--- ray/src/util/dctimestep.c	2009/06/21 21:42:12	2.7
+++ ray/src/util/dctimestep.c	2009/07/02 02:13:08	2.10
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char RCSid[] = "$Id: dctimestep.c,v 2.7 2009/06/21 21:42:12 greg Exp $";
+static const char RCSid[] = "$Id: dctimestep.c,v 2.10 2009/07/02 02:13:08 greg Exp $";
 #endif
 /*
  * Compute time-step result using Daylight Coefficient method.
@@ -38,7 +38,7 @@ cm_alloc(int nrows, int ncols)
 	CMATRIX	*cm;
 
 	if ((nrows <= 0) | (ncols <= 0))
-		return(NULL);
+		error(USER, "attempt to create empty matrix");
 	cm = (CMATRIX *)malloc(sizeof(CMATRIX) +
 				3*sizeof(COLORV)*(nrows*ncols - 1));
 	if (cm == NULL)
@@ -294,12 +294,11 @@ static CMATRIX *
 cm_bsdf(const struct BSDF_data *bsdf)
 {
 	CMATRIX	*cm = cm_alloc(bsdf->nout, bsdf->ninc);
-	COLORV	*mp = cm->cmem;
 	int	nbadohm = 0;
 	int	nneg = 0;
 	int	r, c;
 	
-	for (c = 0; c < cm->ncols; c++, mp += 3) {
+	for (c = 0; c < cm->ncols; c++) {
 		float	dom = getBSDF_incohm(bsdf,c);
 		FVECT	v;
 		
@@ -313,10 +312,11 @@ cm_bsdf(const struct BSDF_data *bsdf)
 
 		for (r = 0; r < cm->nrows; r++) {
 			float	f = BSDF_value(bsdf,c,r);
+			COLORV	*mp = cm_lval(cm,r,c);
 
 			if (f <= .0) {
 				nneg += (f < -FTINY);
-				continue;
+				f = .0f;
 			}
 			mp[0] = mp[1] = mp[2] = f * dom;
 		}