So I've been messing around with Project Tango, and noticed that if I turn on a motion tracking app, and leave the device on a table(blocking all cameras), the motion tracking goes off in crazy directions and makes incredibly wrong predictions on where I'm going (I'm not even moving, but the device thinks I'm going 10 meters to the right). I'm wondering if their is some exception that can be thrown or some warning or api call I can call to stop this from happening.
if you block all the camera, there is not features camera can capture. so motion tracking may be in two stages: 1. No moving, 2. drifting to Hawaii.
either ways may happen. If you did block the fisheye camera, yes, this is expected.
For API, There is a way to handle it. Please check life cycle for motiontracking concept
For example for C/C++ : https://developers.google.com/project-tango/apis/c/c-motion-tracking
if API detected pose_data as TANGO_POSE_INVALID, the motion tracking system can be reinitialized in two ways. If config_enable_auto_recovery was set to true, the system will immediately enter the TANGO_POSE_INITIALIZING state. It will use the last valid pose as the starting point after recovery. If config_enable_auto_recovery was set to false, the system will essentially pause and always return poses as TANGO_POSE_INVALID until TangoService_resetMotionTracking() is called. Unlike auto recovery, this will also reset the starting point after recovery back to the origin.
Also you can add Handling Adverse Situations with UX-Framework to your app. check the link: https://developers.google.com/project-tango/ux/ux-framework-exceptions
The last solution is by write the function handle driftting by measuring velocity of pose_data and call TangoService_resetMotionTracking() and so on.