--- ray/src/px/pinterp.c	1989/12/10 17:34:13	1.1
+++ ray/src/px/pinterp.c	1989/12/13 12:41:25	1.4
@@ -17,6 +17,8 @@ static char SCCSid[] = "$SunId$ LBL";
 #define pscan(y)	(ourpict+(y)*ourview.hresolu)
 #define zscan(y)	(ourzbuf+(y)*ourview.hresolu)
 
+#define ABS(x)		((x)>0?(x):-(x))
+
 VIEW	ourview = STDVIEW(512);		/* desired view */
 
 double	zeps = 0.001;			/* allowed z epsilon */
@@ -250,31 +252,57 @@ float	*zline;
 
 fillpicture()				/* fill in empty spaces */
 {
+	int	*yback, xback;
 	int	y;
-	COLR	cfill;
-	register int	x, xblank;
-	
+	COLR	pfill;
+	register int	x, i;
+							/* get back buffer */
+	yback = (int *)malloc(ourview.hresolu*sizeof(int));
+	if (yback == NULL) {
+		perror(progname);
+		return;
+	}
+	for (x = 0; x < ourview.hresolu; x++)
+		yback[x] = -2;
+							/* fill image */
 	for (y = 0; y < ourview.vresolu; y++) {
-		xblank = -1;
+		xback = -2;
 		for (x = 0; x < ourview.hresolu; x++)
-			if (zscan(y)[x] <= 0.0) {
-				if (xblank < 0)
-					xblank = x;
-			} else if (xblank >= 0) {
-				if (xblank == 0 || zscan(y)[xblank-1] < zscan(y)[x])
-					copycolr(cfill, pscan(y)[x]);
+			if (zscan(y)[x] <= 0.0) {	/* empty pixel */
+				if (yback[x] == -2) {
+					for (i = y+1; i < ourview.vresolu; i++)
+						if (zscan(i)[x] > 0.0)
+							break;
+					if (i < ourview.vresolu
+				&& (y <= 0 || zscan(y-1)[x] < zscan(i)[x]))
+						yback[x] = i;
+					else
+						yback[x] = y-1;
+				}
+				if (xback == -2) {
+					for (i = x+1; x < ourview.hresolu; i++)
+						if (zscan(y)[i] > 0.0)
+							break;
+					if (i < ourview.hresolu
+				&& (x <= 0 || zscan(y)[x-1] < zscan(y)[i]))
+						xback = i;
+					else
+						xback = x-1;
+				}
+				if (xback < 0 && yback[x] < 0)
+					continue;
+				if (yback[x] < 0 || ABS(x-xback) <= 1
+					|| ( ABS(y-yback[x]) > 1
+				&& zscan(yback[x])[x] < zscan(y)[xback] ))
+					copycolr(pscan(y)[x],pscan(y)[xback]);
 				else
-					copycolr(cfill, pscan(y)[xblank-1]);
-				for ( ; xblank < x; xblank++)
-					copycolr(pscan(y)[xblank], cfill);
-				xblank = -1;
+					copycolr(pscan(y)[x],pscan(yback[x])[x]);
+			} else {				/* full pixel */
+				yback[x] = -2;
+				xback = -2;
 			}
-		if (xblank > 0) {
-			copycolr(cfill, pscan(y)[xblank-1]);
-			for ( ; xblank < ourview.hresolu; xblank++)
-				copycolr(pscan(y)[xblank], cfill);
-		}
 	}
+	free((char *)yback);
 }