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tmek
Up and Coming
November 12, 2013

Question about VSYNC not reliably working

I've been wondering why sometimes vsync doesn't always seem to work even when it's specified to be on and I'm running an application full screen. This is something I've noticed on both ATI and NVIDIA in several games even games (not just Rift games) that have an explicit vsync setting and running full screen.

I'll make sure vsync is on the app is full screen (not borderless windowed) and that vsync is set to use application setting or is set to on in my graphics drivers. Yet it's like the graphics card drivers are ignoring the setting and i'll see horrible tearing. This isn't always the case because sometimes vsync does actually work.

Is this known issue? Maybe something to do with Windows 8? Or cloning or extending desktops?

    5 replies

    renderingpipeli
    Up and Coming
    November 12, 2013
    As soon as you have two displays VSync will break on one of them. The displays have there own clock and the GPU can adjust to that clock but not the other way around (thats one thing that G-Sync will fix). So if you have two screens and they are not in sync by chance, you will have tearing on one of them. On Linux you can chose which screen to sync to, maybe you don't have that option on windows - in that case only use the Rift.
    tmekAuthor
    Up and Coming
    November 12, 2013
    "renderingpipeline" wrote:
    As soon as you have two displays VSync will break on one of them. The displays have there own clock and the GPU can adjust to that clock but not the other way around (thats one thing that G-Sync will fix). So if you have two screens and they are not in sync by chance, you will have tearing on one of them. On Linux you can chose which screen to sync to, maybe you don't have that option on windows - in that case only use the Rift.


    Thanks for the explanation, that makes a lot of sense. In my scenario I'm cloning the game/desktop to my Sony monitor and the Rift but it can only sync to one. They are both set to 60hz but which one it winds up v-syncing to is anyone's guess each time you run an app which is why it seems to work some of the time but not others.
    tmekAuthor
    Up and Coming
    November 12, 2013
    So after reading this thread on mtbs3d I learned, at least with the Nvidia control panel you can actually specify which display should be used as the "clone source" when cloning.

    I tested it and it seems to work exactly as desired. When I clone my desktop to both Rift and Sony monitor and I set my Rift as the "clone source", I can run a game with v-sync and the Rift has no tearing while the Sony does. If I set the Sony to the clone source, the Rift gets tearing and the Sony doesn't!

    Edit: Also apparently with ATI in catalyst, under desktop management, you can right click the screen for Rift DK and select 'preferred screen'.


    cybereality
    Inspiring
    November 13, 2013
    Awesome! Thanks for posting the fix.
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    ad2003
    Up and Coming
    February 12, 2014
    Hey,
    thanks for the tip! I had the same issues. But now it works!

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