--- ray/src/px/pcond4.c	1996/10/04 16:10:43	3.3
+++ ray/src/px/pcond4.c	1996/10/05 08:05:27	3.6
@@ -99,8 +99,11 @@ compveil()				/* compute veiling image */
 					t2 = DOT(rdirscan(py)[px],
 							rdirscan(y)[x]);
 					if (t2 <= FTINY) continue;
+					/*	use approximation instead
 					t2 = acos(t2);
 					t2 = 1./(t2*t2);
+					*/
+					t2 = .5 / (1. - t2);
 					copycolor(ctmp, fovscan(y)[x]);
 					scalecolor(ctmp, t2);
 					addcolor(vsum, ctmp);
@@ -177,7 +180,12 @@ double	La;
 	};
 	double	l10La;
 	register int	i;
-					/* interpolate/extrapolate data */
+					/* check limits */
+	if (La <= 7.85e-4)
+		return(resfreq[0]);
+	if (La >= 1.78e3)
+		return(resfreq[NPOINTS-1]);
+					/* interpolate data */
 	l10La = log10(La);
 	for (i = 0; i < NPOINTS-2 && l10lum[i+1] <= l10La; i++)
 		;
@@ -196,11 +204,8 @@ int	y;
 	register COLOR	*sl0, *sl1, *mysl;
 	register int	i;
 
-	if (y < sb->nread - sb->nscans) {
-		fprintf(stderr, "%s: internal - cannot backspace in getascan\n",
-				progname);
-		exit(1);
-	}
+	if (y < sb->nread - sb->nscans)			/* too far back? */
+		return(NULL);
 	for ( ; y >= sb->nread; sb->nread++) {		/* read as necessary */
 		mysl = bscan(sb, sb->nread);
 		if (sb->sampr == 1) {
@@ -211,6 +216,8 @@ int	y;
 			}
 		} else {
 			sl0 = getascan(sb->next, 2*y);
+			if (sl0 == NULL)
+				return(NULL);
 			sl1 = getascan(sb->next, 2*y+1);
 			for (i = 0; i < sb->len; i++) {
 				copycolor(mysl[i], sl0[2*i]);
@@ -283,6 +290,12 @@ SCANBAR	*sb;
 	double	dx, dy;
 	int	ix, iy;
 
+	if (sb->sampr == 1) {		/* no need to interpolate */
+		sl0 = getascan(sb, y);
+		copycolor(col, sl0[x]);
+		return;
+	}
+					/* compute coordinates for sb */
 	ix = dx = (x+.5)/sb->sampr - .5;
 	if (ix >= sb->len-1) ix--;
 	dx -= (double)ix;
@@ -291,6 +304,11 @@ SCANBAR	*sb;
 	dy -= (double)iy;
 					/* get scanlines */
 	sl0 = getascan(sb, iy);
+	if (sl0 == NULL) {
+		fprintf(stderr, "%s: internal - cannot backspace in ascanval\n",
+				progname);
+		exit(1);
+	}
 	sl1 = getascan(sb, iy+1);
 					/* 2D linear interpolation */
 	copycolor(col, sl0[ix]);
@@ -355,9 +373,10 @@ initacuity()			/* initialize variable acuity sampling 
 			}
 			fcross(cp, diffx, diffy);
 			omega = 0.5 * sqrt(DOT(cp,cp));
-			tsampr(x,y) = PI/180. / sqrt(omega) /
-					hacuity(plum(fovscan(y)[x]));
-			if (tsampr(x,y) > maxsr)
+			if (omega <= FTINY)
+				tsampr(x,y) = 1.;
+			else if ((tsampr(x,y) = PI/180. / sqrt(omega) /
+					hacuity(plum(fovscan(y)[x]))) > maxsr)
 				maxsr = tsampr(x,y);
 		}
 					/* copy perimeter (easier) */