---
tags: AR Foundation
---

# AR Foundation 偵測圖片置放物件（包含多圖片偵測）

參考影片 作者 [Dilmer Valecillos](https://github.com/dilmerv)
{%youtube cWEhMlN_bSk %}

Github
https://github.com/dilmerv/UnityARFoundationEssentials

1. 開啟3D專案
2. 使用 Package Manager，需要安裝 AR Foundation 套件，看你是使用什麼平台，選擇 ARCore XR Plugin 或 ARKit XR Plugin 套件至少一項
4. 刪除既有場景的攝影機物件
5. 新增物件 XR -> AR Session Origin
6. 新增物件 XR -> AR Session
7. 設計要置放的物件，並且做成預置物件
8. 在 Project 視窗按右滑鼠鍵新增一個 Reference Image Library （Create -> XR -> Reference Image Library），這是用來管理所有需要偵測（追蹤）的圖片，設定方式可參考下圖，需要偵測的圖片請放到 Project 裡面，拖進這個物件，建議 Name 取一個有意義的名字，Specify Size 請勾選，設定大小大概0.1-0.2（可能要多測幾次），這個物件可以同時設定多種圖片


9. 將 TrackedImageInfoManager 程式碼匯入專案，並且置放到 AR Session Origin 中
10. 在 AR Session Origin 中增加 AR Tracked Image Manager 設定可以參考下圖，Seialized Library 放入你設定的 Reference Image Library，Max Number Of Moving Image 請設定你要偵測圖片的數量，Tracled Image Prefab 放入你要顯示的預置物件（步驟7）


11. 專案匯出設定為 Android，Player 設定如下：
* Graphics API 把 Vulkan 移下或者移除
* Minimun API Level 至少要有 API Level 24
* Scripting Beckend 設定為 IL2CPP
12. Project Setting 的 XR Plug-in Management 設定，選擇 Android 的 ARCore 與 ARKit (iOS)
12. 安裝到手機測試

## TrackedImageInfoManager

using UnityEngine;
using UnityEngine.XR.ARFoundation;

[RequireComponent(typeof(ARTrackedImageManager))]
public class TrackedImageInfoManager : MonoBehaviour
{
    ARTrackedImageManager m_TrackedImageManager;

    void Awake()
    {
        m_TrackedImageManager = GetComponent<ARTrackedImageManager>();
    }

    void OnEnable()
    {
        m_TrackedImageManager.trackedImagesChanged += OnTrackedImagesChanged;
    }

    void OnDisable()
    {
        m_TrackedImageManager.trackedImagesChanged -= OnTrackedImagesChanged;
    }

    void OnTrackedImagesChanged(ARTrackedImagesChangedEventArgs eventArgs)
    {
        foreach (var trackedImage in eventArgs.added)
        {
            // Give the initial image a reasonable default scale
            trackedImage.transform.localScale = new Vector3(0.1f, 0.1f, 0.1f);
        }
    }
}

## 多圖片偵測

這邊所謂多圖片偵測是指我們讓不同圖片，能夠顯示不同的物件。

1. 一開始步驟跟單圖片步驟 1-7 均相同，請注意將要顯示的物件做成預置物件後，預置物件的名稱請取有意義的名稱，因為這必須要與 Reference Image Library 圖片名稱相對應
:::info
以下我們假設有兩個物件要顯示，名稱分別為「Capsule」與「Cube」
:::
3. 在 Project 視窗按右滑鼠鍵新增一個 Reference Image Library （Create -> XR -> Reference Image Library），多圖片設定可以按 Add Image 新增，設定方式可參考下圖，==**Name 要與相對應的預置物件名稱相同，不能有誤**==，Specify Size 請勾選，設定大小大概0.1-0.2（可能要多測幾次）

3. 在 AR Session Origin 中增加 AR Tracked Image Manager，Seialized Library 放入你設定的 Reference Image Library，Max Number Of Moving Image 請設定你要偵測圖片的數量，Tracled Image Prefab 留空即可
4. 將 TrackedImageInfoMultipleManager 程式碼匯入專案，並且置放到 AR Session Origin 中，Ar Objects To Place 項目請依照你要顯示的預置物件數量，依照 Reference Image Library 相對應圖片的順序放入

5. 專案匯出與上述相同

## TrackedImageInfoMultipleManager

using System.Collections.Generic;
using UnityEngine;
using UnityEngine.XR.ARFoundation;
using UnityEngine.UI;
using UnityEngine.XR.ARSubsystems;

[RequireComponent(typeof(ARTrackedImageManager))]
public class TrackedImageInfoMultipleManager : MonoBehaviour
{
    [SerializeField]
    private GameObject[] arObjectsToPlace;

    [SerializeField]
    private Vector3 scaleFactor = new Vector3(0.1f,0.1f,0.1f);

    private ARTrackedImageManager m_TrackedImageManager;

    private Dictionary<string, GameObject> arObjects = new Dictionary<string, GameObject>();

    private string currentActiveImage;

    void Awake()
    {        
        m_TrackedImageManager = GetComponent<ARTrackedImageManager>();
        
        // setup all game objects in dictionary
        foreach(GameObject arObject in arObjectsToPlace)
        {
            GameObject newARObject = Instantiate(arObject, Vector3.zero, Quaternion.identity);
            newARObject.name = arObject.name;
            arObjects.Add(arObject.name, newARObject);
        }
    }

    void OnEnable()
    {
        m_TrackedImageManager.trackedImagesChanged += OnTrackedImagesChanged;
    }

    void OnDisable()
    {
        m_TrackedImageManager.trackedImagesChanged -= OnTrackedImagesChanged;
    }  

    void OnTrackedImagesChanged(ARTrackedImagesChangedEventArgs eventArgs)
    {
        foreach (ARTrackedImage trackedImage in eventArgs.added)
        {
            currentActiveImage = trackedImage.referenceImage.name;
            UpdateARImage(trackedImage, currentActiveImage);
        }

        foreach (ARTrackedImage trackedImage in eventArgs.updated)
        {
            if (trackedImage.trackingState == TrackingState.Tracking)
            {
                currentActiveImage = trackedImage.referenceImage.name;
                AssignGameObject(currentActiveImage, trackedImage.transform.position);
            }
            else
            {
                if (currentActiveImage != trackedImage.referenceImage.name)
                {
                    ReAssignGameObject(trackedImage.referenceImage.name, trackedImage.transform.position);
                }
            }
        }

        //foreach (ARTrackedImage trackedImage in eventArgs.removed)
        //{            
        //    arObjects[trackedImage.name].SetActive(false);            
        //}
    }

    private void UpdateARImage(ARTrackedImage trackedImage, string name)
    {      
        AssignGameObject(name, trackedImage.transform.position);

        Debug.Log($"trackedImage.referenceImage.name: {trackedImage.referenceImage.name}");
    }

    void AssignGameObject(string name, Vector3 newPosition)
    {
        if(arObjectsToPlace != null)
        {
            GameObject goARObject = arObjects[name];
            goARObject.SetActive(true);
            goARObject.transform.position = newPosition;
            goARObject.transform.localScale = scaleFactor;
            foreach(GameObject go in arObjects.Values)
            {
                Debug.Log($"Go in arObjects.Values: {go.name}");
                if(go.name != name)
                {
                    go.SetActive(false);
                }
            } 
        }
    }

    void ReAssignGameObject(string name, Vector3 newPosition)
    {
        if (arObjectsToPlace != null)
        {
            GameObject goARObject = arObjects[name];
            goARObject.SetActive(true);
            goARObject.transform.position = newPosition;
            goARObject.transform.localScale = scaleFactor;
            foreach (GameObject go in arObjects.Values)
            {
                if (go.name == name)
                {
                    go.SetActive(false);
                }
            }
        }
    }
}

### 附註與提醒

* 有的時候物件顯示可能很怪，你需要設定它的預置物件 Transform 大小，這部分可能要多測試。
* 程式「TrackedImageInfoMultipleManager」在原作者 [Dilmer Valecillos](https://github.com/dilmerv) 初始的版本有點問題，因此根據 [Iraklis Bekiaris](https://stackoverflow.com/users/5590224/iraklis-bekiaris) 的[修改](https://stackoverflow.com/questions/64246226/artrackedimage-switches-only-at-the-first-time)，將「TrackedImageInfoMultipleManager」修正以上的版本。