--- ray/src/rt/ambient.c	2005/04/19 01:15:06	2.58
+++ ray/src/rt/ambient.c	2007/09/15 05:16:10	2.66
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char	RCSid[] = "$Id: ambient.c,v 2.58 2005/04/19 01:15:06 greg Exp $";
+static const char	RCSid[] = "$Id: ambient.c,v 2.66 2007/09/15 05:16:10 greg Exp $";
 #endif
 /*
  *  ambient.c - routines dealing with ambient (inter-reflected) component.
@@ -140,7 +140,7 @@ extern void
 setambient(void)				/* initialize calculation */
 {
 	int	readonly = 0;
-	long  pos, flen;
+	long	flen;
 	AMBVAL	amb;
 						/* make sure we're fresh */
 	ambdone();
@@ -160,7 +160,7 @@ setambient(void)				/* initialize calculation */
 		readonly = (ambfp = fopen(ambfile, "r")) != NULL;
 	if (ambfp != NULL) {
 		initambfile(0);			/* file exists */
-		pos = ftell(ambfp);
+		lastpos = ftell(ambfp);
 		while (readambval(&amb, ambfp))
 			avinsert(avstore(&amb));
 		nambshare = nambvals;		/* share loaded values */
@@ -174,26 +174,26 @@ setambient(void)				/* initialize calculation */
 			return;			/* avoid ambsync() */
 		}
 						/* align file pointer */
-		pos += (long)nambvals*AMBVALSIZ;
+		lastpos += (long)nambvals*AMBVALSIZ;
 		flen = lseek(fileno(ambfp), (off_t)0, SEEK_END);
-		if (flen != pos) {
+		if (flen != lastpos) {
 			sprintf(errmsg,
 			"ignoring last %ld values in ambient file (corrupted)",
-					(flen - pos)/AMBVALSIZ);
+					(flen - lastpos)/AMBVALSIZ);
 			error(WARNING, errmsg);
-			fseek(ambfp, pos, 0);
+			fseek(ambfp, lastpos, SEEK_SET);
 #ifndef _WIN32 /* XXX we need a replacement for that one */
-			ftruncate(fileno(ambfp), (off_t)pos);
+			ftruncate(fileno(ambfp), (off_t)lastpos);
 #endif
 		}
 	} else if ((ambfp = fopen(ambfile, "w+")) != NULL) {
 		initambfile(1);			/* else create new file */
+		lastpos = ftell(ambfp);
 	} else {
 		sprintf(errmsg, "cannot open ambient file \"%s\"", ambfile);
 		error(SYSTEM, errmsg);
 	}
-	nunflshed++;	/* lie */
-	ambsync();
+	ambsync();			/* load previous values */
 }
 
 
@@ -275,29 +275,30 @@ multambient(		/* compute ambient component & multiply 
 		goto dumbamb;
 
 	if (ambacc <= FTINY) {			/* no ambient storage */
+		copycolor(acol, aval);
 		rdepth++;
-		d = doambient(acol, r, aval, intens(aval)*r->rweight,
-							NULL, NULL);
+		d = doambient(acol, r, r->rweight, NULL, NULL);
 		rdepth--;
 		if (d <= FTINY)
 			goto dumbamb;
-		multcolor(aval, acol);
+		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, aval, nrm, rdepth-1);
+	d = makeambient(acol, r, nrm, rdepth-1);
 	rdepth--;
 	if (d > FTINY) {
 		multcolor(aval, acol);		/* got new value */
@@ -351,7 +352,7 @@ 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.
@@ -430,34 +431,39 @@ 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,
 	RAY  *r,
-	COLOR  ac,
 	FVECT  rn,
 	int  al
 )
 {
 	AMBVAL	amb;
-	double	coef;
 	FVECT	gp, gd;
-						/* compute weight */
-	amb.weight = pow(AVGREFL, (double)al);
-	coef = intens(ac)*r->rweight;
-	if (coef < 0.1*amb.weight)		/* heuristic */
-		amb.weight = coef;
+	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, ac, amb.weight, gp, gd);
-	if (amb.rad <= FTINY)
+	amb.rad = doambient(acol, r, amb.weight, gp, gd);
+	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;
@@ -858,6 +864,8 @@ aflock(			/* lock/unlock ambient file */
 {
 	static struct flock  fls;	/* static so initialized to zeroes */
 
+	if (typ == fls.l_type)		/* already called? */
+		return;
 	fls.l_type = typ;
 	if (fcntl(fileno(ambfp), F_SETLKW, &fls) < 0)
 		error(SYSTEM, "cannot (un)lock ambient file");
@@ -871,12 +879,10 @@ ambsync(void)			/* synchronize ambient file */
 	AMBVAL	avs;
 	register int  n;
 
-	if (nunflshed == 0)
+	if (ambfp == NULL)	/* no ambient file? */
 		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;
@@ -886,7 +892,7 @@ ambsync(void)			/* synchronize ambient file */
 			if (ambinp == NULL)
 				error(SYSTEM, "fdopen failed in ambsync");
 		}
-		if (fseek(ambinp, lastpos, 0) < 0)
+		if (fseek(ambinp, lastpos, SEEK_SET) < 0)
 			goto seekerr;
 		while (n >= AMBVALSIZ) {	/* load contributed values */
 			if (!readambval(&avs, ambinp)) {
@@ -899,9 +905,10 @@ 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
@@ -912,10 +919,12 @@ ambsync(void)			/* synchronize ambient file */
 		error(CONSISTENCY, errmsg);
 	}
 #endif
-syncend:
 	n = fflush(ambfp);			/* calls write() at last */
-	if ((lastpos = lseek(fileno(ambfp), (off_t)0, SEEK_CUR)) < 0)
+	if (n != EOF)
+		lastpos += (long)nunflshed*AMBVALSIZ;
+	else if ((lastpos = lseek(fileno(ambfp), (off_t)0, SEEK_CUR)) < 0)
 		goto seekerr;
+		
 	aflock(F_UNLCK);			/* release file */
 	nunflshed = 0;
 	return(n);
@@ -929,7 +938,7 @@ seekerr:
 extern int
 ambsync(void)			/* flush ambient file */
 {
-	if (nunflshed == 0)
+	if (ambfp == NULL)
 		return(0);
 	nunflshed = 0;
 	return(fflush(ambfp));