[Radiance-general] genBSDF

[Greg Ward]

The default genBSDF +b option should work fine.  Radiance knows how to reverse directions on transmission if it has to, but the direction is usually out the window, so +b is what you want.

The reason the code favors the "Transmission Front" data is because some Window6 files contain "filler" information for the "Transmission Back" data that is unreliable.  If both are present, it is safer to use the "Front" data for that reason.  In the case of genBSDF, there is no concern, since it doesn't fake its output.

Best,
-Greg

> From: Jia Hu <hujia06 at gmail.com>
> Date: February 20, 2014 8:16:54 PM GMT+01:00
> 
> Hi, 
> 
> I looked at the genbsdf.pl.  It seems that genBSDF +f will generate the Tranmission Front (defined in xml file) and genBSDF +b will generate "Transmission Back" in xml.  
> 
>  However, bsdf_m.c code prefers the "Transmission Front" data. So when using genbsdf, is that a good pratice to add +f, which generate "Transmission Front" that is preferred by Radiance?
> 
> 
> 	if (!sdata)
> 		return RC_FAIL;
> 	/*
> 	 * Remember that front and back are reversed from WINDOW 6 orientations
> 	 * Favor their "Front" (incoming light) since that's more often valid
> 	 */
> 	tfront = !strcasecmp(sdata, "Transmission Back");
> 	if (!strcasecmp(sdata, "Transmission Front") ||
> 			tfront & (sd->tf == NULL)) {
> 		if (sd->tf != NULL)
> 			SDfreeSpectralDF(sd->tf);
> 		if ((sd->tf = SDnewSpectralDF(1)) == NULL)
> 			return RC_MEMERR;
> 		df = sd->tf;
> 	} else if (!strcasecmp(sdata, "Reflection Front")) {
> 		if (sd->rb != NULL)	/* note back-front reversal */
> 			SDfreeSpectralDF(sd->rb);
> 		if ((sd->rb = SDnewSpectralDF(1)) == NULL)
> 			return RC_MEMERR;
> 		df = sd->rb;
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