Serge, as Robert says, TwinView is what you need.
Here's the deal. On Nvidia non-Quadro cards on Linux, the only way to
guarantee no tearing on one screen is:
UBB flipping enabled,
full screen OpenGL app, no obstructions,
Vsync flag with that screen number - there's an environment variable.
For dual screens, TwinView, with both screens with the *exact* same
res and rate - same modeline, basically,
one OpenGL window/context filling both screens.
The way you're doing, with two contexts, will tear.
On Quadro cards, almost all conditions are lifted.
Bruce
On Apr 20, 2010, at 6:44 AM, Serge Lages wrote:
Hi all,
I'm currently having a problem with NVidia hardware on Linux, it's
not directly OSG related, but I hope someone here can help me.
Here is my setup :
Ubuntu 9.10
195.36.15 NVidia drivers
2 GTX 285 graphic cards (one DVI, one VGA and one HDMI port)
4 screens (2 screens on each cards), all independents (no twinview)
Compiz disabled
On this setup, I have an OSG application running full-screen on all
4 screens (a CompositeViewer with 4 views). My app is running at
60fps when VSync is on, it's the screens refresh rate.
When I enable "Sync to VBlank" in the Nvidia-settings, here is the
current result :
- On the first screen of each cards (plugged on the DVI port), the
VSync is perfect, no tearing.
- On the second screen of each cards (plugged on the VGA port),
tearing is noticeable on the upper part of the screens (I have a
line about 100 pixel far from the top of the screens).
=> Result : 2 screens without tearing, 2 screens with tearing in a
specific location. It seems VSync is not really performed on the
second screen of each cards.
I have also tested on GTX285 cards with 2 DVI ports with the same
result.
Another note : the 4 screens are the same, all plugged in VGA with
the same resolution (using an adaptor when plugged in the card DVI
ports). I've tested with other screens with the same result.
Anyone knows where this problem comes from ? And any idea how to
solve it ? Is it a bug in recent drivers, maybe I should test olders ?
Thanks in advance for your help.
Best regards,
--
Serge Lages
http://www.tharsis-software.com
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