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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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An Edge-Preserving, Data-Dependent Triangulation Scheme for Hierarchical Rendering

An Edge-Preserving, Data-Dependent Triangulation Scheme for ...

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IEEE Scientific Visualization Conference (SciVis)

作者： J.C. Barnes B. Hamann K.I. Joy Center for Image Processing and Integrated Computing (CIPIC) Department of Computer Science University of California Davis CA USA

In many applications one is concerned with the approximation of functions from a finite set of given data sites with associated function values. We describe a construction of a hierarchy of triangulations which approximate the given data at varying levels of detail. Intermediate triangulations can be associated with a particular level of the hierarchy by considering their approximation errors. This paper presents a new data-dependent triangulation scheme for multi-valued scattered data in the plane. We perform piecewise linear approximation based on data-dependent triangulations. Our scheme preserves edges (discontinuities) that might exist in a given data set by placing vertices close to edges. We start with a coarse, data-dependent triangulation of the convex hull of the given data sites and subdivide triangles until the error of the piecewise linear approximation implied by a triangulation is smaller than some tolerance.

关键词： Piecewise linear approximation Scattering Approximation error Rendering (computer graphics) image processing Iterative algorithms Piecewise linear techniques computer science Application software Identity-based encryption

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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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Cluster-Based Generation of Hierarchical Surface Models

Cluster-Based Generation of Hierarchical Surface Models

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IEEE Scientific Visualization Conference (SciVis)

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

We present a highly efficient, automatic method for the generation of hierarchical surface triangulations. Given a set of scattered points in three-dimensional space, without known connectivity information, our method reconstructs a valid triangulated surface model in a two-step procedure. First, we apply clustering to the set of given points and identify point subsets in locally nearly planar regions. Second, we construct a surface triangulation from the output of the clustering step. The output of the clustering step is a set of 2-manifold tiles, which locally approximate the underlying, unknown surface. We construct the triangulation of the entire surface by triangulating the individual tiles and triangulating the gaps between the tiles. Since we apply point clustering in a hierarchical fashion we can generate model hierarchies by triangulating various levels resulting from the hierarchical clustering step.

关键词： Surface reconstruction Tiles Electrical capacitance tomography image processing computer science Reconstruction algorithms Scattering image reconstruction Read only memory Data mining

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Multiresolution and Adaptive Rendering Techniques for Structured, Curvilinear Data

Multiresolution and Adaptive Rendering Techniques for Struct...

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IEEE Scientific Visualization Conference (SciVis)

作者： W.C. Wynn J.F. Barnes B. Hamann M. Miller Department of Computer Science North Carolina State University Chapel Hill USA Center for Image Processing and Integrated Computing (CIPIC) Department of Computer Science University of California Davis USA Lawrence Livermore National Laboratory University of California USA

In many applications one is concerned with techniques for visualizing data sets with real-time interaction. One technique for providing real-time performance is through the use of multiresolution techniques. These techniques provide multiple representations of a data set at different levels of detail. The idea is to select a level of detail that can be rendered within the user's time constraints. We discuss a mechanism which renders finer-detailed representations where the data set has a high frequency, and coarser representations where the data set has lower frequency. We present a new technique for storing curvilinear data sets within a quadtree representation and discuss two rendering schemes: an anti-aliasing scheme and a scheme for maintaining a specified frame rate.

关键词： computer science Postal services Data visualization image processing Laboratories Rendering (computer graphics) Application software Ear Degradation Robustness

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Two applications of wavelets and related techniques in medical imaging

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Annals of Biomedical Engineering 1995年第5期23卷 637-665页

作者： Healy Jr., Dennis M. Lu, Jian Weaver, John B. Department of Mathematics and Computer Science Dartmouth College Hanover 03755 NH United States Center for Image Processing and Integrated Computing University of California Davis CA United States Department of Diagnostic Radiology Dartmouth-Hitchcock Medical Center Lebanon NH United States

We present two applications of wavelet and related techniques to problems arising in medical imaging. Both make considerable use of the edge detection and classification properties of wavelet-type representations. First we describe simple and effective techniques for image denoising and contrast enhancement based on the multiscale edge representation of images. These techniques are sufficiently flexible to successfully address the varying requirements posed by several different medical imaging modalities in common use today. Experimental results are presented to illustrate the application of these techniques to various types of medical images. Next we describe adapted waveform encoding, a technique for magnetic resonance imaging. One advantage of this technique istthat it can be used to efficiently encode edge features of the object being imaged. This has a particular diagnostic application in tracking heart wall thickness during the cardiac cycle, which we present along with some experimental results along this line. We also present an analysis of the signal-to-noise ratios of images formed with this technique, as this is a factor of paramount importance in MRI. The fact that wavelet schemes tend to concentrate energy near edge features makes the result rather different than that found in standard Fourier based approaches. We indicate an exciting potential application of our technique: reducing spectral leakage in phosphorus spectroscopy. © 1995 Biomedical Engineering Society.

关键词： image enhancement Magnetic resonance imaging

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Texture analysis in the presence of speckle noise 12

Texture analysis in the presence of speckle noise

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12th Annual International Geoscience and Remote Sensing Symposium, IGARSS 1992

作者： Schistad, Anne H. Jain, Anil K. Norwegian Computing Center P.O. Box 114 Blindern Oslo 3N-0314 Norway Pattern Recognition and Image Processing Lab. Computer Science Department Michigan State University East LansingMI48824 United States

ISBN: (纸本)0780301382

We investigate the performance of selected texture models for the purpose of land use classification. The texture models are evaluated based on the resulting classification error rates. Three classes of texture models are evaluated: fractal models, lognormal random fields and grey level co-occurrence matrices. The effect of filtering and noise transformation is investigated. The lognormal random field model gives the best performance. © IEEE 1992.

关键词： Land use

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Medial axis representation and encoding of scanned documents

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Journal of Visual Communication and image Representation 1991年第2期2卷 151-165页

作者： Brandt, Jonathan W. Jain, Anil K. Ralph Algazi, V. Computer Vision Research Lab CIPIC: The Center for Image Processing and Integrated Computing United States Department of Electrical Engineering and Computer Science University of California Davis CA 95616 United States

The medial axis transform (MAT) is a sparse representation of shape, which, being reversible, has potential for binary image compression. The MAT also provides structural information not accessible with alternative binary image codes. This structural information is often used for line extraction and pattern recognition. Therefore, the MAT occupies an interesting middle ground between lower-level, compressible image codes and higher-level, meaningful image representations. In an attempt to realize this middle ground, a MAT-based coding scheme which respects its structural properties is developed. The MAT-based coding method is applied to the CCITT facsimile test images. The resulting compression is comparable to that of known coding schemes for textual and somewhat better for graphical data. Some simple modifications to improve skeleton coding performance are suggested. To substantiate the claim that the MAT is effective for higher-level processing, the representation is extended to perform line segment and curve extraction. The extraction takes place under the control of a global error tolerance parameter and thus provides a new method to trade off data compression with distortion for binary images. © 1991.

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Improved color flow mapping using the wideband maximum likelihood estimator

Improved color flow mapping using the wideband maximum likel...

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IEEE Symposium (IUS) Ultrasonics

作者： K.W. Ferrara V.R. Algazi Department of Electrical Engineering California State University Sacramento CA USA Center for Image Processing and Integrated Computing University of California Davis CA USA Department of Electrical Engineering and Computer Science University of California Davis CA USA

The use of the wideband maximum likelihood estimator (MLE) is shown to improve the color flow mapping of the blood velocity profile. Using a transmitted signal with a significant fractional bandwidth, it is shown that the wideband MLE improves the quality of the color flow estimate and simultaneously allows an increase in the frame rate. It is the improved global accuracy of the estimate, with the use of a new signaling scheme, that allows an increase in the frame rate of the display. The signaling scheme interleaves transmission of pulses in two or three directories. This interleaving, with nonperiodic transmission, reduces the total number of pulses required to achieve a fixed level of local and global accuracy. To study the overall estimator performance, the authors evaluate the expected estimator output and demonstrate that the width of the mainlobe and height of subsidiary peaks are reduced through the use of this estimator and signaling scheme.< >

关键词： Wideband Maximum likelihood estimation Blood Displays Simultaneous localization and mapping Transducers Acoustic propagation Delay estimation image processing Bandwidth

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