Automated sequence arrangement of 3D point data for surface fitting in reverse engineering

This paper mainly discusses the methodology through which one can sequence the 3D point data derived from either contact or noncontact measuring device. As an input into computer-aided design (CAD), the ordered data serves as input to fit smooth surfaces. Such an arrangement of 3D point data tempts to integrate a computer-controlled coordinate measuring system with a CAD system, and thereby establish a reverse engineering system for 3D sculptured surface design. For sequencing the measured point data, this paper adopts resorts to cross-checking the data with distances and angles, so as to categorize and index the points. Once the ordered point data are ensured, the cubic non-uniform B-spline (NUB) mathematical model is used for fitting the points into smooth surfaces. In addition to control points, the parameters of NUB curves or surfaces manage to designate knot points which are able to turn unequidistant measured points into smooth curves or surfaces, while at the same time retaining the function of shape local-control. This allows the designer to adjust local areas of curves or surfaces and thereby create a geometric shape fulfilling all designing functions. Aside from a discussion on fundamental methodology of point-sequencing, this research also focuses on the development of reverse-engineering system software. The user can input 3D point data of different formats, and the developed system will find control points to establish the NUB surface model. This system is most characterized by its elimination of any complicated manual work involved in pre-processing 3D point data. (C) 1998 Elsevier Science B.V.