EG2013

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https://diglib.eg.org/handle/10.2312/298

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Browsing EG2013 by Subject "and object representations"

Now showing 1 - 6 of 6
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    Bilateral Hermite Radial Basis Functions for Contour-based Volume Segmentation
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Ijiri, Takashi; Yoshizawa, Shin; Sato, Yu; Ito, Masaaki; Yokota, Hideo; I. Navazo, P. Poulin
    In this paper, we propose a novel contour-based volume image segmentation technique. Our technique is based on an implicit surface reconstruction strategy, whereby a signed scalar field is generated from user-specified contours. The key idea is to compute the scalar field in a joint spatial-range domain (i.e., bilateral domain) and resample its values on an image manifold. We introduce a new formulation of Hermite radial basis function (HRBF) interpolation to obtain the scalar field in the bilateral domain. In contrast to previous implicit methods, bilateral HRBF (BHRBF) generates a segmentation boundary that passes through all contours, fits high-contrast image edges if they exist, and has a smooth shape in blurred areas of images. We also propose an acceleration scheme for computing B-HRBF to support a real-time and intuitive segmentation interface. In our experiments, we achieved high-quality segmentation results for regions of interest with high-contrast edges and blurred boundaries.
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    Coupled Quasi-harmonic Bases
    (The Eurographics Association and Blackwell Publishing Ltd., 2013) Kovnatsky, Artiom; Bronstein, Michael M.; Bronstein, Alexander M.; Glashoff, Klaus; Kimmel, Ron; I. Navazo, P. Poulin
    The use of Laplacian eigenbases has been shown to be fruitful in many computer graphics applications. Today, state-of-the-art approaches to shape analysis, synthesis, and correspondence rely on these natural harmonic bases that allow using classical tools from harmonic analysis on manifolds. However, many applications involving multiple shapes are obstacled by the fact that Laplacian eigenbases computed independently on different shapes are often incompatible with each other. In this paper, we propose the construction of common approximate eigenbases for multiple shapes using approximate joint diagonalization algorithms, taking as input a set of corresponding functions (e.g. indicator functions of stable regions) on the two shapes. We illustrate the benefits of the proposed approach on tasks from shape editing, pose transfer, correspondence, and similarity.
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    Direct Contouring of Implicit Closest Point Surfaces
    (The Eurographics Association, 2013) Auer, Stefan; Westermann, Rüdiger; M.- A. Otaduy and O. Sorkine
    Constructing a (signed) distance field and contouring its zero level set are two important steps in many surface reconstruction methods. While most high-quality distance transforms compute the distance to the surface as well as the closest point on it, the contouring step typically uses only the distance and omits the closest point information. Our novel closest point contouring algorithm (CPC) uses the full closest point field, and, thus, allows improving existing methods for high-quality triangle mesh reconstruction based on implicit function models: Since we select the vertex positions directly from the set of closest points, all triangle vertices are guaranteed to lie exactly on the zero-contour and no approximations are necessary. By employing recent findings in the context of so-called embedding techniques, we derive a formulation of the mean curvature vector on the closest point representation and use this formulation to properly select the vertices to be triangulated. In combination with a new table-based triangulation scheme this allows us to detect and preserve sharp features, and to avoid small degenerated triangles in smooth areas. CPC can handle open and non-orientable surfaces, and its data-parallel nature makes it well suited for GPUs.
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    Modeling Terrains and Subsurface Geology
    (The Eurographics Association, 2013) Natali, Mattia; Lidal, Endre M.; Parulek, Julius; Viola, Ivan; Patel, Daniel; M. Sbert and L. Szirmay-Kalos
    The process of creating terrain and landscape models is important in a variety of computer graphics and visualization applications, from films and computer games, via flight simulators and landscape planning, to scientific visualization and subsurface modelling. Interestingly, the modelling techniques used in this large range of application areas have started to meet in the last years. In this state-of-the-art report, we present two taxonomies of different modelling methods. Firstly we present a data oriented taxonomy, where we divide modelling into three different scenarios: the data-free, the sparse-data and the dense-data scenario. Then we present a workflow oriented taxonomy, where we divide modelling into the separate stages necessary for creating a geological model. We start the report by showing that the new trends in geological modelling are approaching the modelling methods that have been developed in computer graphics. We then give an introduction to the process of geological modelling followed by our two taxonomies with descriptions and comparisons of selected methods. Finally we discuss the challenges and trends in geological modelling.
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    Time-variant Volumetric Colors for Metamorphosis
    (The Eurographics Association, 2013) Fryazinov, Oleg; Sanchez, Mathieu; Adzhiev, Valery; Pasko, Alexander; Miguel Chover and A. Augusto de Sousa
    We propose to treat any changes in colors and textures in shape metamorphosis between two objects as time- dependent transformations of the volumetric distribution of materials. The main idea is to represent geometry of both objects with scalar fields with distance properties, to leave a time gap in where the geometric metamorphosis happens, and to use the scalar fields to apply shape-driven interpolation to volumetric material attributes within this time gap. The proposed solution is analytical, does not require heavy numerical computations essential to fluid simulations, and can be implemented in real-time applications.
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    Transfinite Surface Patches Using Curved Ribbons
    (The Eurographics Association, 2013) Várady, Tamás; Salvi, Péter; Rockwood, Alyn; M.- A. Otaduy and O. Sorkine
    An important problem in Computer Aided Design is to create digital representations for complex free-form objects that produce nice, predictable shapes and facilitate real-time editing in 3D. The clue to curve network-based design is the construction of smoothly connected multi-sided patches. A new type of transfinite surface, called Composite Ribbon (CR) patch is introduced, that is a combination of curved ribbons and ensures G1 continuity over non-regular, convex polygonal domains. After discussing the construction and the preferred parameterization scheme, a few simple examples conclude the paper.