Re: Alpha and anti-aliasing...

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Angus Dorbie (dorbie++at++sgi.com)
Fri, 08 May 1998 19:35:55 -0700

Allan Schaffer wrote:
>
> On May 8, 2:23pm, Jan Barglowski wrote:
> > This is probably a really easy question to answer. I have a cloud
> > texture that is in rgba format. I texture it to a square and view
> > the file in perfly. The texture looks to have 2 bits of alpha, unless
> > I turn off anti-aliasing! Now, I don't want to turn off antialiasing
> > for my main app, so how do I solve this?
>
> Angus is correct about the transparency setting and Marcus about
> texture; just to clarify the overall point you'll have to do both
> things they say.

Sorry, but the original poster mentioned that the problem
was solved when he disabled anti-aliasing. An important
clue meaning that he already has sufficient precision in
texture memory and the problem was entirely due to
multisample mask transparency, not internal texture
format.

> You're running into two of the places where Performer's default
> behavior chooses 'fast' instead of 'high quality': #1 with
> transparency (when ms is enabled it uses subpixel alpha by default
> instead of blending) and #2 with texture formats (textures are
> reduced to 16 bits by default)

Yes but this gives 4 bits or 8 bits of precision (depending
on RGBA or IA components) which gives 16 or 256 shades of
alpha, not ~4.

Cheers,Angus.

-- 
"Only the mediocre are always at their best." -- Jean Giraudoux 


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