[Bug] Low FPS results in face tracking to stop working

[siliconstudio-yunying-hu]

Unity bug report case number
IN-65645

Describe the bug
In scenes with low FPS, face tracking won't work.

To Reproduce

1. Artifically lower the FPS of the Face Tracking -> Face Regions scene by adding Application.targetFrameRate = 10; to ARCoreFaceRegionManager.cs's Update() function
2. Build project, and run on device
3. Open Face Tracking -> Face Regions scene
4. The 3 gizmo's won't be applied to the face regions

Expected behavior
FPS shouldn't be a factor for face tracking to work

Actual behavior
Face tracking stops working for scenes with low FPS

Smartphone:

• Device: Google Pixel6 Pro
• OS: Android version 14
• Unity version: 2023.2.2f1
• ARFoundation version: 6.0.0-pre.5

[andyb-unity]

This doesn't appear to be a bug to me. ARFaceManager (and indeed, all manager components) will only ask ARCore for updates at the frequency of the framerate of the app. If the framerate drops below a certain level, I would expect that ARCore can no longer achieve face tracking.

I would advise you to increase your framerate.