Re: Multisample Masks

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Rémi Arnaud (remi++at++remi.asd.sgi.com)
Tue, 25 Feb 1997 16:35:35 -0800 (PST)

Mark Baranowski wrote:
>
> Hi,
>
> I wan't to fade certain geometry in and out of my scene. I am running
> on an Onyx iR Performer 2.1, Open GL compilation.
>
> It seems that it should be pretty straightforward to do using the
> multisample mask in a pre&post draw callback for the nodes I wish to
> fade (i.e. using glSampleMaskSGIS in a pre draw to effectively set the
> level of transparency I want, and then reset the mask in a post draw).
>
> Will this work? (Isn't it how Performer implements it's fade LOD
> feature) It seems much simpler than having to modify the alpha in
> materials/colours associated with the geometry etc. Is there anything
> I should be aware of wrt doing this?
>
> Any advice greatfully received.
>

 Sure it will work if you also use:
 glEnable(GL_SAMPLE_MASK_SGIS); and glDisable...

 For optimisation, try not to call enable and disable in each callback.
 You can do it by grouping all objects that have to have that callback
 in a bin.

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