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Now showing 1 - 10 of 13
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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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    An Edge-based Approach to Adaptively Refining a Mesh for Cloth Deformation
    (The Eurographics Association, 2009) Simnett, Timothy J. R.; Laycock, Stephen D.; Day, Andy M.; Wen Tang and John Collomosse
    Simulating cloth in real-time is a challenging endeavour due to the number of triangles necessary to depict the potentially frequent changes in curvature, in combination with the physics calculations which model the deformations. To alleviate the costs, adaptive methods are often employed to refine the mesh in areas of high curvature, however, they do not often consider a decimation or coarsening of areas which were refined previously. In addition to this, the triangulation and consistency checks required to maintain a continuous mesh can be prohibitively time consuming when attempting to simulate larger pieces of cloth. In this paper we present an efficient edge-based approach to adaptively refine and coarsen a dynamic mesh, with the aim to exploit the varied nature of cloth by trading the level of detail in flat parts for increased detail in the curved regions of the cloth. An edge-based approach enables fast incremental refinement and coarsening, whereby only two triangles need updating on each split or join of an edge. The criteria for refinement includes curvature, edge length and edge collisions. Simple collision detection is performed allowing interactions between the cloth and the other objects in the environment.
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    A Benchmarking Framework for Static Collision Detection
    (The Eurographics Association, 2008) Diktas, Engin Deniz; Sahiner, Ali Vahit; Ik Soo Lim and Wen Tang
    Performanceof static collision detection queries depends on the type of the hierarchy chosen as well as the relative positioning of the colliding objects. In order to evaluate the performance of bounding volume hierarchies, relevant criteria that affect the query performance need to be determined and the sample space should be generated accordingly. In this paper we present a benchmarking framework for evaluating the performance of various static collision detection algorithms. In this framework, instances of a moving rigid object are placed on the surface of another instance of the same object fixed at a certain position, where the contact occurs for the first time. Then by offsetting the surface inwards (outwards) we generate new surfaces that are at a certain fixed negative (positive) distance to the original surface. Placing the moving object on these offset surfaces makes the object penetrate (approach) the fixed object at a fixed distance. For offset surface generation we create a signed distance field and run marching cubes algorithm on it.
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    Collision Detection for Deformable Objects using Octrees
    (The Eurographics Association, 2006) Madera, F. A.; Day, A. M.; Laycock, S. D.; Louise M. Lever and Mary McDerby
    We present an algorithm for collision detection between multiple deformable objects translating in a large environment. We use Spatial Partitioning to subdivide the scene and a Bounding Volume Hierarchy to decompose the objects, using octrees in both cases. The algorithm is divided in two parts, the Broad and Narrow Phases, with objects that can be rigid or deformable. In the Broad Phase, an octree is used to partition the scene and cull away the object s Bounding Volumes that are distant. In the Narrow Phase, a hierarchical decomposition of Axis Aligned Bounding Boxes or spheres is employed to reduce the number of primitives in the pairwise comparisons. In summary this work is a general-purpose collision detection technique for performing real time collision detection of deformable bodies in interactive 3D applications.
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    Higher Dimensional Vector Field Visualization: A Survey
    (The Eurographics Association, 2009) Peng, Zhenmin; Laramee, Robert S.; Wen Tang and John Collomosse
    Vector field visualization research has evolved very rapidly over the last two decades. There is growing consensus amongst the research community that the challenge of two-dimensional vector field visualization is virtually solved as a result of the tremendous amount of effort put into this problem. Two-dimensional flow, both steady and unsteady can be visualized in real-time, with complete coverage of the flow without much difficulty. However, the same cannot be said of flow in higher-spatial dimensions, e.g. surfaces in 3D (2.5D) or volumetric flow (3D). We present a survey of higher-spatial dimensional flow visualization techniques based on the presumption that little work remains for the case of two-dimensional flow whereas many challenges still remain for the cases of 2.5D and 3D domains. This survey provides the most up-to-date review of the state-of-the-art of flow visualization in higher dimensions. The reader is provided with a high-level overview of research in the field highlighting both solved and unsolved problems in this rapidly evolving direction of research.
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    Real-Time Modelling of the Action of Wind on Liquid Surfaces
    (The Eurographics Association, 2006) Bristol, Amanda; Varsamidis, Thomas; Louise M. Lever and Mary McDerby
    This work in progress aims to model the appearance of the surface of various liquids, when force from a virtual wind is applied. The physical effects caused by a wind force include waves and spray. The appearance of these effects is dependent upon the physical characteristics of a liquid, such as viscosity and surface tension. Much of the realistic work carried out in this area has depended upon non real-time methods such as frame-by-frame rendering and animation. Alternatively, supercomputers have been used to process visualisation models which use large quantities of data. This study aims to produce realistic effects with an attractive appearance, in real time. Work will also be carried out to explore the possibilities of modelling breaking waves in real time.
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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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    Topological Descriptor for CAD Models with Inner Cavities
    (The Eurographics Association, 2006) Symonova, O.; Dao, M.-S.; Amicis, R. De; Ucelli, G.; S. Battiato and G. Gallo and F. Stanco
    The current work introduces an algorithm for constructing Reeb graph for CAD models and their inner cavities. The nodes of the graph represent areas of the manifold of the model where topological changes occur. Edges of the graph encode information about connections between such areas. The outline for the topological graph matching is given for detection of graph (sub)isomorphism. The proposed Reeb graph structure can be used as a descriptor of CAD models in the retrieval process.
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    Data-driven Tetrahedral Mesh Subdivision
    (The Eurographics Association, 2006) Rodríguez, Lyudmila; Navazo, Isabel; Vinacua, Álvar; Pere Brunet and Nuno Correia and Gladimir Baranoski
    Given a tetrahedral mesh immersed in a voxel model, we present a method to refine the mesh to reduce the discrepancy between interpolated values based on either scheme at arbitrary locations. An advantage of the method presented is that it requires few subdivisions and all decisions are made locally at each tetrahedron. We discuss the algorithm s performance and applications.