> On 7/28/2011 12:25 PM, PC John wrote:
>>>> To simplify the things, I want to have one pigment for OpenGL
>>>> emissive color and another pigment for OpenGL diffuse color.
>>>> POV-Ray should compute the lighting on both of them and the
>>>> final color would be sum of these. Is it possible to do
>>>> this in POV-Ray?
>>>
>>> If I get it correctly:
>>> OpenGL povray
>>> =========+=========
>>> emissive | ambient
>>> diffuse | diffuse
>>>
>>> To perform a sum, use the average pigment with relevant map
>>>
>>>> http://wiki.povray.org/content/Documentation:Reference_Section_5.3#Average
>>>>
>>
>> Things are more difficult:
>>
>> OpenGL povray
>> ===============+================
>> ambient COLOR | ambient COLOR
>> diffuse COLOR | diffuse float
>> specular COLOR | specular float
>> emission COLOR | (no equivalent, but can be emulated by ambient)
>>
>> In OpenGL, ambient color is real color used for the computation of
>> ambient light
>> contribution to the final color, while ambient on povray side is just
>> pigment
>> filter.
>>
>> In OpenGL diffuse, specular and emission are all colors that can be
>> completely
>> different colors while povray's diffuse and specular is just float
>> multiplying
>> pigment color.
>>
>> As a result, OpenGL allows to specify for example blue diffuse color -
>> e.g.
>> object is blue when lit by the light coming from the scene, and red
>> ambient
>> light (e.g. surface shines red, provided that there is global ambient
>> light in
>> the scene).
>>
>> You may wonder why I need this, but it would allow to correctly show
>> all the
>> models that are used in OpenSceneGraph, OpenGL, DirectX, and real-time
>> graphics
>> in general.
>>
>> Thanks for any good advice,
>> John
>>
>>
> Hmm. This may be a kind of interesting point. Not sure if such exists,
> but its not completely improbable that an objects optical properties
> would cause its "reflective" color to be slightly different than its
> real one, like red, when looked at directly, but say, blue when seeing
> the diffuse/specular results. Maybe the odd paint they make that seems
> to change color, by angle, as an example, where its the reflected light
> that determines that?

You can use the aoi pattern.
You can greatly alter the appearance of a surface just by changing it's 
brilliance value.
You can add some reflection, and make it variable relative to the 
incident angle, or make it coloured:
reflection{color, color [fresnel] [metallic float] [exponent float] 
[falloff float]}

This is a VALID reflection statement:

reflection{rgb<1, 0.5, 0.1> rgb<0, 0.2, 1>}

It will reflect orange when viewed perpendicularly, and greenish blue 
when viewed tengentialy.



Alain

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