"Christopher James Huff" <cja### [at] gmailcom> wrote in message 
news:cjameshuff-87CB6C.19220409032005@news.povray.org...
> In article <422f4268$1@news.povray.org>,
> "Jeremy M. Praay" <jer### [at] questsoftwarecom> wrote:
>
>> What are the benefits of using the reflective spectral data (e.g.
>> RS_White_Paint_1) over normal pigments?  Is it simply that the RS values
>> will look better under a much wider range of lighting?  Is it ok to mix
>> normal rgb pigments (e.g. rgb <1,0.8, 0.6>) along with the RS values?
>
> I'm not sure what Lightsys uses, but it sounds like it simply uses a
> greater number of samples for color. Real world color is a mess of
> wavelengths from a continuous spectrum. Not all light sources emit
> evenly through the entire visible spectrum, and most materials reflect
> very unevenly, with complicated variations of reflection as a function
> of wavelength. The same object can have very different appearances under
> two lights that both appear to be "white". The effect is especially
> important in highly monochromatic light, such as that from low-pressure
> sodium street lights. 3 channels simply aren't enough to simulate this
> kind of effect. The effects can be subtle or glaringly obvious,
> depending on the situation.
>


Thanks.  That's along the lines of what I was thinking.  As a real-world 
example, where I work, I sit under some strange yellow flourescent lights. 
Some of the papers strewn around my desk look white, others look very yellow 
or grey.  If I pick up those same papers and take them into my boss's office 
(different type of flourescent lights), they all look white.

Like I said to Jaime, I would guess that the reflectance values in POV-Ray 
probably are less significant than some of the other things we guess at in 
the finish statement (or at least I guess at them), like specular, phong, 
reflection, diffuse, brilliance, etc.  I think it would be nice if POV-Ray 
had more materials predefined using more physically accurate data.  Lightsys 
is a great step in that direction.  Does anyone know where to get 
information on those finish values?

-- 
Jeremy
www.beantoad.com

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