Re: pfAntialias and the alpha buffer

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John Rohlf (jrohlf++at++tubes)
Mon, 9 Jan 95 10:21:22 PST

>
>
> We are using an RE2 and would like to render into the alpha buffer
> (to create masks for downstream video keying) without turning off
> antialiasing - is this possible?
>
> It seems that pfAntialias(PFAA_ON) configures things so that the
> alpha buffers are totally bypassed. I realize that with an RE2,
> antialiasing and transparency are obtained from multisampling.
> But for our application we do not want to use the alpha buffers
> for transparency, just for creating the masks.
>

        If you use PFTR_BLEND_ALPHA type transparency you will render
alpha into the frame buffer. Usage:

        pfTransparency(PFTR_BLEND_ALPHA);

                or

        pfGStateMode(gstate, PFSTATE_TRANSPARENCY, PFTR_BLEND_ALPHA);

Alternately you can bypass Performer transparency and
use msalpha(MSA_MASK) rather than the default Performer mechanism of
msalpha(MSA_MASK_ONE).
         

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