Direct segmentation of smooth, multiple point regions

The purpose of reverse engineering is to convert a large point cloud into an accurate, fair and consistent CAD model. For a class of conventional engineering objects we have the ´a priori´ assumption that the object is bounded exclusively by simple, analytic surfaces. In this case it is possible to generate the model with a minimal amount of user interaction. The key issue is segmentation, i.e., to separate the point cloud into smaller regions, where each can be approximated by a single surface. While this is relatively simple, where the regions are bounded by sharp edges, problems arise when smoothly connected regions need to be separated. The direct segmentation method described in this paper is based on a special sequence of tests, by means of which a large point cloud can be robustly splitted into smaller subregions until no further subdivision is possible. Surfaces of linear extrusion and revolution are also detected. The structure of the smooth, multiple regions is the basis of constrained surface fitting in the final model building phase.