Mesh Coding Research Articles

Semi-regular representation and progressive compression of 3-D dynamic mesh sequences

We propose an algorithm that represents three-dimensional dynamic objects with a semi-regular mesh sequence and compresses the sequence using the spatiotemporal wavelet transform. Given an irregular mesh sequence, we construct a semi-regular mesh structure for the first frame and then map it to subsequent frames based on the hierarchical motion estimation. The regular structure of the resulting mesh sequence facilitates the application of advanced coding schemes and other signal processing techniques. To encode the mesh sequence compactly, we develop an embedded coding scheme, which supports signal-to-noise ratio and temporal scalability modes. Simulation results demonstrate that the proposed algorithm provides significantly better compression performance than the static mesh coder, which encodes each frame independently.

Rate-distortion-optimized predictive compression of dynamic 3D mesh sequences

Compression of computer graphics data such as static and dynamic 3D meshes has received significant attention in recent years, since new applications require transmission over channels and storage on media with limited capacity. This includes pure graphics applications (virtual reality, games) as well as 3DTV and free viewpoint video. Efficient compression algorithms have been developed first for static 3D meshes, and later for dynamic 3D meshes and animations. Standard formats are available for instance in MPEG-4 3D mesh compression for static meshes, and Interpolator Compression for the animation part. For some important types of 3D objects, e.g. human head or body models, facial and body animation parameters have been introduced. Recent results for compression of general dynamic meshes have shown that the statistical dependencies within a mesh sequence can be exploited well by predictive coding approaches. Coders introduced so far use experimentally determined or heuristic thresholds for tuning the algorithms. In video coding, rate-distortion (RD) optimization is often used to avoid fixed thresholds and to select the optimum prediction mode. We applied these ideas and present here an RD-optimized dynamic 3D mesh coder. It includes different prediction modes as well as an RD cost computation that controls the mode selection across all possible spatial partitions of a mesh to find the clustering structure together with the associated prediction modes. The general coding structure is derived from statistical analysis of mesh sequences and exploits temporal as well as spatial mesh dependencies. To evaluate the coding efficiency of the developed coder, comparative coding results for mesh sequences at different resolutions were carried out.

Geometry-guided progressive lossless 3D mesh coding with octree (OT) decomposition

A new progressive lossless 3D triangular mesh encoder is proposed in this work, which can encode any 3D triangular mesh with an arbitrary topological structure. Given a mesh, the quantized 3D vertices are first partitioned into an octree (OT) structure, which is then traversed from the root and gradually to the leaves. During the traversal, each 3D cell in the tree front is subdivided into eight childcells. For each cell subdivision, both local geometry and connectivity changes are encoded, where the connectivity coding is guided by the geometry coding. Furthermore, prioritized cell subdivision is performed in the tree front to provide better rate-distortion (RD) performance. Experiments show that the proposed mesh coder outperforms the kd-tree algorithm in both geometry and connectivity coding efficiency. For the geometry coding part, the range of improvement is typically around 10%~20%, but may go up to 50%~60% for meshes with highly regular geometry data and/or tight clustering of vertices.

On the Optimality of Valence‐based Connectivity Coding

Abstract We show that the average entropy of the distribution of valences in valence sequences for the class of manifold 3D triangle meshes and the class of manifold 3D polygon meshes is strictly less than the entropy of these classes themselves. This implies that, apart from a valence sequence, another essential piece of information is needed for valence‐based connectivity coding of manifold 3D meshes. Since there is no upper bound on the size of this extra piece of information, the result implies that the question of optimality of valence‐based connectivity coding is still open.

An efficient 3D mesh compression technique based on triangle fan structure

In this paper, we propose an efficient compression algorithm for 3D triangular meshes, consisting of topology data and geometry data. First, the vertex degree warping technique is proposed to compress the topology data losslessly. The proposed algorithm exploits the geometrical information to efficiently encode the topology data, while most conventional algorithms process the topology data and the geometry data independently. Second, the dual parallelogram prediction technique is proposed as an effective geometry prediction scheme. By using forward and backward parallelograms, the proposed algorithm provides smaller prediction errors than the conventional parallelogram prediction scheme. Simulation results on various mesh models demonstrate that the proposed algorithm yields higher compression ratio than the conventional mesh compression algorithms proposed in Touma and Gotsman (Proceedings of the Graphics Interface ’98, June 1998, pp. 26–34) and MPEG-4 3D mesh coding (3DMC) standard ISO/IEC 14496-2 (Information Technology – Coding of Audio-Visual Objects – Part 2: Visual, July 2001. The 3DMC reference software is available from http://www.sait.samsung.co.kr/shhc).

Mesh coding: Application to texture and scalable 3D scene coding

Cet article examine le probleme de la compression de textures et de maillages 3D. La topologie des maillages triangulaires est compressee par une methode de conquete d’aretes exploitant les valences des sommets, tandis que les positions des sommets sont codees par une methode de prediction multiple associee a un codeur arithmetique. La scalabilite est alors obtenue sur les positions via une version adaptee aux nombres flottants du codage par plans de bits. La texture appliquee au maillage 3D est quant a elle approximee par une technique hybride combinant interpolation affine et transformee DCT sur les triangles d’un modele de maillage hierarchique emboite.