ARFoundation 2 image tracking with many ref images and many objects

Hi,

I'm looking at the the ARFoundation examples -> https://github.com/Unity-Technologies/arfoundation-samples/tree/master/Assets/Scenes/ImageTracking

What's the best approach for having one object created for each tracked image? Using ARKit I created a GenerateImageAnchor for each Reference Image and Prefab To Generate, but I don't see a similar approach for ARFoundation Image tracking.

Thanks!

 

I am having the same problem here. Any help would be much appreciated.

 

I'm really confused, why they haven't included that feature in the first place; image tracking is kinda useless if you cant generate different prefabs for each reference image. Maybe I'm just too spoiled from the ARKit...

Anyway, I followed the little guide by @Skeketor23 ( https://forum.unity.com/threads/arfoundation-and-2d-image-target-tracking.538062/page-3#post-4556173 ), but couldn't make it work.

I simply put my prefabs in the ressources folder and named theme accordingly to their respective image in the referenceImageLibrary.
Working with the trackableID might be better, but I'm not entirely sure how to use them in that case (are they known a priori? Meaning before building my project?). That would not solve the issue though, I would still face the same problem:
I can't find a way to assign the prefabs to their respective image. The documentation isn't really helping either in that regard.

(It's hard to tell what's actually going on because of the lack of a remote for the editor.)

 

I use the reference image name and instantiate a prefab

Code (CSharp):

1. private void OnTrackedImagesChanged(ARTrackedImagesChangedEventArgs eventArgs)
2.         {
3.             for (int i = 0; i < eventArgs.added.Count; i++)
4.             {
5.                 eventArgs.added[i].referenceImage.name;
6. // use that to get the gname
7. }
8. }

Here's an example of using the tracked image event -> https://github.com/Unity-Technologi.../ImageTracking/TrackedImageInfoManager.cs#L97

 

I too am trying to add this functionality.
So Spider did you end up making your own or amending the Tracked Image Manager? Would you mind posting the whole class? Thanks!

 

You should never add code to a framework, you should create classes that encapsulate and adapt the framework. Otherwise you make it impossible to easily update the framework. So yes, I created my own class. My class has a lot of code that is specific to my project so I'm not going to share it. I just added a listener to the event, just like here -> https://github.com/Unity-Technologi.../ImageTracking/TrackedImageInfoManager.cs#L97

Then, iterated over the other Lists like I said.

Another tip, when I instantiate my GameObject, I am adding the ARTrackedImage as the parent.

 

Thanks, Spider. I am fairly new to C# and OOP as I'm more of a tech artist being tasked with implementing AR in Unity. I'm concurrently going through these tuts: http://rbwhitaker.wikidot.com/c-sharp-tutorials as I try to dev this app. Wish me luck!

 

Maybe this will work for you ->

Code (CSharp):

1.  
2. private void OnTrackedImagesChanged(ARTrackedImagesChangedEventArgs eventArgs)
3.         {
4.             ARTrackedImage trackedImage = null;
5.  
6.             for (int i = 0; i < eventArgs.added.Count; i++)
7.             {
8.                 trackedImage = eventArgs.added[i];
9.                 // instantiate AR object, set trackedImage.transform
10.                 // use a Dictionary, the key could be the trackedImage, or the name of the reference image -> trackedImage.referenceImage.name
11.                 // the value of the Dictionary is the AR object you instantiate.
12.             }
13.  
14.             for (int i = 0; i < eventArgs.updated.Count; i++)
15.             {
16.                 trackedImage = eventArgs.updated[i];
17.                 if (trackedImage.trackingState == TrackingState.Tracking)
18.                 //if (trackedImage.trackingState != TrackingState.None)
19.                 {
20.                     // set AR object to active, use Dictionary to get AR object based on trackedImage
21.                     // you can also include TrackingState.Limited by checking for None
22.                 }
23.                 else
24.                 {
25.                     // set active to false
26.                 }
27.             }
28.  
29.             for (int i = 0; i < eventArgs.removed.Count; i++)
30.             {
31.                 // destroy AR object, or set active to false. Use Dictionary.
32.             }
33.         }
34.  

 

Sorry to dig this thread up over and over, but I think it might be helpful for other people working with ImageTracking in the future:

trackedImage.trackingState (in your example): Does it ever change from "tracking" to "none" for you guys? Although the camera loses the image, the TrackingState remains "tracking" (which is really weird to me).

I managed to instantiate different prefabs for different images quite easily after having the name avialable (referenceImage.name), load them from the resources folder and assign them their respective parent, but they remain active, even though the imageAnchor is nowhere to be found.

Do I misunderstand the concept of the TrackingStates or is it simply buggy?

 

use this to deactivate or hide you AR Objects:

Code (CSharp):

1. for (int i = 0; i < eventArgs.removed.Count; i++)
2.             {
3.                 // destroy AR object, or set active to false. Use Dictionary.
4.             }

 

TrackingState has three states:
TrackingState.Limited
TrackingState.None
TrackingState.Tracking

 

Thanks for the quick reply! I am aware of the three TrackingStates. Even with your attempt, it doesn't want to work for me (my guess is that it's never changing to the trackingState none (or limited)):

Code (CSharp):

1. for (int i = 0; i < eventArgs.removed.Count; i++)
2.         {
3.             trackedImage = eventArgs.removed[i];
4.             NamePrefab = trackedImage.referenceImage.name;
5.             TempPrefab = trackedImage.transform.Find(NamePrefab).gameObject;
6.             Destroy(TempPrefab);
7.         }
8.  

 

The code you shared is not using the "updated" List. You are using the "removed" List. So the "none" state not working is irrelevant, right? I have not tested the "none" state, but I do know that for me the "limited" state does work, and that is why I'm ignoring it, because my ARObjects would do strange things if they were visible and the TrackingState was "limited". Also, using Find is cpu intensive. You should store a local reference to your AR GameObject. Use a Dictionary with the referenceImage.name as the key, and the AR GameObject as the value. and maybe there is an issue with how you are trying to find the AR GameObject, are you using the referenceImage.name as the name for your AR GameObject? When you instantiate a Prefab it adds [clone] (or something like that) to the end of the name. Regardless, I recommend that you do not use this approach, use a Dictionary.

 

You can see my app that uses ARFoundation image tracking here -> http://www.superherorobot.com/projects/crispr-3d/

 

First of all: Thanks for the idea with the dictionary. For me, this only solved my issue to an extend, because it will only switch to trackingState.limited, if you lay down the device on a table and wait for ~2 seconds (found it out through pure chance with some debug logs). The problem is: only then the prefab.setactive is set to be false. The ARKit directly changes the state directly after losing its ImageAnchor, 2 seconds seem to be quite long (besides the annoying laying down part, which is extremely weird). I assume you didn't have the same experience?

I created a video to further show my problem:
https://drive.google.com/open?id=1XP4dkKymXubgTILautDcOvTu1eNBtijf

The debug log shows the following:
"we are in the updateCycle with trackingstate Tracking"
or
"we are in the updateCycle with trackingstate!= Tracking"

2nd one only appears after laying down the device. Holding it still without image in the camera view doesnt result in a trackingState change to limited... -.-

Your app looks very clean, good job!

 

Thank you for your compliment. I'm sorry, but I don't fully understand your issue. In my app, when users show the camera the image marker (playing card), the AR object shows, when the card is hidden, the object doesn't show. There are 13 AR objects in my app that show for each type of card. My app works like Vuforia (on iOS only because ARKit tracks moving images while ARCore does not). I am using the approach I shared, and I'm ignoring the "Limited" state. When it's "Tracking" I show the ARObject, when it's "None" or "Limited" I hide it. And I use the "remove" list to hide AR Objects. And it works perfectly. I do not know what else I can do to help you. Good luck!

 

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using System;
5. using UnityEngine.XR.ARSubsystems;
6. using UnityEngine.XR.ARFoundation;
7.  
8. public class ARPerImage : MonoBehaviour
9. {
10.    
11.             Dictionary<string, GameObject> myPrefabsDictionary =
12.             new Dictionary<string, GameObject>();
13.            
14.             List<GameObject> o = new List<GameObject>();
15.            
16.     // Start is called before the first frame update
17.     void Start()
18.     {
19.         myPrefabsDictionary.Add("Rafflesia", Resources.Load("Rafflesia") as GameObject);
20.         myPrefabsDictionary.Add("Logo", Resources.Load("Logo") as GameObject);
21.         myPrefabsDictionary.Add("QRCode", Resources.Load("QRCode") as GameObject);
22.     }
23.  
24.     // Update is called once per frame
25.     void Update()
26.     {
27.        
28.     }
29.    
30.         private void Awake()
31.     {
32.         var arTrackedImageManager = gameObject.GetComponent<ARTrackedImageManager>();
33.         arTrackedImageManager.trackedImagesChanged += OnTrackedImagesChanged;
34.     }
35.    
36.     private void OnTrackedImagesChanged(ARTrackedImagesChangedEventArgs eventArgs)
37.     {
38.         ARTrackedImage trackedImage = null;
39.         // Check the new tracked images
40.         for (int i = 0; i < eventArgs.added.Count; i++)
41.         {
42.             trackedImage = eventArgs.added[i];
43.             string imgName = trackedImage.referenceImage.name; // this is the name in the library
44.             GameObject prefab = myPrefabsDictionary[imgName];
45.             o.Add( Instantiate(prefab, trackedImage.transform));
46.         }
47.        
48.         for (int i = 0; i < eventArgs.updated.Count; i++)
49.         {
50.             trackedImage = eventArgs.updated[i];
51.             if (trackedImage.trackingState == TrackingState.Tracking)
52.                 o[i].active=true;
53.             else
54.                 o[i].active=false;
55.                
56.         }
57.        
58.         for (int i = 0; i < eventArgs.removed.Count; i++)
59.         {
60.                 o[i].active=false;
61.                
62.         }
63.     }
64.  
65. }
66.  

can anyone help me figure this out? the object is spawning alright, but it keeps active event if i point to another target.....

 

@brunno159 seems to be an Android specific problem: https://github.com/Unity-Technologies/arfoundation-samples/issues/157

 

Hi Bruno,

I tried running your code on my project (changing the Gameobject names in the Dictionary and such to match my own) but I wasn't able to even spawn any objects at all with my images.

I have all the Objects I want to spawn inside a folder named Resources (to be able to use the Resources.Load, but I wasn't able to call the Gameobjects and I can't seem to get a console log when running it on my iOS to check for errors..

I imagine you are using Android but could you give some light to this?

Thank you!

 

I've been struggling with this, but managed to stitch something together (for iOS) using the different topics on this forum.
I've taken a slightly different approach, using a serialized array to store the connections between image targets and prefabs via the Inspector. I'm actually using GameObjects already in the scene instead of instantiating prefabs from Project, because I want changes in the objects (e.g. animations, user interactions) to stay in tact between tracking sessions, so to speak.

Code (CSharp):

1.  
2. using System.Collections;
3. using System.Collections.Generic;
4. using UnityEngine;
5. using UnityEngine.UI;
6. using UnityEngine.XR.ARSubsystems;
7. using UnityEngine.XR.ARFoundation;
8.  
9. [System.Serializable]
10. public class MarkerPrefabs
11. {
12.     public string marker;
13.     public GameObject targetPrefab;
14. }
15.  
16. public class SwitchPrefab : MonoBehaviour
17. {
18.     /* Insepctor array */
19.     public MarkerPrefabs[] markerPrefabCombos;
20.     ARTrackedImageManager m_TrackedImageManager;
21.  
22.     void Awake()
23.     {
24.         m_TrackedImageManager = GetComponent<ARTrackedImageManager>();
25.     }
26.  
27.     void OnEnable()
28.     {
29.         m_TrackedImageManager.trackedImagesChanged += OnTrackedImagesChanged;
30.     }
31.  
32.     void OnDisable()
33.     {
34.         m_TrackedImageManager.trackedImagesChanged -= OnTrackedImagesChanged;
35.     }
36.  
37.     private void OnTrackedImagesChanged(ARTrackedImagesChangedEventArgs eventArgs)
38.     {
39.         foreach (var trackedImage in eventArgs.updated)
40.         {
41.         /* If an image is properly tracked */
42.         if (trackedImage.trackingState == TrackingState.Tracking) {
43.              
44.                 /* Loop through image/prefab-combo array */
45.                 for(int i = 0; i < markerPrefabCombos.Length; i++)
46.                 {
47.                     /* If trackedImage matches an image in the array */
48.                     if (markerPrefabCombos[i].marker==trackedImage.referenceImage.name) {
49.  
50.                         /* Set the corresponding prefab to active at the center of the tracked image */                    
51.                         markerPrefabCombos[i].targetPrefab.SetActive(true);
52.                         markerPrefabCombos[i].targetPrefab.transform.position = trackedImage.transform.position;
53.                     }
54.                 }            
55.             /* If not properly tracked */
56.             } else {
57.  
58.                 /* Deactivate all prefabs */
59.                 for(int i = 0; i < markerPrefabCombos.Length; i++) {
60.                     markerPrefabCombos[i].targetPrefab.SetActive(false);
61.                 }
62.             }
63.         }
64.     }
65.  
66. }
67.  

 

Thank you jpvanmuijen for sharing this.

Basically, I wanted to make app which shows different 3d animations based on different tracked images. I want to get access to these 3d objects too so that I can do animation/scale/translate etc.

Actually I added this script to ARSessionOrigin Object along with other scripts like ArSessionObject,ArTrackedImageManager and TrackedImageInfoManager. I also added my game objects and set MarkerPrefabCombos with respective tracked imagenames.
Still I am not able to get gameobject to be spawned on trackedimage.

I am also confused like, is TrackedImagePrefab provided in ArTrackedImageManager also gets added to the scene?

Can you help me to fix this?


Thank you.

 

I can't quite figure out what's wrong in your case, but attached is an image of my setup. Hope this helps.
In the meantime I've extended my project with an on-marker video player, you can ignore that.

Also, make sure to hide the prefabs in the scene on start, to prevent them from floating around in AR.
I use the script below on the Markers object in my scene, nothing fancy.

Code (CSharp):

1. void Start()
2. {
3.     foreach( Transform child in transform )
4.     {
5.         child.gameObject.SetActive( false );
6.     }
7. }

 

Thank you jpvanmuijen for helping, i will check this and update you

 

@jpvanmuijen Thank you! I was able to get this working but it hasn't been consistent. The camera recognizes the first image, sets it's prefab to active then it recognizes the second image, sets the second image prefab to active. After each prefab has been activated, only the second image prefab is able to become active again. Maybe this is only an Android issue? I'm thinking maybe it has to do with how ARCore is handling tracking states? Any guidance would be greatly appreciated. Thanks!

 

Did you figure this out?

Edit -
I changed the second condition to TrackingState.None and it works well!

 

Yup! Changing the first condition to TrackingState.Limited worked for me too.

 

What do you mean the first TrakingState.Limited condition. could you show in the code?

 

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEngine.UI;
5. using UnityEngine.XR.ARSubsystems;
6. using UnityEngine.XR.ARFoundation;
7.  
8. [System.Serializable]
9. public class MarkerPrefabs
10. {
11.     public string marker;
12.     public GameObject targetPrefab;
13. }
14.  
15. public class SwitchPrefabManager : MonoBehaviour
16. {
17.     /* Insepctor array */
18.     public MarkerPrefabs[] markerPrefabCombos;
19.     ARTrackedImageManager m_TrackedImageManager;
20.  
21.     void Awake()
22.     {
23.         Application.targetFrameRate = 60;
24.         m_TrackedImageManager = GetComponent<ARTrackedImageManager>();
25.     }
26.  
27.     void OnEnable()
28.     {
29.         m_TrackedImageManager.trackedImagesChanged += OnTrackedImagesChanged;
30.     }
31.  
32.     void OnDisable()
33.     {
34.         m_TrackedImageManager.trackedImagesChanged -= OnTrackedImagesChanged;
35.     }
36.  
37.     private void OnTrackedImagesChanged(ARTrackedImagesChangedEventArgs eventArgs)
38.     {
39.  
40.             foreach (var trackedImage in eventArgs.updated)
41.         {
42.             /* If an image is properly tracked */
43.             if (trackedImage.trackingState == TrackingState.Tracking || trackedImage.trackingState == TrackingState.Limited)
44.             {
45.  
46.                 /* Loop through image/prefab-combo array */
47.                 for (int i = 0; i < markerPrefabCombos.Length; i++)
48.                 {
49.                     /* If trackedImage matches an image in the array */
50.                     if (markerPrefabCombos[i].marker == trackedImage.referenceImage.name)
51.                     {
52.  
53.                         /* Set the corresponding prefab to active at the center of the tracked image */
54.                         markerPrefabCombos[i].targetPrefab.SetActive(true);
55.                         markerPrefabCombos[i].targetPrefab.transform.position = trackedImage.transform.position;
56.                     }
57.                  
58.                 }
59.  
60.                 /* If not properly tracked */
61.             }
62.             else if (trackedImage.trackingState == TrackingState.None)
63.             {
64.                  //Deactivate all prefabs */
65.                 for (int i = 0; i < markerPrefabCombos.Length; i++)
66.                 {
67.                     markerPrefabCombos[i].targetPrefab.SetActive(false);
68.                 }
69.             }
70.         }
71.     }
72. }

 

Thank You! I got it now!

 

I made a Test with the code above. Well, I could be able to track each object with respective imageMark but the every objects that are not tracked remains in the scene...like floating in the air. Any help with that? I´m using AR foundation and Android...

 

Hello,

Here me code to track multi image with multi GameObject. The prefab need ARTrackedImage component to know if you want to remove the object when the tracking is None or Limited.

Code (CSharp):

1. using System.Collections.Generic;
2. using UnityEngine;
3. using UnityEngine.XR.ARFoundation;
4.  
5. public class MultiImageTracker : MonoBehaviour
6. {
7.     private ARTrackedImageManager m_trackedImageManager;
8.  
9.     [SerializeField]
10.     private TrackedPrefab[] prefabToInstantiate;
11.  
12.     private Dictionary<string, GameObject> instanciatePrefab;
13.  
14.     private void Awake()
15.     {
16.         m_trackedImageManager = GetComponent<ARTrackedImageManager>();
17.         instanciatePrefab = new Dictionary<string, GameObject>();
18.     }
19.  
20.     private void OnEnable()
21.     {
22.         m_trackedImageManager.trackedImagesChanged += OnTrackedImageChanged;
23.     }
24.  
25.     private void OnDisable()
26.     {
27.         m_trackedImageManager.trackedImagesChanged -= OnTrackedImageChanged;
28.     }
29.  
30.     private void OnTrackedImageChanged(ARTrackedImagesChangedEventArgs eventArgs)
31.     {
32.         foreach (ARTrackedImage addedImage in eventArgs.added)
33.         {
34.             InstantiateGameObject(addedImage);
35.         }
36.  
37.         foreach (ARTrackedImage updatedImage in eventArgs.updated)
38.         {
39.             if(updatedImage.trackingState == UnityEngine.XR.ARSubsystems.TrackingState.Tracking)
40.             {
41.                 UpdateTrackingGameObject(updatedImage);
42.             }
43.             else if(updatedImage.trackingState == UnityEngine.XR.ARSubsystems.TrackingState.Limited)
44.             {
45.                 UpdateLimitedGameObject(updatedImage);
46.             }
47.             else
48.             {
49.                 UpdateNoneGameObject(updatedImage);
50.             }
51.         }
52.  
53.         foreach (ARTrackedImage removedImage in eventArgs.removed)
54.         {
55.             DestroyGameObject(removedImage);
56.         }
57.     }
58.  
59.     private void InstantiateGameObject(ARTrackedImage addedImage)
60.     {
61.         for (int i = 0; i < prefabToInstantiate.Length; i++)
62.         {
63.             if (addedImage.referenceImage.name == prefabToInstantiate[i].name)
64.             {
65.                 GameObject prefab = Instantiate<GameObject>(prefabToInstantiate[i].prefab, transform.parent);
66.                 prefab.transform.position = addedImage.transform.position;
67.                 prefab.transform.rotation = addedImage.transform.rotation;
68.  
69.                 instanciatePrefab.Add(addedImage.referenceImage.name, prefab);
70.             }
71.         }
72.     }
73.  
74.     private void UpdateTrackingGameObject(ARTrackedImage updatedImage)
75.     {
76.  
77.         for (int i = 0; i < instanciatePrefab.Count; i++)
78.         {
79.             if (instanciatePrefab.TryGetValue(updatedImage.referenceImage.name, out GameObject prefab))
80.             {
81.                 prefab.transform.position = updatedImage.transform.position;
82.                 prefab.transform.rotation = updatedImage.transform.rotation;
83.                 prefab.SetActive(true);
84.             }
85.         }
86.     }
87.  
88.     private void UpdateLimitedGameObject(ARTrackedImage updatedImage)
89.     {
90.         for (int i = 0; i < instanciatePrefab.Count; i++)
91.         {
92.             if (instanciatePrefab.TryGetValue(updatedImage.referenceImage.name, out GameObject prefab))
93.             {
94.                 if(!prefab.GetComponent<ARTrackedImage>().destroyOnRemoval)
95.                 {
96.                     prefab.transform.position = updatedImage.transform.position;
97.                     prefab.transform.rotation = updatedImage.transform.rotation;
98.                     prefab.SetActive(true);
99.                 }
100.                 else
101.                 {
102.                     prefab.SetActive(false);
103.                 }
104.  
105.             }
106.         }
107.     }
108.  
109.     private void UpdateNoneGameObject(ARTrackedImage updateImage)
110.     {
111.         for(int i = 0; i < instanciatePrefab.Count; i++)
112.         {
113.             if(instanciatePrefab.TryGetValue(updateImage.referenceImage.name, out GameObject prefab))
114.             {
115.                 prefab.SetActive(false);
116.             }
117.         }
118.     }
119.  
120.     private void DestroyGameObject(ARTrackedImage removedImage)
121.     {
122.         for (int i = 0; i < instanciatePrefab.Count; i++)
123.         {
124.             if (instanciatePrefab.TryGetValue(removedImage.referenceImage.name, out GameObject prefab))
125.             {
126.                 instanciatePrefab.Remove(removedImage.referenceImage.name);
127.                 Destroy(prefab);
128.             }
129.         }
130.     }
131. }
132.  
133. [System.Serializable]
134. public struct TrackedPrefab
135. {
136.     public string name;
137.     public GameObject prefab;
138. }

Maybe some improvement can be make.

Best regards,
Alexis

 

Thanks a lot Alexis, Worked Like a Sharm! Great Work!

 

hello,

did you tried this solution with ARTrackedObject?
Removed not calling.
Is there anyway to get the trigger when an object gets removed from the scene. Attaching screenshot also

 

I think the removed event is not call (Same think for ImageTracked). May be try to check the Tracking statement in event.uptaded.

Code (CSharp):

1.            
2. if(trackedObject.trackingState == UnityEngine.XR.ARSubsystems.TrackingState.Tracking)
3. {
4.                // Do something
5. }
6. else if(trackedObject.trackingState == UnityEngine.XR.ARSubsystems.TrackingState.Limited)
7. {
8.                 // Do something
9. }
10. else
11. {
12.                  // Do something
13. }

And disable the prefab on TrakingState.Limited.

 

hello,
Thank you for the reply. i tried but when i remove the object OntrackedObjectsChanged not getting called. See below the code.

Code (CSharp):

1.  
2. void OnEnable()
3.     {
4.         m_TrackedObjectManager.trackedObjectsChanged += OntrackedObjectsChanged;
5.  
6.     }
7.  
8.     void OnDisable()
9.     {
10.         Debug.Log("ondisable");
11.         m_TrackedObjectManager.trackedObjectsChanged -= OntrackedObjectsChanged;
12.  
13.     }
14.    
15.     void UpdateInfo(ARTrackedObject trackedObject)
16.     {
17.         Debug.Log(trackedObject.trackingState + "--TTTTTT--");
18.  
19.         if (trackedObject.trackingState == UnityEngine.XR.ARSubsystems.TrackingState.Tracking)
20.             Debug.Log("TrackingIn...");
21.         else if (trackedObject.trackingState == UnityEngine.XR.ARSubsystems.TrackingState.Limited)
22.             Debug.Log("Limited...");
23.  
24.         else
25.             Debug.Log("Else...");
26.  
27.     }
28.     void OntrackedObjectsChanged(ARTrackedObjectsChangedEventArgs eventArgs)
29.     {
30.    
31.  
32.         foreach (var trackedObject in eventArgs.updated)
33.             UpdateInfo(trackedObject);
34.  
35.         foreach (var trackedObject in eventArgs.removed)
36.             UpdateInfo(trackedObject);
37.     }
38.  

 

Hi,

Yes, the eventArgs.removed is never called.

You need to disable your object in:

Code (CSharp):

1. else if (trackedObject.trackingState == UnityEngine.XR.ARSubsystems.TrackingState.Limited)
2.             Debug.Log("Limited...");

This will be called when your object is not tracked "correctly" (ex: when is not in the scene).

Here some explanations about image tracking but I think it's the same explanations for object tracking.

Best,
Alexis

 

As with many others, eventArgs.removed never gets called for me. Can you post details of which version of Unity/ARFoundation you're using?

 

You can try this one
https://github.com/codemaker2015/ARFoundation-Dynamic-Image-Database-Creation

 

I downloaded and ran this. Looks basically like it takes the first library of just maps and inserts the other images. Is that correct?

Also, can you explain your ARFoundationSessionStack a bit? Is all of this needed just for a tracked image? I was able to instantiate objects with just the AR Tracked Image Manager, the AR Session, and Ar Session Origin but your version seems to keep the object from floating off much better than that version.

 

Found my answer to the above questions - a lot of my issue was that 2019.2 has some issues with spawning 2D objects as the prefab. Also answered my other question about how the code works by just examining it more - thanks for posting the sample @codemaker2015.

 

@Alexis-Dev : With your example it works like a charm. Any idea why the axis always stays and the object does not rotate with the tracked image?

 

Hi @carlastreckwall,

I don't have this problem... The rotation is update in the script.

What is your devise?

Best,
Alexis

 

Yes that was what I thought… I am working unity 2019.4, AR Foundation 3.1.3 and an Iphone XS iOS 13.5.1.

Update: I found the mistake. Apparently my prefab does not rotate as the code suggests, all other prefabs work fine! Thx a lot!

 

Great!
When I will have some time, I will rework this code to make it more flexible.

Best,
Alexis

 

man, i'm brazilian, i was in need of a code like this, you just helped me a lot with this, i made a point of logging in to thank you for that, you are awesome !!!!

 

Thanks!

 

Ok I have another question maybe one of you already came across: I want the prefab not to be destroyed when tracking is lost, only when another image tracker is found so they don't overlay. Any ideas guys?

 

You need to write your own code to do that.
When the tracking is lost, the image state is TrackingState.Limited, don't call a function to destroy it.
Check the image have state equal to TrackingState.Tracking, if it's not relate to your prefab, destroy it and instantiate the other prefab.

Best,
Alexis

 

Hi,

May be this ARFoundation sample will help you.

 

@fabisfab: Are you sure the naming is correct? Your reference in MultiImageTracker should be precisely the same names as the images in the ReferenceImageLabrary.