Re: Alphatexture + multisampling

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Angus Dorbie (dorbie++at++multipass.engr.sgi.com)
Tue, 21 Oct 1997 09:29:33 -0700

On Oct 21, 2:32pm, Klaus Otto wrote:
> Subject: Alphatexture + multisampling
> Hi performers,
>
> A short question regarding alphatexture and multisampling.
> I am using 6.2 on a 2 RM RE2, performer 2.0 (no patches),
> perfly, MultiGen file.
>
> In perfly, when i look at a textured polygon with non-constant alpha
> I see severe banding when antialiasing is on.
> The texture is perfectly interpolated when antialiasing is switched off.
> Banding appears no matter which texture mode is set in MultiGen.
> Is this due to the non-existing patches?
> I thought I saw it ok. What is the point i am missing?

Multisample alpha uses a subpixel screendoor mask for
fast order invariant zbuffered transparency rendering.

Due to the limited number of samples there's a quantizing
effect which is undesirable in some situations.

You can use blended alpha in an antialiased scene if you
change the type of pfTransparency set in the geostates to
PFTR_BLEND_ALPHA.

Cheers,Angus.
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