Recently, I found the BSDF file generated by Window lbnl and Radiance genBSDF is a little different. The standard BSDF xml files used in Window are “dual-band” where there are sets of values for two wavelength ranges (Solar and Visible). However, when usually running genBSDF in Raidance for daylighting simulation, there is just a result for a “single-band” material (usually visible). And also, there is no section with material data at the top(like ThermalConductivity, Emissivity).
If I want to load the BSDF files into Window for thermal properties calculation, I have to make the Xml file from radiance to be like the standard one in Window. I’ve been told that I can run genBSDF in radiance for two times to get a solar band and a visible band, and to combine those two into one XML file. However, I don’t know the efficient procedure. And also, I don’t know how to add the materia data like Emissivity into the top few lines in XML.
One more thing. I’ve tried to use BSDF2KLEMS command for the XML generated by genBSDF. There are material data (like ThermalConductivity) in the top few lines of the file after running the command.
I don’t know if this is the right move, but it indeed generated the tags with data.
The interaction between Radiance and WINDOW is not very well worked out, I’m afraid, as the tools serve slightly different purposes. WINDOW is used more for thermal and solar gain analysis, and Radiance is tailored for illumination studies.
The extra metadata needed by WINDOW can be set with the -W option and adding appropriate -s options to your genBSDF command. These options are briefly documented in the genBSDF man page. (See also the wrapBSDF man page for a list of metadata variables.)
There is no efficient procedure for adding solar and visible wavebands, though this would be a reasonable thing to add with the new spectral rendering capabilities in Radiance. However, you can compute tristimulus color using the genBSDF -C option, which may be useful in Radiance, though it is not understood by WINDOW. Again, the two systems are not very compatible.
Thanks a lot! I have tried the input-W option in genBSDF, and the generated XML file is following a standard template of Window with material data like ThermalConductivity, EmissivityFront in the very first few lines. However, I don’t know how these properties are calculated in genBSDF. Are they just default values for a standard template, or they are actually calculated using the input rad file?
They are NOT calculated by genBSDF. You need to edit these in the XML yourself, or use the genBSDF -s option to assign them according to the list in the wrapBSDF man page, which is what I was trying to explain.
I read from Window Technical Documentation, that Window uses genBSDF to generate the layer properties in three wavelength bands(Solar, Visible, IR), and hemispherical emissivity and TIR are obtained by integrating the BSDFs for the IR band.
Window uses genBSDF to generate the BSDF in Solar. Visible, and IR bands. The emissivity and TIR are obtained by integrating the BSDFs for the IR band. I think the formulas may be: （According to Kirchhoff law, the emissivity equals the absorption）
τ denotes BTDF value, Ω denotes projected solid angls for the klems patch, R denotes BRDF value.
（According to Kirchhoff law, the emissivity equals the absorption）