OpenXR Plugin

OpenXR is an open, royalty-free standard developed by Khronos that aims to simplify AR/VR development by allowing developers to seamlessly target a wide range of AR/VR devices.

Requirements

This version of OpenXR is compatible with the following versions of the Unity Editor:

• 2021.3 LTS+

Runtimes

Unity's OpenXR plug-in should work with any device that supports conformant OpenXR runtimes. The following is a list of known runtimes that you may want to target:

Runtime	Build target	Preferred Graphics API	Feature Parity	Known Limitations
Windows Mixed Reality	Windows 64-bit	DX11	Full feature parity via Mixed Reality OpenXR Plugin for Unity
HoloLens 2	UWP arm64	DX11	Full feature parity via Mixed Reality OpenXR Plugin for Unity
Oculus PC + Link	Windows 64-bit	DX11	HMD + Controllers	Oculus Integration package features not available
Meta Quest	Android arm64	Vulkan	HMD + Controllers via Meta Quest Support Feature
Magic Leap 2	Android x64	Vulkan	Full feature parity via Magic Leap Unity Overview OpenXR
All other conformant runtimes (eg. SteamVR)	Windows 64-bit	DX11	HMD + Controllers	Given the unbounded combinations of possible hardware/software configurations, Unity is unable to test or guarantee that all configurations will work optimally. SteamVR Plugin features not available

To help the community as a whole, Unity will continue to submit any runtime issues, and contribute conformance tests and specification changes to the Khronos working group.

OpenXR Loader

Each release of the OpenXR Plugin is linked against the Khronos Group OpenXR-SDK. This repository contains the authoritative public OpenXR headers, source code and build scripts used to generate the OpenXR Loader dll/so/libraries.

This release is linked against the OpenXR-SDK version 1.1.36.

Additionally, you can access the current OpenXR Runtime through the scripting API via OpenXRRuntime.version. This returns a string representing the semantic versioning of the current OpenXR Runtime.

Considerations before porting to OpenXR

Unity does not yet provide out-of-the-box solutions to the following when using OpenXR, however there may be platform-specific plugins or third party solutions available:

• Controller / hand models
• Finger tracking
• Augmented reality / mixed reality features
• Composition layers
• Overlays
• Foveated rendering

Getting started

To enable OpenXR in your project, follow the steps below:

1. Open the Project Settings window (menu: Edit > Project Settings), and select XR Plug-in Management.
2. Enable the OpenXR option and any Feature Groups for the runtimes you intend to target.
3. In the OpenXR > Features tab, select the interaction profile of the device you are testing with.
4. In the OpenXR tab, make sure the current active runtime is set to the hardware you are testing with. See the Choose an OpenXR runtime to use in Play mode for more information.

See Project configuration for additional information about setting up your project to use an OpenXR plug-in.

Project validation

Project validation is a feature the Unity OpenXR package has to assess configuration correctness of your project depending on the platform you are planning to build for. Unity will raise errors and warnings at build time if your project is not compatible with OpenXR.

For more information on how project validation works in OpenXR, see Project validation.

Troubleshooting

If you experience an issue, please file a bug. When you do, please also check the log file to see if Unity supports the combination of OpenXR runtimes and features you are using. The log file will provide additional guidance.

Unity generates a diagnostic log in either the Player or Editor log, depending on where you run the application. The diagnostic log starts with ==== Start Unity OpenXR Diagnostic Report ==== and ends with ==== End Unity OpenXR Diagnostic Report ==== log entries. It contains information about your application, Unity version, OpenXR runtime, OpenXR Extensions, and other aspects that can help diagnose issues.

The most important part of the diagnostic log is the section marked ==== OpenXR Support Details ====. This section provides some simple information on what parts of your application Unity supports, what it might not support, and what to do before submitting an issue or requesting assistance.

Examples

Diagnostic log OpenXR Support Details section when running with Unity supported items

[XR] [58328] [12:54:14.788][Info   ] ==== OpenXR Support Details ====
[XR] [58328] [12:54:14.788][Info   ] OpenXR Runtime:
[XR] [58328] [12:54:14.788][Info   ]     <Some company>, which is a Unity supported partner
[XR] [58328] [12:54:14.788][Info   ] Unity OpenXR Features:
[XR] [58328] [12:54:14.788][Info   ]     Android , ControllerSampleValidation Standalone, Standalone : Unity
[XR] [58328] [12:54:14.788][Info   ] Unity Support:
[XR] [58328] [12:54:14.788][Info   ]     Unity supports the runtime and Unity OpenXR Features above. When requesting assistance, please copy the OpenXR section from ==== Start Unity OpenXR Diagnostic Report ==== to ==== End Unity OpenXR Diagnostic Report ==== to the bug or forum post.

Diagnostic log OpenXR Support Details section when running with items not supported by Unity

[XR] [58328] [12:54:14.788][Info   ] ==== OpenXR Support Details ====
[XR] [58328] [12:54:14.788][Info   ] OpenXR Runtime:
[XR] [58328] [12:54:14.788][Info   ]     <Some company>, which is not a Unity supported partner
[XR] [58328] [12:54:14.788][Info   ] Unity OpenXR Features:
[XR] [58328] [12:54:14.788][Info   ]     Android , ControllerSampleValidation Standalone, Standalone : Unity
[XR] [58328] [12:54:14.788][Info   ] Unity Support:
[XR] [58328] [12:54:14.788][Info   ]     Unity doesn't support some aspects of the runtime and Unity OpenXR Features above. Please attempt to reproduce the issue with only Unity supported aspects before submitting the issue to Unity.

Known issues

• For projects targeting HoloLens 2 that are using Out of the Box Unity OpenXR support, Project Settings - > Player - > Resolution and Presentation - > Run in Background must be enabled. For projects that are using the Microsoft OpenXR extended support package this is not required.
• An issue with an invalid stage space during startup may cause problems with the XR Origin component from the com.unity.xr.interaction.toolkit package, or the camera offset component in the com.unity.xr.legacyinputhelpers package. These packages will be updated shortly to contain fixes for this issue. Until then the workaround is to use the Floor Device Tracking Option setting.
• OpenXR doesn't currently provide a way to get Acceleration and AngularAcceleration values on input devices, so these values will always be zero.

Upgrading a project to use OpenXR

OpenXR is a plug-in in Unity's XR plug-in architecture. Unity recommends using the XR Interaction Toolkit for input and interactions. If you are using any platform-vendor specific toolkits, please see the platform-vendor specific documentation on how to integrate those toolkits with OpenXR. Vendors are still in the process of adding OpenXR support to their toolkits; please make sure you check supported status before enabling OpenXR in your project.

The core steps to upgrade a project to use OpenXR are the setup instructions at the top. In addition, you might need to do some of the following:

1. Update to the latest supported version of Unity before implementing OpenXR. Some APIs that your project relies on might have been changed or removed, and this will let you easily distinguish which changes are a result of the new Unity version and which come from OpenXR.
2. Disable XR SDK plug-ins that are also supported by OpenXR. There is a good chance that OpenXR supports your target device, so enabling a competing XR SDK plug-in may cause unexpected behavior. In Project Settings > XR Plug-in Management, uncheck the plug-in provider(s) for your target device(s).
3. Update your input code if your project doesn't use the new Input System. For more information, see the Quick start guide in the Input System package documentation.
4. Change quality settings. It is possible that switching over to the OpenXR provider will affect your application's visual quality. You can adjust the quality settings of your project (menu: Edit > Project Settings > Player, then select the Quality tab) to try getting your old visuals back.

OpenXR concepts

Understanding OpenXR's action-based input

See OpenXR Input Documentation.

OpenXR features

Features allow third parties to extend Unity's base support for OpenXR. They bring the functionality of OpenXR spec extensions to the Unity ecosystem, but Unity is not involved in their development.

Features might integrate into the Unity XR Plug-in framework to provide data to other XR subsystems (for example, providing meshing or plane data for AR use cases which are not yet standardized in OpenXR 1.0).

Features are a collection of Unity Assets that can be distributed through the Package Manager, Asset Store, or any other mechanism.

General features

• Mock Runtime (Note: Enabling this will take over whatever current OpenXR runtime you might be using.)
• XR performance settings

Interaction profile features

• Eye Gaze Interaction
• Microsoft Hand Interaction
• HTC Vive Controller
• Khronos Simple Controller
• Microsoft Motion Controller
• Oculus Touch Controller
• Valve Index Controller

Accessing features at runtime via script

You can also access all the settings in the Features window through script. The scripting API documentation in this package provides information on all APIs you can use for feature support. The code samples below illustrate some of the common tasks.

Iterating over all features

    BuildTargetGroup buildTargetGroup = BuildTargetGroup.Standalone;
    FeatureHelpers.RefreshFeatures(buildTargetGroup);
    var features = OpenXRSettings.Instance.GetFeatures();
    foreach (var feature in features)
    {
        // Toggle feature on/off
        feature.enabled = ...;
    }

Getting a specific feature by type

    var feature = OpenXRSettings.Instance.GetFeature<MockRuntime>();

    // Toggle feature on/off
    feature.enabled = ...;

Iterating over all feature groups

Feature groups are an Editor-only concept and as such can only be accessed in the Unity Editor.

#if UNITY_EDITOR
    BuildTargetGroup buildTargetGroup = BuildTargetGroup.Standalone;
    var featureSets = OpenXRFeatureSetManager.FeatureSetsForBuildTarget(buildTargetGroup);
    foreach(var featureSet in featureSets)
    {
        var featureSetId = featureSet.featureSetId;
        // ...
    }
#endif

Iterating over features in a feature group

Feature groups are an Editor-only concept and as such can only be accessed in the Unity Editor.

#if UNITY_EDITOR
    var featureSet = OpenXRFeatureSetManager.GetFeatureSetWithId(buildTargetGroup, featureSetId); // featureSetId set earlier
    var features = FeatureHelpers.GetFeaturesWithIdsForActiveBuildTarget(featureSet.featureIds);
    foreach (var feature in features)
    {
        // ... Do something with the feature.
    }
#endif

Implementing a feature

Anyone can add new features. To learn more, see documentation on how to add a feature to Unity's OpenXR support.

References

• https://www.khronos.org/openxr/
• https://www.khronos.org/registry/OpenXR/specs/1.0/html/xrspec.html