Arcore-unity-sdk: How to pause/resume an ARCore Session ?

[reed-alpert]

I'd like to pause and then resume an existing ARCore Session (not destroy, just pause/resume).

My use case is GVR/ARCore combined (I know, not officially supported, but it works well). When the ARCore loses tracking the GVR and ARCore rotations get out of sync, and walking towards a game object may move you backwards or sideways.

The Release Notes say you can pause and resume a session, but the resume is done via ArCoreUnity_resumeSession and there is no corresponding ArCoreUnity_pauseSession in libarcore_unity_api.so, although there are both an ArSession_resume and ArSession_pause in the C API.

Is there a way with the Unity SDK to do this?

[fredsa]

Hi Reed!

This should be fixed in an upcoming release. Feel free to add the missing C# code to your project for the time being.

[reed-alpert]

I've added C# access for ARSession_pause and ARSession_resume. When pausing, the ARCore no longer reports changes in position, but when resumed seems to try to recover. That is, if I pause, rotate 90 degrees, and then resume ARCore will try to set itself as if it has been active the entire time. Is this by design?

If so, what does the pause/resume accomplish? Are CPU requirements reduced during that time.

[fredsa]

Pause/resume will allow you to temporarily suspend AR functionality, incl. AR tracking and processing. CPU/GPU processing related to ARCore will be paused. What will remain is some memory usage, include data for the paused AR session.

[Sarghm]

Hey @reed-alpert - would you be able to share how you added the ARSession_pause and ARSession_resume C# access with me? Trying to accomplish this on my side and struggling to find what should be added where.

Thanks!

[reed-alpert]

Hi @Sarghm, I've attached the 3 files I changed in ARCore cs code. For the initial session connect it still calls ArCoreUnity_resumeSession as before, but after that I pair the calls to ARSession_pause and ARSession_resume. My comment token is "ARSPIN" where I made changes. I also added a few changes for the IL2CPP build, but those are not required for using the pause and resume.

ARCoreMods.zip

[Sarghm]

@reed-alpert Thank you so much for this - have implemented this and works flawlessly, will definitely tide me over until the final release!

[arghyasur1991]

Is this fixed in ARCore v1.0? If yes, Please let me know what apis I need to use for the same

[andrelevi]

+1, I would also like to know if this is officially implemented in 1.0.

[chaosemer]

You can now toggle ARCore tracking by enabling and disabling the ARCoreSession component.

[rkachach]

@chaosemer please, can you explain how to enable/disable the session. Right now I'm developing an arcore based app where the user can do screen captures. I'm doing the capture by using the ProjectionManager.createScreenCaptureIntent() .. as result, this starts a new activity to capture the screen, when back (onResume()) I'm losing all the context of my current session which is annoying. I'm wondering if the there's some workaround to avoid losing the session data in this situation.

[pablisho]

Hi, to pause/resume the session enable/disable the ARCoreSession component. To destroy/create new session, destroy/create a new ARCoreSession component. I believe when you are switching to and from your other activity your session is being destroyed and you're creating a new one, is that your case?

[rkachach]

Thanks Pablo, I'm not using Unity. Finally I managed to solve the issue I was facing (I was doing some extra checks on Anchors ..). Anyway thanks for your help.

[nico74]

Hi,

It works with enable/disable ARcoreSession component...but it freeze the camera...no more motion Tracking...is it normal ?
I would like to pause Arcoresession (pause tracking) but continue to have motion tracking to move around the object...is it possible ?
Thanks

[nico74]

just some precision : i would likr to lock a model because when you move/rotate in your real room and come back to the model...the model is not placed exactly where i pose it...you know what I mean ?

So i would like to lock a model once i pose the model in Ar scene :) and can have the motion tracking to move around :)
Many Thanks for helping

[fredsa]

Hi @nico74,

Positional tracking requires the ARCore Session to be active. This is because motion tracking is performed by ARCore.
In other words, ARCore is not just trying to understand the scene, but is also responsible for positional tracking.

[Kitwradr]

Hi, to pause/resume the session enable/disable the ARCoreSession component. To destroy/create new session, destroy/create a new ARCoreSession component. I believe when you are switching to and from your other activity your session is being destroyed and you're creating a new one, is that your case?

Hi @pablisho ,
How do we achieve this? Can you post some sample code , I am changing between different canvases and only specific canvases require AR core to be running , What is the best way to reset/pause ARcore sessions?
I have this component attached in canvas

[kushal98]

Hi, to pause/resume the session enable/disable the ARCoreSession component. To destroy/create new session, destroy/create a new ARCoreSession component. I believe when you are switching to and from your other activity your session is being destroyed and you're creating a new one, is that your case?

Hi @pablisho,
Thats exactly happening in my case when i am returning from other activity a new session gets created what should i do to resume the previous session after i return from other activity? and Also if i want to access the camera in the other activity is it possible?