--- ray/src/rt/ambcomp.c	2014/06/19 16:26:55	2.63
+++ ray/src/rt/ambcomp.c	2014/08/21 10:33:49	2.65
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char	RCSid[] = "$Id: ambcomp.c,v 2.63 2014/06/19 16:26:55 greg Exp $";
+static const char	RCSid[] = "$Id: ambcomp.c,v 2.65 2014/08/21 10:33:49 greg Exp $";
 #endif
 /*
  * Routines to compute "ambient" values using Monte Carlo
@@ -78,7 +78,9 @@ ambsample(				/* initial ambient division sample */
 	hlist[1] = j;
 	hlist[2] = i;
 	multisamp(spt, 2, urand(ilhash(hlist,3)+n));
-	if (!n) {			/* avoid border samples for n==0 */
+					/* avoid coincident samples */
+	if (!n && (0 < i) & (i < hp->ns-1) &&
+			(0 < j) & (j < hp->ns-1)) {
 		if ((spt[0] < 0.1) | (spt[0] >= 0.9))
 			spt[0] = 0.1 + 0.8*frandom();
 		if ((spt[1] < 0.1) | (spt[1] >= 0.9))
@@ -217,7 +219,7 @@ samp_hemi(				/* sample indirect hemisphere */
 			wt > (d = 0.8*intens(rcol)*r->rweight/(ambdiv*minweight)))
 		wt = d;			/* avoid ray termination */
 	n = sqrt(ambdiv * wt) + 0.5;
-	i = 1 + 5*(ambacc > FTINY);	/* minimum number of samples */
+	i = 1 + 8*(ambacc > FTINY);	/* minimum number of samples */
 	if (n < i)
 		n = i;
 					/* allocate sampling array */
@@ -693,7 +695,7 @@ doambient(				/* compute ambient component */
 		return(0);
 
 	if ((ra == NULL) & (pg == NULL) & (dg == NULL) ||
-			(hp->sampOK < 0) | (hp->ns < 4)) {
+			(hp->sampOK < 0) | (hp->ns < 9)) {
 		free(hp);		/* Hessian not requested/possible */
 		return(-1);		/* value-only return value */
 	}