Patent ID: 6169550
Filing Date: 2001-01-02
Classification: G06T

Abstract:
A method for enabling drawing by a computer having a processor, a memory, and a graphic output device, of overlapped two-dimensional shapes and two-dimensional projections of three-dimensional shapes onto a projection plane for viewing from a scene-viewing position in a system of world coordinates (X, Y, Z) wherein the projection plane is disposed orthogonally at a Z-position on the world Z-coordinate, the method comprising the steps of: (a) providing class libraries for storage in the computer memory from which(1) a two-dimensional geometry object may be instantiated to represent a two-dimensional shape and having an order attribute representing an overlapping position for depicting the two-dimensional shape on the projection plane positioned orthogonally to the world Z-coordinate, and (2) a three-dimensional geometry object may be instantiated to represent a three-dimensional shape and having a Z-value representing a position of the three-dimensional shape on the world Z-coordinate; and (b) providing a run-time environment to (1) support the instantiation of the two-dimensional and three-dimensional geometry objects and (2) perform the steps of: (A) sorting one or more of the two-dimensional geometry objects by their respective order attributes into a sorting table in the memory, (B) inserting one of the three-dimensional geometry objects into the sorting table ahead of the two-dimensional objects if the respective Z-value is such that the projection plane position is between the three-dimensional object and the viewing position, (C) inserting one of the three-dimensional geometry objects into the sorting table behind the two-dimensional objects if the respective Z-value is such that the three-dimensional object is between the projection plane position and the viewing position, and (D) rendering the two-dimensional shapes and the two-dimensional projection of the three-dimensional shape in the composite order of the sorting table to depict an overlapped appearance thereof.