these samples opt for, is to simply not draw
        // anything. That way the device will continue to show the last frame
        // drawn, possibly even with reprojection. Alternately you could
        // re-draw the scene again with the last known good pose (which is now
        // likely to be wrong), clear to black, or draw a head-locked message
        // for the user indicating that they should try to get back to an area
        // with better tracking. In all cases it's possible that the device
    