A complete system for recovery of 3D shapes from engineering drawings

Converting paper-based engineering drawings into CAD model files is a tedious process, and automating the conversion of such drawings represents tremendous time and labor savings. We present a complete system which interprets such 2D paper-based engineering drawings, constructs solid models, and outputs 3D CAD-like files. While most existing systems assume that the engineering drawings have already been preprocessed to remove the dimensioning lines, this system is truly complete: It performs the detection of dimension sets, the extraction of object lines, and the assembly of 3D objects from object fines. A knowledge-based method is used to extract dimension sets and text from ANSI engineering drawings, and a graphics recognition procedure is used to extract complete object lines. In addition, a general-purpose dashed line recognition algorithm is presented. The focus of this paper, however is on the 3D interpretation of the object lines, which is accomplished using a technique that can accommodate auxiliary views in addition to the standard orthogonal set, along with planar spherical, and cylindrical object surfaces. Drawings with misaligned views and missing lines can also be interpreted. Extensive experimental results are presented.