--- ray/src/common/bsdf.c	2011/04/24 20:16:52	2.25
+++ ray/src/common/bsdf.c	2011/04/25 15:48:05	2.26
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char RCSid[] = "$Id: bsdf.c,v 2.25 2011/04/24 20:16:52 greg Exp $";
+static const char RCSid[] = "$Id: bsdf.c,v 2.26 2011/04/25 15:48:05 greg Exp $";
 #endif
 /*
  *  bsdf.c
@@ -496,7 +496,7 @@ SDsizeBSDF(double *projSA, const FVECT v1, const RREAL
 	SDError		ec;
 	int		i;
 					/* check arguments */
-	if ((projSA == NULL) | (v1 == NULL))
+	if ((projSA == NULL) | (v1 == NULL) | (sd == NULL))
 		return SDEargument;
 					/* initialize extrema */
 	switch (qflags) {
@@ -516,11 +516,12 @@ SDsizeBSDF(double *projSA, const FVECT v1, const RREAL
 		rdf = sd->rf;
 	else
 		rdf = sd->rb;
-	tdf = NULL;			/* transmitted component? */
-	if (v2 != NULL && v1[2] > 0 ^ v2[2] > 0) {
-		rdf = NULL;
-		tdf = sd->tf;
-	}
+	tdf = sd->tf;
+	if (v2 != NULL)			/* bidirectional? */
+		if (v1[2] > 0 ^ v2[2] > 0)
+			rdf = NULL;
+		else
+			tdf = NULL;
 	ec = SDEdata;			/* run through components */
 	for (i = (rdf==NULL) ? 0 : rdf->ncomp; i--; ) {
 		ec = (*rdf->comp[i].func->queryProjSA)(projSA, v1, v2,