void ITrackableEventHandler.OnTrackableStateChanged(TrackableBehaviour.Status previousStatus, TrackableBehaviour.Status newStatus)
{
if (newStatus == TrackableBehaviour.Status.TRACKED)
{
GameMgr.Activate();
}
else if (newStatus == TrackableBehaviour.Status.NOT_FOUND)
{
GameMgr.Desactivate();
}
}