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Item 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 GrimsteadReal-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.Item 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 CollomosseSimulating 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.Item Higher Dimensional Vector Field Visualization: A Survey(The Eurographics Association, 2009) Peng, Zhenmin; Laramee, Robert S.; Wen Tang and John CollomosseVector 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.Item 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 GrimsteadA 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.Item Surfel Based Geometry Reconstruction(The Eurographics Association, 2010) Andersen, Vedrana; Aanæs, Henrik; Bærentzen, Jacob Andreas; John Collomosse and Ian GrimsteadWe 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.Item Distance Based Feature Detection on 3D Point Sets(The Eurographics Association, 2009) Ramli, Ahmad; Ivrissimtzis, Ioannis; Wen Tang and John CollomosseWe propose a distance based algorithm for implicit feature detection on 3D point sets. Instead of directly determining whether a point belongs to a feature of the 3D point set or not, we first compute the distance between the point and its nearest feature. The obtained distance function is filtered, removing noise and outliers, and the features of the point set are computed as the zero set of the filtered function. Initial tests show that the proposed method is robust and can deal with amount of noise usually expected in a point set.