>= Unity 2020.1 compatible persistent, local WorldAnchorStore

[tmhab]

Describe the problem

Unity 2020.1 will remove WorldAnchorStore functionality.

Describe the solution you'd like

WorldAnchorManager wrapping another solution that allows for local, persistent world anchors.

Describe alternatives you've considered

• Using Azure Cloud, which while allowing a number of free requests per month, requires a credit card attached to an Azure account.
• Using deprecated code with warnings in it like https://www.anderslundgren.se/creating-local-world-anchors-on-hololens-2/ and staying on 2019 for the forseeable future.

Additional context

N/A

[keveleigh]

This is coming! We've been working with Unity to add an extension to the Windows XR Plugin to allow for anchor store access for XRAnchor/XRReferencePoint.

[tmhab]

Fantastic; good to hear! I'll be looking forward to seeing it implemented 👍

[keveleigh]

Finally an update! The API has shipped (or will ship any moment) in the 2.5 package.

The APIs to use are TryGetAnchorStoreAsync and the resulting XRAnchorStore APIs.

Happy to provide some additional examples of use if requested, and we should update WorldAnchorStore in MRTK to support this API.

[wspaas]

@keveleigh I am trying to write an implementation that uses the new API for placing, saving and sharing Spatial Anchors.

I got this to work using the XRReferencePointSubsystem and XRAnchorStore. My Code is based on an example found here:
https://forum.unity.com/threads/world-anchors-on-the-hl2-with-the-new-xr-plugin.1035256/#post-6711919

But currently my code only allows me to persistently save anchors on 1 device (local). I would like to share the saved Anchor to another device. Only Saving the TrackableId seems to be insufficient to 'find' the Anchor when not saved to the XRAnchorStore (which is only local data, I assume).

What is the best way to share the locations of these anchors between devices (without using Azure)?

I found this class in the native UWP code:
https://docs.microsoft.com/en-us/uwp/api/windows.perception.spatial.spatialanchortransfermanager?view=winrt-19041

Is there an already existing implementation of this within the Unity API? Or some examples of how to best combine this with the existing API? Or maybe there is an entirely different way which I overlooked?

Thanks in advance!

[NoTuxNoBux]

I think before there was the WorldAnchorTransferBatch in C# as documented by this documentation page, but maybe this is for the deprecated API and an equivalent doesn't exist yet in the new API?

[tmhab]

@wspaas I'm very interested in your findings when you hopefully find a solution, please update us if you make progress :)

[zantiu]

Any update on this?

[Axiang666]

Looking forward to the update

[Kent1LG]

Hello, my team and I also really need a solution on this when it's possible ! Any news?

[NLR-L]

Hi, are there any updates?

[shoukailiang]

Hello,I also need a solution.

[JulieMo3]

Still looking for a solution. Any news?

[NLR-L]

I'm sorry I can't post the complete solution.

But you can make use of the unity ArFoundation package, to convert an anchor to an anchor pointer. This pointer can be converted to the Windows.Perception.Spatial.SpatialAnchor.

How you can do this can be found in this thread. When using OpenXR as the XR plugin you need to do the extra step that's done in OP's last post. https://forum.unity.com/threads/arfoundation-aranchor-nativeptr-needs-extra-conversion-for-openxr.1199446/

This pointer works with OpenXR but also with the WindowsMixedReality XR plugin.

Then you can use this SpatialAnchor together with the SpatialAnchorExporter to export your anchors.

When you read out this data you can import it with the SpatialAnchorTransferManager.

The position of the anchor can be calculated by combining the code from within the Azure Spatial Anchor Manager with the Unity Spatial Coordinate system.

SpatialCoordinateSystem unityWorldCoordinateSystem = PerceptionInterop.GetSceneCoordinateSystem(Pose.identity) as SpatialCoordinateSystem;
SpatialCoordinateSystem anchorCoordinateSystem = anchor.CoordinateSystem;
System.Numerics.Matrix4x4? anchorToUnityWorld = anchorCoordinateSystem.TryGetTransformTo(unityWorldCoordinateSystem);
if (anchorToUnityWorld.HasValue)
{
    System.Numerics.Quaternion anchorToUnityWorldRotationNative = System.Numerics.Quaternion.CreateFromRotationMatrix(anchorToUnityWorld.Value);

    // The anchor world rotation
    Quaternion anchorToUnityWorldRotation = ToUnityQuaternion(anchorToUnityWorldRotationNative);

    // The anchor world position
    Vector3anchorToUnityWorldTranslation = ToUnityVector3(anchorToUnityWorld.Value.Translation);
} 
else 
{
    throw new InvalidOperationException("Couldn't compute a native anchor pose");
}

This way you can import/export anchors without having to use Azure.

[keveleigh]

For OpenXR, we have some samples showing off the new XRAnchorStore APIs: https://github.com/microsoft/OpenXR-Unity-MixedReality-Samples/blob/3917606bae2dd495cdd5680d33701ccd2caee3d7/BasicSample/Assets/ARAnchor/Scripts/AnchorsSample.cs#L51

[Morgan-6Freedom]

What's the status ? What is the solution to share a world anchor locally between 2 HL2 ?

• Can we follow this guide to share anchors locally ?
• Should we follow this sample instead ?
• Or should we use this sample ?

[IssueSyncBot]

We appreciate your feedback and thank you for reporting this issue.

Microsoft Mixed Reality Toolkit version 2 (MRTK2) is currently in limited support. This means that Microsoft is only fixing high priority security issues. Unfortunately, this issue does not meet the necessary priority and will be closed. If you strongly feel that this issue deserves more attention, please open a new issue and explain why it is important.

Microsoft recommends that all new HoloLens 2 Unity applications use MRTK3 instead of MRTK2.

Please note that MRTK3 was released in August 2023. It features an all-new architecture for developing rich mixed reality experiences and has a minimum requirement of Unity 2021.3 LTS. For more information about MRTK3, please visit https://www.mixedrealitytoolkit.org.

Thank you for your continued support of the Mixed Reality Toolkit!