Resolved Reset AR Session

Is there a way to reset the AR session?

I tried to use this in, but it seems it does not do anything:
ARSubsystemManager.DestroySubsystems();
ARSubsystemManager.CreateSubsystems();

Sometimes the tracking goes wrong or when reopening an app all es messed up and I want to give the users to reset the scene. Then all planes have to removed and the tracking points and so on.
For ARKit I had a script that can do this, but now with foundation it seems a bit more difficult.

 

You should be able to destroy the ARSession GameObject and Instantiate a new one to achieve this.

 

Thanks. Will try that.
And then it is just a matter of destroying the visual planes to have a clean new session?

 

Did this work for you? I tried this but when but i get this error when enabeling the newly spawned arsession: InvalidOperationException: Cannot start AR session because there is no session subsystem

 

Same here, "InvalidOperationException: Cannot start AR session because there is no session subsystem." when enabling ARSession. I also get it if I load from SampleScene to another scene and then try to load SampleScene again.

Update: Exception only occurs in the Editor.

 

Hi. Did destroying the AR Session object and re-instantiating work for anyone? I get a black screen when I do that.

 

I'm also getting a black screen, instead of the camera feed, after destroying the ARSession component and then adding it back to the same gameObject.

 

I couldn't find a nice way to reset the session. For now I get all the planes and point clouds and destroy/disable them manually.

 

If I'm reloading AR scene for the second time, I'm getting the "Cannot start AR session.." error, and device is not tracking any planes, due to session fail

 

I just did a test on a Pixel where I enabled/disabled the ARSession component, and also Destroyed and Instantiated it. All seemed to work as expected.

For this particular issue:

What device and OS version?

 

I have the same issue when loading scene again. Just one note that I'm using multiple scenes loaded additively and AR session lives in the scene from scene load.

 

I can't already reproduce this exact error, it's been lost in the iterations of fixing attempts.
The thing is I was trying to fix nonexistent error, because it was only in the Editor, as soon as I built my app for device, everything went okay.
I used directives for ARSubsystemManager functions, because all of the systems are null in the editor, therefore it can't function properly.

So it looks like this and works like charm even when reloading scene:

Code (CSharp):

1. void Start()
2.     {
3. #if !UNITY_EDITOR
4.         ARSubsystemManager.DestroySubsystems();
5.         ARSubsystemManager.CreateSubsystems();
6.         ARSubsystemManager.StopSubsystems();
7.         arSession.gameObject.SetActive(false);
8. #endif
9.     }
10.  
11. public async void StartTracking()
12.     {
13. #if !UNITY_EDITOR
14.         arSession.gameObject.SetActive(true);
15.         ARSubsystemManager.StartSubsystems();
16.         arPlaneManager.planeAdded += PlaneTracked;
17. #else
18.         //here comes some emulation of plane tracking for Editor:
19.         //PlaceInfinitePlane(Vector3.zero);
20.         //await new WaitForSeconds(1f);
21.         //OnPlaneTracked?.Invoke();
22. #endif
23.     }
24.  

May it help someone to figure out how to handle reload of ar session =)

 

Same here. I think multiple scenes is breaking something.

 

We're also having the same issue with reloading the scene a second time and getting a black screen. Samsung S8 and Android, and iPhone 7 Plus and iOS 12

 

Same problem here

 

For your information, there is a method Reset() on ARSession component.
See https://docs.unity3d.com/Packages/c...pi/UnityEngine.XR.ARFoundation.ARSession.html
Seems to work as expected

 

But how we can call that method? I have a button that calls "ResetDemo" function to load the firstScene and reset the ARKit but doestn works :

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using System.Text;
4. using UnityEngine;
5. using UnityEngine.XR.ARFoundation;
6. using UnityEngine.XR.ARSubsystems;
7. using UnityEditor;
8. using UnityEngine.SceneManagement;
9.  
10. public class HumanBodyTracker : MonoBehaviour
11. {
12. ....
13.     private void Reset() {
14.          Debug.Log("Reseting....");
15.     }
16.  
17.     public void ResetDemo()
18.     {
19.         Reset();
20.         SceneManager.LoadScene("StartScene");
21.         Debug.Log("Loading Start Scene...");
22.         message = "Loading Start Scene...";
23.  
24.     }

 

You have to get a reference to the ARSession in your scene to be able to call the Reset(). You can either get it by placing your script on the same GameObject, as the ARSession is on

Code (CSharp):

1. ARSession arSession = GetComponent<ARSession>();
2. arSession.Reset();

or you can link it by inserting a serialized field and set the reference in the inspector

Code (CSharp):

1. using UnityEngine.XR.ARFoundation;
2.  
3. [SerializeField]
4. private ARSession _arSession;
5.  
6.  

and call it in your method as follows

Code (CSharp):

1. _arSession.Reset();

Unfortunately this Reset() doesn't solve the problem with the black screen in my project... So I raise my hand to say: "Same problem here"

 

Thanks, works like "its reseting" but same issue, black screen I think that maybe we need to store the gameobjects inside of the session...

 

The Reset() works fine, if you don't leave the scene and stay in the AR-scene. As I can see from your posting you are then also loading another scene within your special reset, so this causes the black screen. Comment that out, so your app stays in the same scene and try the reset again.

The problems stays the same: If you leave an AR-scene and later return to an AR-scene the background is just black

 

Hi, I didn't play with multiple scenes yet, so I'm not sure if it's relevant, in chapter 20 of the "Unity AR & VR, by Tutorial" book, they have two scenes, and they add to the ARSession and ARSessionOrigin gameobjects a DontDestroyOnLoad script so those objects are not destroyed when switching scene.

using UnityEngine;
public class DontDestroyOnLoad : MonoBehabiour {
void Awake()
{
DontDestroyOnLoad(gameObject);
}
}

 

Thanks for your hint with the "DontDestroyOnLoad" script. I just tried your solution, but sadly that didn't fix the problem. I then also placed the script on the AR-camera (where the background and manager scripts are placed on), but that also didn't fix it and I'm getting still the black screen after loading a AR-scene more than once

 

Ok, the black screen after scene-change is more easier to fix, than I thought! I created a small example project to commit a bugreport and while creating that project I discovered that I was just about to install the preview package of ARFoundation, again. As a software-developer one should be aware that preview versions might not be that 100% tested and debugged... so I went with the latest version without "preview" and the problem was solved. So just install the packages that are NOT in preview and the black screen is gone. Only fools like me install preview packages and wonder, why they aren't perfectly working So sorry for all confusions from my side to this topic.

The project now works with the followig packages:

• ARFoundation 2.1.3
  
• ARCore 2.1.1
  
• ARKit 2.1.1

I hope this might help somebody else

 

Welp, I did set those packages and the problem persist... still black camera, I see is a common issue on forums

 

Hmm, for my project this helps to fix the black screen problem after scene-change and didn't introduce it at reset. Also my sample-project does the Reset() and scene-change without the black screen multiple times.
You are right, many people seem to report this issue, but the progression of ARFoundation is quite quick and maybe also the problems of these people are already fixed.
Do you do some extra tasks in your reset-method that might cause problems? Are there any errors in the debug-output in the logcat?

 

Hello there!

I have a problem, when resetting the ARSession. I get a "rainbow disorder" which maybe has something to do with the camera texture, because you cant see it, if there is some GUI above.

Do you guys may know how to avoid this? I attached one image, so you can get a better idea about the problem.

It always appears when calling arSession.Reset(), or sometimes when reopen the Application and you´re in the active Session Screen.

Every suggestion would be Great - Thank you very much!

 

Are there any fixes yet? I have the same bug. It's not a big problem as everything works fine again after a second or so, but I have a loading screen in my app as well, so I might as well place that one there instead if possible.

 

Reset() shouldn't really be called in playmode or at runtime, it's not actually designed to do what the name implies in this context. It's for editor time only and is a base MonoBehviour method, not a method of the AR Session.

https://docs.unity3d.com/ScriptReference/MonoBehaviour.Reset.html

 

You can still hide it in a derived class and do whatever you want to do. note that they marked it as public, so you can call it from your script...

 

Which is almost never a good idea.

Reset() is documented to provide editor only functionality at the MonoBehaviour level then that functionality is hidden and reimplemented to provide entirely different runtime functionality at the ARSession level, that's straight up poor API design and I hope unity change it in the future.

Just because you can isn't a good enough reason to justify the confusion this raises.

 

How to solve this problem after reset arsession

 

How can we reset a MARS session to freshly generate/scan a new ground plane without the need of shutting down the app and restarting it?

 

As others pointed out before, one should call the arSession.Reset() to reset the AR session.

But. Some AR subsystems don't reset properly after calling arSession.Reset(). Here are some example of such subsystems:

• Feature points detected by ARPointCloudManager will not reset.
  
• ARKit World Map will not clear the applied world map.
• ARMeshManager will not reset detected meshes.
• ARCameraManager.currentConfiguration will not be reset to the initial value.
• ...probably, some other places I don't know of.

Solution:
To reset AR session completely, I use this method (official AR Foundation Samples repo uses it too):

Code (CSharp):

1.  
2. var xrManagerSettings = UnityEngine.XR.Management.XRGeneralSettings.Instance.Manager;
3. xrManagerSettings.DeinitializeLoader();
4. UnityEngine.SceneManagement.SceneManager.LoadScene(UnityEngine.SceneManagement.SceneManager.GetActiveScene().buildIndex); // reload current scene
5. xrManagerSettings.InitializeLoaderSync();
6.  

 

Thank you, your code helped me! I do not get a black screen, so sorry I can't help you there.

 

You are an absolute life saver!

Could you point me in the direction where to find this code in the official ARfoundation samples repo? I only found the part where they use

Code (CSharp):

1. LoaderUtility.Initialise()

and

Code (CSharp):

1. LoaderUtility.Deinitialise()

but I found that it doesn't always work, especially when going from AR scene to AR scene. It seems to work when going from NON AR Scene to AR Scene and back, which is what they do in the repo.

 

LoaderUtility.Initialise/Deinitialise() is just a handy wrapper for XRGeneralSettings.Instance.Manager.DeinitializeLoader/InitializeLoaderSync(). The only reason why I use the latter is that it works both in AR Foundation 3 and 4.

 

Thank you! This makes sense, I thought it could be the case.

However, I noticed that the ARFoundation samples repo uses this sequnce to load an AR scene from a non AR scene:

Code (CSharp):

1. LoaderUtility.Initialize();
2. SceneManager.LoadScene(sceneName, LoadSceneMode.Single);

while when going from an AR scene to a non AR scene (the main menu) they use this sequence:

Code (CSharp):

1.             SceneManager.LoadScene("Menu", LoadSceneMode.Single);
2. LoaderUtility.Deinitialize();

which kind of makes sense.

However, do you think to go from an AR scene to anothe AR scene I should do the following?:

Code (CSharp):

1. LoaderUtility.Initialize();
2. SceneManager.LoadScene(sceneName, LoadSceneMode.Single);
3. LoaderUtility.Deinitialize();

Also do you know why the Deinitialize() function is called after the scene load call?

When I do this however, I receive this error in the Logcat (Android). See atached image.

Many Thanks and sorry for all the questions!

 

Can we also disable the AR session?

 

We try to clear AR session without changing scene with this code :

Code (CSharp):

1. public void ResetSession() {
2.    LoaderUtility.Deinitialize ();
3.    LoaderUtility.Initialize ();
4. }

But camera video does not restart.
We use Unity 2020.3.5f1 with ARFoundation 4.1.7.

Why doesn't it work ?

 

Hi everyone!
I am currently working on a little demo app that includes 2 scenes that work with the image tracking manager of AR foundation. If I switch between those scenes in one session with an intermediate switch to a scene-picking menu, they don't behave correctly - for instance, the 2nd scene loads the prefab instantly when the reference image for scene 1 is still open.
So I figured calling

LoaderUtility.Deinitialize()

on the "return" button and the initialize-equivalent in the main menu would do the job, just like it does in the foundation samples and as described here.

However, my application freezes whenever I switch back to the main menu, when the

LoaderUtility.Deinitialize()

-method is called and I get the following error log in my Android LogCat:

[XRInputSubsystem] A device disconnection with the id 0 has been reported but no device with that id was connected.

I am working with Unity version 2020.3.12f1 and AR Foundation version 4.1.7
For my UI I work with the preview.14 version of UI builder and UI toolkit. Using the unity build-in ui-system for the back button instead didn't stop the freezing problem.

Any idea anyone what I can do about this or someone with the same issue when calling that method?
Cheers!

 

Hi all, it seems that after initializing/deinitializing the AR foundation subsystems multiple times in a row, there's a memory leak that causes my application to crash. Has anyone else experienced memory/performance issues when using LoaderUtility.Initlialize/Deinitialize and/or xrManagerSettings.Initialize/DeinitializeLoader()?

 

Thank you so much!!!!!
Its really helpful solution!!!

 

I have found this, but I have found even worse problems when trying to use two different modes of AR in the same application. I switch between face tracking and image recognition, so I start two different AR sessions. I am yet to get this to work on Android. I get completely random results varying from nothing at all / black screen to unresponsive sessions and crashes as well. It seems like it leaves old ARSessions kicking around in the backbround no matter what you try to do to dispose of them. Reset() is completely useless (but I read earlier this is editor only so no surprise this has sent me on a wild goose chase). I have also tried everything from instantiating sessions via prefab, as well as loading additive scenes and unloading them and keeping the ARSession and just using enable / disable and activating all the other components I need as per mode of operation. I have also tried various versions of ARKit, 4.1.7 as well as 4.2.0 and different versions of Unity, currently on latest Nothing works. If anyone can demonstrate how to switch between face recognition (front camera) and image recognition (rear camera), I will be amazed and grateful.

 

Please check out the AR Foundation samples repository, specifically the WorldCameraWithUserFacingFaceTracking scene.
https://github.com/Unity-Technologies/arfoundation-samples#worldcamerawithuserfacingfacetracking

This is the script that toggles the camera direction.
https://github.com/Unity-Technologi...s/FaceTracking/ToggleCameraFacingDirection.cs