Progressive Coding and Illumination and View Dependent Transmission of 3D Meshes Using R-D Optimization

Abstract — For transmitting complex 3D models over bandwidth-limited networks, efficient mesh coding and transmission are indispensable. The state-of-the-art 3D mesh transmission system employs wavelet-based progressive mesh coder, which converts an irregular mesh into a semi-regular mesh and directly applies the zerotree-like image coders to compress the wavelet vectors, and view-dependent transmission, which saves the transmission bandwidth through only delivering the visible portions of a mesh model. We propose methods to improve both progressive mesh cod-ing and transmission based on thorough rate-distortion (R-D) analysis. In particular, by noticing that the dependency among the wavelet coefficients generated in remeshing is not being considered in the existing approaches, we propose to introduce a preprocessing step to scale up the wavelets so that the inherent dependency of wavelets can be truly understood by the zerotree-like image compression algorithms. The weights used in the scaling process are carefully designed through thoroughly analyzing the distortions of wavelets at different refinement levels. For the transmission part, we propose to incorporate the illumination effects into the existing view-depend progressive mesh transmission system to further improve the performance. We develop a novel distortion model that considers both illumi-nation distortion and geometry distortion. Based on our proposed distortion model, given the viewing and lighting parameters, we are able to optimally allocate bits among different segments in real time. Simulation results show significant improvements in both progressive compression and transmission. Index Terms — Progressive mesh coding, progressive mesh transmission, rate-distortion analysis, view dependent, illumina-tion dependent, semi-regular meshes. I