Spatial Anchor Example

This section includes an example of using Unity's AR Foundation to create local anchors on the Magic Leap 2 headset.

Simple Example

This example script illustrates how to utilize Unity's ARFoundation AR Anchors on Magic Leap's OpenXR SDK. Using input actions, users can create and delete anchors in the AR space. The script maintains manages a list of active anchors, which is used to query the anchors for additional information specific to the Magic Leap platform, such as confidence.

caution

This feature requires the SPATIAL_ANCHORS permission to be enabled in your project's Manifest Settings. (Edit > Project Settings > Magic Leap > Manifest Settings)

Prerequisites

Before using spatial anchors, ensure your project has the necessary permissions and subsystems activated:

• Spatial Anchors Permission: Activate SPATIAL_ANCHORS in Edit > Project Settings > Magic Leap > Manifest Settings.
• OpenXR Feature: Enable the Magic Leap 2 Spatial Anchor Subsystem in Window > XR Plugin Manager > OpenXR Settings.
• AR Anchor Manager: For Spatial Anchor to be tracked properly, add the ARAnchorManager component to the XROrigin in your scene and assigned to the anchorManager property.
• Controller Transform: Before running the script, make sure to assign the Transform that will be used to set the position and rotation of the newly created anchors

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.InputSystem;
using UnityEngine.XR.ARFoundation;
using UnityEngine.XR.ARSubsystems;
using UnityEngine.XR.Management;
using UnityEngine.XR.OpenXR.Features.MagicLeapSupport;

public class SpatialAnchorsTest : MonoBehaviour
{
    // Reference to the ARAnchorManager component, used for anchor creation and management.
    [SerializeField]
    private ARAnchorManager anchorManager;

    // Reference to the XRController that will be used to position the Anchors
    [SerializeField]
    private Transform controllerTransform;

    // Input actions for capturing position, rotation, menu interaction, and the bumper press.
    [SerializeField]
    public InputAction menuInputAction = new InputAction(binding: "<XRController>/menuButton", expectedControlType: "Button");
    [SerializeField]
    public InputAction bumperInputAction = new InputAction(binding: "<XRController>/gripButton", expectedControlType: "Button");

    // Active subsystem used for querying anchor confidence.
    private MLXrAnchorSubsystem activeSubsystem;

    // List of active anchors tracked by the script.
    private List<ARAnchor> activeAnchors = new List<ARAnchor>();

    // Coroutine started on MonoBehaviour Start to ensure subsystems are loaded before enabling input actions.
    private IEnumerator Start()
    {
        // Waits until AR subsystems are loaded before proceeding.
        yield return new WaitUntil(AreSubsystemsLoaded);

        // Enabling input actions.
        menuInputAction.Enable();
        bumperInputAction.Enable();

        // Registering input action callbacks.
        menuInputAction.performed += OnMenu;
        bumperInputAction.performed += OnBumper;
    }

    // Cleanup of input actions when the GameObject is destroyed.
    void OnDestroy()
    {
        menuInputAction.Dispose();
        bumperInputAction.Dispose();
    }

    // Update loop to log the status of active anchors every frame.
    void Update()
    {
        string anchorsStatusText = "Anchor Position | Tracking State | Confidence";

        // Iterating through active anchors to log their position, tracking state, and confidence.
        foreach (ARAnchor anchor in activeAnchors)
        {
            MLXrAnchorSubsystem.AnchorConfidence anchorCon = MLXrAnchorSubsystem.AnchorConfidence.NotFound;
            if (anchor.trackingState == TrackingState.Tracking && activeSubsystem != null)
            {
                anchorCon = activeSubsystem.GetAnchorConfidence(anchor);
            }
            anchorsStatusText += $"{anchor.gameObject.transform.position} - {anchor.trackingState} - {anchorCon}\n";
        }

        // Only log the status of anchors if there is at least 1 active anchor.
        if (activeAnchors.Count > 0)
        {
            Debug.Log(anchorsStatusText);
        }
    }

    // Checks if the Magic Leap Anchor Subsystem is loaded 
    private bool AreSubsystemsLoaded()
    {
        if (XRGeneralSettings.Instance == null || XRGeneralSettings.Instance.Manager == null || XRGeneralSettings.Instance.Manager.activeLoader == null) return false;
        activeSubsystem = XRGeneralSettings.Instance.Manager.activeLoader.GetLoadedSubsystem<XRAnchorSubsystem>() as MLXrAnchorSubsystem;
        return activeSubsystem != null;
    }

    // Callback for creating a new anchor when the bumper button is pressed.
    private void OnBumper(InputAction.CallbackContext obj)
    {
        // Reading the current position and rotation from the input actions.
        Pose currentPose = new Pose(controllerTransform.position, controllerTransform.rotation);
        
        Debug.Log("SpatialAnchorsTest: Bumper hit, creating Anchor at " + currentPose);

        // Instantiating a new anchor at the current pose and adding it to the list of active anchors.
        GameObject newAnchor = Instantiate(anchorManager.anchorPrefab, currentPose.position, currentPose.rotation);
        ARAnchor newAnchorComponent = newAnchor.AddComponent<ARAnchor>();
        activeAnchors.Add(newAnchorComponent);
    }

    // Callback for deleting the most recently added anchor when the menu button is pressed.
    private void OnMenu(InputAction.CallbackContext obj)
    {
        if (activeAnchors.Count > 0)
        {
            Debug.Log("SpatialAnchorsTest: Menu hit, Deleting Anchor at " + activeAnchors[activeAnchors.Count - 1].transform.position);
            
            // Removing the last anchor from the scene and the list of active anchors.
            Destroy(activeAnchors[activeAnchors.Count - 1].gameObject);
            activeAnchors.RemoveAt(activeAnchors.Count - 1);
        }
    }
}