--- ray/src/rt/ambient.c	2004/03/30 16:13:00	2.56
+++ ray/src/rt/ambient.c	2007/09/14 00:50:31	2.64
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char	RCSid[] = "$Id: ambient.c,v 2.56 2004/03/30 16:13:00 schorsch Exp $";
+static const char	RCSid[] = "$Id: ambient.c,v 2.64 2007/09/14 00:50:31 greg Exp $";
 #endif
 /*
  *  ambient.c - routines dealing with ambient (inter-reflected) component.
@@ -24,7 +24,9 @@ static const char	RCSid[] = "$Id: ambient.c,v 2.56 200
 
 extern char  *shm_boundary;	/* memory sharing boundary */
 
-#define	 MAXASET	511	/* maximum number of elements in ambient set */
+#ifndef  MAXASET
+#define	 MAXASET	2047	/* maximum number of elements in ambient set */
+#endif
 OBJECT	ambset[MAXASET+1]={0};	/* ambient include/exclude set */
 
 double	maxarad;		/* maximum ambient radius */
@@ -190,8 +192,7 @@ setambient(void)				/* initialize calculation */
 		sprintf(errmsg, "cannot open ambient file \"%s\"", ambfile);
 		error(SYSTEM, errmsg);
 	}
-	nunflshed++;	/* lie */
-	ambsync();
+	ambsync();			/* load previous values */
 }
 
 
@@ -252,13 +253,14 @@ ambnotify(			/* record new modifier */
 
 
 extern void
-ambient(		/* compute ambient component for ray */
-	COLOR  acol,
+multambient(		/* compute ambient component & multiply by coef. */
+	COLOR  aval,
 	register RAY  *r,
 	FVECT  nrm
 )
 {
 	static int  rdepth = 0;			/* ambient recursion */
+	COLOR	acol;
 	double	d, l;
 
 	if (ambdiv <= 0)			/* no ambient calculation */
@@ -272,42 +274,50 @@ ambient(		/* compute ambient component for ray */
 		goto dumbamb;
 
 	if (ambacc <= FTINY) {			/* no ambient storage */
+		copycolor(acol, aval);
 		rdepth++;
 		d = doambient(acol, r, r->rweight, NULL, NULL);
 		rdepth--;
 		if (d <= FTINY)
 			goto dumbamb;
+		copycolor(aval, acol);
 		return;
 	}
 
 	if (tracktime)				/* sort to minimize thrashing */
 		sortambvals(0);
-						/* get ambient value */
+						/* interpolate ambient value */
 	setcolor(acol, 0.0, 0.0, 0.0);
 	d = sumambient(acol, r, nrm, rdepth,
 			&atrunk, thescene.cuorg, thescene.cusize);
 	if (d > FTINY) {
-		scalecolor(acol, 1.0/d);
+		d = 1.0/d;
+		scalecolor(acol, d);
+		multcolor(aval, acol);
 		return;
 	}
 	rdepth++;				/* need to cache new value */
 	d = makeambient(acol, r, nrm, rdepth-1);
 	rdepth--;
-	if (d > FTINY)
+	if (d > FTINY) {
+		multcolor(aval, acol);		/* got new value */
 		return;
+	}
 dumbamb:					/* return global value */
-	copycolor(acol, ambval);
-	if ((ambvwt <= 0) | (navsum == 0))
+	if ((ambvwt <= 0) | (navsum == 0)) {
+		multcolor(aval, ambval);
 		return;
+	}
 	l = bright(ambval);			/* average in computations */
 	if (l > FTINY) {
 		d = (log(l)*(double)ambvwt + avsum) /
 				(double)(ambvwt + navsum);
 		d = exp(d) / l;
-		scalecolor(acol, d);		/* apply color of ambval */
+		scalecolor(aval, d);
+		multcolor(aval, ambval);	/* apply color of ambval */
 	} else {
 		d = exp( avsum / (double)navsum );
-		setcolor(acol, d, d, d);	/* neutral color */
+		scalecolor(aval, d);		/* neutral color */
 	}
 }
 
@@ -341,7 +351,7 @@ sumambient(	/* get interpolated ambient value */
 		 */
 		if (av->lvl > al)	/* list sorted, so this works */
 			break;
-		if (av->weight < r->rweight-FTINY)
+		if (av->weight < 0.9*r->rweight)
 			continue;
 		/*
 		 *  Ambient radius test.
@@ -420,31 +430,39 @@ sumambient(	/* get interpolated ambient value */
 				break;
 		}
 		if (j == 3)
-			wsum += sumambient(acol, r, rn, al, at->kid+i, ck0, s);
+			wsum += sumambient(acol, r, rn, al,
+						at->kid+i, ck0, s);
 	}
 	return(wsum);
 }
 
 
 extern double
-makeambient(	/* make a new ambient value */
+makeambient(		/* make a new ambient value for storage */
 	COLOR  acol,
-	register RAY  *r,
+	RAY  *r,
 	FVECT  rn,
 	int  al
 )
 {
 	AMBVAL	amb;
 	FVECT	gp, gd;
-						/* compute weight */
-	amb.weight = pow(AVGREFL, (double)al);
-	if (r->rweight < 0.1*amb.weight)	/* heuristic */
-		amb.weight = r->rweight;
+	int	i;
+
+	amb.weight = 1.0;			/* compute weight */
+	for (i = al; i-- > 0; )
+		amb.weight *= AVGREFL;
+	if (r->rweight < 0.1*amb.weight)	/* heuristic override */
+		amb.weight = 1.25*r->rweight;
+	setcolor(acol, AVGREFL, AVGREFL, AVGREFL);
 						/* compute ambient */
 	amb.rad = doambient(acol, r, amb.weight, gp, gd);
-	if (amb.rad <= FTINY)
+	if (amb.rad <= FTINY) {
+		setcolor(acol, 0.0, 0.0, 0.0);
 		return(0.0);
-						/* store it */
+	}
+	scalecolor(acol, 1./AVGREFL);		/* undo assumed reflectance */
+						/* store value */
 	VCOPY(amb.pos, r->rop);
 	VCOPY(amb.dir, r->ron);
 	amb.lvl = al;
@@ -858,12 +876,10 @@ ambsync(void)			/* synchronize ambient file */
 	AMBVAL	avs;
 	register int  n;
 
-	if (nunflshed == 0)
-		return(0);
 	if (lastpos < 0)	/* initializing (locked in initambfile) */
 		goto syncend;
-				/* gain exclusive access */
-	aflock(F_WRLCK);
+				/* gain appropriate access */
+	aflock(nunflshed ? F_WRLCK : F_RDLCK);
 				/* see if file has grown */
 	if ((flen = lseek(fileno(ambfp), (off_t)0, SEEK_END)) < 0)
 		goto seekerr;
@@ -886,9 +902,10 @@ ambsync(void)			/* synchronize ambient file */
 			avinsert(avstore(&avs));
 			n -= AMBVALSIZ;
 		}
+		lastpos = flen - n;
 		/*** seek always as safety measure
 		if (n) ***/			/* alignment */
-			if (lseek(fileno(ambfp), (off_t)(flen-n), SEEK_SET) < 0)
+			if (lseek(fileno(ambfp), (off_t)lastpos, SEEK_SET) < 0)
 				goto seekerr;
 	}
 #ifdef  DEBUG
@@ -901,8 +918,11 @@ ambsync(void)			/* synchronize ambient file */
 #endif
 syncend:
 	n = fflush(ambfp);			/* calls write() at last */
-	if ((lastpos = lseek(fileno(ambfp), (off_t)0, SEEK_CUR)) < 0)
-		goto seekerr;
+	if (n == EOF) {
+		if ((lastpos = lseek(fileno(ambfp), (off_t)0, SEEK_CUR)) < 0)
+			goto seekerr;
+	} else
+		lastpos += (long)nunflshed*AMBVALSIZ;
 	aflock(F_UNLCK);			/* release file */
 	nunflshed = 0;
 	return(n);
@@ -916,8 +936,6 @@ seekerr:
 extern int
 ambsync(void)			/* flush ambient file */
 {
-	if (nunflshed == 0)
-		return(0);
 	nunflshed = 0;
 	return(fflush(ambfp));
 }