US Patent 7324121 Adaptive manipulators

A method of repositioning a manipulator in relation to a viewport is provided in a system for interacting with a three-dimensional object configured with a manipulator. The object and the manipulator are drawn in the viewport and the position of the manipulator is constrained to lie along the viewing axis between the viewport and the object. The manipulator is represented by a geometry corresponding to the function of the manipulator. The position of the manipulator is modified as needed so that it is not obscured by other objects in the scene. Furthermore, the position of the manipulator is modified as needed following a rotation or scaling operation so that it is oriented for ease of selection by a user.