Gentlemen,
I am very sorry to bug you with a question about a videogame, but I am obliged
to do so by my two-year old boy, who simply loves Tux in ppracer... So, in order
to avoid disappointing him, I'm fighting a desperate battle against video
drivers, kernel modules, GL libraries ad whatnot. I am writing to you guys
because hopefully you will make some sense out of my experience and be able to
guide me in filing appropriate bug reports.
The problem: after dist-upgrading my Debian Testing R51 Thinkpad with i855GM
graphics processor, ppracer started flickering very badly, with about half of
the screen at a time being "blacked out"--the black-out area changing with every
refresh of the screen. It looks as if ppracer were trying to synchronize with
the video cards refresh rate but were failing miserably. The graphics is so bad
that I am unable to read the frame rate which appears at the side of the screen.
With xorg 6.9 ppracer worked perfectly.
Now the background of the problem:
A recent dist-upgrade to Debian Testing has removed the xserver-xorg 6.9 package
group and installed xorg 7.0.22. After updating my kernel to 2.6.16-2-686 I was
able to get DRI and 3D acceleration back to work--sort of. All games have become
significantly slower, albeit not like software rendering. I would estimate that
on average frame rates have dropped by about 15~20%. By adding
LIBGL_DEBUG=verbose to my environment I get the following messages when I start
any OpenGL app:
libGL warning: 3D driver claims to not support visual 0x23
libGL warning: 3D driver claims to not support visual 0x25
libGL warning: 3D driver claims to not support visual 0x27
libGL warning: 3D driver claims to not support visual 0x29
libGL warning: 3D driver claims to not support visual 0x2b
libGL warning: 3D driver claims to not support visual 0x2d
libGL warning: 3D driver claims to not support visual 0x2f
libGL warning: 3D driver claims to not support visual 0x31
I have never seen glxgears run slower than it does now, but it no longer prints
the frame rates to its stdout/stderr, so I am unable to quote a frame rate
value. Yet, I know that hardware acceleration is happening because glxgears is
not hogging the processor, as it does when I run it through an ssh-forwarded X
connection. I have tried using ppracer like a blind man--the graphics being so
bad that it is almost completely unintelligible--and the responsiveness is
acceptable, which again indicates that hardware acceleration is taking place.
This flicker is not an issue with other games such as supertux, chromium, gl-117
and armagetron, which all run acceptable, if only a little slower than before
the dist-upgrade. It is an issue with both ppracer 0.3.1-7 in Debian Testing
(Etch) and ppracer 0.5alpha from projects.planetpenguin.de .
My only guess is that something in the synchronization mechanism between GL
clients and the graphics hardware has broken over the Xorg 7.0 update. Is this
at all possible? Does anyone have a clue as to what's going on? Which component
is more likely to be responsible: xorg's i810 driver, the kernel's i915 DRI
module, or ppracer? How can I investigate the problem further?
Thanks to all who have taken time to read my post and additional thanks to all
who will take time to answer it.
Alex
--
*********************************************************************
Ing. Alessandro Baretta
Studio Baretta
http://studio.baretta.com/
Consulenza Tecnologica e Ingegneria Industriale
Technological Consulting and Industrial Engineering
Headquarters
tel. +39 02 370 111 55
fax. +39 02 370 111 54
Lab
tel. +39 02 9880 271
fax. +39 02 9828 0296
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