ARCoreのサンプルを用いて、オブジェクトを決まった数設置したい

現在ARCoreを用いてARコンテンツを作る練習をしています。
サンプルのHalloARを用いています。このサンプルは平面に制限なくオブジェクトが置けるのですが、
設置できるオブジェクトを1~3つぐらいの少数にしたいです。
とりあえずオブジェクトの設置の部分であろうプログラムです。
ヒントでもいいので教えていただけるとありがたいです。

Unity
1namespace GoogleARCore.Examples.HelloAR
2{
3    using System.Collections.Generic;
4    using GoogleARCore;
5    using GoogleARCore.Examples.Common;
6    using UnityEngine;
7    using UnityEngine.EventSystems;
8
9#if UNITY_EDITOR
10    // Set up touch input propagation while using Instant Preview in the editor.
11    using Input = InstantPreviewInput;
12#endif
13
14    /// <summary>
15    /// Controls the HelloAR example.
16    /// </summary>
17    public class HelloARController : MonoBehaviour
18    {
19        /// <summary>
20        /// The first-person camera being used to render the passthrough camera image (i.e. AR
21        /// background).
22        /// </summary>
23        public Camera FirstPersonCamera;
24
25        /// <summary>
26        /// A prefab to place when a raycast from a user touch hits a vertical plane.
27        /// </summary>
28        public GameObject GameObjectVerticalPlanePrefab;
29
30        /// <summary>
31        /// A prefab to place when a raycast from a user touch hits a horizontal plane.
32        /// </summary>
33        public GameObject GameObjectHorizontalPlanePrefab;
34
35        /// <summary>
36        /// A prefab to place when a raycast from a user touch hits a feature point.
37        /// </summary>
38        public GameObject GameObjectPointPrefab;
39
40        /// <summary>
41        /// The rotation in degrees need to apply to prefab when it is placed.
42        /// </summary>
43        private const float k_PrefabRotation = 180.0f;
44
45        /// <summary>
46        /// True if the app is in the process of quitting due to an ARCore connection error,
47        /// otherwise false.
48        /// </summary>
49        private bool m_IsQuitting = false;
50
51
52        /// <summary>
53        /// The Unity Awake() method.
54        /// </summary>
55        public void Awake()
56        {
57            // Enable ARCore to target 60fps camera capture frame rate on supported devices.
58            // Note, Application.targetFrameRate is ignored when QualitySettings.vSyncCount != 0.
59            Application.targetFrameRate = 60;
60        }
61
62        /// <summary>
63        /// The Unity Update() method.
64        /// </summary>
65        public void Update()
66        {
67            _UpdateApplicationLifecycle();
68           
69            Touch touch;
70            
71            if (Input.touchCount < 1 || (touch = Input.GetTouch(0)).phase != TouchPhase.Began)
72            {
73                return;
74            }
75         
76            if (EventSystem.current.IsPointerOverGameObject(touch.fingerId))
77            {
78                return;
79            }
80
81
82            // Raycast against the location the player touched to search for planes.
83            TrackableHit hit;
84            TrackableHitFlags raycastFilter = TrackableHitFlags.PlaneWithinPolygon |
85                TrackableHitFlags.FeaturePointWithSurfaceNormal;
86
87            if (Frame.Raycast(touch.position.x, touch.position.y, raycastFilter, out hit))
88            {
89                // Use hit pose and camera pose to check if hittest is from the
90                // back of the plane, if it is, no need to create the anchor.
91                if ((hit.Trackable is DetectedPlane) &&
92                    Vector3.Dot(FirstPersonCamera.transform.position - hit.Pose.position,
93                        hit.Pose.rotation * Vector3.up) < 0)
94                {
95                    Debug.Log("Hit at back of the current DetectedPlane");
96                }
97                else
98                {
99                    // Choose the prefab based on the Trackable that got hit.
100                    GameObject prefab;
101                    if (hit.Trackable is FeaturePoint)
102                    {
103                        prefab = GameObjectPointPrefab;
104                    }
105                    else if (hit.Trackable is DetectedPlane)
106                    {
107                        DetectedPlane detectedPlane = hit.Trackable as DetectedPlane;
108                        if (detectedPlane.PlaneType == DetectedPlaneType.Vertical)
109                        {
110                            prefab = GameObjectVerticalPlanePrefab;
111                        }
112                        else
113                        {
114                            prefab = GameObjectHorizontalPlanePrefab;
115                        }
116                    }
117                    else
118                    {
119                        prefab = GameObjectHorizontalPlanePrefab;
120                    }
121
122                    // Instantiate prefab at the hit pose.
123                    var gameObject = Instantiate(prefab, hit.Pose.position, hit.Pose.rotation);
124
125                    // Compensate for the hitPose rotation facing away from the raycast (i.e.
126                    // camera).
127                    gameObject.transform.Rotate(0, k_PrefabRotation, 0, Space.Self);
128
129                    // Create an anchor to allow ARCore to track the hitpoint as understanding of
130                    // the physical world evolves.
131                    var anchor = hit.Trackable.CreateAnchor(hit.Pose);
132
133                    // Make game object a child of the anchor.
134                    gameObject.transform.parent = anchor.transform;
135                }
136            }
137        }
138
139        /// <summary>
140        /// Check and update the application lifecycle.
141        /// </summary>
142        private void _UpdateApplicationLifecycle()
143        {
144            // Exit the app when the 'back' button is pressed.
145            if (Input.GetKey(KeyCode.Escape))
146            {
147                Application.Quit();
148            }
149
150            // Only allow the screen to sleep when not tracking.
151            if (Session.Status != SessionStatus.Tracking)
152            {
153                Screen.sleepTimeout = SleepTimeout.SystemSetting;
154            }
155            else
156            {
157                Screen.sleepTimeout = SleepTimeout.NeverSleep;
158            }
159
160            if (m_IsQuitting)
161            {
162                return;
163            }
164
165            // Quit if ARCore was unable to connect and give Unity some time for the toast to
166            // appear.
167            if (Session.Status == SessionStatus.ErrorPermissionNotGranted)
168            {
169                _ShowAndroidToastMessage("Camera permission is needed to run this application.");
170                m_IsQuitting = true;
171                Invoke("_DoQuit", 0.5f);
172            }
173            else if (Session.Status.IsError())
174            {
175                _ShowAndroidToastMessage(
176                    "ARCore encountered a problem connecting.  Please start the app again.");
177                m_IsQuitting = true;
178                Invoke("_DoQuit", 0.5f);
179            }
180        }
181
182        /// <summary>
183        /// Actually quit the application.
184        /// </summary>
185        private void _DoQuit()
186        {
187            Application.Quit();
188        }
189
190        /// <summary>
191        /// Show an Android toast message.
192        /// </summary>
193        /// <param name="message">Message string to show in the toast.</param>
194        private void _ShowAndroidToastMessage(string message)
195        {
196            AndroidJavaClass unityPlayer = new AndroidJavaClass("com.unity3d.player.UnityPlayer");
197            AndroidJavaObject unityActivity =
198                unityPlayer.GetStatic<AndroidJavaObject>("currentActivity");
199
200            if (unityActivity != null)
201            {
202                AndroidJavaClass toastClass = new AndroidJavaClass("android.widget.Toast");
203                unityActivity.Call("runOnUiThread", new AndroidJavaRunnable(() =>
204                {
205                    AndroidJavaObject toastObject =
206                        toastClass.CallStatic<AndroidJavaObject>(
207                            "makeText", unityActivity, message, 0);
208                    toastObject.Call("show");
209                }));
210            }
211        }
212    }
213}

行動規範の内容に同意します

回答1件

ベストアンサー

以下の処理でGameObjectを生成しているので、生成する度にカウントチェックすることで対処するのはいかがでしょうか。

GameObject生成処理抜粋

C#
1// 修正前
2
3// Instantiate prefab at the hit pose.
4var gameObject = Instantiate(prefab, hit.Pose.position, hit.Pose.rotation);
5
6// Compensate for the hitPose rotation facing away from the raycast (i.e.
7// camera).
8gameObject.transform.Rotate(0, k_PrefabRotation, 0, Space.Self);
9
10// Create an anchor to allow ARCore to track the hitpoint as understanding of
11// the physical world evolves.
12var anchor = hit.Trackable.CreateAnchor(hit.Pose);
13
14// Make game object a child of the anchor.
15gameObject.transform.parent = anchor.transform;

C#
1// 修正後
2// １、インスタンス変数としてカウントアップ用変数を、クラスの先頭に宣言
3private int objCount = 0;
4
5
6// ３、カウント数チェック
7if (objCount > 3) {
8    return
9}
10
11// Instantiate prefab at the hit pose.
12var gameObject = Instantiate(prefab, hit.Pose.position, hit.Pose.rotation);
13
14// Compensate for the hitPose rotation facing away from the raycast (i.e.
15// camera).
16gameObject.transform.Rotate(0, k_PrefabRotation, 0, Space.Self);
17
18// Create an anchor to allow ARCore to track the hitpoint as understanding of
19// the physical world evolves.
20var anchor = hit.Trackable.CreateAnchor(hit.Pose);
21
22// Make game object a child of the anchor.
23gameObject.transform.parent = anchor.transform;
24
25// ２、カウントアップ用変数をインクリメント
26objCount++;