--- ray/src/rt/ambcomp.c	2014/05/07 01:16:02	2.49
+++ ray/src/rt/ambcomp.c	2014/05/08 04:02:40	2.53
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char	RCSid[] = "$Id: ambcomp.c,v 2.49 2014/05/07 01:16:02 greg Exp $";
+static const char	RCSid[] = "$Id: ambcomp.c,v 2.53 2014/05/08 04:02:40 greg Exp $";
 #endif
 /*
  * Routines to compute "ambient" values using Monte Carlo
@@ -105,7 +105,7 @@ vdb_edge(int db1, int db2)
 	case VDB_xY:	return(db2==VDB_x ? VDB_y : VDB_X);
 	case VDB_Xy:	return(db2==VDB_y ? VDB_x : VDB_Y);
 	}
-	error(INTERNAL, "forbidden diagonal in vdb_edge()");
+	error(CONSISTENCY, "forbidden diagonal in vdb_edge()");
 	return(-1);
 }
 
@@ -272,10 +272,10 @@ static void
 ambsupersamp(double acol[3], AMBHEMI *hp, int cnt)
 {
 	float	*earr = getambdiffs(hp);
-	double	e2sum = 0;
+	double	e2sum = 0.0;
 	AMBSAMP	*ap;
 	RAY	ar;
-	COLOR	asum;
+	double	asum[3];
 	float	*ep;
 	int	i, j, n;
 
@@ -288,7 +288,7 @@ ambsupersamp(double acol[3], AMBHEMI *hp, int cnt)
 	for (ap = hp->sa, i = 0; i < hp->ns; i++)
 	    for (j = 0; j < hp->ns; j++, ap++) {
 		int	nss = *ep/e2sum*cnt + frandom();
-		setcolor(asum, 0., 0., 0.);
+		asum[0] = asum[1] = asum[2] = 0.0;
 		for (n = 1; n <= nss; n++) {
 			if (!getambsamp(&ar, hp, i, j, n)) {
 				nss = n-1;
@@ -299,7 +299,7 @@ ambsupersamp(double acol[3], AMBHEMI *hp, int cnt)
 		if (nss) {		/* update returned ambient value */
 			const double	ssf = 1./(nss + 1);
 			for (n = 3; n--; )
-				acol[n] += ssf*colval(asum,n) +
+				acol[n] += ssf*asum[n] +
 						(ssf - 1.)*colval(ap->v,n);
 		}
 		e2sum -= *ep++;		/* update remainders */
@@ -537,7 +537,7 @@ add2gradient(FVECT grad, FVECT egrad1, FVECT egrad2, F
 
 
 /* Compute anisotropic radii and eigenvector directions */
-static int
+static void
 eigenvectors(FVECT uv[2], float ra[2], FVECT hessian[3])
 {
 	double	hess2[2][2];
@@ -559,9 +559,10 @@ eigenvectors(FVECT uv[2], float ra[2], FVECT hessian[3
 	if (i == 1)			/* double-root (circle) */
 		evalue[1] = evalue[0];
 	if (!i || ((evalue[0] = fabs(evalue[0])) <= FTINY*FTINY) |
-			((evalue[1] = fabs(evalue[1])) <= FTINY*FTINY) )
-		error(INTERNAL, "bad eigenvalue calculation");
-
+			((evalue[1] = fabs(evalue[1])) <= FTINY*FTINY) ) {
+		ra[0] = ra[1] = maxarad;
+		return;
+	}
 	if (evalue[0] > evalue[1]) {
 		ra[0] = sqrt(sqrt(4.0/evalue[0]));
 		ra[1] = sqrt(sqrt(4.0/evalue[1]));
@@ -722,30 +723,42 @@ ambdirgrad(AMBHEMI *hp, FVECT uv[2], float dg[2])
 static uint32
 ambcorral(AMBHEMI *hp, FVECT uv[2], const double r0, const double r1)
 {
-	uint32	flgs = 0;
-	int	i, j;
-					/* circle around perimeter */
+	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));
+	double		avg_d = 0;
+	uint32		flgs = 0;
+	int		i, j;
+					/* don't bother for a few samples */
+	if (hp->ns < 12)
+		return(0);
+					/* check distances overhead */
+	for (i = hp->ns*3/4; i-- > hp->ns>>2; )
+	    for (j = hp->ns*3/4; j-- > hp->ns>>2; )
+		avg_d += ambsam(hp,i,j).d;
+	avg_d *= 4.0/(hp->ns*hp->ns);
+	if (avg_d*r0 >= 1.0)		/* ceiling too low for corral? */
+		return(0);
+	if (avg_d >= max_d)		/* insurance */
+		return(0);
+					/* else circle around perimeter */
 	for (i = 0; i < hp->ns; i++)
 	    for (j = 0; j < hp->ns; j += !i|(i==hp->ns-1) ? 1 : hp->ns-1) {
 		AMBSAMP	*ap = &ambsam(hp,i,j);
 		FVECT	vec;
 		double	u, v;
-		double	ang;
+		double	ang, a1;
 		int	abp;
-		if (ap->d <= FTINY)
-			continue;
+		if ((ap->d <= FTINY) | (ap->d >= max_d))
+			continue;	/* too far or too near */
 		VSUB(vec, ap->p, hp->rp->rop);
 		u = DOT(vec, uv[0]) * ap->d;
 		v = DOT(vec, uv[1]) * ap->d;
 		if ((r0*r0*u*u + r1*r1*v*v) * ap->d*ap->d <= 1.0)
 			continue;	/* occluder outside ellipse */
 		ang = atan2a(v, u);	/* else set direction flags */
-		ang += 2.0*PI*(ang < 0);
-		ang *= 16./PI;
-		if ((ang < .5) | (ang >= 31.5))
-			flgs |= 0x80000001;
-		else
-			flgs |= 3L<<(int)(ang-.5);
+		for (a1 = ang-.5*ang_res; a1 <= ang+.5*ang_res; a1 += ang_step)
+			flgs |= 1L<<(int)(16/PI*(a1 + 2.*PI*(a1 < 0)));
 	    }
 	return(flgs);
 }
@@ -802,7 +815,7 @@ doambient(				/* compute ambient component */
 		return(-1);		/* return value w/o Hessian */
 	}
 	cnt = ambssamp*wt + 0.5;	/* perform super-sampling? */
-	if (cnt > 0)
+	if (cnt > 8)
 		ambsupersamp(acol, hp, cnt);
 	copycolor(rcol, acol);		/* final indirect irradiance/PI */
 	if ((ra == NULL) & (pg == NULL) & (dg == NULL)) {
@@ -816,6 +829,7 @@ doambient(				/* compute ambient component */
 		K = 1.0;
 		pg = NULL;
 		dg = NULL;
+		crlp = NULL;
 	}
 	ap = hp->sa;			/* relative Y channel from here on... */
 	for (i = hp->ns*hp->ns; i--; ap++)
@@ -851,7 +865,8 @@ doambient(				/* compute ambient component */
 			if (ra[0] > maxarad)
 				ra[0] = maxarad;
 		}
-		if (crlp != NULL)	/* flag encroached directions */
+					/* flag encroached directions */
+		if ((wt >= 0.5-FTINY) & (crlp != NULL))
 			*crlp = ambcorral(hp, uv, ra[0]*ambacc, ra[1]*ambacc);
 		if (pg != NULL) {	/* cap gradient if necessary */
 			d = pg[0]*pg[0]*ra[0]*ra[0] + pg[1]*pg[1]*ra[1]*ra[1];