: ActiveCube is a bi-directional user interface that supports a person's creative work through constructing and interacting with 3-D virtual objects by using actual physical cubes. With this flexible interface, the user can easily construct various 3-D structures in a virtual environment by simply combining the cubes. All of the faces of the cubes are the same and can be connected to any face of any other cube. A computer recognizes the constructed 3-D structure in real-time, so consistency is always maintained between the real environment and its corresponding representation in a virtual environment. Each cube is equipped with a processor for autonomous simulation and communication functions between cubes. A cube also utilizes a sensor for detecting the operational intention of the user and/or a display/actuator used as an output channel. Users can interact with ActiveCube in various ways by using the sensors, and the response to the interaction is also shown by displays/actuator...