cshake nous illumina en ce 2009-02-15 00:10 -->
> Hello all,
> 
> I'm working a theatrical lighting system library for povray, based on LightSysIV
> and CIE by Jaime and Ive, and I'm running into two problems with spotlights.
> 
> The first is trying to simulate a PARCan
> <http://en.wikipedia.org/wiki/Parabolic_aluminized_reflector_light>, which is
> an instrument with a lens that produces a soft-edged oval shape.
> I've already implemented the standard spotlight with the built in function (with
> beam and field angle), but can't figure this out without creating a complex
> glass-textured asymmetrical solid lens. Does anyone know how to create this
> effect?
> 
> The second is a problem with the color of the falloff of the standard spotlight.
> If I use a light color that is slightly off-white (to be exact, using
> Blackbody(3200) from CIE), the center of the beam is the correct color but it
> changes from light yellow-ish to a deep orange between the beam radius and
> falloff radius. This is projecting onto a pure white surface (diffuse 1 ambient
> 0), and using light fading. I didn't specify the fade_color, since I assume it
> is black? How can I get rid of this effect, as it doesn't model real light
> behavior at all? (possibly helpful addition: the original light color is way
> over rgb 1.0 (closer to rgb 1*10000), to allow for a distant light)
> 
> Thanks for any help!
> 
> 
Blackbody(3200) is rather redish, not slightly off-white, similar to a spotlight 
running with a much lower voltage than it's rating.
A value around 4500 to 5000 would give you a much yellower tint. And around 6500 
will be close to white. 7000 will give a marked blue cast.

If you see the cender of the beam in a weak reflector, it will look prety orange.

fade_color is NOT used for lights, but for coloured transparent materials and is 
found in the interior block of such objects.

-- 
Alain
-------------------------------------------------
Fundamentalism: If shit happens to a televangelist, it's okay.

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