MRTK style grab interactable for Unity's XRTK

ARGrabInteractable.cs

using UnityEngine;
using UnityEngine.XR.Interaction.Toolkit;
using UnityEngine.XR.Interaction.Toolkit.AR;

[RequireComponent(typeof(ARSelectionInteractable))]
public class ARGrabInteractable : ARBaseGestureInteractable
{ 
    private const float PositionSpeed = 12f;
    private const float DiffThreshold = 0.0001f;

    private Vector3 _targetLocalPosition;
    private Transform _instanceTransform;
    private bool _isActive;
    private float distanceToScreen;

    protected override void Awake()
    {
        base.Awake();
        _instanceTransform = transform;
    }

    /// <inheritdoc />
    public override void ProcessInteractable(XRInteractionUpdateOrder.UpdatePhase updatePhase)
    {
        base.ProcessInteractable(updatePhase);
        if (_isActive &&
            updatePhase == XRInteractionUpdateOrder.UpdatePhase.Dynamic)
        {
            UpdatePosition();
        }
    }

    /// <inheritdoc />
    protected override bool CanStartManipulationForGesture(DragGesture gesture)
    {
        // If the gesture isn't targeting this item, don't start manipulating.
        return gesture.targetObject != null && gesture.targetObject == gameObject;
    }
    
    /// <inheritdoc />
    protected override void OnStartManipulation(DragGesture gesture)
    {
        distanceToScreen = arSessionOrigin.camera.WorldToScreenPoint(_instanceTransform.position).z;
    }


    /// <inheritdoc />
    protected override void OnContinueManipulation(DragGesture gesture)
    {
        _isActive = true;
        var screenPosition = new Vector3(gesture.position.x, gesture.position.y, distanceToScreen);
        _targetLocalPosition = arSessionOrigin.camera.ScreenToWorldPoint(screenPosition);
    }

    /// <inheritdoc />
    protected override void OnEndManipulation(DragGesture gesture)
    {
        _isActive = false;
    }

    private void UpdatePosition()
    {
        var oldLocalPosition = _instanceTransform.position;
        var newLocalPosition = Vector3.Lerp(
            oldLocalPosition, _targetLocalPosition, Time.deltaTime * PositionSpeed);

        var diffLength = (_targetLocalPosition - newLocalPosition).magnitude;
        if (diffLength < DiffThreshold)
        {
            newLocalPosition = _targetLocalPosition;
            _isActive = false;
        }

        _instanceTransform.position = newLocalPosition;
    }
}