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Pacific Conference on computer graphics and Applications

作者： D. Steiner A. Fischer CMSR Laboratory for Computer Graphics and CAD Department of Mechanical Engineering Technion-Israel Institute of Technology Haifa Israel

ISBN: (纸本)0769512275

Reverse engineering (RE) deals with an enormous number of irregular and scattered digitized points that require intensive processing in order to reconstruct the surfaces of an object. Surface reconstruction of freeform objects is based on geometrical and topological criteria. Current fitting methods reconstruct an object using a bottom-up approach, from points to a dense mesh, and finally into smoothed connected freeform sub-surfaces. This type of reconstruction, however, can cause topological problems that lead to undesired surface fitting results. Such problems are particularly common with concave shapes. To avoid problems of this type, the paper proposes a new method that automatically detects the topological structure of an object as a base for surface fitting. The topological reconstruction method described in the paper is based on two stages: (1) creating 3D non-self-intersecting iso-curves from a 3D triangular mesh and (2) extracting a topological graph. The feasibility of the proposed topological reconstruction method is demonstrated on several examples using freeform objects with complex topologies.

关键词： Topology Surface fitting Surface reconstruction Shape Reconstruction algorithms Reverse engineering Laboratories computer graphics Mechanical engineering Scattering

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A review of technical advances in virtual colonoscopy

A review of technical advances in virtual colonoscopy

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10th World Congress on Medical Informatics, MEDINFO 2001

作者： Vos, Frans Serlie, Iwo Van Gelder, Rogier Stoker, J. Vrooman, Henri Post, Frits Pattern Recognition Group Delft University of Technology Lorentzweg 1 2628 CJ Delft Netherlands Computer Graphics and CAD CAM Group Delft University of Technology Delft Netherlands Biomedical Imaging Group Rotterdam Erasmus University Rotterdam Rotterdam Netherlands Department of Radiology Academic Medical Center Amsterdam Netherlands

ISBN: (纸本)1586031945

Early detection of polyps has proven to lead to a decrease in incidence of colon cancer. In the past few years, virtual colonoscopy has been developed as a patient-friendly screening technique. The procedure comprises the following steps. First, the patient's colon is cleansed and transanally inflated with air. Subsequently, a 3D image volume is acquired of the abdomen by CT or MRI. Finally, the bowel surface is extracted and visualized, after which the physician virtually navigates through the colon and examines the surface for abnormalities. This paper describes the progress in research for virtual colonoscopy. © 2001 IMIA. All right reserved.

关键词： Medical informatics

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Fusion of two different motion cues for intelligent video surveillance

Fusion of two different motion cues for intelligent video su...

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IEEE Region 10 International Conference TENCON

作者： Liyuan Li M.K.H. Leung Center for Graphics and Imaging Technology Nanyang Technological University Singapore School of Computer Engineering Nanyang Technological University Singapore

Detecting the presence of people and suspicious objects are the essential tasks for security surveillance. This paper presents a new real-time system for this purpose. Two motion cues from background subtraction and temporal differencing are employed to not only get reliable motion detection but also identify detected objects in the scene. A fuzzy reasoning technique is developed to detect and locate motion objects from vertical projection of motion cues. The background model is updated on both pixel level and region level to adapt both slow illumination changes and sudden extraneous events. This new background maintenance technique makes the system able to work under varying environments. The system has been run round the clock in real scenes and the performance is very promising.

关键词： Video surveillance Object detection Motion detection Layout Real time systems Security Humans Pixel Telephony Morphological operations

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Multiresolution texture for photorealistic rendering

Multiresolution texture for photorealistic rendering

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Spring Conference on computer graphics

作者： H. Mayer F. Leberl A. Bornik J. Bauer K. Karner Institute for Computer Graphics and Vision Graz University of Technology Austria VRVis Research Center for Virtual Reality and Visualization Austria

This paper presents a method to automatically calculate texture maps for a given 3D object from a sequence of images. It is used in our image-based modeling approach after the registration of the images and the geometric modeling has been done. We show that the presented method uses the information from all images by implicitly applying a weighting function. Using this approach, the consideration of modeled occlusions as well as the detection and removal of non-modeled occlusions is accomplished. The final resolution of the texture maps can be adjusted on a pixel/cm basis.

关键词： Image reconstruction Solid modeling Rendering (computer graphics) computer graphics Layout Virtual reality Visualization computer vision Cities and towns Geometry

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Computed tomography angiography: a case study of peripheral vessel investigation 01

Computed tomography angiography: a case study of peripheral ...

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IEEE Conference on Visualization

作者： A. Kanitsar D. Fleischmann R. Wegenkittl D. Sandner P. Felkel E. Groller Institute of Computer Graphics and Algorithms University of Technology Vienna Austria TIANI Medgraph Austria VRVis Center Vienna Austria Department of Radiology University of Technology Vienna Austria

ISBN: (纸本)0780372018

This paper deals with vessel exploration based on computed tomography angiography. Large image sequences of the lower extremities are investigated in a clinical environment. Two different approaches for peripheral vessel diagnosis dealing with stenosis and calcification detection are introduced. The paper presents an automated vessel-tracking tool for curved planar reformation. An interactive segmentation tool for bone removal is proposed.

关键词： Computed tomography Angiography computer aided software engineering Extremities Visualization Diseases computer graphics Radiology Image segmentation Bones

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Making the DDA run: two-dimensional ray traversal using runs and runs of runs

Making the DDA run: two-dimensional ray traversal using runs...

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Australasian computer Science Conference

作者： P. Stephenson B. Litow Fraunhofer Center for Research in Computer Graphics Inc. Providence RI USA School of Information Technology James Cook University Townsville Australia

ISBN: (纸本)0769509630

Iterative algorithms based on runs, and runs of runs are presented to calculate the cells of the two-dimensional lattice intersected by a line of real slope and intercept. The technique is applied to the problem of traversing a ray through a two-dimensional grid. Using runs or runs of runs provides a significant improvement in the efficiency of ray traversal for all but very short path lengths when compared to the DDA algorithm implemented using floating or fixed point arithmetic.

关键词： Iterative algorithms Visualization computer vision Lattices computer graphics Information technology Arithmetic Geometry Ray tracing Biomedical imaging

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3D metamorphosis between different types of geometric models

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computer graphics Forum 2001年第3期20卷 36-48页

作者： Breen, David E. Mauch, Sean Whitaker, Ross T. Mao, Jia Computer Graphics Group California Institute of Technology Pasadena CA United States SCI Institute School of Computing University of Utah Salt Lake City UT United States

We present a powerful morphing technique based on level set methods, that can be combined with a variety of scan conversion/model processing techniques. Bringing these techniques together creates a general morphing approach that allows a user to morph a number of geometric model types in a single animation. We have developed techniques for converting several types of geometric models (polygonal meshes, CSG models and MRI scans) into distance volumes, the volumetric representation required by our level set morphing approach. The combination of these two capabilities allows a user to create a morphing sequence regardless of the model type of the source and target objects, freeing him/her to use whatever model type is appropriate for a particular animation.

关键词： Three dimensional computer graphics

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Reconstructing surfaces using anisotropic basis functions

Reconstructing surfaces using anisotropic basis functions

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International Conference on computer Vision (ICCV)

作者： Huong Quynh Dinh G. Turk G. Slabaugh Graphics Visualization and Usability CenterCollege of Computing Georgia Institute of Technology USA School of Electrical and Computer Engineering Center for Signal and Image Processing Georgia Institute of Technology USA

ISBN: (纸本)0769511430

Point sets obtained from computer vision techniques are often noisy and non-uniform. We present a new method of surface reconstruction that can handle such data sets using anisotropic basis functions. Our reconstruction algorithm draws upon the work in variational implicit surfaces for constructing smooth and seamless 3D surfaces. Implicit functions are often formulated as a sum of weighted basis functions that are radially symmetric. Using radially symmetric basis functions inherently assumes, however that the surface to be reconstructed is, everywhere, locally symmetric. Such an assumption is true only at planar regions, and hence, reconstruction using isotropic basis is insufficient to recover objects that exhibit sharp features. We preserve sharp features using anisotropic basis that allow the surface to vary locally. The reconstructed surface is sharper along edges and at corner points. We determine the direction of anisotropy at a point by performing principal component analysis of the data points in a small neighborhood. The resulting field of principle directions across the surface is smoothed through tensor filtering. We have applied the anisotropic basis functions to reconstruct surfaces from noisy synthetic 3D data and from real range data obtained from space carving.

关键词： Surface reconstruction Anisotropic magnetoresistance Image reconstruction Surface fitting Optical noise Shape Polynomials computer vision Surface emitting lasers Space technology

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Mechanically based design: adaptive refinement for B-spline finite element

Mechanically based design: adaptive refinement for B-spline ...

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International Conference on Shape Modeling and Applications

作者： P. Kagan A. Fischer P. Bar-Yoseph Laboratory for Computer Graphics and CAD Mechanical Engineering Department Technion-Israel Institute of Technology Haifa Israel Computational Mechanics Laboratory Mechanical Engineering Department Technion-Israel Institute of Technology Haifa Israel

ISBN: (纸本)0769508537

This paper presents a method for adaptive refinement within an integrated mechanically based CAE system. The system uses a mechanical B-spline finite element model for both geometric design and mechanical analysis. A technique for locally refining a solution by B-spline finite elements is presented. The key component in the proposed method is the linear coordinate transformation introduced into the refined element. The transformation is constructed in such a way that the transformed nodal configuration of the refined element is identical to the nodal configuration of the neighbor elements. Therefore, the assembly proceeds in the regular fashion, while the C/sup 0/ continuity is forced along the inter-element boundary exactly. The proposed adaptive refinement method has been implemented both for surface and solid design without substantial differences in technical complexity. Its feasibility as applied to sculptured surface and solid objects is demonstrated by several examples.

关键词： Spline Finite element methods computer aided engineering Shape Laboratories Solid modeling Algorithm design and analysis computer graphics Design automation Mechanical engineering

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Virtual dissection of the colon based on helical CT data-can it be done?

Virtual dissection of the colon based on helical CT data-can...

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International Symposium on Image and Signal Processing and Analysis

作者： E. Sorantin E. Balogh A. Vilanova i Bartroli K. Palagyi L.G. Nyul Department of Radiology University of Graz Graz Austria Department of Informatics University of Szeged Szeged Hungary Institute of Computer Graphics and Algorithms University of Technology Vienna Vienna Austria

ISBN: (纸本)9539676940

Colorectal cancer is the third most commonly diagnosed cancer; and colonic polyps are known precursors of that particular cancer. Virtual dissection refers to a display technique for polyp detection based on helical CT data, where the colon is dissected and flattened as on the pathologist's table. The approach and image processing as well as the early experience are described in this paper.

关键词： Colonography Colon Computed tomography Cancer Colonic polyps Informatics Image reconstruction Humans Hospitals Image processing

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