Advancing Fan-Front: An Efficient Connectivity Compression Technique for Large 3D Triangle Meshes

In this paper we present a new algorithm for compressing large 3D triangle meshes through the successive conquest of triangle fans. In this algorithm, a triangle fan is the sequence of adjacent triangles incident on a start vertex of a boundary edge called as the “gate.” As each fan is conquered, the current mesh boundary is advanced by the fanfront and the gate(s) for conquering the rest of the mesh is(are) identified. The process is continued till the entire mesh is traversed. The mesh is then compactly encoded as a sequence of fan configuration codes. In the earlier reported techniques, the conquest is usually a triangle, a vertex or an edge at a time, and the number of symbols in the resulting encoding is of the order of the total number of triangles, vertices or edges respectively. On the other hand, the number of fans is typically one fourth of the total number of triangles and the number of fan configurations is bounded by the vertex valence variation. While the number of distinct fan configurations depends on the variation in the degree of fans, only a few of these fan configurations occur with high frequency, enabling very high connectivity information compression using range encoding. A simple implementation shows considerable improvements, on the average, in bit-rate per vertex, compared to earlier reported techniques.