 +182,9 @@ int  mod;
 					/* hack for irradiance calculation */
 		if (do_irrad && !(r->crtype & ~(PRIMARY|TRANS))) {
 			if (irr_ignore(m->otype)) {
+#if  MAXLOOP
 				depth--;
+#endif
 				raytrans(r);
 				return(1);
 			}
@@ -181,7 +194,9 @@ int  mod;
 					/* materials call raytexture */
 		gotmat = (*ofun[m->otype].funp)(m, r);
 	}
+#if  MAXLOOP
 	depth--;
+#endif
 	return(gotmat);
 }
 
@@ -221,11 +236,13 @@ raytexture(r, mod)			/* get material modifiers */
 RAY  *r;
 int  mod;
 {
-	static int  depth = 0;
 	register OBJREC  *m;
+#if  MAXLOOP
+	static int  depth = 0;
 					/* check for infinite loop */
 	if (depth++ >= MAXLOOP)
 		objerror(r->ro, USER, "modifier loop");
+#endif
 					/* execute textures and patterns */
 	for ( ; mod != OVOID; mod = m->omod) {
 		m = objptr(mod);
@@ -241,7 +258,9 @@ int  mod;
 			objerror(r->ro, USER, errmsg);
 		}
 	}
+#if  MAXLOOP
 	depth--;			/* end here */
+#endif
 }
 
 
@@ -270,9 +289,9 @@ double  coef;
 		backmat = rayshade(&br, back);
 					/* check for transparency */
 	if (backmat ^ foremat)
-		if (backmat)
+		if (backmat && coef > FTINY)
 			raytrans(&fr);
-		else
+		else if (foremat && coef < 1.0-FTINY)
 			raytrans(&br);
 					/* mix perturbations */
 	for (i = 0; i < 3; i++)