1. An interface for producing an input from an absolute pose of an item associated with a user in a three-dimensional environment, said interface comprising: a) at least one stationary object having at least one feature detectable via an electromagnetic radiation, said at least one feature presenting a sufficient number of non-collinear optical inputs for establishing a stable frame in said three-dimensional environment; b) a unit on-board said item for receiving said non-collinear optical inputs; c) processing electronics for recovering said absolute pose from said non-collinear optical inputs in terms of absolute pose parameters in said stable frame and for generating a signal related to at least one of said absolute pose parameters; d) an application employing said signal in said input; whereby said absolute pose comprises at least three translational degrees of freedom and at least three rotational degrees of freedom, and said at least one absolute pose parameter is related to at least one among said at least three translational degrees of freedom and said at least three rotational degrees of freedom by a mapping.