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Anticleric
Inspiring
December 19, 2013

DirectX 11 tracking "inertia" in unity

After some experimentation with the unity intigration I've found that you get a strange "inertia effect" when moving your head when DirectX 11 is checked on in player options in Unity.

The effect was first reported to me by drash after playing "The Room". I narrowed it down to the DirectX 11 option and it was reported as fixed.

I also created a basic scene in Unity and tested it off and on. Same thing. Weird head lag with it on and smooth as silk with it off.

Not sure if this is a known issue. Searched the forums and didn't find anything.

This is fairly critical if confirmed. This effect contributes a great deal to the VR sickness epidemic being reported by many.
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    32 replies

    Anonymous
    December 19, 2013
    I'm going to guess that this might have something to do with frame rates and prediction. If you can track your framerates with and without dx11 setting on, that might be a clue. If not, good hunting.

    Perfect prediction, Rift improvement idea:
    viewtopic.php?f=55&t=5018
    AnticlericAuthor
    Inspiring
    December 19, 2013
    It's not a frame rate thing. It only affects the head tracking. Both modes report 60fps and moving with the mouse etc is still smooth. Only when you move your head do you notice the problem.
    IRIS VR - TECHNOLUST - KERSER - BODY/MIND/CHANGE - QUANTUM CAPTURE - OCCUPIED VR
    geekmaster
    Up and Coming
    December 19, 2013
    Latency and frame rate are independent qualities. In fact, double-buffering (or quad-buffering) may be used to increase frame rate at the EXPENSE of increased latency. For the Rift, lower latency is generally preferred over higher frame rate.

    Extra latency (delayed frames) will be perceived as head tracking "inertia" (delay), as you described. It sounds to me like a latency problem caused by extra frame buffering delays when you select DX11. These may well be driver-dependent (and hardware-dependent), so may not affect everybody. Perhaps a different video device driver may have different symptoms.

    You may want to try a different video device driver for your video card, or perhaps even a different video card. If you are using an HDMI output on your video card, you may want to try a DVI output (with the adapter). Or switch which video device is the primary monitor. Or try it on a different computer...
    This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
    cybereality
    Inspiring
    December 19, 2013
    This is strange but I just tried it and can confirm it feels more laggy w/ DirectX 11 enabled.

    Let me see if I can get to the bottom of this.
    AMD Ryzen 7 1800X | MSI X370 Titanium | G.Skill 16GB DDR4 3200 | EVGA SuperNOVA 1000 | Corsair Hydro H110i Gigabyte RX Vega 64 x2 | Samsung 960 Evo M.2 500GB | Seagate FireCuda SSHD 2TB | Phanteks ENTHOO EVOLV
    Tamulur
    Up and Coming
    December 20, 2013
    Thanks geekmaster, that is very interesting info. It might well be a general delay of frames, because my Hydra hands are delayed as well when switching to DirectX 11. I tried using DVI instead of HDMI and cloing vs extending the display, but that made no difference. I also got lag when the Rift was the only display connected. My graphics card is a GeForce GTX 680 with the newest driver.
    AnticlericAuthor
    Inspiring
    December 20, 2013
    My machine specs are:

    Core i7-4770K 3.5Hz Overclocked and liquid cooled to 4.2
    16GB RAM
    Windows 7 Home Premieum 64bit
    Nvidia 560 ti (latest drivers)
    SSD drive
    etc etc..

    Have reports from 2 others also. Not sure of their specs.
    IRIS VR - TECHNOLUST - KERSER - BODY/MIND/CHANGE - QUANTUM CAPTURE - OCCUPIED VR
    drash
    Inspiring
    December 20, 2013
    Nvidia GTX 680 here as well (I also felt that latency from Anticleric's first dx11 build of his demo).
    Titans of Space PLUS for Quest is now available on DrashVR.com
    geekmaster
    Up and Coming
    December 20, 2013
    Perhaps DX11 needs some additional configuration options, which are not being selected during initialization. The defaults may be different in a way that increases latency, when compared to previous versions. There is probably a way to change the initialization or other run-time options to decrease latency when using DX11, making this a potential software issue involving the app.
    This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.
    cybereality
    Inspiring
    December 20, 2013
    One of the devs here said that it may be an issue of DX11 enabling triple-buffering or something like that.
    AMD Ryzen 7 1800X | MSI X370 Titanium | G.Skill 16GB DDR4 3200 | EVGA SuperNOVA 1000 | Corsair Hydro H110i Gigabyte RX Vega 64 x2 | Samsung 960 Evo M.2 500GB | Seagate FireCuda SSHD 2TB | Phanteks ENTHOO EVOLV
    AnticlericAuthor
    Inspiring
    December 20, 2013
    "cybereality" wrote:
    One of the devs here said that it may be an issue of DX11 enabling triple-buffering or something like that.


    Maybe or something?
    Are they going to try to address it? Would be nice to use dx11 without making my users throw up :P
    IRIS VR - TECHNOLUST - KERSER - BODY/MIND/CHANGE - QUANTUM CAPTURE - OCCUPIED VR
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