[UE 5.7.3] MRUK Error 3: Anchor Discovery Failed with Epic Native OpenXR and DX12

Development Platform & Builds XR Development
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Hello everyone,

I’m currently developing a Mixed Reality project in Unreal Engine 5.7.3 targeting Meta Quest 3 via Link. I am facing a critical incompatibility between the MetaXR/MRUK plugin and the DirectX 12 rendering pipeline.

The Context: My project relies on features that require DX12. I am using a recompiled version of the MetaXR Plugin (v1.115.0) and MRUK.

The Problem:

  1. Oculus OVRPlugin Backend: If I use this recommended path, the scene/anchor data loads correctly, but the rendering is broken in DX12 (one eye flickers or remains white). This appears to be related to HZB/Occlusion regressions in UE 5.7.

  2. Epic Native OpenXR Backend: If I use this path, the rendering is perfect in both eyes, but MRUK fails to fetch real-world data. I get the following errors:

    • MRUK Shared: OpenXR not initialized. Can not start anchor discovery.

    • Failed to start anchor discovery: 3.

What I’ve already tried:

  • Added com.oculus.permission.USE_ANCHOR_API and com.oculus.permission.USE_SCENE to Extra Permissions.

  • Verified that ‘Anchor Support’ and ‘Scene Support’ are enabled in the MetaXR plugin settings.

The Question: It seems the Epic Native OpenXR instance is not correctly registering the Meta vendor extensions required for Scene/Anchors when used outside of the official Meta Engine Fork.

Has anyone successfully bypassed ‘Error 3’ while using the Epic Native backend in UE 5.7? Is there a specific configuration in DefaultEngine.ini or a C++ modification in the plugin’s GetRequiredExtensions method to force these extensions to load on a standard Epic build?

Thanks for any help!

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I’ve tested on 5.6 and still have the same issue.

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The MetaXR plugin for 5.7 (not released yet) will default to use our native OpenXR backend instead of legacy OVR. Not all MetaXR plugin features prior to the 5.7 version works without OVR, so I’d recommend you try the 5.7 version when it comes out.

Note that Passthrough via Link is only supported for development purposes and last time I used it Mobile Preview - Vulkan was required for passthrough to work.