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Registered: ‎06-04-2011
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Assigning a Bidirectional Reflectance Distribution Function (BRDF) to surfaces

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06-04-2011 10:41 PM

I'd like to simulate some microoptical (prism-film like) features in a daylighting analysis, utlimately producing annual light availability maps (false color, with shadowing).


Since I don't know how to capture the optical functions in Ecotect, I am considering to simulate/measure these as BRDFs and then assign BRDFs (as kind of a black-box approach) to the respective surfaces. I know Radiance can work well with BRDFs. But is this possible in Ecotect as well? And how do I assign a BRDF to a surface?


Thanks for any help.





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Re: Assigning a Bidirectional Reflectance Distribution Function (BRDF) surface

06-05-2011 03:05 PM in reply to: TrisQ

I'm in the same situation like you , and this is what I'm going to do , I'm going to assign any material from Ecotect's library to the window , something like Double_Glazed_Alum material or any other material , then I'm going to create a material file (.rad File) with the same name and place it in the same file's directory , the file for prismatic materials with two bidirectional refraction is something like that


void prism2 id
9 coef1 dx1 dy1 dz1 coef2 dx2 dy2 dz2
4 A1 A2 A3 A4



A1: refractive index (around 1.5)

A2: The thickness of the triangular prism

A3: The height of the upper triangular prism

A4: The height of the lower triangular prism

( I attached a picture of the prismatic glazing so you know what are the variables mean)



then when you export to radiance check the box that says check for .rad materials , Radiance will use the file you created instead of ecotect's material, you can import Radiance's result back to ectotect for further analysis. I doubt that you can produce annual daylighting Availability because I asked the same question to Cristoph Reinhart , the Creator of Daysim and this is what he said:


"the reason for Daysim crashing is that function file (*.cal) materials
cannot be handled by the modified rtrace_dc version that Daysim uses to
calculate the daylight coefficients for the different sensor points. I
wish that I could easily solve this but the Radiance code surrounding
function files is somewhat of a mystery to me."

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