Practical noob questions about OpenXR


I’m trying to get the best performance out of my Quest 2 / RTX2060Super in Project Cars 2 but after googling and trying things for 2 days i feel like i still don’t understand what is actually going on here. So, Quest 2 as i understand has OpenXR support in the headset, but when you want to run PC2 you have 3 options in the Steam - run PC2, run PC2 (SteamVR mode), run PC2 (OpenVR mode). All 3 options work (i get PC2 working inside Quest 2) but i don’t know what actual mode i’m running in. Can somebody explain this to me because i can’t find concrete info when googling. Thx.


OpenXR is a specification for an API. Each device that supports OpenXR provides a runtime that implements that API. Additionally, SteamVR includes an OpenXR runtime for all (or most?) devices supported by SteamVR.
One of the installed OpenXR runtimes is current (on Windows, this is selected through a registry key) and that is the one an application using OpenXR will talk to. SteamVR and the Oculus app have a button somewhere in their settings panels to make them the current OpenXR runtime respectively.

What your game is really doing in the different modes probably only the developer can answer reliably, especially what the difference between SteamVR mode and OpenVR mode is. My understanding has always been that OpenVR is the name of the API that SteamVR is built on and SteamVR is basically just the marketing name for it.

This is so messy but it seems i got some answers after 3 days. Dealing Project Cars 2 it seems that this game ALWAYS run in Oculus mode (OpenXR), no meter whether i choose SteamVR or OpenVR. How did i came to this conslusion. I have app called fpsVR that shows FPS and many other system parameters and that app runs only in SteamVR. So while i run SteamVR inside Quest 2 this app runs fine. The moment i click on Project Cars 2, fpsVR is not working anymore. However, there is a third app called OpenVR Advanced Settings. If i enable “Force SteamVR” inside that app then things change. It seems that in this case Project Cars 2 is running in SteamVR because then i get fpsVR running too so i have “FPS/other things” displayed inside Project Cars 2. Now i still have to see if i can run OpenComposite and OpenXR toolkit. This is so crazy, you need to be a nuclear scientist to catch all this.

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