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On Fri, 29 Sep 2000 08:28:05 -0400, Alexander Enzmann wrote:
>>
>> (A) I render a white torus on a red background with AA on
>> and alpha channel on too.
>
>If you are going to do compositing, you should probably use a black
>background. That way there's no extraneous color contributions.
That's not true. You'll get dark fringes as the black darkens whatever it's
averaged with.
>Then you shouldn't have used a red background. However, since you know
>the color you originally used for a background, you can remove it from
>the image:
> - multiply the original background color by the alpha value
> - subtract from the pixel
> - hope there weren't any out of range values anywhere along the way.
It seems that if this works manually, it should work for POV when +UA is
specified. I agree with Rune; I can't think of a single instance where it
would be a good thing to average in the background color when the user
requests an alpha channel.
>I disagree. That would be different from almost every image processing
>package in existence (besides not being possible without also storing
>the entire background along with every image).
I'm not sure I follow this statement.
--
Ron Parker http://www2.fwi.com/~parkerr/traces.html
My opinions. Mine. Not anyone else's.
Proudly not helping RIAA and SDMI steal my rights --
http://www.eff.org/Misc/EFF/Newsletters/EFFector/HTML/effect13.08.html
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