Triangular Mesh Progressive Compression Algorithm

With the development of 3D modeling and 3D scanning technology, the number and the complexity of the 3D geometry data sets are growing rapidly, which contradicts the limited network bandwidth badly. To solve this conflict, the PC (Progressive Compression) approach is proposed. It gets rid of the disadvantage that a model cannot display until the data is received completely, and realizes progressive transmission mode in which mesh model decompresses and displays while transmitting. As a typical example of PC, PM (Progressive Mesh) does a poor job in simplification efficiency and topology compression ratio. To solve the problem, a new PC scheme basing PM is presented in this paper.In this scheme, a mesh is simplified as PM by REP (Related Edge Priority) method, which using QEM (Quadric Error Metrics) as the simplification metric. For the higher topology compression ratio of PM, the related edges of the former edge collapsed are given priority for collapse, and a error threshold is used for restricting this priority. Moreover, before collapse, each edge has to pass Pre-collapse analysis, which is responsible for the simplification quality by selecting the right edge. In PM the topology data of each vertex split record is expressed as two triangles. According to REP, most of the triangles can be found around the ones of the former record, so each of these can be expressed as two simple numbers. Finally, Huffman coding scheme is adopted to encode the numbers. The vertex of each vertex split record is encoded by unit cube code scheme, and the center of the base mesh is taken as the origin of the unit cube.For the application of PC in the network, two modes of progressive transmission (P2P and B/S) are presented. A multi-resolution model generation system-AutoLOD-is developed with the scheme above. The structure is designed for the data storage of triangular mesh, in which the vertex, edge and face interconnect. In order to import STL flie efficiently, the triple tree search method is proposed. A compact data format for storage and transmission of progressive mesh (PM) is proposed.