From: Marcin Romaszewicz (marcin++at++sgi.com)
Date: 10/17/2002 19:09:21
What hardware are you running on and why do you need to read the
framebuffer? The best bet to improving performance is to see if its
possible to do what you want without glReadPixels. On a PC, the
performance hit for that function is staggering, on an sgi machine (IR
especially), it's much less, but still high. If you need to read the
pixels for use in rendering, on a PC it will be cheaper to render directly
to a texture if your video card supports it. If you are running on an sgi
machine, experiment with different read formats, once you find one that
does not require a conversion, the performance should be around 80
Mpixels/sec on an IR class machine, meaning if all you do is glReadPixels,
you would be able to maintain 60 Hz, anything else will drop you to 30.
-- Marcin
On Thu, 17 Oct 2002, ken sartor wrote:
>
> pfHi -
>
> Does anyone have a suggestion on how one might read pixels from the
> framebuffer during a realtime simulation? When i merely read the pixels,
> my simulation slows down more that an order of magnitude! Is there some
> more efficient way to accomplish this (i am using glReadPixels currently)?
> Or perhaps a hardware solution?
>
> TIA.
>
> ken
>
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