Source for uniform sky

radiance-general
1

Hi,

Very basic question:

When simulating uniform sky, I see that usually “source” geometry is used, with 180degree angle.

However, “source” also has a direction vector associated with it. Seeing as the sky is uniform, what’s the physical meaning of this directionality?

Thanks

2

It’s so that Radiance ‘knows’ that the sky is up. Which isn’t as odd as it sounds, since a 180 source with a direction vector ‘0 0 -1’ is used to model the ‘glowing’ ground. See Section 2.3 here:

Best
John

Daylight Experts Ltd.
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Associate Editor Lighting Research & Technology