AddRaycast() always returns null

[kenhuang1964]

I am trying to initialize persistent raycast according to https://docs.unity3d.com/Packages/com.unity.xr.arfoundation@5.1/manual/features/raycasts.html but it always returns null. I am using AR Foundation 5.1.1 and my iPad, which has LIDAR.

Here is the relevant part of my code:

    private ARRaycastManager raycastManager;
    private Vector2 screenCenter;
    private ARRaycast persistentRaycast;

    private void Awake()
    {
        raycastManager = GetComponent<ARRaycastManager>();
        screenCenter = new Vector2(Screen.width / 2, Screen.height / 2);
        persistentRaycast = raycastManager.AddRaycast(screenCenter, 3.0f);
        if (persistentRaycast == null)
        {
            Debug.LogError("PersistentRaycast was not created successfully.");
        }
// ...

[andyb-unity]

Have you looked at the logs? I would expect there to be a relevant error message in the console.