Virtual machining techniques for modifying computer models of parts

Abstract

Methods and apparatus for representing a three-dimensional object by means of a High Density Point Data Model (HDPDM) consisting of a large number of individual data values, each of which specifies the coordinates of a point on the surface of a three dimensional object. An initial HDPDM is produced by scanning a physical object, tessellating the elements of a CAD representation of the object surface, or evaluating mathematical expressions which describe the surface. Further data values define a virtual tool surface which is spaced from the modeled object surface. The projection of the virtual tool surface on the object surface along projection lies parallel to a defined axis of projection identifies selected points on the surface which are modified by effectively moving them to the tool surface. The tool surface may be translated with respect to the object surface along a predetermined trajectory, with the tool surface being iteratively used to operate on an area of projection on the model surface to provide a virtual machining process which performs free-form alterations on the data model. The finished data model may then be used to create a physical part or generate an output CAD or mathematical model which defines a free-form part.