[Radiance-general] Annual simulations + BSDF

[Andrew McNeil]

Hi Everyone,

I¹m trying to figure out how to incorporate clearshade from panelite (
http://www.e-panelite.com/downloads/Panelite_IGU_Oct08.pdf ) into an annual
daylight simulation.

I¹m considering the three-phase method Greg described on slide 11 of in his
workshop #6 talk:
http://www.radiance-online.org/radiance-workshop6/GregWard/WardUsingBTDF_tal
k.pdf

Which in theory seems pretty straight forward:
1 ­ determine daylight coefficients incident on the glazing
2 ­ use a BSDF to define the relationship between incident light directions
and exiting light distribution for the glazing.
3 ­ determine the relationship between exiting light directions and
illuminance in the space.
4 ­ multiply results by many other results to produce an annual illuminance
profile.

However I face a couple of challenges for which I seek advice:

Challenge 1 ­ I don¹t have BSDF data from panelite, they are looking into
having a sample measured but that won¹t help me right now.  I was thinking
that I could build a radiance model of panelite and use rtconrib to generate
a BSDF of sorts.  Is this a terrible idea?

Challenge 2 ­ Writing a rtcontrib expression to separate contributions
according to exiting direction from the portal.  Can I use directions from
treganza.cal?  Is there some reason that this isn¹t a good idea?  Klems
directions has been mentioned.  I have no knowledge of klems directions.  Is
that a better alternative?

And I guess the overall questions:  Are there more challenges I have yet to
discover?  Is anyone who has done this willing to share experiences?  Would
I be better off creating a model with thousands of cylinders between glass
panes and using rtcontrib + brute force?  Is there an even better method
that I haven¹t discovered trolling through archives?

Thanks,
Andy

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