Hi all,
Warning, this is off-topic osg-users list, but in desperation I just
wanted to check if any of the OpenGL gurus on this list have ever
experienced something similar:
Our application uses glReadPixels to read 1920x1080 rgb frame from from
the nvidia graphics card so that we can send it out on SDI on a
different video board. This has been working for us for years.
However, a client of ours is currently experiencing a significant
rendering slowdown after using the application for some time
(20-30minutes). After lots of debugging we have found that on the client
machine, it is the glReadPixels call that suddenly starts using 800+
milliseconds to read a frame, while it normally only takes about 8+- ms.
Restarting the application temporarily resolves the issue. glReadPixels
is back to 8ms avg for about 20-30 minutes, and then suddenly drops to
800ms and stays there until application is restarted. No GL Errors are
reported in conjunction with the performance drop.
The catch is that we have not been able to reproduce this on our own
developer machine (same OS version, software, drivers, same application
setup and data). The one known difference between client and dev
machines are the graphics card (they use GT9800 and GTX285, while we
have tested 8800 and GT460)?? Not being able to reproduce the issue
makes debugging very cumbersome:(
Have anyone seen any similar sudden performance drop issue with
glReadPixels? Any theories on what the cause could be and where to look?
Any help, hints or ideas are all more than welcome. You could answer me
directly instead of bothering the osg-users list if you prefer. I'll
post the solution if/when we find it.
Best regards,
John
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