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Item Surface Reconstruction from Unstructured 3D Data(Blackwell Science Ltd and the Eurographics Association, 1996) Algorri, Maria-Elena; Schmitt, FrancisBuilding 3 0 models from unstructured data is a problem that arises increasingly as new 30 scanning technology is able to produce large and complex databases of full 3 0 information. Huge efforts put into segmenting entire sets of 20 images demand robust tools that are then able to reconstruct any arbitrary 30 surface segmented from the images. In this paper we propose an algorithmic methodology that automatically produces a surface from a set of points in ?3 about which we have no topological knowledge. Our method uses a spatial decomposition and a surface tracking algorithm to produce a rough approximation S of the unknown manifold S. The produced surface S serves as a robust initialisation for a physically based modeling technique that yields the fine details of S and so improves the quality of the reconstruction.Item Mesh Simplification(Blackwell Science Ltd and the Eurographics Association, 1996) Algorri, Maria-Elena; Schmitt, FrancisMesh simplification is an important stage after surface reconstruction since the models produced can contain a large number of polygons making them difficult to manipulate. In this paper we present a mesh simplification algorithm to reduce the number of vertices in a dense mesh of triangles. The algorithm is based on edge operations that are performed in the inside of independent clusters distributed over the entire mesh. The clusters are well-characterized regions that can successfully accept simplification operations. The simplification operations produce only local transformations on the mesh. This region-based, distributed approach permits to easily track and control the changes in the triangulation and avoids the appearance of particular cases that would require a special handling. The algorithm uses two user-specified parameters to guide the operations. These parameters allow various simplification strategies that are illustrated on several dense triangulations.