--- ray/src/rt/ambient.c	2014/04/19 19:20:47	2.75
+++ ray/src/rt/ambient.c	2014/05/06 17:15:11	2.85
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char	RCSid[] = "$Id: ambient.c,v 2.75 2014/04/19 19:20:47 greg Exp $";
+static const char	RCSid[] = "$Id: ambient.c,v 2.85 2014/05/06 17:15:11 greg Exp $";
 #endif
 /*
  *  ambient.c - routines dealing with ambient (inter-reflected) component.
@@ -52,7 +52,6 @@ static int  nunflshed = 0;	/* number of unflushed ambi
 #endif
 
 
-static double  qambacc = 0.;		/* ambient accuracy to the 1/4 power */
 static double  avsum = 0.;		/* computed ambient value sum (log) */
 static unsigned int  navsum = 0;	/* number of values in avsum */
 static unsigned int  nambvals = 0;	/* total number of indirect values */
@@ -110,17 +109,17 @@ setambres(				/* set ambient resolution */
 						/* set min & max radii */
 	if (ar <= 0) {
 		minarad = 0;
-		maxarad = thescene.cusize / 2.0;
+		maxarad = thescene.cusize*0.5;
 	} else {
 		minarad = thescene.cusize / ar;
-		maxarad = 64 * minarad;			/* heuristic */
-		if (maxarad > thescene.cusize / 2.0)
-			maxarad = thescene.cusize / 2.0;
+		maxarad = 64.0 * minarad;		/* heuristic */
+		if (maxarad > thescene.cusize*0.5)
+			maxarad = thescene.cusize*0.5;
 	}
 	if (minarad <= FTINY)
-		minarad = 10*FTINY;
+		minarad = 10.0*FTINY;
 	if (maxarad <= minarad)
-		maxarad = 64 * minarad;
+		maxarad = 64.0 * minarad;
 }
 
 
@@ -129,13 +128,11 @@ setambacc(				/* set ambient accuracy */
 	double  newa
 )
 {
-	double  ambdiff;
-
-	if (newa < 0.0)
-		newa = 0.0;
-	ambdiff = fabs(newa - ambacc);
-	if (ambdiff >= .01 && (ambacc = newa) > FTINY) {
-		qambacc = sqrt(sqrt(ambacc));
+	static double	olda;		/* remember previous setting here */
+	
+	newa *= (newa > 0);
+	if (fabs(newa - olda) >= .05*(newa + olda)) {
+		ambacc = newa;
 		if (nambvals > 0)
 			sortambvals(1);		/* rebuild tree */
 	}
@@ -357,12 +354,37 @@ sumambient(		/* get interpolated ambient value */
 	FVECT  c0,
 	double	s
 )
-{					/* initial limit is ambacc radians */
-	const double	maxangle = (ambacc-PI/2.)*pow(r->rweight,0.13) + PI/2.;
+{			/* initial limit is 10 degrees plus ambacc radians */
+	const double	minangle = 10.0 * PI/180.;
+	double		maxangle = minangle + ambacc;
 	double		wsum = 0.0;
 	FVECT		ck0;
 	int		i, j;
 	AMBVAL		*av;
+
+	if (at->kid != NULL) {		/* sum children first */				
+		s *= 0.5;
+		for (i = 0; i < 8; i++) {
+			for (j = 0; j < 3; j++) {
+				ck0[j] = c0[j];
+				if (1<<j & i)
+					ck0[j] += s;
+				if (r->rop[j] < ck0[j] - OCTSCALE*s)
+					break;
+				if (r->rop[j] > ck0[j] + (1.0+OCTSCALE)*s)
+					break;
+			}
+			if (j == 3)
+				wsum += sumambient(acol, r, rn, al,
+							at->kid+i, ck0, s);
+		}
+					/* good enough? */
+		if (wsum >= 0.05 && s > minarad*10.0)
+			return(wsum);
+	}
+					/* adjust maximum angle */
+	if (at->alist != NULL && (at->alist->lvl <= al) & (r->rweight < 0.6))
+		maxangle = (maxangle - PI/2.)*pow(r->rweight,0.13) + PI/2.;
 					/* sum this node */
 	for (av = at->alist; av != NULL; av = av->next) {
 		double	d, delta_r2, delta_t2;
@@ -389,53 +411,37 @@ sumambient(		/* get interpolated ambient value */
 		if (delta_r2 >= maxangle*maxangle)
 			continue;
 		/*
+		 *  Modified ray behind test
+		 */
+		VSUB(ck0, r->rop, av->pos);
+		d = DOT(ck0, uvw[2]);
+		if (d < -minarad*ambacc-.001)
+			continue;
+		d /= av->rad[0];
+		delta_t2 = d*d;
+		if (delta_t2 >= ambacc*ambacc)
+			continue;
+		/*
 		 *  Elliptical radii test based on Hessian
 		 */
 		decodedir(uvw[0], av->udir);
 		VCROSS(uvw[1], uvw[2], uvw[0]);
-		VSUB(ck0, av->pos, r->rop);
 		d = DOT(ck0, uvw[0]) / av->rad[0];
-		delta_t2 = d*d;
+		delta_t2 += d*d;
 		d = DOT(ck0, uvw[1]) / av->rad[1];
 		delta_t2 += d*d;
-		if (delta_t2 >= qambacc*qambacc)
+		if (delta_t2 >= ambacc*ambacc)
 			continue;
 		/*
-		 *  Intersection behind test
-		 */
-		d = 0.0;
-		for (j = 0; j < 3; j++)
-			d += (r->rop[j] - av->pos[j])*(uvw[2][j] + r->ron[j]);
-		if (d*0.5 < -minarad*ambacc-.001)
-			continue;
-		/*
 		 *  Extrapolate value and compute final weight (hat function)
 		 */
 		extambient(ct, av, r->rop, rn, uvw);
 		d = tfunc(maxangle, sqrt(delta_r2), 0.0) *
-			tfunc(qambacc, sqrt(delta_t2), 0.0);
+			tfunc(ambacc, sqrt(delta_t2), 0.0);
 		scalecolor(ct, d);
 		addcolor(acol, ct);
 		wsum += d;
 	}
-	if (at->kid == NULL)
-		return(wsum);
-					/* sum children */
-	s *= 0.5;
-	for (i = 0; i < 8; i++) {
-		for (j = 0; j < 3; j++) {
-			ck0[j] = c0[j];
-			if (1<<j & i)
-				ck0[j] += s;
-			if (r->rop[j] < ck0[j] - OCTSCALE*s)
-				break;
-			if (r->rop[j] > ck0[j] + (1.0+OCTSCALE)*s)
-				break;
-		}
-		if (j == 3)
-			wsum += sumambient(acol, r, rn, al,
-						at->kid+i, ck0, s);
-	}
 	return(wsum);
 }
 
@@ -461,7 +467,7 @@ makeambient(		/* make a new ambient value for storage 
 						/* compute ambient */
 	i = doambient(acol, r, amb.weight, uvw, amb.rad, amb.gpos, amb.gdir);
 	scalecolor(acol, 1./AVGREFL);		/* undo assumed reflectance */
-	if (i <= 0)				/* no Hessian => no storage */
+	if (i <= 0 || amb.rad[0] <= FTINY)	/* no Hessian or zero radius */
 		return(i);
 						/* store value */
 	VCOPY(amb.pos, r->rop);
@@ -534,7 +540,7 @@ avinsert(				/* insert ambient value in our tree */
 	at = &atrunk;
 	VCOPY(ck0, thescene.cuorg);
 	s = thescene.cusize;
-	while (s*(OCTSCALE/2) > av->rad[1]*qambacc) {
+	while (s*(OCTSCALE/2) > av->rad[1]*ambacc) {
 		if (at->kid == NULL)
 			if ((at->kid = newambtree()) == NULL)
 				error(SYSTEM, "out of memory in avinsert");