--- ray/src/rt/ambient.c	1995/05/03 09:46:27	2.30
+++ ray/src/rt/ambient.c	1995/10/24 13:33:23	2.33
@@ -18,7 +18,12 @@ static char SCCSid[] = "$SunId$ LBL";
 
 #include  "random.h"
 
+#ifndef  OCTSCALE
 #define	 OCTSCALE	1.0	/* ceil((valid rad.)/(cube size)) */
+#endif
+#ifndef  AMBVWT
+#define  AMBVWT		250	/* relative ambient value weight (# calcs) */
+#endif
 
 typedef struct ambtree {
 	AMBVAL	*alist;		/* ambient value list */
@@ -54,8 +59,9 @@ static int  nunflshed = 0;	/* number of unflushed ambi
 #define MAX_SORT_INTVL	(SORT_INTVL<<4)
 #endif
 
+static COLOR  avsum = BLKCOLOR;		/* computed ambient value sum */
+static unsigned int  nambvals = 0;	/* number of computed ambient values */
 static unsigned long  ambclock = 0;	/* ambient access clock */
-static unsigned int  nambvals = 0;	/* number of stored ambient values */
 static unsigned long  lastsort = 0;	/* time of last value sort */
 static long  sortintvl = SORT_INTVL;	/* time until next sort */
 
@@ -103,18 +109,13 @@ int  ar;
 setambacc(newa)				/* set ambient accuracy */
 double  newa;
 {
-	static double  oldambacc = -1.0;
+	double  ambdiff;
 
-	ambacc = newa < 0.0 ? 0.0 : newa;	/* may be done already */
-	if (oldambacc < -FTINY)
-		oldambacc = ambacc;	/* do nothing first call */
-	if (fabs(newa - oldambacc) < 0.01)
-		return;			/* insignificant -- don't bother */
-	if (ambacc <= FTINY)
-		return;			/* cannot build new tree */
-					/* else need to rebuild tree */
-	sortambvals(1);
-	oldambacc = ambacc;		/* remeber setting for next call */
+	if (newa < 0.0)
+		newa = 0.0;
+	ambdiff = fabs(newa - ambacc);
+	if (ambdiff >= .01 && (ambacc = newa) > FTINY && nambvals > 0)
+		sortambvals(1);			/* rebuild tree */
 }
 
 
@@ -196,7 +197,7 @@ register RAY  *r;
 		rdepth++;
 		d = doambient(acol, r, r->rweight, NULL, NULL);
 		rdepth--;
-		if (d == 0.0)
+		if (d <= FTINY)
 			goto dumbamb;
 		return;
 	}
@@ -206,16 +207,25 @@ register RAY  *r;
 	setcolor(acol, 0.0, 0.0, 0.0);
 	d = sumambient(acol, r, rdepth,
 			&atrunk, thescene.cuorg, thescene.cusize);
-	if (d > FTINY)
+	if (d > FTINY) {
 		scalecolor(acol, 1.0/d);
-	else {
-		d = makeambient(acol, r, rdepth++);
-		rdepth--;
+		return;
 	}
+	rdepth++;				/* need to cache new value */
+	d = makeambient(acol, r, rdepth-1);
+	rdepth--;
 	if (d > FTINY)
 		return;
 dumbamb:					/* return global value */
 	copycolor(acol, ambval);
+#if  AMBVWT
+	if (nambvals == 0)
+		return;
+	scalecolor(acol, (double)AMBVWT);
+	addcolor(acol, avsum);			/* average in computations */
+	d = 1.0/(AMBVWT+nambvals);
+	scalecolor(acol, d);
+#endif
 }
 
 
@@ -279,8 +289,7 @@ double	s;
 		 *  Jittering final test reduces image artifacts.
 		 */
 		wt = sqrt(e1) + sqrt(e2);
-		wt *= .9 + .2*urand(9015+samplendx);
-		if (wt > ambacc)
+		if (wt > ambacc*(.9+.2*urand(9015+samplendx)))
 			continue;
 		if (wt <= 1e-3)
 			wt = 1e3;
@@ -322,11 +331,11 @@ int  al;
 	FVECT	gp, gd;
 						/* compute weight */
 	amb.weight = pow(AVGREFL, (double)al);
-	if (r->rweight < 0.2*amb.weight)	/* heuristic */
+	if (r->rweight < 0.1*amb.weight)	/* heuristic */
 		amb.weight = r->rweight;
 						/* compute ambient */
 	amb.rad = doambient(acol, r, amb.weight, gp, gd);
-	if (amb.rad == 0.0)
+	if (amb.rad <= FTINY)
 		return(0.0);
 						/* store it */
 	VCOPY(amb.pos, r->rop);
@@ -427,6 +436,7 @@ register AMBVAL  *aval;
 	copystruct(av, aval);
 	av->latick = ambclock;
 	av->next = NULL;
+	addcolor(avsum, av->val);	/* add to sum for averaging */
 	nambvals++;
 	return(av);
 }
@@ -663,7 +673,7 @@ int	always;
 		free((char *)avlist2);
 						/* compute new sort interval */
 		sortintvl = ambclock - lastsort;
-		if (sortintvl > MAX_SORT_INTVL)
+		if (sortintvl >= MAX_SORT_INTVL/2)
 			sortintvl = MAX_SORT_INTVL;
 		else
 			sortintvl <<= 1;	/* wait twice as long next */