AW: Re: How to simulate an artificial sun

Hi Greg,
thanks a lot for answer. That's exactly the solution I was looking for.
I don't care to much about the fall-off at the edges of my model. This
approximation meets all my expectations.

Kind regards,


-----Ursprüngliche Nachricht-----
Von: Greg Ward [mailto:[email protected]]
Gesendet: Freitag, 29. Mai 2009 19:41
An: Radiance general discussion
Betreff: Re: [Radiance-general] How to simulate an artificial sun

Hi Kai,

Is the 20,000 lux measured at the source or at the receiving surface?

You are best off using the "source" type with a 1.5-degree solid angle,
even though your source is not infinitely distant. Do you care very
much about the fall-off at the edges of your model? You could create an
aperture that passes the infinitely distant source -- essentially a
large opaque ring with a 70 cm hole in the appropriate place. Does the
behavior of the light source have to precisely match, or is an
approximation such as this good enough?

Does this make sense?

From: "Kai Babetzki" <[email protected]>
Date: May 29, 2009 9:32:26 AM PDT

Dear Radiance Community,
I'm trying to compare measurements done in an artificial sky with
radiance simulations. The problem I'm currently facing is how to model

a lamp with a diameter of 70 centimeter that produces 20000 lux with
an aperture of 1.5° (nearly parallel light) in Radiance?

Will be the only possibility to measure the existing lamp in a
photogoniometer and use the ies format data files? Or are there other
and maybe easier ways to simulate such an artificial sun lamp in
Radiance? Some quick and dirty way would be nice!

Kind regards,

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