Hi John, It sounds like you have gen lock that locks the swap buffers of the graphics cards, but you don't have a swap ready implemented for your cluster. Swap ready is a synchronization prior to the dispatch of the call to swap buffers, this sync prevents an application from advancing to the next frame without all the machines/cards having got to a point where they are all ready to swap.
Robert. On Mon, Feb 2, 2009 at 4:54 PM, John Aughey <[email protected]> wrote: > I have a problem with 2 independent view windows getting out of sync in a > multi-channel system. Bear with me while I explain the configuration. > > My current test system is one machine with 2 nVidia Quadro FX 4600 graphics > cards. These cards are genlocked with the GSync2 option card. Each video > card renders one half of a video frame which is then combined in the display > hardware. > > My test scene is nothing but a spinning cube with 5 black faces and 1 white > face. Each frame the cube is rotated 90 degrees showing 3 frames of black > and 1 frame of white. GL is synced to VBLANK with the __GL_SYNC_TO_VBLANK > environment variable. > > The behavior I'm seeing is when the program first starts the top and bottom > half are in perfect sync. What is displayed is 3 frames of black and 1 > frame of white producing a seizure-enducing strobe effect. However, after a > short period of time (5-10 seconds), the bottom half (second video card) is > 1 frame behind the top half. Visually you see the top half strobe slightly > before the bottom half (verified with light sensors and a scope). > > The CPU load is very low (extremely simple scene). I am running in > SIngleThreaded mode, and the threading mode doesn't seem to effect the > problem. > > I have had this same problem where the two graphics cards were split across > two different machines (2 computers, 2 graphics cards, genlocked with > gsync2). In the scene, you will see the two halves looking as they should > then after a while you'll see the two halves torn by 1 frame, then after a > while they appear to re-sync back up (somewhat dependent on scene content). > But while they are split, the system still runs at 60Hz so it is not in a > constant overload condition. > > I believe the problem may lie in the rendering pipeline on the graphics > card, and I need to figure out how to keep multiple pipelines in sync with > each other. > > Has anyone else had this problem or knows what I can do to address this > synchronization problem? > > Thank you > John > > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > > _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
