For development with Unity and Steam Frame we recommend targeting Android and Unity's built-in OpenXR plugin. We have a package you can install that assists with access to some additional built-in features, and includes the Steam Frame Controller OpenXR interaction profile. Development is pretty straight forward with the exception of needing to launch Lepton Development and adb connect before deploying to the headset.

First, make sure you have turned on Developer Mode as described in Setting up your Steam Frame for development. This will let you deploy to the headset.

Valve OpenXR Utilities Package

These features, with the exception of the interaction profile, are mostly simple interfaces to enable existing Unity functionality. For help with the features themselves please see the linked Unity documentation pages.

To install this package open the package manager, click the + then Install package from git url and enter this url: https://github.com/ValveSoftware/Unity.git?path=com.valvesoftware.openxr.utils

• Steam Frame Controller OpenXR Interaction Profile - This feature lets you bind your Unity Actions to Steam Frame Controller buttons.
  Requirements: OpenXR
  
  
• Valve Utils: Settings for Unity's Foveated Rendering - This provides access to the Unity feature for Foveated Rendering. It supports eye-tracking and allows a greater range of Unity and OpenXR versions than are supported by the official plugin. Unity documentation
  Requirements: Unity 2022.3+, Unity OpenXR Plugin v1.9.1+, URP, Vulkan
  
  
• Valve Utils: Settings for Unity's Multiview Render Regions - This provides access to the Unity feature for Multiview Render Regions. This prevents rendering to regions that are not visible to the user through the headset. Unity documentation
  Requirements: Unity 6.1+, Unity OpenXR Plugin 1.14.1+, Vulkan, Multiview
  
  
• Valve Utils: Lepton Validation - This feature checks through your Unity project and lets you know if there are things setup that will cause the build to fail to run locally on Lepton (Steam Frame's Android translation layer).
  Requirements: Unity OpenXR Plugin v1.9.1+
  
  
• Valve Utils: Refresh Rate - This feature lets you query and request refresh rates on the headset via the XR_FB_display_refresh_rate OpenXR extension. Currently in SteamVR we only expose the currently in-use refresh rate.
  Requirements: OpenXR

Project Settings

These settings are required for Android OpenXR builds to work on the Steam Frame.

• Enable OpenXR - Enable the OpenXR Plugin (Project settings > XR Management)
  
• Disable Meta XR - Disable all Meta XR and Meta Quest OpenXR Features (Project Settings > XR Management > OpenXR > OpenXR Feature Groups)
  Note: New versions of the OpenXR Package have fixed having the Meta Quest Support feature enabled while deploying to non-meta headsets, but we recommend turning it off if your application doesn't load into VR correctly.
  
• Minimum API Level - Android 10 (API Level 29) or Android 11 (API level 30)
  
• Target API Level - Automatic (or after your minimum)
  
• Scripting Backend - IL2CPP
  
• Target Architecture - ARM64
  
• Graphics - Vulkan (recommended) or OpenGL
  
• Add Input Profile - Add Steam Frame Controller to your list of Enabled Interaction Profiles on the Android tab. (Project Settings > XR Management > OpenXR)

Steam Frame Controllers

By default the controllers will show up to your games as emulating Oculus Touch, you can bind to those controls and it will work. If you would like to bind to Frame Controller specific buttons or have Frame Controller specific offsets you can use the interaction profile provided in the package described above. We've tried to create aliases for the buttons that make sense. Please let us know if you have feedback on this.

Play-in-Editor

Deploying to the headset can be time consuming when trying to iterate quickly. If you setup your project to run OpenXR on Standalone (desktop) you can just hit Play in the editor and do most of your gameplay testing on PC through SteamVR, even while you're project currently targets Android. Remember to add the Steam Frame Controller to the list of Enabled Interaction Profiles on the Windows/Mac/Linux tab for the bindings to be the same as when on Android.

Building to Steam Frame

Building to Steam Frame is similar to building to other standalone headsets or mobile devices using adb. Refer to this article to get started: Connecting adb to Lepton

Once connected to Lepton Development via adb, select Build and Run under Build Settings.

Steamworks .NET

The main branch of https://github.com/rlabrecque/Steamworks.NET includes Android support, but is not in a release yet. For now you can you can add the package to Unity via the git url: https://github.com/rlabrecque/Steamworks.NET.git?path=/com.rlabrecque.steamworks.net

Eye Tracking

Our current support for eye tracking in Unity uses the Eye Gaze Interaction feature. There’s examples of using this in the XR Interaction Toolkit samples. You can learn more about the feature here: Eye Gaze Interaction | OpenXR Plugin | 1.0.3

Notes

• Unity Profiler - Once adb is connected the Unity Profiler should be able to connect as well.
  
• Unity Logcat - The Unity Logcat package found in the Unity Registry section of the Package Manager should work once adb is connected. This gives you nice filtered logs from your game. See the Unity documentation
  
• Multiple HMDs - Disconnect other HMDs, (such as Quest), from your USB while building and debugging. Otherwise, it tends to auto-install to USB. Also if you're testing streaming you will want to disconnect wired headsets as well (e.g. Index).
  
• Multiple adb versions - If you get the error message:
  
  Unable to reconnect device. error: protocol fault (couldn't read status length): connection reset
  That probably means you have something else trying to use adb. Make sure things like Android Studio are closed.
  
  If you’re struggling with keeping adb connected make sure you’re using the same version of ADB as unity is trying to use.