--- ray/src/rt/ambient.c	1996/02/14 15:43:22	2.36
+++ ray/src/rt/ambient.c	1998/06/17 13:29:55	2.44
@@ -1,4 +1,4 @@
-/* Copyright (c) 1995 Regents of the University of California */
+/* Copyright (c) 1996 Regents of the University of California */
 
 #ifndef lint
 static char SCCSid[] = "$SunId$ LBL";
@@ -50,13 +50,14 @@ static int  nunflshed = 0;	/* number of unflushed ambi
 #endif
 #endif
 #ifndef SORT_INTVL
-#define SORT_INTVL	(SORT_THRESH*256)
+#define SORT_INTVL	(SORT_THRESH<<1)
 #endif
 #ifndef MAX_SORT_INTVL
-#define MAX_SORT_INTVL	(SORT_INTVL<<4)
+#define MAX_SORT_INTVL	(SORT_INTVL<<6)
 #endif
 
-static COLOR  avsum = BLKCOLOR;		/* computed ambient value sum */
+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 */
 static unsigned int  nambshare = 0;	/* number of values from file */
 static unsigned long  ambclock = 0;	/* ambient access clock */
@@ -69,15 +70,17 @@ static long  sortintvl = SORT_INTVL;	/* time until nex
 	 * through memory on a multiprocessor, when we want to avoid
 	 * claiming our own memory (copy on write).  Go ahead anyway
 	 * if more than two thirds of our values are unshared.
+	 * Compile with -Dtracktime=0 to turn this code off.
 	 */
+#ifndef tracktime
 #define tracktime	(shm_boundary == NULL || nambvals > 3*nambshare)
+#endif
 
 #define	 AMBFLUSH	(BUFSIZ/AMBVALSIZ)
 
 #define	 newambval()	(AMBVAL *)bmalloc(sizeof(AMBVAL))
 
-extern long  ftell(), lseek();
-static int  initambfile(), avsave(), avinsert(), sortambvals();
+static int  initambfile(), avsave(), avinsert(), sortambvals(), avlmemi();
 static AMBVAL  *avstore();
 #ifdef  F_SETLKW
 static  aflock();
@@ -121,7 +124,7 @@ double  newa;
 setambient(afile)			/* initialize calculation */
 char  *afile;
 {
-	long  headlen;
+	long  pos, flen;
 	AMBVAL	amb;
 						/* init ambient limits */
 	setambres(ambres);
@@ -137,11 +140,20 @@ char  *afile;
 						/* open ambient file */
 	if ((ambfp = fopen(afile, "r+")) != NULL) {
 		initambfile(0);
-		headlen = ftell(ambfp);
+		pos = ftell(ambfp);
 		while (readambval(&amb, ambfp))
 			avinsert(avstore(&amb));
 						/* align */
-		fseek(ambfp, -((ftell(ambfp)-headlen)%AMBVALSIZ), 1);
+		pos += (long)nambvals*AMBVALSIZ;
+		flen = lseek(fileno(ambfp), 0L, 2);
+		if (flen != pos) {
+			sprintf(errmsg,
+			"ignoring last %ld values in ambient file (corrupted)",
+					(flen - pos)/AMBVALSIZ);
+			error(WARNING, errmsg);
+			fseek(ambfp, pos, 0);
+			ftruncate(fileno(ambfp), pos);
+		}
 		nambshare = nambvals;
 	} else if ((ambfp = fopen(afile, "w+")) != NULL)
 		initambfile(1);
@@ -182,7 +194,7 @@ register RAY  *r;
 FVECT  nrm;
 {
 	static int  rdepth = 0;			/* ambient recursion */
-	double	d;
+	double	d, l;
 
 	if (ambdiv <= 0)			/* no ambient calculation */
 		goto dumbamb;
@@ -202,8 +214,9 @@ FVECT  nrm;
 			goto dumbamb;
 		return;
 	}
-						/* resort memory? */
-	sortambvals(0);
+
+	if (tracktime)				/* sort to minimize thrashing */
+		sortambvals(0);
 						/* get ambient value */
 	setcolor(acol, 0.0, 0.0, 0.0);
 	d = sumambient(acol, r, nrm, rdepth,
@@ -219,12 +232,18 @@ FVECT  nrm;
 		return;
 dumbamb:					/* return global value */
 	copycolor(acol, ambval);
-	if (ambvwt <= 0 | nambvals == 0)
+	if (ambvwt <= 0 | navsum == 0)
 		return;
-	scalecolor(acol, (double)ambvwt);
-	addcolor(acol, avsum);			/* average in computations */
-	d = 1.0/(ambvwt+nambvals);
-	scalecolor(acol, d);
+	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 */
+	} else {
+		d = exp( avsum / (double)navsum );
+		setcolor(acol, d, d, d);	/* neutral color */
+	}
 }
 
 
@@ -249,7 +268,7 @@ double	s;
 					/* do this node */
 	for (av = at->alist; av != NULL; av = av->next) {
 		if (tracktime)
-			av->latick = ambclock++;
+			av->latick = ambclock;
 		/*
 		 *  Ambient level test.
 		 */
@@ -394,10 +413,10 @@ int  creat;
 	setbuf(ambfp, bmalloc(BUFSIZ+8));
 	if (creat) {			/* new file */
 		newheader("RADIANCE", ambfp);
-		fprintf(ambfp, "%s -av %g %g %g -ab %d -aa %g ",
+		fprintf(ambfp, "%s -av %g %g %g -aw %d -ab %d -aa %g ",
 				progname, colval(ambval,RED),
 				colval(ambval,GRN), colval(ambval,BLU),
-				ambounce, ambacc);
+				ambvwt, ambounce, ambacc);
 		fprintf(ambfp, "-ad %d -as %d -ar %d %s\n",
 				ambdiv, ambssamp, ambres,
 				octname==NULL ? "" : octname);
@@ -433,14 +452,19 @@ avstore(aval)				/* allocate memory and store aval */
 register AMBVAL  *aval;
 {
 	register AMBVAL  *av;
+	double	d;
 
 	if ((av = newambval()) == NULL)
 		error(SYSTEM, "out of memory in avstore");
 	copystruct(av, aval);
 	av->latick = ambclock;
 	av->next = NULL;
-	addcolor(avsum, av->val);	/* add to sum for averaging */
 	nambvals++;
+	d = bright(av->val);
+	if (d > FTINY) {		/* add to log sum for averaging */
+		avsum += log(d);
+		navsum++;
+	}
 	return(av);
 }
 
@@ -543,28 +567,33 @@ int	(*f)();
 }
 
 
-static AMBVAL	**avlist1, **avlist2;	/* ambient value lists for sorting */
+static struct avl {
+	AMBVAL	*p;
+	unsigned long	t;
+}	*avlist1;			/* ambient value list with ticks */
+static AMBVAL	**avlist2;		/* memory positions for sorting */
 static int	i_avlist;		/* index for lists */
 
 
 static
 av2list(av)
-AMBVAL	*av;
+register AMBVAL	*av;
 {
 #ifdef DEBUG
 	if (i_avlist >= nambvals)
 		error(CONSISTENCY, "too many ambient values in av2list1");
 #endif
-	avlist1[i_avlist] = avlist2[i_avlist] = av;
-	i_avlist++;
+	avlist1[i_avlist].p = avlist2[i_avlist] = av;
+	avlist1[i_avlist++].t = av->latick;
 }
 
 
 static int
-alatcmp(avp1, avp2)			/* compare ambient values for MRA */
-AMBVAL	**avp1, **avp2;
+alatcmp(av1, av2)			/* compare ambient values for MRA */
+struct avl	*av1, *av2;
 {
-	return((**avp2).latick - (**avp1).latick);
+	register long  lc = av2->t - av1->t;
+	return(lc<0 ? -1 : lc>0 ? 1 : 0);
 }
 
 
@@ -576,7 +605,7 @@ AMBVAL	**avp1, **avp2;
 }
 
 
-#ifdef DEBUG
+#if 1
 static int
 avlmemi(avaddr)				/* find list position from address */
 AMBVAL	*avaddr;
@@ -603,7 +632,7 @@ int	always;
 	AMBVAL	tav, *tap, *pnext;
 	register int	i, j;
 					/* see if it's time yet */
-	if (!always && (ambclock < lastsort+sortintvl ||
+	if (!always && (ambclock++ < lastsort+sortintvl ||
 			nambvals < SORT_THRESH))
 		return;
 	/*
@@ -622,13 +651,15 @@ int	always;
 	 * tree will be rebuilt with the new accuracy parameter.
 	 */
 	if (tracktime) {		/* allocate pointer arrays to sort */
-		avlist1 = (AMBVAL **)malloc(nambvals*sizeof(AMBVAL *));
 		avlist2 = (AMBVAL **)malloc(nambvals*sizeof(AMBVAL *));
-	} else
-		avlist1 = avlist2 = NULL;
-	if (avlist2 == NULL) {		/* no time tracking -- rebuild tree? */
-		if (avlist1 != NULL)
-			free((char *)avlist1);
+		avlist1 = (struct avl *)malloc(nambvals*sizeof(struct avl));
+	} else {
+		avlist2 = NULL;
+		avlist1 = NULL;
+	}
+	if (avlist1 == NULL) {		/* no time tracking -- rebuild tree? */
+		if (avlist2 != NULL)
+			free((char *)avlist2);
 		if (always) {		/* rebuild without sorting */
 			copystruct(&oldatrunk, &atrunk);
 			atrunk.alist = NULL;
@@ -655,22 +686,22 @@ int	always;
 		if (i_avlist < nambvals)
 			error(CONSISTENCY, "missing ambient values in sortambvals");
 #endif
-		qsort((char *)avlist1, nambvals, sizeof(AMBVAL *), alatcmp);
+		qsort((char *)avlist1, nambvals, sizeof(struct avl), alatcmp);
 		qsort((char *)avlist2, nambvals, sizeof(AMBVAL *), aposcmp);
 		for (i = 0; i < nambvals; i++) {
-			if (avlist1[i] == NULL)
+			if (avlist1[i].p == NULL)
 				continue;
 			tap = avlist2[i];
 			copystruct(&tav, tap);
-			for (j = i; (pnext = avlist1[j]) != tap;
+			for (j = i; (pnext = avlist1[j].p) != tap;
 					j = avlmemi(pnext)) {
 				copystruct(avlist2[j], pnext);
 				avinsert(avlist2[j]);
-				avlist1[j] = NULL;
+				avlist1[j].p = NULL;
 			}
 			copystruct(avlist2[j], &tav);
 			avinsert(avlist2[j]);
-			avlist1[j] = NULL;
+			avlist1[j].p = NULL;
 		}
 		free((char *)avlist1);
 		free((char *)avlist2);
@@ -731,7 +762,13 @@ ambsync()			/* synchronize ambient file */
 		if (fseek(ambinp, lastpos, 0) < 0)
 			goto seekerr;
 		while (n >= AMBVALSIZ) {	/* load contributed values */
-			readambval(&avs, ambinp);
+			if (!readambval(&avs, ambinp)) {
+				sprintf(errmsg,
+				"ambient file corrupted near character %ld",
+						flen - n);
+				error(WARNING, errmsg);
+				break;
+			}
 			avinsert(avstore(&avs));
 			n -= AMBVALSIZ;
 		}