[osg-users] Latency

Voerman, L. l.voerman at rug.nl
Tue Oct 2 00:26:40 PDT 2018

Hi David,
are your cards running in "quadro mosaic" mode or are they configured as
independent cards? Our win7 machine is driving 6 channels from 2 cards for
a cylindrical theatre, and have no problem running in full sync (stereo as
well as monoscopic view).

On Mon, Oct 1, 2018 at 7:25 PM David Heitbrink <david-heitbrink at uiowa.edu>

> I currently have an odd problem I am stuck on. I have a system with 2
> Quadro P5000 cards- driving 3 displays that are warped and blended on a 120
> degree dome. Running Windows 10.  The application is ground vehicle
> simulation -  I have pretty high rates of optical flow. Each display is
> running its own process, they receive a UDP broadcast with position update
> information. What I am seeing is 1 of the displays is off by 1 frame 95% of
> the time. When this happens....my blending fails and I get a large seam in
> my scene. I added logging as to the eye point position as well as high
> frequency counter time.
> From what I can tell from the logs, the return from the VSync's
> (viewer->frame() ) are all within 200 microseconds, and the eye point
> position and data frame number (i.e. the frame number for my incoming data)
> is the same across all of the channels.
> So I strongly suspect this has something to do with the graphics
> card/driver's own internal frame buffering....and there is not a lot I can
> do about it.
> This leaves me with a couple of real issues.....
> 1) Programmatically cannot tell if a channel is a frame behind or not.
> Basically I added buffering for the other 2 channels for position
> information......and my seam goes away 95% of the time
> 2) Since things are not 100% the same.......I randomly get a seam 5% of
> the time (assuming I am buffering).
> At this point I don't know what to do.....I have talked to NVidia about
> this, they mentioned making sure DPI scaling in windows is set to 100%
> and/or setting up the app to be DPI aware. I have done this.....but I get
> the same result.
> Any advice and/or speculative guesses on this would be great.
> ------------------
> Read this topic online here:
> http://forum.openscenegraph.org/viewtopic.php?p=75001#75001
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