Re: Using RGBwritemask with Performer

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Angus Dorbie (dorbie++at++bitch.reading.sgi.com)
Fri, 6 Oct 1995 09:35:04 +0100

This is a nice idea, but would only really work in very specific colour map
cases. The problem you would have if you tried this in RGB mode is that you'd
see the background through the objects you were drawing, unless they were a
lot brighter or happened to contain all the background bits over their entire
area. You'd also be pretty limited in what intensities & colours you could use
in the background & database.

Investigate storing your background in the accumulation buffer then when
you want to renew it copy it through to the framebuffer, you can be
selective about how much you copy by using scrmask.

On Oct 5, 6:01pm, Michael J. Williams wrote:
> Subject: Using RGBwritemask with Performer
>
>
> I am hoping to use Performer to manage some models over top of
> a detailed background. The plan is to draw the background (having
> about 30 colors) and then use RGBwritemask to protect it. We want
> to then use the remaining bitplanes to draw our models (5 colors)
> as fast as possible without having to keep drawing the background.
>
> Has anybody implemented a system this way (using RGBwritemask
> in effect to get an underlay plane with more than 4 colors)?
> The GL manual suggests that this can be done, but will Performer
> prevent us from doing this?
>
> We are on an Indigo2 Extreme, running IRIX 5.2, and Performer
> 1.2. We are currently drawing the background, and using lrectread/
> lrectwrite to save it, and then restore it at the beginning of each
> frame. The lrectwrite takes 120 milliseconds, and is killing our
> timing.
>
>
> Thanks
> Mike Williams
> mwilliam++at++ldsa.com
>
>
>-- End of excerpt from Michael J. Williams

-- 
Angus Dorbie,
Silicon Graphics Ltd, UK
dorbie++at++reading.sgi.com

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