Unity ARKitを用いてUnityちゃんを出現させたい！

前提・実現したいこと

・Unity AR Hit test Exampleの中のCollision LayerにARKitPlaneを追加したい
・UnityのARKitを使ってUnityちゃんをカメラ越しの平面上に出現させたい。

発生している問題・エラーメッセージ

Unityちゃんを出現させること自体はできているんですが、落ちていってどこかへ消えてしまう。
おそらくUnity AR Hit test Exampleの中のCollision LayerのなかにARKitPlane（カメラ越しで認識された平面を床として扱う？）がないからだと思います。

該当のソースコード

Scriptと書いてあるので、該当するcsファイルを確認したところ

C#
1using System;
2using System.Collections.Generic;
3
4using UnityEngine.EventSystems;
5
6namespace UnityEngine.XR.iOS
7{
8	public class UnityARHitTestExample : MonoBehaviour
9	{
10		public Transform m_HitTransform;
11		public float maxRayDistance = 30.0f;
12		public LayerMask collisionLayer = 1 << 10;  //ARKitPlane layer ←多分これ
13
14
15        bool HitTestWithResultType (ARPoint point, ARHitTestResultType resultTypes)
16        {
17            List<ARHitTestResult> hitResults = UnityARSessionNativeInterface.GetARSessionNativeInterface ().HitTest (point, resultTypes);
18            if (hitResults.Count > 0) {
19                foreach (var hitResult in hitResults) {
20                    Debug.Log ("Got hit!");
21                    m_HitTransform.position = UnityARMatrixOps.GetPosition (hitResult.worldTransform);
22                    m_HitTransform.rotation = UnityARMatrixOps.GetRotation (hitResult.worldTransform);
23                    Debug.Log (string.Format ("x:{0:0.######} y:{1:0.######} z:{2:0.######}", m_HitTransform.position.x, m_HitTransform.position.y, m_HitTransform.position.z));
24                    return true;
25                }
26            }
27            return false;
28        }
29
30      
31
32
33        // Update is called once per frame
34        void Update()
35        {
36#if UNITY_EDITOR   //we will only use this script on the editor side, though there is nothing that would prevent it from working on device
37            if (Input.GetMouseButtonDown(0))
38            {
39                Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
40                RaycastHit hit;
41
42                //we'll try to hit one of the plane collider gameobjects that were generated by the plugin
43                //effectively similar to calling HitTest with ARHitTestResultType.ARHitTestResultTypeExistingPlaneUsingExtent
44                if (Physics.Raycast(ray, out hit, maxRayDistance, collisionLayer))
45                {
46                    //we're going to get the position from the contact point
47                    m_HitTransform.position = hit.point;
48                    Debug.Log(string.Format("x:{0:0.######} y:{1:0.######} z:{2:0.######}", m_HitTransform.position.x, m_HitTransform.position.y, m_HitTransform.position.z));
49
50                    //and the rotation from the transform of the plane collider
51                    m_HitTransform.rotation = hit.transform.rotation;
52                }
53            }
54            #else
55            if (Input.touchCount > 0 && m_HitTransform != null) && IsPointerOverUIObject()
56			{
57				var touch = Input.GetTouch(0);
58				if (touch.phase == TouchPhase.Began || touch.phase == TouchPhase.Moved)
59				{
60					var screenPosition = Camera.main.ScreenToViewportPoint(touch.position);
61					ARPoint point = new ARPoint {
62						x = screenPosition.x,
63						y = screenPosition.y
64					};
65
66                    // prioritize reults types
67                    ARHitTestResultType[] resultTypes = {
68						//ARHitTestResultType.ARHitTestResultTypeExistingPlaneUsingGeometry,
69                        ARHitTestResultType.ARHitTestResultTypeExistingPlaneUsingExtent, 
70                        // if you want to use infinite planes use this:
71                        //ARHitTestResultType.ARHitTestResultTypeExistingPlane,
72                        //ARHitTestResultType.ARHitTestResultTypeEstimatedHorizontalPlane, 
73						//ARHitTestResultType.ARHitTestResultTypeEstimatedVerticalPlane, 
74						//ARHitTestResultType.ARHitTestResultTypeFeaturePoint
75                    }; 
76					
77                    foreach (ARHitTestResultType resultType in resultTypes)
78                    {
79                        if (HitTestWithResultType (point, resultType))
80                        {
81                            return;
82                        }
83                    }
84				}
85			}
86#endif
87
88        }
89
90	
91	}
92}
93
94