--- ray/src/rt/ambcomp.c	2014/05/19 20:23:48	2.62
+++ ray/src/rt/ambcomp.c	2014/10/23 18:19:14	2.68
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char	RCSid[] = "$Id: ambcomp.c,v 2.62 2014/05/19 20:23:48 greg Exp $";
+static const char	RCSid[] = "$Id: ambcomp.c,v 2.68 2014/10/23 18:19:14 greg Exp $";
 #endif
 /*
  * Routines to compute "ambient" values using Monte Carlo
@@ -21,7 +21,7 @@ static const char	RCSid[] = "$Id: ambcomp.c,v 2.62 201
 #include  "ambient.h"
 #include  "random.h"
 
-#ifdef NEWAMB
+#ifndef OLDAMB
 
 extern void		SDsquare2disk(double ds[2], double seedx, double seedy);
 
@@ -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))
@@ -178,7 +180,6 @@ ambsupersamp(AMBHEMI *hp, int cnt)
 	float	*earr = getambdiffs(hp);
 	double	e2rem = 0;
 	AMBSAMP	*ap;
-	RAY	ar;
 	float	*ep;
 	int	i, j, n, nss;
 
@@ -608,8 +609,8 @@ static uint32
 ambcorral(AMBHEMI *hp, FVECT uv[2], const double r0, const double r1)
 {
 	const double	max_d = 1.0/(minarad*ambacc + 0.001);
-	const double	ang_res = 0.5*PI/(hp->ns-1);
-	const double	ang_step = ang_res/((int)(16/PI*ang_res) + (1+FTINY));
+	const double	ang_res = 0.5*PI/hp->ns;
+	const double	ang_step = ang_res/((int)(16/PI*ang_res) + 1.01);
 	double		avg_d = 0;
 	uint32		flgs = 0;
 	FVECT		vec;
@@ -640,7 +641,7 @@ ambcorral(AMBHEMI *hp, FVECT uv[2], const double r0, c
 		if ((r0*r0*u*u + r1*r1*v*v) * ap->d*ap->d <= u*u + v*v)
 			continue;	/* occluder outside ellipse */
 		ang = atan2a(v, u);	/* else set direction flags */
-		for (a1 = ang-.5*ang_res; a1 <= ang+.5*ang_res; a1 += ang_step)
+		for (a1 = ang-ang_res; a1 <= ang+ang_res; a1 += ang_step)
 			flgs |= 1L<<(int)(16/PI*(a1 + 2.*PI*(a1 < 0)));
 	    }
 					/* add low-angle incident (< 20deg) */
@@ -693,7 +694,7 @@ doambient(				/* compute ambient component */
 		return(0);
 
 	if ((ra == NULL) & (pg == NULL) & (dg == NULL) ||
-			(hp->sampOK < 0) | (hp->ns < 4)) {
+			(hp->sampOK < 0) | (hp->ns < 6)) {
 		free(hp);		/* Hessian not requested/possible */
 		return(-1);		/* value-only return value */
 	}