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Start date: 2010 × Subject: Categories and Subject Descriptors (according to ACM CCS): I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling × End date: 2019 ×

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Now showing 1 - 8 of 8
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    Modeling Liquidus Hypersurfaces through Simplicial Complexes
    (The Eurographics Association, 2010) Natali, Mattia; Attene, Marco; Ottonello, Giulio; Enrico Puppo and Andrea Brogni and Leila De Floriani
    This paper describes an operational pipeline that exploits computational geometry to derive useful knowledge about the crystallization behaviour of materials composed of varying amounts of pure components. Starting from existing knowledge related to the pure components, we compute the Gibbs free energy of all their possible compositions in a given range of temperatures, both in liquid and solid phases. Then, we exploit the convex hull method to derive the coexistence of solid and liquid phases, and model the resulting liquidus hypersurface as a simplicial complex. On such a complex, we propose novel tools to robustly compute descent lines describing the crystallization path induced by heat loss for any initial composition in the system.
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    An Improved Discrete Level of Detail Model Through an Incremental Representation
    (The Eurographics Association, 2010) Ribelles, Jose; López, Angeles; Belmonte, Oscar; John Collomosse and Ian Grimstead
    Real-time applications such as computer and video games, virtual reality and scientific simulation require rendering of complex models for realism. Graphics rendering engines include multiresolution modelling techniques to accelerate the visualization process. The Discrete Level of Detail framework (DLoD) is usually the most popular while the Continuous Level of Detail framework (CLoD) is still not as widely used by software developers. In this paper, we first discuss the benefits and drawbacks of both frameworks. Then, we present a model based on coding a discrete number of levels of detail (LoDs), with more LoDs coded than is usual in DLoD, and with an incremental representation, which is often used in CLoD. This model obtains a performance similar to DLoD by providing optimized LoDs for efficient visualization, while the popping effect is imperceptible. We present specific proposals for each of the three main stages involved in multiresolution processing: geometry simplification, construction of the incremental representation and retrieval of either uniform or view-dependent LoDs.
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    Heat Diffusion Approach for Feature-based Body Scans Analysis
    (The Eurographics Association, 2011) Lovato, Christian; Zancanaro, C.; Castellani, Umberto; Giachetti, Andrea; H. Laga and T. Schreck and A. Ferreira and A. Godil and I. Pratikakis and R. Veltkamp
    In this paper we propose the use of spectral shape analysis techniques for selection and classification of anthro- pometric points extracted from human-body scans. Few feature points are detected by exploiting the capability of heat diffusion process in capturing the extremities of surface protrusions which are often related to anthropometric landmarks. Then, a heat kernel signature is computed for each feature point which are associated to its seman- tic group by employing a learning-by-example procedure exploiting manual point labeling provided by an expert anthropometrist. Detected points are not clearly the same precise anatomical locations used in standard anthro- pometric procedures, but their matching can be useful for different applications like automatic model registration or simple body type evaluation. Experimental tests carried out on several subjects with different anthropometric characteristics show encouraging results demonstrating the potential usefulness of the approach as well as the necessity of further investigation on point description and matching.
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    QEM-Filtering: A New Technique for Feature-Sensitive Terrain Mesh Simplification
    (The Eurographics Association, 2010) Löffler, Falko; Schumann, Heidrun; Reinhard Koch and Andreas Kolb and Christof Rezk-Salama
    Terrain simplification generates multi-resolution models, from which - traditionally - irregular or semi-regular triangulations are extracted to render a terrain at a suitable level of detail. Recent terrain simplification techniques, in contrast, rely on GPU-friendly regular grids and generate multiple resolutions by applying the filtering and sub-sampling paradigm. However, due to the smoothing and uniform sampling, these techniques sparsely approximate the terrain surface. Consequently, in order to guarantee a certain error threshold, considerably more triangles need to be rendered. In this paper, we present a novel feature-sensitive simplification technique. Our approach follows the aforementioned paradigm. The key idea is to maintain the regularity while recomputing the vertex positions by taking a specific error metric into account, namely the quadric error metric (QEM). Compared to previous approaches, we apply the paradigm to the grid of vertex-associated quadrics. From these we extract vertices of the new resolution by relying on quadric error minimization. We, thus, maintain the regular grid structure while preserving terrain features. Compared to methods, which are solely based on vertex-filtering and sub-sampling, our approach reduces the approximation error. As a consequence, we require fewer triangles, which improves the rendering performance.
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    A Practical Guide to Polygon Mesh Repairing
    (The Eurographics Association, 2012) Campen, Marcel; Attene, Marco; Kobbelt, Leif; Renato Pajarola and Michela Spagnuolo
    Digital 3D models are key components in many industrial and scientific sectors. In numerous domains polygonmeshes have become a de facto standard for model representation. In practice meshes often have a number ofdefects and flaws that make them incompatible with quality requirements of specific applications. Hence, repairingsuch defects in order to achieve compatibility is a highly important task - in academic as well as industrial applications. In this tutorial we first systematically analyze typical application contexts together with their requirementsand issues, as well as the various types of defects that typically play a role. Subsequently, we considerexisting techniques to process, repair, and improve the structure, geometry, and topology of imperfect meshes,aiming at making them appropriate to case-by-case requirements. We present seminal works and key algorithms,discuss extensions and improvements, and analyze the respective advantages and disadvantages depending onthe application context. Furthermore, we outline directions where further research is particularly important orpromising.
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    Continuous Deformations of Implicit Surfaces
    (The Eurographics Association, 2010) Esturo, Janick Martinez; Rössl, Christian; Theisel, Holger; Reinhard Koch and Andreas Kolb and Christof Rezk-Salama
    We introduce an approach for the continuous deformation of implicit surfaces which considers properties of all isosurfaces of a volume data set simultaneously. This is achieved by integrating divergence-free vector fields which is carried out by an efficient backward Lagrangian integration scheme. Our deformation guarantees volume preservation inside each isosurface as well as the preservation of continuity and topology of every isosurface. For visualization and interaction, we offer a real-time mode that allows interactive working on the resolution of the underlying volumetric grid as well as a grid resolution independent mode offering exact extraction of arbitrary isosurfaces. We apply the approach to the deformation of measured volume data sets as well as to the design of complex implicit shapes with a simple pre-defined topology.
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    3D Modelling of Complex Biological Structures: The Oviduct
    (The Eurographics Association, 2010) Burkitt, Mark; Romano, Daniela M.; Walker, Dawn C.; Fazeli, Alireza; John Collomosse and Ian Grimstead
    A novel technique using a particle system constrained by Newtonian forces is presented for the algorithmic construction of small scale, complex 3D biological structures based on real world biological data. This allows models of structures too small to be accurately recreated using medical imaging technologies such as Magnetic Resonance Imaging (MRI) to be created. The resulting model provides a geometrically realistic 3D environment which can be used to study the biological interactions which occur within. The technique is used to create a model of an oviduct, but could also be applied to similar organs such as the colon. The model is validated using measurements and visual comparisons from biological data. Finally, the technique is implemented using single-core and multi-core CPU techniques and using GPU acceleration. The performance of each implementation is then compared.
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    Surfel Based Geometry Reconstruction
    (The Eurographics Association, 2010) Andersen, Vedrana; Aanæs, Henrik; Bærentzen, Jacob Andreas; John Collomosse and Ian Grimstead
    We propose a method for retrieving a piecewise smooth surface from noisy data. In data acquired by a scanning process sampled points are almost never on the discontinuities making reconstruction of surfaces with sharp features difficult. Our method is based on a Markov Random Field (MRF) formulation of a surface prior, with the surface represented as a collection of small planar patches, the surfels, associated with each data point. The main advantage of using surfels is that we avoid treating data points as vertices. MRF formulation of the surface prior allows us to separately model the likelihood (related to the mesh formation process) and the local surface properties. We chose to model the smoothness by considering two terms: the parallelism between neighboring surfels, and their overlap. We have demonstrated the feasibility of this approach on both synthetical and scanned data. In both cases sharp features were precisely located and planar regions smoothed.