Multi-isosurface Extraction Algorithm

Isosurface extraction is one of the important algorithms in the volume data visualization, which was widely applied in implicit surface modeling, virtual surgical planning, information visualization, 3D geological modeling and reverse engineering. After the state-of-the-art of the volume data visualization and several important algorithms are introduced briefly, we draw that the current volume data visualization algorithms can no longer meet the increasing requirements in the virtual surgery, 3D geological modeling and analysis, reverse engineering and other related fields.In this thesis, a new multi-isosurface extraction algorithm is proposed, which can extract multiple isosurfaces in one pass. The topological connection information among the isosurfaces can be maintained correctly, i.e., they share the common vertices, edges and surfaces in the junctions of the isosurfaces. The result isosurfaces can not only contain more details of the volume data, but also is convenient to be edited for the further processing.The proposed multi-isosurface extraction algorithm is based on the Skeleton Climbing method. First the iso-points are computed on the voxel edge, and then the iso-points are connected to obtain the iso-surface edges in the voxel face, and then the edges are connected correctly to form the spatial polygon, and finally the polygons are triangulated into the mesh in the voxel. The data types and the data structures used in the algorithm are also introduced. The kernel of the proposed algorithm, i.e., how to compute the intersections between the multi-isosurface and the voxel, are discussed in detail. Similar to the classical isosurface algorithms, the ambiguity and singularity are also carefully considered step by step.The algorithm has been implemented on a desktop PC with PIV 2.0G and 1.5G memory. The comparisons are made between the proposed algorithm and the classical isosurface algorithms. In addition, the advantage of the multi-isosurface extraction algorithm in the surface editing is also indicated and illustrated. Finally, several potential applications of the proposed algorithm are given.The main contributions can be summarized as:1. A new multi-isosurface extraction algorithm is proposed and accomplished, where the extracted isosurfaces has the correct topological connections, i.e.,they share common vertices, edges and surfaces in the junctions.2. The ambiguitv and singularity of the proposed algorithm are discussed carefully step and step.