Re: Writing to individual pixel colour components.

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Angus Dorbie (dorbie++at++bitch.reading.sgi.com)
Fri, 6 Sep 1996 19:17:59 +0100

While I can't see a way of doing this in a single pass, you don't have to
perform two passes on the scene.

You could try drawing the scene once and writing an image to the framebuffer
which will set the relevant pixel components to black. Maybe use a subtractive
blend equation to limit this second pass to DC = 1, and avoid having to use
colour masking and stipple patterns.

My apologies if you've already come up with this.

Rgds,
Angus.

On Sep 5, 9:00am, Graham Jones wrote:
> Subject: Re: Writing to individual pixel colour components.
> Remi Arnaud wrote:
> >
> > On Sep 4, 9:30am, Graham Jones wrote:
> > > Subject: Writing to individual pixel colour components.
>
> > > Consider two pixels side by side - when I draw an image I want to
> > > set the red component of one pixel and the green component of the
> > > other, without affecting the other colour components of the two
> > > pixels - this is repeated over the whole image.
>
> > That's an interresting problem !
>
> Too true!
>
> > I don't see any 1 pass solution if your database have textures.
>
> I need to be able to this with any possible image, textured models,
> non-textured models, images themselves etc etc.
>
> Surprisingly (hmmm, not too surprising I guess, I am using iR) the
> trials I've done using pre-rendered images works pretty fast - now I
> have to do the work to get Performer to render in this way.
>
> Graham.
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>-- End of excerpt from Graham Jones

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