--- ray/src/util/dctimestep.c	2012/02/21 20:09:25	2.19
+++ ray/src/util/dctimestep.c	2012/11/02 00:26:55	2.23
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char RCSid[] = "$Id: dctimestep.c,v 2.19 2012/02/21 20:09:25 greg Exp $";
+static const char RCSid[] = "$Id: dctimestep.c,v 2.23 2012/11/02 00:26:55 greg Exp $";
 #endif
 /*
  * Compute time-step result using Daylight Coefficient method.
@@ -252,8 +252,29 @@ not_handled:
 	return(NULL);	/* gratis return */
 }
 
-/* Multiply two matrices (or a matrix and a vector) and allocate the result*/
+/* Scale a matrix by a single value */
 static CMATRIX *
+cm_scale(const CMATRIX *cm1, const COLOR sca)
+{
+	CMATRIX	*cmr;
+	int	dr, dc;
+
+	cmr = cm_alloc(cm1->nrows, cm1->ncols);
+	if (cmr == NULL)
+		return(NULL);
+	for (dr = 0; dr < cmr->nrows; dr++)
+	    for (dc = 0; dc < cmr->ncols; dc++) {
+	        const COLORV	*sp = cm_lval(cm1,dr,dc);
+		COLORV		*dp = cm_lval(cmr,dr,dc);
+		dp[0] = sp[0] * sca[0];
+		dp[1] = sp[1] * sca[1];
+		dp[2] = sp[2] * sca[2];
+	    }
+	return(cmr);
+}
+
+/* Multiply two matrices (or a matrix and a vector) and allocate the result */
+static CMATRIX *
 cm_multiply(const CMATRIX *cm1, const CMATRIX *cm2)
 {
 	CMATRIX	*cmr;
@@ -301,7 +322,7 @@ cm_bsdf(const COLOR bsdfLamb, const COLOR specCol, con
 	int	nbadohm = 0;
 	int	nneg = 0;
 	int	r, c;
-					/* reciprocity is "transparent" */
+					/* loop over incident angles */
 	for (c = 0; c < cm->ncols; c++) {
 		const double	dom = mBSDF_incohm(bsdf,c);
 					/* projected solid angle */
@@ -330,15 +351,80 @@ cm_bsdf(const COLOR bsdfLamb, const COLOR specCol, con
 	return(cm);
 }
 
+/* Convert between input and output indices for reciprocity */
+static int
+recip_out_from_in(const SDMat *bsdf, int in_recip)
+{
+	FVECT	v;
+
+	if (!mBSDF_incvec(v, bsdf, in_recip+.5))
+		return(in_recip);		/* XXX should be error! */
+	v[2] = -v[2];
+	return(mBSDF_outndx(bsdf, v));
+}
+
+/* Convert between output and input indices for reciprocity */
+static int
+recip_in_from_out(const SDMat *bsdf, int out_recip)
+{
+	FVECT	v;
+
+	if (!mBSDF_outvec(v, bsdf, out_recip+.5))
+		return(out_recip);		/* XXX should be error! */
+	v[2] = -v[2];
+	return(mBSDF_incndx(bsdf, v));
+}
+
+/* Convert a BSDF to our matrix representation, applying reciprocity */
+static CMATRIX *
+cm_bsdf_recip(const COLOR bsdfLamb, const COLOR specCol, const SDMat *bsdf)
+{
+	CMATRIX	*cm = cm_alloc(bsdf->ninc, bsdf->nout);
+	int	nbadohm = 0;
+	int	nneg = 0;
+	int	r, c;
+					/* loop over incident angles */
+	for (c = 0; c < cm->ncols; c++) {
+		const int	ro = recip_out_from_in(bsdf,c);
+		const double	dom = mBSDF_outohm(bsdf,ro);
+					/* projected solid angle */
+		nbadohm += (dom <= 0);
+
+		for (r = 0; r < cm->nrows; r++) {
+			const int	ri = recip_in_from_out(bsdf,r);
+			float		f = mBSDF_value(bsdf,ri,ro);
+			COLORV		*mp = cm_lval(cm,r,c);
+					/* check BSDF value */
+			if ((f <= 0) | (dom <= 0)) {
+				nneg += (f < -FTINY);
+				f = .0f;
+			}
+			copycolor(mp, specCol);
+			scalecolor(mp, f);
+			addcolor(mp, bsdfLamb);
+			scalecolor(mp, dom);
+		}
+	}
+	if (nneg | nbadohm) {
+		sprintf(errmsg,
+		    "BTDF has %d negatives and %d bad incoming solid angles",
+				nneg, nbadohm);
+		error(WARNING, errmsg);
+	}
+	return(cm);
+}
+
 /* Load and convert a matrix BSDF from the given XML file */
 static CMATRIX *
-cm_loadBSDF(char *fname)
+cm_loadBSDF(char *fname, COLOR cLamb)
 {
-	CMATRIX	*Tmat;
-	char	*fpath;
-	SDError	ec;
-	SDData	myBSDF;
-	COLOR	bsdfLamb, specCol;
+	CMATRIX		*Tmat;
+	char		*fpath;
+	int		recip;
+	SDError		ec;
+	SDData		myBSDF;
+	SDSpectralDF	*tdf;
+	COLOR		bsdfLamb, specCol;
 					/* find path to BSDF file */
 	fpath = getpath(fname, getrlibpath(), R_OK);
 	if (fpath == NULL) {
@@ -349,15 +435,25 @@ cm_loadBSDF(char *fname)
 	ec = SDloadFile(&myBSDF, fpath);
 	if (ec)
 		error(USER, transSDError(ec));
-	if (myBSDF.tf == NULL || myBSDF.tf->ncomp != 1 ||
-			myBSDF.tf->comp[0].func != &SDhandleMtx) {
+	ccy2rgb(&myBSDF.tLamb.spec, myBSDF.tLamb.cieY/PI, bsdfLamb);
+	recip = (myBSDF.tb == NULL);
+	tdf = recip ? myBSDF.tf : myBSDF.tb;
+	if (tdf == NULL) {		/* no non-Lambertian transmission? */
+		if (cLamb != NULL)
+			copycolor(cLamb, bsdfLamb);
+		SDfreeBSDF(&myBSDF);
+		return(NULL);
+	}
+	if (tdf->ncomp != 1 || tdf->comp[0].func != &SDhandleMtx) {
 		sprintf(errmsg, "unsupported BSDF '%s'", fpath);
 		error(USER, errmsg);
 	}
 					/* convert BTDF to matrix */
-	ccy2rgb(&myBSDF.tLamb.spec, myBSDF.tLamb.cieY/PI, bsdfLamb);
-	ccy2rgb(&myBSDF.tf->comp[0].cspec[0], 1., specCol);
-	Tmat = cm_bsdf(bsdfLamb, specCol, (SDMat *)myBSDF.tf->comp[0].dist);
+	ccy2rgb(&tdf->comp[0].cspec[0], 1., specCol);
+	Tmat = recip ? cm_bsdf_recip(bsdfLamb, specCol, (SDMat *)tdf->comp[0].dist)
+			: cm_bsdf(bsdfLamb, specCol, (SDMat *)tdf->comp[0].dist);
+	if (cLamb != NULL)		/* Lambertian is included */
+		setcolor(cLamb, .0, .0, .0);
 					/* free BSDF and return */
 	SDfreeBSDF(&myBSDF);
 	return(Tmat);
@@ -466,7 +562,7 @@ hasNumberFormat(const char *s)
 int
 main(int argc, char *argv[])
 {
-	CMATRIX			*cvec;
+	CMATRIX			*cvec;		/* component vector result */
 
 	progname = argv[0];
 
@@ -479,17 +575,24 @@ main(int argc, char *argv[])
 
 	if (argc > 3) {				/* VTDs expression */
 		CMATRIX	*svec, *Dmat, *Tmat, *ivec;
+		COLOR	tLamb;
 						/* get sky vector */
 		svec = cm_load(argv[4], 0, 1, DTascii);
 						/* load BSDF */
-		Tmat = cm_loadBSDF(argv[2]);
+		Tmat = cm_loadBSDF(argv[2], tLamb);
 						/* load Daylight matrix */
-		Dmat = cm_load(argv[3], Tmat->ncols, svec->nrows, DTfromHeader);
+		Dmat = cm_load(argv[3], Tmat==NULL ? 0 : Tmat->ncols,
+					svec->nrows, DTfromHeader);
 						/* multiply vector through */
 		ivec = cm_multiply(Dmat, svec);
 		cm_free(Dmat); cm_free(svec);
-		cvec = cm_multiply(Tmat, ivec);	/* cvec = component vector */
-		cm_free(Tmat); cm_free(ivec);
+		if (Tmat == NULL) {		/* diffuse only */
+			cvec = cm_scale(ivec, tLamb);
+		} else {			/* else apply BTDF matrix */
+			cvec = cm_multiply(Tmat, ivec);
+			cm_free(Tmat); 
+		}
+		cm_free(ivec);
 	} else {				/* else just use sky vector */
 		cvec = cm_load(argv[2], 0, 1, DTascii);
 	}