The Compositing feature ?

[Olivier Fourdan]

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Niels Rasmussen wrote:

> It works with compiz (another settings in xorg.conf) so it should works with
> my video card.
> 
> Maybe some settings are missing ? I've followed the instructions in the FAQ.

Compiz is an OpenGL compositor, ie it uses OpenGL to render the whole
desktop and speed up alpha compositing. It requires a video card that
support OpenGL and a driver that is able to make use of it.

xfwm4 uses XRender, which doesn't use OpenGL. It's more widely
available, but rarely accelerated. In Xorg 7.x, Xrender uses MMX and SSE
to accelerate the alpha compositing, but it' still not very fast if you
have a lot of transparency (like you did in your screenshot, almost
every window is transparent)

nVidia implements xRender in hardware with its closed source proprietary
driver.  ATI doesn't.

But there are other acceleration architecture that you can try on ATI,
like EXA. I've read that EXA can give as good results as nVidia
accelerated XRender but I have never tried EXA myself (I have an nVidia
card and accelerated render work just very well).

In the future, we might see acceleration architectures that use OpenGL
to accelerate XRender, like "Glucose" which was announced by Zack Rusin
last summer. I don't know the status of this news implementation.

So, in a nutshell, on ATI, use EXA.

HTH
Olivier.


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