Re: Multisample Masks
Rémi Arnaud (remi++at++remi.asd.sgi.com)
Thu, 27 Feb 1997 20:59:45 -0800 (PST)
Lionel Maiaux wrote:
>
> Rimi Arnaud wrote:
> >
> > 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.
>
> Wy should Mark use glDisable(GL_SAMPLE_MASK_SGIS) ?
>
> Are there other performance reason to not only reset the mask in the
> post draw (as Mark says) or in the pre draw of opaque geometries ?
>
No, there is no performance problem not to disable it, but performer
may disable it, so you'll have to turn it on again.
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