--- ray/src/px/pinterp.c	1990/10/15 11:01:48	1.30
+++ ray/src/px/pinterp.c	1991/02/11 18:10:56	1.32
@@ -465,6 +465,8 @@ FVECT	pos;
 {
 	FVECT	pt, direc;
 	
+	if (pos[2] <= 0)		/* empty pixel */
+		return(-1);
 	if (hasmatrix) {
 		pos[0] += theirview.hoff - .5;
 		pos[1] += theirview.voff - .5;
@@ -505,7 +507,6 @@ int	samp;
 {
 	int	*yback, xback;
 	int	y;
-	COLR	pfill;
 	register int	x, i;
 							/* get back buffer */
 	yback = (int *)malloc(hresolu*sizeof(int));