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Rossignac, Jarek

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Now showing 1 - 4 of 4
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    Sharpen&Bend: Recovering Curved Edges in Triangle Meshes Produced by Feature-Insensitive Sampling
    (Georgia Institute of Technology, 2003) Attene, Marco ; Falcidieno, B. (Bianca) ; Spagnuolo, Michela ; Rossignac, Jarek
    Various 3D acquisition, analysis, visualization and compression approaches sample surfaces of 3D shapes in a uniform fashion, without any attempt to align the samples with the sharp edges and corners of the original shape. Consequently, the interpolating triangle meshes chamfer these sharp features and thus exhibit a relatively large error in their vicinity. We introduce here two new filters that restore a large fraction of the straight or curved sharp edges missed by feature-insensitive sampling processes: (1.) EdgeSharpener restores automatically the sharp edges by identifying and splitting the chamfer edges and by forcing the new vertices to lie on intersections of planes extending the smooth surfaces incident upon these chamfers and (2.) Bender subdivides the resulting triangle mesh using a combination of the Butterfly subdivision scheme, for the smooth portion of the mesh, with a four-point subdivision scheme, for the sharp edges, in order to preserve the sharpness of the recovered sharp edges while bending their polyline approximations into smooth curves. This combined post-processing (named Sharpen&Bend) significantly reduces the error produced by feature-insensitive sampling processes. For example, we have observed that the L2 error introduced by the SwingWrapper remeshing-based compressor can often be reduced down to a fifth by executing EdgeSharpener alone after decompression, with no additional information. For meshes produced by retiling shapes with curved edges, this error may be further reduced by two thirds if we follow the EdgeSharpening phase by Bender. Thus the combined Sharpen&Bend process takes a triangle mesh produced by a feature-insensitive sampling of a curved shape with sharp curved features and automatically refines the mesh to produce a more accurate approximation of the initial shape.
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    Edge-Sharpener: Recovering Sharp Features in Triangulations of Non-adaptively Re-meshed Surfaces
    (Georgia Institute of Technology, 2003) Attene, Marco ; Falcidieno, B. (Bianca) ; Rossignac, Jarek ; Spagnuolo, Michela
    3D scanners, iso-surface extraction procedures, and several recent geometric compression schemes sample surfaces of 3D shapes in a regular fashion, without any attempt to align the samples with the sharp edges and corners of the original shape. Consequently, the interpolating triangle meshes chamfer these sharp features and thus exhibit significant errors. The new Edge-Sharpener filter introduced here identifies the chamfer edges and subdivides them and their incident triangles by inserting new vertices and by forcing these vertices to lie on intersections of planes that locally approximate the smooth surfaces that meet at these sharp features. This post-processing significantly reduces the error produced by the initial sampling process. For example, we have observed that the L2 error introduced by the SwingWrapper remeshing-based compressor can be reduced down to a fifth by executing Edge-Sharpener after decompression, with no additional information
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    Blowing Bubbles for the Multi-Scale Analysis and Decomposition of Triangle-Meshes
    (Georgia Institute of Technology, 2003) Mortara, Michela ; Patane, Giuseppe ; Spagnuolo, Michela ; Falcidieno, B. (Bianca) ; Rossignac, Jarek
    Tools for the automatic decomposition of a surface into shape features will facilitate the editing, matching, texturing, morphing, compression, and simplification of 3D shapes. Different features, such as flats, limbs, tips, pits, and various blending shapes that transition between them may be characterized in terms of local curvature and other differential properties of the surface or in terms of a global skeletal organization of the volume it encloses. Unfortunately, both solutions are extremely sensitive to small perturbations in the surface smoothness and to quantization effects when they operate on triangulated surfaces. Thus, we propose a multi-resolution approach, which not only estimates the curvature of a vertex over neighborhoods of variable size, but also takes into account the topology of the surface in that neighborhood. Our approach is based on blowing a spherical bubble at each vertex and studying how the intersection of that bubble with the surface evolves. We describe an efficient approach for computing these characteristics for a sampled set of bubble radii and for using them to identify features, based on easily formulated filters, that may capture the needs of a particular application.
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    SwingWrapper: Retiling Triangle Meshes for Better Compression
    (Georgia Institute of Technology, 2002) Attene, Marco ; Falcidieno, B. (Bianca) ; Spagnuolo, Michela ; Rossignac, Jarek
    We focus on the lossy compression of manifold triangle meshes. Our SwingWrapper approach partitions the surface of an original mesh M into simply connected regions, called triangloids. From these, we generate a new mesh M'. Each triangle of M' is an approximation of a triangloid of M. By construction, the connectivity of M' is fairly regular and can be compressed to less than a bit per triangle using EdgeBreaker or one of the other recently developed schemes. The locations of the vertices of M' are compactly encoded with our new prediction technique, which uses a single correction parameter per vertex. Differently from typical compression algorithms, SwingWrapper attempts to reach a user-defined output file size rather than, for example, not to exceed a given error bound. For a variety of popular models, a rate of 0.4 bits/triangle yields an L2 distortion of about 0.01% of the bounding box diagonal. The proposed solution may also be used to encode crude meshes for adaptive transmission or for controlling subdivision surfaces