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A new algorithm is proposed to compress animated 3D mesh models. First, an input mesh model is partitioned into segments, and each segment is motion compensated from that of the previous time instance. Then, the motion residuals are effectively compressed by using a transform coding method. It is shown that the proposed algorithm yields a much higher compression ratio than the MPEG-4 codec.
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Introduction: 3D animation models are popularly used in various multi- media applications, such as Internet services, computer graphics, and synthetic imaging systems. The MPEG-4 SNHC 3DMC [1] group developed a graphic codec to compress the triangle connectivity and vertex positions of 3D static meshes. One can straightforwardly apply the codec to compress a sequence of 3D static models to achieve the coding task of animated meshes. However, with this approach, the tem- poral correlation between adjacent mesh frames cannot be exploited. Lengyel [2] and Ahn [3] proposed mesh sequence coding algorithms to exploit the temporal correlation. These algorithms cannot provide suffi- cient quality reconstruction at low bit rates and, as a consequence, it is difficult to distribute 3D animation contents in real-time over a network of relatively low bandwidth.
A more efficient compression algorithm to encode animated mesh models is proposed in this Letter. First, a graphic model is partitioned into several segments, and each segment is treated as a minimum unit for coding. With the aid of the segmentation process, we can borrow the well-developed concept in video coding techniques by considering a segment as the counterpart of a macroblock. More specifically, an input mesh sequence is classified into two types of meshes: intra-coded meshes (intra-meshes) and inter-coded meshes (inter-meshes). Then, intra-meshes are compressed without reference to other meshes, while the motion-compensated prediction is employed for the coding of inter- meshes to exploit the temporal correlation.
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