We have an app that enables and disables trackers depending on needs/context. We have been experiencing an issue on iOS where occasionally, but often, after returning to the app from background that the smart terrain system is broken. A shortened version of our logs look:
[ARManager] App Unpaused INFO/AR(11251) 2020-05-22 14:12:00: Vuforia resumed. Start Vuforia Engine [VF_PlatformController] OnVuforiaPaused: False [ARManager] UpdateTrackers: imageTracker: False deviceTracker: True surfaceTracker: True faceTracker: False [VF_Tracker] TryEnableTracker on: ImageTracker : False [VF_Tracker] Successfully stopped tracker: Vuforia.ObjectTracker [VF_Tracker] TryEnableTracker on: DeviceTracker : True Starting Positional Device Tracker. [VF_Tracker] Successfully started tracker: Vuforia.PositionalDeviceTrackerImpl [VF_Tracker] TryEnableTracker on: SufaceTracker : True Starting Smart Terrain [VF_Tracker] Successfully started tracker: Vuforia.SmartTerrainImpl [VF_SurfaceTracker] Checking for plane hit ERROR/AR(11251) 2020-05-22 14:12:04: Failed to do hit test. DeviceTracker seems to not have been started. [VF_SurfaceTracker] CheckForPlaneHit FAIL at screenPosition: (0.5, 0.5, 0.5)
At that point, after getting the "Failed to do hit test. DeviceTracker seems to not have been started", I am unable to get the smart terrain tracker to work even after trying to restart it and the positional device tracker. Only restarting the app will resolve the issue.