--- ray/src/rt/rv3.c	1990/01/19 00:00:31	1.12
+++ ray/src/rt/rv3.c	1990/02/22 11:46:15	1.13
@@ -18,7 +18,11 @@ static char SCCSid[] = "$SunId$ LBL";
 
 #include  "random.h"
 
+#ifndef WFLUSH
+#define WFLUSH		30		/* flush after this many rays */
+#endif
 
+
 getrect(s, r)				/* get a box */
 char  *s;
 register RECT  *r;
@@ -130,6 +134,8 @@ paint(p, xmin, ymin, xmax, ymax)	/* compute and paint 
 register PNODE  *p;
 int  xmin, ymin, xmax, ymax;
 {
+	extern long  nrays;
+	static long  lastflush = 0;
 	static RAY  thisray;
 	double  h, v;
 	register int  i;
@@ -157,6 +163,11 @@ int  xmin, ymin, xmax, ymax;
 	scalecolor(p->v, exposure);
 
 	(*dev->paintr)(greyscale?greyof(p->v):p->v, xmin, ymin, xmax, ymax);
+
+	if (dev->flush != NULL && nrays - lastflush >= WFLUSH) {
+		lastflush = nrays;
+		(*dev->flush)();
+	}
 }