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Linus Trinus

November 27, 2020


I've been playing with VR and ran across LinusTrinus, a somewhat-raw but quite functional bit of code that allows an Android phone with the Trinus VR client app to connect to Linux to make it into a SteamVR-compatible 3DOF headset. While it does not allow movement tracking, and only rotation, it is sufficient for a subset of SteamVR games.

The code isn't very well documented, so for anyone who may want to try to use it, here's a little outline of how it works:

  • The Trinus app on the phone is a client. It sends rotation information to the server on Linux, and displays forwarded graphics on the phone screen.
  • The LinusTrinus server on the computer is essentially a bridge between a slightly-tweaked SteamVR sample driver, and the Trinus client. Most importantly, it uses ffmpeg to copy an area of the screen directly to the Trinus app.
  • The slightly-tweaked sample SteamVR driver receives the rotation data from LinusTrinus and outputs the VR view in a standard, but frameless, window displayed on the desktop.

There are three issues a new user will run into quite quickly:

  • If you don't build the sample SteamVR driver in the subfolder first, the app will appear to do nothing, and SteamVR won't even start.
  • If you don't fix the ffmpeg command in the server so it looks at the correct VT display for your distro, you'll just get a black screen in Trinus, even though the on-screen window will appear to work.
  • If the on-screen window gets obscured (say, by the VR app's window), the video will get screwed up. This can be easily fixed by clicking in the VR output, typing ALT+SPACE, then selecting "Always On Top" from the GNOME Shell pop-up.

I've fixed the first two in my fork of the LinusTrinus repo, and was able to get it to work, but performance is not so great.


Categorized as: Android | Games | Linux | Steam | VR


6 Comments

  1. ItsJustSomeDude says:

    Hey! This looks really promising. I had tried LinusTrinus in the past, but didn't really get anywhere with it. I am hoping that this will work better than last time I tried. One question I have, does this use Trinus CardBoard VR, or just Trinus VR (the daydream one)?

    • BroWren says:

      You'll want to use the Cardboard version. The free one should be good enough for testing it out. :)

      • ItsJustSomeDude says:

        Ok, I was able to get it to link with my phone and show the upper left corner of my screen. However, it does not connect with SteamVR at all. I ran `make` in the main directory, and it failed, saying that it could not find `openvr_driver.h`. I then downloaded it from the Valve OpenVR Git repository and placed it in the `samples` folder. Now, it gives the following error:

        ```
        CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
        Please set them or make sure they are set and tested correctly in the CMake files:
        OPENVR_LIBRARIES
        linked by target "driver_linus_trinus" in directory /home/matthias/Downloads/LinusTrinus2/LinusTrinus/samples/driver_linus_trinus

        -- Generating done
        CMake Generate step failed. Build files cannot be regenerated correctly.

        ```

        I know I am missing something. Do I need to link the OpenVR SDK somewhere? And if so, how?

        Thank you!

        • BroWren says:

          Yep, you probably need to install the OpenVR development package. On Ubuntu it's libopenvr-dev. You might also need to install libopenvr-api1 to install the libraries.

          Hope that helps!

  2. Genos says:

    Really Thank you man, this was awesome! I was lost beacuse of the missing documentation, but this site (With a pretty cool design btw) help me a lot. Thanks again :)

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