Contouring medial surface of thin plate structure using local marching cubes

Abstract

This paper describes an algorithm for contouring a medial surface from CT (computed tomography) data of a thin plate structure. Thin plate structures are common in mechanical structures such as car body shells. When designing the thin plate structures in CAD (computer aided design) and CAE (computer aided engineering) systems, their shapes are usually represented as surface models associated with their thickness values. In this research we are aiming at extracting medial surface models of a thin plate structure from its CT data so as to be used in CAD and CAE systems. However, in such CT data, each voxel in region around the medial surface can not be classified inside or outside, so we can not easily apply iso-surfacing method to contour the medial surface. From the above motives, we first extract medial cells (cubes comprising eight neighboring voxels) from the CT data using a skeletonization method so as to apply cubes algorithm to extract the medial surface. It is not, however, guaranteed that the cubes algorithm can contour those medial cells (in short, not marching cubeable). We developed cell operations which correct topological connectivity so as to guarantee such cubeability. We then apply our method to assign virtual signs to the voxels to apply the cubes algorithm. And last, we map thicknesses of thin plate structure to the triangle meshes as textures. A prototype system is developed to show some experimental results.