[Radiance-general] BSDF orientation and implementation

[Chris Coulter]

Good morning Gurus!

I have worked through the 3- and 5-phase tutorials in hopes of being able to apply a BSDF to one of my projects. This project will be using micro-louver cellular structures imbedded within an IGU, in both skylights and vertical windows. I think I understand the general process, but wanted to ask a few questions before getting too far down the road...

The skylights and windows are all different sizes and the windows are in multiple orientations (of course). My understanding of the BSDF and seemingly from this mail (http://www.radiance-online.org/pipermail/radiance-general/2011-November/008248.html), I should be able to calculate the BSDF once for my system. I was planning model the louvers as 1m by 1m, but run genBSDF with the -dim arguments smaller than this. Is this the correct approach? Ideally I would not calculate the BSDF for each orientation, assuming that micro-louver geometry does not change.

In my BSDF material definition, I would alter the up vector according to the surface being applied - the up vector matches the BSDF orientation (calculated in xy space) to the specific geometry's orientation (0 0 1 for a window). If the louver are rotated within the IGU assembly (rz -45) for a skylight, I can account for this with the up vector of 1 1 0 (surface normal is 0 0 1). This would hold true for rotation within the vertical apertures as well. Each different up vector would be a different BSDF material.

Lastly, if the glazing properties (VLT) are not defined yet, can I import the BSDF file into Window and create multiple options for IGU's with varying properties? It seems so from David Geisler-Moroder's presentation at the 2012 Workshop (http://radiance-online.org/community/workshops/2012-copenhagen/Day1/Geisler-Moroder/geisler-moroder_BSDF_tutorial_s.pdf). Certainly skylights and windows will have different VLT and it would again be nice to not be required to run genBSDF multiple times.

I am in the process of working through the steps on my own, but wanted to ask these questions while I'm waiting on genBSDF.


Any help is much appreciated, as always.

Chris Coulter
Senior Lighting Designer
Buro Happold Consulting Engineers
100 Broadway, 23rd Floor
New York, NY 10005
Tel: 212.334.2025
Direct: 212.616.0254
Email: chris.coulter at burohappold.com
Website: www.burohappold.com

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