--- ray/src/rt/m_mirror.c	1991/07/16 15:56:46	1.2
+++ ray/src/rt/m_mirror.c	1992/11/20 12:09:16	2.2
@@ -40,14 +40,16 @@ register RAY  *r;
 					/* check arguments */
 	if (m->oargs.nfargs != 3 || m->oargs.nsargs > 1)
 		objerror(m, USER, "bad number of arguments");
-					/* check if source ray */
-	if (r->rsrc >= 0) {			/* aiming for somebody */
-		if (source[r->rsrc].so != r->ro)
-			return;				/* but not us */
-	} else if (m->oargs.nsargs > 0) {	/* else call substitute? */
+					/* check for substitute material */
+	if (m->oargs.nsargs > 0 &&
+			(r->rsrc < 0 || source[r->rsrc].so != r->ro)) {
 		rayshade(r, modifier(m->oargs.sarg[0]));
 		return;
 	}
+					/* check for bad source ray */
+	if (r->rsrc >= 0 && source[r->rsrc].so != r->ro)
+		return;
+
 	if (r->rod < 0.)		/* back is black */
 		return;
 					/* get modifiers */
@@ -74,6 +76,10 @@ register RAY  *r;
 		pdot = raynormal(pnorm, r);	/* use textures */
 		for (i = 0; i < 3; i++)
 			nr.rdir[i] = r->rdir[i] + 2.*pdot*pnorm[i];
+						/* check for penetration */
+		if (DOT(nr.rdir, r->ron) <= FTINY)
+			for (i = 0; i < 3; i++)
+				nr.rdir[i] = r->rdir[i] + 2.*r->rod*r->ron[i];
 	}
 	rayvalue(&nr);
 	multcolor(nr.rcol, mcolor);