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VRWorks broken with dual GPU SLI?

Discussion in 'AR/VR (XR) Discussion' started by mikerz1985, May 17, 2018.

  1. mikerz1985

    mikerz1985

    Joined:
    Oct 23, 2014
    Posts:
    79
    Hi all --

    I've been wondering if anyone else is encountering this issue; I haven't seen it mentioned anywhere.

    I have two GTX 1080 Ti's SLIed together. If I attempt to use Single Pass (Instanced), then unity crashes immediately on hitting play. If I use regular Single Pass, then it runs but only renders a pure black screen.

    If I disable SLI, then Single Pass Instanced runs but only renders the left eye. Single Pass does run with SLI turned off.

    I've tried Unity 2017.4.1f1 as recommended by Nvidia https://assetstore.unity.com/packages/tools/particles-effects/nvidia-vrworks-83505

    I've also used 2018.1.0f2 and 2018.2.0b4

    I created a new project, only imported VRWorks and added it to the camera, and was able to see the issue behaving the same way. I've specified Direct3D11, and also tried Direct3D12 and Vulkan -- same issues.

    I already submitted a ticket to Unity, and emailed Nvidia on Monday with no response.

    I was using it with the Vive Pro, as well as the regular Vive
     
    mikerz1985, May 17, 2018
    #1

  2. Bodyclock

    Bodyclock

    Joined:
    May 8, 2018
    Posts:
    172
    Hi, I know this is late and I don't know if you have an answer but this is my experience.

    I have exactly the same setup as you including the Vive Pro. I loaded VRWorks and had the console display SLI and MRS detected. All good. I then switched to Single Pass Stereo in Unity as described on the Nvidia page here. Same as you, black screen.
    But thinking about it, I don't think SPS is designed to work with SLI as each GPU is rendering one eye. If you look at the documentation it says:

    Here are the valid feature configurations based on your project type:
    • Desktop (non-VR) projects
      • MRS
    • VR projects (SLI not detected)
      • MRS, SPS, SPS + LMS
    • VR projects (SLI detected)
      • MRS
    Which would seem to imply that only MRS is available if you run SLI. I think the initial setup on the Nvidia page with SPS on in Unity is for non-SLI setups only.

    So, I switched back to Multi-pass in Unity and it worked fine. I could enable MRS (not sure about this yet, it looks a little weird). I haven't seriously tested performance yet but anecdotally it seems much better.

    TLDR: Use multi-pass with SLI.

    Cheers

    Chris
     
    Bodyclock, Jul 18, 2018
    #2