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Old 01-09-06, 07:12 PM   #2
JaXXoN
Registered User
 
Join Date: Jul 2005
Location: Munich
Posts: 910
Default Re: TwinView - Xinerama with 2+1 display setup

My experience is that Xinerama actually scales pretty well for OpenGL.
The overhead is only recoginzable for small GL windows, like the default
300x300 glxgears window. I also have a twinview+xinerama setup
with two cards and three displays:

When glxgears is displayed at default size (300x300), on the first card
(left+middle LCD), it has 16070 fps and on the second card (right LCD),
there are 16360 fps. When the window is placed "in between" the middle
and the right LCD (so that each card has to render 1/2 of the window),
frame rates drop to 10507 fps (-35%).

Situation is different for a glxgears windows size of 1600x1200: on the
first card, i get 1107 fps, on the second card, there are 1131 fps and
"in between" the result is 1990 fps (+80%).

I guess the first card is a little bit slower than the second one (both
7800GTX) because there are two RAMDACs active for the left and
the middle LCD while the second card only needs to feed the right LCD.

BTW.: UT2004 works also great at 3840x1024 (there is a size limit
of 4096x4096 pixels for OpenGL applications) - there are only a very
few maps that are extreme slow. I guess these maps have been
created on windows boxes using direct3d, and rendering on opengl
is slower because it tries to be more accurate!?

Concerning video playback: i can run three xine players simultaniously
at "full screen" (each player one display) and full speed (at least i
couldn't recognize a frame rate drop).

regards

Bernhard
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