Summary form only given. Octree decomposition has been proven to be one of the most successful approaches for progressive geometry compression of 3D models. An octree is built up by recursively subdividing the bounding box of 3D models into a number of sub-cells. Each node of the octree has an 8-bit-binary code called occupancy code, indicating the non- emptiness of its children, given a pre-defined traversal order. Then the point positions can be represented by a sequence of occupancy codes. Typically, the non-empty child-cells are close to evenly distributed among the 8 candidate positions. It has been proposed to change the traversal order based on the probabilities of the child-cells being non-empty; then the statistical distribution of the occupancy codes becomes more concentrated, which is beneficial for compression. We observe an intrinsic property of 3D models that their tangent-planes tend to be continuous at high fidelity layers. Thus, we take the tangent-plane continuity as a criterion for the non-emptiness estimation. The continuity is measured by the surface area of the convex hull which is formed by current child-cell's centroid and centroids of the parent neighbors. Our algorithm results in more concentrated distribution of occupancy code than the existing reordering approach. Therefore, our codec outperforms the existing work significantly.
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