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Proceedings of the conference on Visualization '99: celebrating ten years

作者： Bjoern Heckel Gunther Weber Bernd Hamann Kenneth I. Joy Center for Image Processing and Integrated Computing (CIPIC) Computer Science Department University of California Davis AG Graphische Datenverarbeitung and Computergeometrie Fachbereich Informatik Universität Kaiserslautern Germany

ISBN: (纸本)9780780358973

We present a method for the hierarchical representation of vector fields. Our approach is based on iterative refinement using clustering and principal component analysis. The input to our algorithm is a discrete set of points with associated vectors. The algorithm generates a top-down segmentation of the discrete field by splitting clusters of points. We measure the error of the various approximation levels by measuring the discrepancy between streamlines generated by the original discrete field and its approximations based on much smaller discrete data sets. Our method assumes no particular structure of the field, nor does it require any topological connectivity information. It is possible to generate multiresolution representations of vector fields using this approach.

关键词： binary-space partitioning data simplification Hardy's multiquadric method vector field visualization

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Construction of vector field hierarchies

Construction of vector field hierarchies

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IEEE Conference on Visualization

作者： B. Heckel G. Weber B. Hamann K.I. Joy Center for Image Processing and Integrated Computing (CIPIC) Computer Science Department University of California Davis USA AG Graphische Datenverarbeitung and Computergeometrie Fachbereich Informatik Universität Kaiserslautern Germany

Presents a method for the hierarchical representation of vector fields. Our approach is based on iterative refinement using clustering and principal component analysis. The input to our algorithm is a discrete set of points with associated vectors. The algorithm generates a top-down segmentation of the discrete field by splitting clusters of points. We measure the error of the various approximation levels by measuring the discrepancy between streamlines generated by the original discrete field and its approximations based on much smaller discrete data sets. Our method assumes no particular structure of the field, nor does it require any topological connectivity information. It is possible to generate multi-resolution representations of vector fields using this approach.

关键词： Data visualization Clustering algorithms image processing Computer science Iterative algorithms Iterative methods Principal component analysis Computational modeling Computer simulation

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Optimal linear spline approximation of digitized models

Optimal linear spline approximation of digitized models

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International Conference on Information Visualisation (IV)

作者： B. Hamann O. Kreylos G. Monno A.E. Uva Center for Image Processing and Integrated Computing (CIPIC) Department of Computer Science University of California Davis USA Dipartimento di Progettazione e Produzione Industriale Politecnico di Bari Bari Italy

We present a new technique for surface reconstruction of digitized models in three dimensions. Concerning this problem, we are given a data set in three-dimensional space, represented as a set of points without connectivity information, and the goal is to find, for a fixed number of vertices, a set of approximating triangles which minimize the error measured by the displacement from the given points. Our method creates near-optimal linear spline approximations, using an iterative optimization scheme based on simulated annealing. The algorithm adopts the mesh to the data set and moves the triangles to enhance feature lines. At the end, we can use the approach to create a hierarchy of different resolutions for the model.

关键词： Spline Linear approximation Surface reconstruction image reconstruction Shape Sampling methods Clouds Solid modeling Isosurfaces Reconstruction algorithms

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High-quality rendering of smooth isosurfaces

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Computer Animation and Virtual Worlds 1999年第2期10卷

作者： Eric LaMar Bernd Hamann Kenneth I. Joy Center for Image Processing and Integrated Computing (CIPIC) Department of Computer Science University of California Davis CA 95616 8562 U.S.A.

Animation and visualization of rectilinear data require interpolation schemes for smooth image generation. Piecewise trilinear interpolation, the de facto standard for interpolating rectilinear data, usually leads to significant visual artifacts in the resulting imagery. These artifacts reduce the confidence in the resulting visualization and may even lead to false interpretations of the data. This paper is concerned with the generation of smooth isosurface image sequences, obtained by casting rays through the image plane and computing their intersections with an isosurface. We describe a novel solution to this problem: we replace trilinear interpolation by tricubic interpolation, smoothing out the artifacts in the images; and we simplify the ray–isosurface intersection calculations by rotating and resampling the original rectilinear data in a second rectilinear grid—a grid with one family of grid planes parallel to the image plane. Our solution significantly reduces artifacts in individual images and leads to smooth animations. Copyright © 1999 John Wiley & Sons, Ltd.

关键词： animation approximation trilinear splines volume visualization ray casting isosurfaces resampling Catmull–Rom splines Hardy's multiquadric scheme

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Simplification of tetrahedral meshes

Simplification of tetrahedral meshes

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IEEE Conference on Visualization

作者： I.J. Trotts B. Hamann K.I. Joy D.F. Wiley Center for Image Processing and Integrated Computing Department of Computer Science University of California Davis USA

We present a method for the construction of multiple levels of tetrahedral meshes approximating a trivariate function at different levels of detail. Starting with an initial, high-resolution triangulation of a three-dimensional region, we construct coarser representation levels by collapsing tetrahedra. Each triangulation defines a linear spline function, where the function values associated with the vertices are the spline coefficients. Based on predicted errors, we collapse tetrahedron in the grid that do not cause the maximum error to exceed a use-specified threshold. Bounds are stored for individual tetrahedra and are updated as the mesh is simplified. We continue the simplification process until a certain error is reached. The result is a hierarchical data description suited for the efficient visualization of large data sets at varying levels of detail.

关键词： Data visualization Spline Legged locomotion Mesh generation image processing Computer science Acoustic scattering Large-scale systems Temperature dependence Chemicals

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On polyhedral approximations to a sphere 98

On polyhedral approximations to a sphere

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Computer Graphics International

作者： D.E. Fox K.I. Joy Center for Image Processing and Integrated Computing Department of Computer Science University of California Davis CA USA

ISBN: (纸本)9780818684456

The authors investigate methods by which successive approximations to a sphere can be generated from polyhedra. Each approximation can be obtained by bevel-cutting each edge of the previous approximation with a plane tangent to the sphere. They show that each member of the sequence of polyhedra can be associated with a Voronoi tessellation of the sphere. Under this formulation, the bevel-cutting operation can be defined by the insertion of points into the Voronoi tessellation. The algorithm is defined such that affine combinations of the polyhedra will converge to affine operations of the sphere. The method is useful as a modeling operation and as a level-of-detail representation for a sphere.

关键词： Ellipsoids Computer science Design automation Surface reconstruction Computer graphics Solids Writing Lattices Topology Conference proceedings

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Inhomogeneous surface diffusion for image filtering

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International Journal of Imaging Systems and Technology 1998年第5期8卷

作者： Gary E. Ford Adel I. El-Fallah CIPIC Center for Image Processing and Integrated Computing University of California Davis Davis CA 95616

Most of the recent work on inhomogeneous diffusion in image filtering focuses on diffusing the isotope curve. We present a less familiar approach to the development of inhomogeneous diffusion algorithms in which the image is regarded as a surface in three-space. The magnitude of the surface normal controls a diffusion that evolves the image surface at a speed proportional to its mean curvature. A discrete algorithm to implement this proposed diffusion is introduced, and we show experimentally that the algorithm develops singularities that reveal, preserve, and enhance the underlying signal. If the input signal is an isolated noisy edge, this leads to complete noise removal and enhancement without affecting the edge locality. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 450–456, 1997

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Inhomogeneous surface diffusion for image filtering

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INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY 1997年第5期8卷 450-456页

作者： Ford, GE ElFallah, AI CIPIC Center for Image Processing and Integrated Computing University of California Davis Davis CA 95616

关键词： image processing

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Comparative performance of wavelet and JPEG coders at high quality 2

Comparative performance of wavelet and JPEG coders at high q...

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Very High Resolution and Quality Imaging II Conference

作者： Algazi, VR Estes, RR Center for Image Processing and Integrated Computing (CIPIC) University of California Davis Qualimage Inc. Davis CA United States

ISBN: (纸本)0819424366

In recent work, we have examined the performance of wavelet coders using a perceptually relevant image quality metric, the Picture Quality Scale (PQS). In that study, we considered some of the design options available with respect to choice of wavelet basis, quantizer, and method for error-free encoding of the quantized coefficients, including the EZW methodology. A specific combination of these design options provides the best trade off between performance and PQS quality. Here, we extend this comparison by evaluating the performance of JPEG and the previously chosen optimal wavelet scheme, focusing principally on the high quality range.

关键词： coder performance wavelets wavelet transform JPEG perceptual distortion measure image coding

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Smooth hierarchical surface triangulations 97

Smooth hierarchical surface triangulations

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Proceedings of the 8th conference on Visualization '97

作者： Tran S. Gieng Bernd Hamann Kenneth I. Joy Gregory L. Schussman Issac J. Trotts Center for Image Processing and Integrated Computing Department of Computer Science University of California Davis

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