Daniel B. Lysak’s research while affiliated with Pennsylvania State University and other places

. Converting paper-based engineering drawings into CAD model files is a tedious process. Therefore, 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, and outputs 3D models that can be displayed as wireframes. The system performs the detection of dimension sets, the extraction of object lines, and the assembly of 3D objects from the extracted object lines. A knowledge-based method is used to remove dimension sets and text from ANSI engineering drawings, a graphics recognition procedure is used to extract complete object lines, and an evidential rule-based method is utilized to identify view relationships. While these methods are the subject of several of our previous papers, this paper focuses on the 3D interpretation of the object. This is accomplished using a technique based on evidential reasoning and a wide range of rules and heuristics. The system is limited to the interpretation of objects composed of planar, spherical, and cylindrical surfaces. Experimental results are presented.

A method is presented for segmenting engineering drawings into views and identifying the corresponding view points. A set of 2.5D view-based coordinate systems is introduced as an intermediate between the 2D drawing-based system and the 3D object-based coordinates, and a formal technique is developed for constructing transformation matrices between coordinates. The method accommodates auxiliary views in addition to the standard orthogonal set, and the number of views and their positions need not be known a priori. Drawings with moderate errors in line placement and view alignment can also be handled. A rule based approach, using evidential reasoning, is applied for labeling the views.

A method for interpreting engineering drawings with multiple orthogonal views is presented. The number of views required is not fixed and can range from a minimum of two to a maximum of six using a standard drawing layout. The method call handle input views with small errors or inaccuracies and still produce a valid interpretation. The solution is based on a bottom-up approach in which candidate vertices and edges are used to generate a set of possible faces which are in turn assembled into enclosures representing the final object. All possible interpretations consistent with the input views are found, and inconsistent input views are recognized by the fact that no possible consistent interpretation can be obtained