The wrapper algorithm: surface extraction and simplification

The wrapper algorithm (Gueziec and Hummel, 1994) is a rapid and efficient algorithm for extracting and representing surfaces defined as isosurfaces in digitized volumetric data. Unlike the marching cubes algorithm (Lorensen and Cline, 1987), and in agreement with the Payne-Toga algorithm (1990), the authors further decompose the cubical mesh associated with the sampled data into tetrahedral cells. They guarantee the resulting surface representation to be closed and oriented, defined by a valid triangulation of the surface of the body, which in turn is presented as a collection of tetrahedra, some of which are only partly filled. The surface is extracted as a collection of closed triangles, where each triangle is an oriented closed curve contained within a single tetrahedron. The authors´ method is an extension of the work of Doi and Koide (1991). In particular, the surface extraction process is followed by a simplification algorithm, which typically provides between 10 and 20 to 1 compression ratios in the surface representation while respecting a maximum distance bound to the original surface, and without noticeable degradation in surface fidelity. The authors display surfaces of the cranium from CT-scans and cortical surfaces from MR-scans at full resolution as well as synthetic surfaces, which have been extracted and simplified by their method