Solid model input through orthographic views

Abstract

This paper describes the results of basic studies on procedures for creating solid models of component geometry from two-dimensional orthographic projections. An interactive graphic program was developed to allow the input of three orthographic views of a component geometry by digitizing from a drawing. The views may contain straight lines and circular arcs, solid or dashed. No restrictions are placed on the order or direction of lines and arcs in any view. Using an extension of the Wesley-Markowski procedure, the program constructs a three-dimensional solid model of the object. When the projections are ambiguous, multiple solid models are produced. The solid model may contain planar, cylindrical, conical, spherical and toroidal surfaces. Topological information of the solid model is stored in a winged edge structure. Geometric information is stored as vertex coordinates and surface equations. The procedure for 2D-3D conversion provides a powerful new method for manual input of solid models, a common interface to all turnkey graphics systems, and, properly integrated with existing technology for scanning of drawings, a powerful new method for acquisition of CAD/CAM data bases from existing drawings. The procedure is described, examples of typical input and output are shown, and possible extensions are discussed.