[Radiance-general] Perforated window shading

[Thomas Bleicher]

Marcus

Your LUX values will be very low. With a trans material you are basically
reducing the incoming light to about 1/8th of the available light. Your
simple trans material will also not account for indirect light reflected
off the blinds. This can be a substantial part of the transmitted light.

On Wed, Feb 22, 2012 at 6:56 AM, Marcus <jones.0bj3 at gmail.com> wrote:

> What about the transmittedSpecular value?


The transmittedSpecular part can be left at 1 (100%) because the light
passing through the holes will not be modulated. As a result you should see
the projection of the window opening on the floor if direct sunlight hits
it, just as you would see the shape of the window drawn in tiny dots in
real life. With trans you will not be able to model the angular dependent
cut off that you get with small perforated panels.


> Are there i.e. any empirical correlations for equivalent transmissivity as
> a function of hole size and/or void area ratio?


Unfortunately there is no golden rule because every system is different.
You have to look at the system and model it's shading effects as best as
possible. Sometimes this needs more than one calculation:

You could, for example, use your trans material to model only the light
that passes through the holes. Then you model another scene with metal
blinds in their actual size (or perhaps a bit larger) to capture the
indirect reflected light. Add both results together and you have a
reasonable approximation of the real system.

Regards,
Thomas
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