Application of a perspective cursor as a 3D locator device

The functionality of a 3D cursor is described. It can be used as a 3D locator device in such applications as interactive path planning (robotics), motion specification in 3D computer animation design, and wireframe modelling. With respect to the last of these applications, it is important that the cursor can be used either in constructive mode, as a set of three mutually orthogonal rulers, or in trace mode to copy a 2D perspective view of an object while reconstruction its 3D shape. As a special feature, the cursor may be equipped with a mirror of locations in scenes that are (partially) symmetric, but also allows 3D symmetric objects to be entered from 2D (perspective) views, while making use of symmetry as a clue for reconstructing z-coordinates.