--- ray/src/rt/glass.c	1990/03/27 11:40:00	1.3
+++ ray/src/rt/glass.c	1991/05/07 17:45:51	1.6
@@ -60,6 +60,7 @@ register RAY  *r;
 
 	if (r->rod < 0.0)			/* reorient if necessary */
 		flipsurface(r);
+	r->rt = r->rot;				/* default ray length */
 						/* get modifiers */
 	raytexture(r, m->omod);
 	pdot = raynormal(pnorm, r);
@@ -81,12 +82,15 @@ register RAY  *r;
 	}
 						/* transmitted ray */
 	if (rayorigin(&p, r, TRANS, bright(trans)) == 0) {
-		VCOPY(p.rdir, r->rdir);
+		for (i = 0; i < 3; i++)		/* perturb direction */
+			p.rdir[i] = r->rdir[i] - r->pert[i]/RINDEX;
+		normalize(p.rdir);
 		rayvalue(&p);
 		multcolor(p.rcol, r->pcol);	/* modify */
 		multcolor(p.rcol, trans);
 		addcolor(r->rcol, p.rcol);
-		r->rt = r->rot + p.rt;
+		if (bright(p.rcol) > .5)
+			r->rt = r->rot + p.rt;
 	}
 
 	if (r->crtype & SHADOW)			/* skip reflected ray */
@@ -104,7 +108,5 @@ register RAY  *r;
 		rayvalue(&p);
 		multcolor(p.rcol, refl);
 		addcolor(r->rcol, p.rcol);
-		if (bright(refl) > bright(trans))
-			r->rt = r->rot + p.rt;
 	}
 }