--- ray/src/cv/bsdfrbf.c	2013/11/08 23:32:54	2.15
+++ ray/src/cv/bsdfrbf.c	2013/11/08 23:49:07	2.16
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char RCSid[] = "$Id: bsdfrbf.c,v 2.15 2013/11/08 23:32:54 greg Exp $";
+static const char RCSid[] = "$Id: bsdfrbf.c,v 2.16 2013/11/08 23:49:07 greg Exp $";
 #endif
 /*
  * Radial basis function representation for BSDF data.
@@ -151,7 +151,7 @@ smooth_region(int x0, int x1, int y0, int y1)
 	rMtx[2][1] = rMtx[1][2];
 	nvs = rMtx[2][2];
 	if (SDinvXform(rMtx, rMtx) != SDEnone)
-		return(0);
+		return(1);		/* colinear values */
 	A = DOT(rMtx[0], xvec);
 	B = DOT(rMtx[1], xvec);
 	C = DOT(rMtx[2], xvec);