--- ray/src/rt/ambient.c	1995/10/24 13:33:23	2.33
+++ ray/src/rt/ambient.c	1996/07/09 13:32:35	2.38
@@ -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";
@@ -21,9 +21,6 @@ static char SCCSid[] = "$SunId$ LBL";
 #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 */
@@ -60,7 +57,8 @@ static int  nunflshed = 0;	/* number of unflushed ambi
 #endif
 
 static COLOR  avsum = BLKCOLOR;		/* computed ambient value sum */
-static unsigned int  nambvals = 0;	/* number of computed ambient values */
+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 */
 static unsigned long  lastsort = 0;	/* time of last value sort */
 static long  sortintvl = SORT_INTVL;	/* time until next sort */
@@ -69,9 +67,10 @@ static long  sortintvl = SORT_INTVL;	/* time until nex
 	/*
 	 * Track access times unless we are sharing ambient values
 	 * through memory on a multiprocessor, when we want to avoid
-	 * claiming our own memory (copy on write).
+	 * claiming our own memory (copy on write).  Go ahead anyway
+	 * if more than two thirds of our values are unshared.
 	 */
-#define tracktime	(shm_boundary == NULL || ambfp == NULL)
+#define tracktime	(shm_boundary == NULL || nambvals > 3*nambshare)
 
 #define	 AMBFLUSH	(BUFSIZ/AMBVALSIZ)
 
@@ -122,7 +121,7 @@ double  newa;
 setambient(afile)			/* initialize calculation */
 char  *afile;
 {
-	long  headlen;
+	long  pos, flen;
 	AMBVAL	amb;
 						/* init ambient limits */
 	setambres(ambres);
@@ -138,11 +137,20 @@ 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) {
+			error(WARNING,
+			"ignoring last %ld values in ambient file (corrupted)",
+					(flen - pos)/AMBVALSIZ);
+			fseek(ambfp, pos, 0);
+			ftruncate(fileno(ambfp), pos);
+		}
+		nambshare = nambvals;
 	} else if ((ambfp = fopen(afile, "w+")) != NULL)
 		initambfile(1);
 	else {
@@ -176,9 +184,10 @@ OBJECT	obj;
 }
 
 
-ambient(acol, r)		/* compute ambient component for ray */
+ambient(acol, r, nrm)		/* compute ambient component for ray */
 COLOR  acol;
 register RAY  *r;
+FVECT  nrm;
 {
 	static int  rdepth = 0;			/* ambient recursion */
 	double	d;
@@ -205,34 +214,33 @@ register RAY  *r;
 	sortambvals(0);
 						/* get ambient value */
 	setcolor(acol, 0.0, 0.0, 0.0);
-	d = sumambient(acol, r, rdepth,
+	d = sumambient(acol, r, nrm, rdepth,
 			&atrunk, thescene.cuorg, thescene.cusize);
 	if (d > FTINY) {
 		scalecolor(acol, 1.0/d);
 		return;
 	}
 	rdepth++;				/* need to cache new value */
-	d = makeambient(acol, r, rdepth-1);
+	d = makeambient(acol, r, nrm, rdepth-1);
 	rdepth--;
 	if (d > FTINY)
 		return;
 dumbamb:					/* return global value */
 	copycolor(acol, ambval);
-#if  AMBVWT
-	if (nambvals == 0)
+	if (ambvwt <= 0 | nambvals == 0)
 		return;
-	scalecolor(acol, (double)AMBVWT);
+	scalecolor(acol, (double)ambvwt);
 	addcolor(acol, avsum);			/* average in computations */
-	d = 1.0/(AMBVWT+nambvals);
+	d = 1.0/(ambvwt+nambvals);
 	scalecolor(acol, d);
-#endif
 }
 
 
 double
-sumambient(acol, r, al, at, c0, s)	/* get interpolated ambient value */
+sumambient(acol, r, rn, al, at, c0, s)	/* get interpolated ambient value */
 COLOR  acol;
 register RAY  *r;
+FVECT  rn;
 int  al;
 AMBTREE	 *at;
 FVECT  c0;
@@ -296,7 +304,7 @@ double	s;
 		else
 			wt = 1.0 / wt;
 		wsum += wt;
-		extambient(ct, av, r->rop, r->ron);
+		extambient(ct, av, r->rop, rn);
 		scalecolor(ct, wt);
 		addcolor(acol, ct);
 	}
@@ -315,16 +323,17 @@ double	s;
 				break;
 		}
 		if (j == 3)
-			wsum += sumambient(acol, r, al, at->kid+i, ck0, s);
+			wsum += sumambient(acol, r, rn, al, at->kid+i, ck0, s);
 	}
 	return(wsum);
 }
 
 
 double
-makeambient(acol, r, al)	/* make a new ambient value */
+makeambient(acol, r, rn, al)	/* make a new ambient value */
 COLOR  acol;
 register RAY  *r;
+FVECT  rn;
 int  al;
 {
 	AMBVAL	amb;
@@ -346,6 +355,8 @@ int  al;
 	VCOPY(amb.gdir, gd);
 						/* insert into tree */
 	avsave(&amb);				/* and save to file */
+	if (rn != r->ron)
+		extambient(acol, &amb, r->rop, rn);	/* texture */
 	return(amb.rad);
 }
 
@@ -561,7 +572,8 @@ static int
 alatcmp(avp1, avp2)			/* compare ambient values for MRA */
 AMBVAL	**avp1, **avp2;
 {
-	return((**avp2).latick - (**avp1).latick);
+	register long  lc = (**avp2).latick - (**avp1).latick;
+	return(lc<0 ? -1 : lc>0 ? 1 : 0);
 }
 
 
@@ -573,7 +585,7 @@ AMBVAL	**avp1, **avp2;
 }
 
 
-#ifdef DEBUG
+#if  1
 static int
 avlmemi(avaddr)				/* find list position from address */
 AMBVAL	*avaddr;
@@ -728,7 +740,13 @@ 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;
 		}