A user device receives an image stream from the user side of the user device and an image stream from a target side of the user device. The user device acquires a coordinate system for the user, acquires its own coordinate system, and relates the two coordinate systems to a global coordinate system. The user device then determines whether the user has moved and/or whether the user device has moved. Movement of the user and/or the user device is used as input modalities to control the user’s interactions in the augmented reality environment.