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Carandiru
Up and Coming
September 26, 2014

Proposed Model for Presentation without VSYNC



I Believe the Oculus SDK could really benefit from an additional configuration flag that denotes the SDK is being used with no VSYNC. If the Oculus SDK is then told explicitly that DirectX / OpenGL is not using VSYNC I believe it will work very well if EndFrame() takes a timestamp, adds it to the accumlated average(minus this frames wait time) and calculates a continuous average of n frames, then calls Present().
BeginFrame() then delays or waits based on this average, minus say 1ms or 2ms to compensate for error.

I think that the Model Needs to be Changed at very fundamental level to minimize Input Lag. This model presented would achieve significantly better response to have Input equal Output.

I was hoping an Oculus Developer would chime in specifically if this can be done with the SDK. I would like to know, as it could be done manually in my application, but it seems more natural that the SDK do this for you.

Thanks!

    5 replies

    owenwp
    Up and Coming
    September 26, 2014
    This isn't practical for a number of reasons. On a multitasking OS, the error factor can be very large for both the CPU and GPU, which must both be finished with their work at v-blank time, and will change dramatically over time. Usually when you finish doing work on the CPU, the GPU is far from done rendering the frame. You would have to allow much more time than you normally need, making the frame budget even more difficult to meet. You would miss the v-blank quite often and get lots of judder.
    CarandiruAuthor
    Up and Coming
    September 29, 2014
    Anyone else care to chime in?

    What about waiting to draw before expected VSYNC as close as possible?
    http://www.supersinfulsilicon.com/ supersinfulsilicon - software Home of the MaxVR Oculus Rift Video Player https://twitter.com/Carandiru
    Fredz
    Up and Coming
    September 29, 2014
    I think front buffer rendering with asynchronous time warp like it's implemented for the Samsung Gear VR will take care of the problem.
    CarandiruAuthor
    Up and Coming
    October 5, 2014
    "Fredz" wrote:
    I think front buffer rendering with asynchronous time warp like it's implemented for the Samsung Gear VR will take care of the problem.


    Cool is there an detailed information on the async time warp?
    http://www.supersinfulsilicon.com/ supersinfulsilicon - software Home of the MaxVR Oculus Rift Video Player https://twitter.com/Carandiru
    Fredz
    Up and Coming
    October 5, 2014
    Here are the links I collected about it :
    http://vrwiki.wikispaces.com/time+warping#Asynchronous%20time%20warping
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