Classification: UNCLASSIFIED Caveats: FOUO The sync actually blocks on the first open gl call. So your osg update and cull stages will run then you will block on the draw stage until the vsync. Your problem is actually worse than 20ms w/o you knowing it. For Nvidia cards there is a built in 2 frames of latency. So even after your sync you won't see the image you updated come out the DVI until 2 render frames later.
In order for you to do what you want you will need some expensive frame lock hardware with external syncs to run at a multiple of the frame rate. -----Original Message----- From: osg-users-boun...@lists.openscenegraph.org [mailto:osg-users-boun...@lists.openscenegraph.org] On Behalf Of Giovanni Ferrari Sent: Wednesday, June 23, 2010 3:28 AM To: osg-users@lists.openscenegraph.org Subject: [osg-users] OSG and vsync Hi, i'm developing an application that need vsync to avoid tearing but i'm having some problems. Here is the (really simplified) code structure of my application: Code: ... while ( !mViewer->done() ) { mGraph->Update(...); mViewer->frame(); } I've noticed frame() function is blocking when vsync is enabled. This means that i call the frame function, i stay blocked for something like 20ms (50hz PAL), and then i must terminate the Update call in the vsync period otherwise i won't be able to draw a new frame ( the graphic card draw the old content of frame buffer without changes performed in the update function. Changes will be performed in the next frame ). As you can immagine this is a big problem for real-time applications cause i'm introducing 20ms of retard. Is there a way to syncronize frame call without using vsync ? or can i scompose the frame function to be able to separate functions that operate on the graph from those that perform the rendering ? The second solution could help me cause i would be able to operate on the graph with mGraph->Update(...) even if the frame "part" that write the frameBuffer is blocked. I hope i've explained my problem clearly. Thank you! Cheers, Giovanni ------------------ Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=29295#29295 _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.or g Classification: UNCLASSIFIED Caveats: FOUO _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
