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17th Spring Conference on computer graphics, SCCG 2001

作者： Czanner, S. ɰurikovič, R. Inoue, H. Software Dept. Univ. of Aizu Aizu-Wakamatsu City Japan Department of Computer Graphics and Image Processing Faculty of Mathematics Physics and Computer Science Comenius University Bratislava Slovakia

ISBN: (纸本)0769512151

The growth of the brain of a human embryo changes over a long period of time in the body of the mother. So it is very difficult to observe and to understand that process. Therefore, embryologists have found realistic human organ models and animations to be necessary for their studies, but to create realistic human embryo brain models and to perform the animations requires an appropriate methodology. This paper presents a developing methodology based on the brain's functional representation and the convolutions of the surfaces. We employed this methodology to create a growth simulation of a human embryo's brain. The idea behind this technique is as follows. As a first step a 2D central skeleton is created from an artistic drawing and then a 3D skeleton is modeled by adding thickness information. In the next step, the skeletons representing the key-frame models are used to create an animation. At the end, the gap between the key-frame models is filled by suitable interpolation techniques and, finally, the animation is composed. © 2001 IEEE.

关键词： Blending

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A Study of Transfer Function Generation for Time-Varying Volume Data 2

A Study of Transfer Function Generation for Time-Varying Vol...

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2nd IEEE TCVG / Eurographics International Workshop on Volume graphics, VG 2001

作者： Jankun-Kelly, T.J. Ma, Kwan-Liu Visualization And Graphics Research Group Center For Image Processing And Integrated Computing University Of California Department Of Computer Science DavisCA95616 United States

ISBN: (纸本)321183737X

The proper usage and creation of transfer functions for time-varying data sets is an often ignored problem in volume visualization. Although methods and guidelines exist for time-invariant data, little formal study for the timevarying case has been performed. This paper examines this problem, and reports the study that we have conducted to determine how the dynamic behavior of time-varying data may be captured by a single or small set of transfer functions. The criteria which dictate when more than one transfer function is needed were also investigated. Four data sets with different temporal characteristics were used for our study. Results obtained using two different classes of methods are discussed, along with lessons learned. These methods, including a new multiresolution opacity map approach, can be used for semi-automatic generation of transfer functions to explore large-scale time-varying data sets. © VG 2001. All rights reserved.

关键词： Transfer functions

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Simplified kinetic connectivity for rectangles and hypercubes

Simplified kinetic connectivity for rectangles and hypercube...

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2001 Operating Section Proceedings, American Gas Association

作者： Hershberger, John Suri, Subhash Mentor Graphics Corp. 8005 SW Boeckman Road Wilsonville OR Computer Science Department Engineering I University of California Santa Barbara CA

ISBN: (纸本)0898714907

We consider the problem of maintaining connected components in a set of moving objects using the kinetic data structure (KDS) framework. We assume that the motion of each object can be specified by a low-degree algebraic trajectory;this trajectory, however, can be modified in an on-line fashion. While the objects move continuously, their connectivity changes at discrete times. A straightforward dynamic graph approach for maintaining connectivity of n objects has three shortcomings: the graph can have (n2) edges, the update bounds are amortized, and the algorithm is very complicated. Our first result shows that the connectivity for a set of n moving hypercubes can be maintained using a very simple, easy to determine graph with O(n) edges. But this graph still requires a general-purpose dynamic graph scheme for connectivity maintenance. Our main result is a simplified connectivity data structure for moving rectangles in the plane. For this special but important case, we are able to overcome all three shortcomings mentioned above: our graph has O(n) edges;our data structure supports updates in O(log2 n) worst-case time;and the algorithm and data structures are quite a bit simpler than those based on a general dynamic graph scheme. Copyright © 2009 ACM, Inc.

关键词： Algorithms Design Theory Verification

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MPEG-Encoded Light Fields

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Journal of graphics Tools 2001年第2期6卷 1-15页

作者： Jamo van der Linden[a] & Richard Lobb[b] [a] Graphics and Visualisation Group Department of Computer Science University of Auckland Auckland New Zealand E-mail: [b] Graphics and Visualisation Group Department of Computer Science University of Auckland Auckland New Zealand E-mail:

Light fields (or Lumigraphs) are an image-based rendering method. As light fields require a large number of images, memory and disk space requirements are a significant barrier to the practical use of light fields. In this paper, we explain how to greatly reduce the space demands of light fields by encoding them in an MPEG format. The encoding is comprised of an MPEG bitstream and two tables of precomput ed information to aid real-time decoding. By restricting the parameters used for MPEG encoding, and by employing a caching system, new views of the compressed light field can be rendered at fast interactive frame rates on consumer hardware. Compression ratios of around 50:1 are demonstrated. Combined, the speed and compression make the use of light fields practical on consumer hardware.

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Evaluation of diffusion techniques for improved vessel visualization and quantification in three-dimensional rotational angiography 4th

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4th International Conference on Medical Image Computing and computer-Assisted Intervention, MICCAI 2001

作者： Meijering, Erik Niessen, Wiro Weickert, Joachim Viergever, Max Image Sciences Institute University Medical Center Utrecht Heidelberglaan 100 UtrechtNL-3584 CX Netherlands Computer Vision Graphics and Pattern Recognition Group Department of Mathematics and Computer Science University of Mannheim MannheimD-68131 Germany

ISBN: (纸本)3540426973

Three-dimensional rotational angiography (3DRA) is a promising imaging technique which yields high-resolution isotropic 3D images of vascular structures. Raw 3DRA images, however, usually suffer from a high noise level and the presence of other artifacts. For accurate visualization and quantification of vascular anomalies, noise reduction is therefore highly desirable. In this paper we analyze the effects of several linear and nonlinear filtering techniques for that purpose. From the results of in vitro experiments we conclude that edge-enhancing anisotropic diffusion is very suitable for mentioned tasks. However, in view of the computational requirements of this technique, the regularized isotropic nonlinear diffusion scheme may be considered a useful alternative. © Springer-Verlag Berlin Heidelberg 2001.

关键词： Diffusion

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Limb segment pose from range data streams through homogeneous factorization

Limb segment pose from range data streams through homogeneou...

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Proceedings of the 2001 Bioengineering Conference

作者： Alexander, Eugene J. Bregler, Christoph Andriacchi, Thomas P. Biomechanical Engineering Mechanical Engineering Stanford University Stanford CA United States Computer Graphics Computer Science Stanford University Stanford CA United States Orthopedic Surgery Department of Functional Restoration Stanford University Stanford CA United States

The estimation of limb segment pose from range data streams through homogeneous factorization was performed. The technique accounted for skin deformation error by providing an estimate of the shape of the limb segment built up from a linear combination of multiple basis shapes. The technique allowed for the choice of the number of basis shapes and automatically extracts the limb segment location, orientation and shape.

关键词： Biomechanics

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Diffusion-snakes: combining statistical shape knowledge and image information in a variational framework

Diffusion-snakes: combining statistical shape knowledge and ...

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IEEE Workshop on Variational and Level Set Methods in computer Vision

作者： D. Cremers C. Schnorr J. Weickert Computer Vision Graphics and Pattern Recognition Group Department of Mathematics and Computer Science University of Mannheim Mannheim Germany

ISBN: (纸本)076951278X

We present a modification of the Mumford-Shah functional and its cartoon limit which allows the incorporation of statistical shape knowledge in a single energy functional. We show segmentation results on artificial and real-world images with and without prior shape information. In the case of occlusion and strongly cluttered background the shape prior significantly improves segmentation. Finally we compare our results to those obtained by a level-set implementation of geodesic active contours.

关键词： Image segmentation Level set Active contours Spline Shape control Active shape model Equations Statistical learning computer vision computer graphics

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Weight-biased edge-crossover in evolutionary algorithms for two graph problems 01

Weight-biased edge-crossover in evolutionary algorithms for ...

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2001 ACM Symposium on Applied Computing, SAC 2001

作者： Julstrom, Bryant A. Raidl, Günther R. Department of Computer Science St. Cloud State University 720 Fourth Avenue South St. CloudMN56301 United States Institute of Computer Graphics and Algorithms Vienna University of Technology Favoritenstraße 9-11/1861 Vienna1040 Austria

ISBN: (纸本)1581132875

Many optimization problems on weighted graphs seek a subset of the graph's edges that has minimum weight and satisfies the problem's constraints. Two examples are the traveling salesman problem (TSP) and the degree-constrained minimum spanning tree problem (d-MSTP). Heuristics like evolutionary algorithms often construct candidate solutions to such problems iteratively, repeatedly including an edge selected from those currently eligible. Not surprisingly, low-weight edges usually predominate in good and optimal solutions, an observation we confirm empirically for the TSP and the d-MSTP. This suggests that any process that builds candidate solutions should, with higher probability, select edges of lower weight. We incorporate into crossover operators and compare in a genetic algorithm four edge-selection techniques: random, greedy, according to probabilities inversely proportional to the edges' weights, and 2-tournament. Tests on instances of the TSP and the d-MSTP indicate that with the weight-biased techniques, the GA identifies better solutions faster than with random edge-selection. © 2001 ACM.

关键词： Traveling salesman problem

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A flexible polygon representation of multiple overlapping regions of interest for wavelet-based image coding

A flexible polygon representation of multiple overlapping re...

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IEEE International Conference on Image Processing

作者： U. Rauschenbach R. Rosenbaum H. Schumann Corporate Technology SIEMENS AG Munich Germany Computer Science Department Institute of Computer Graphics. University of Rostock Rostock Germany

Image transmission over low-bandwidth channels can be speeded up if the image coding mechanism supports regions of interest (RoIs). By such a scheme, image parts not belonging to RoIs can be encoded at a lower bitrate. This paper describes a flexible dynamic RoI scheme which supports the definition of arbitrarily-shaped RoIs before the start of the transmission process and the refinement of a partially transmitted image by the definition of new RoIs at any time during image transmission. The overhead to represent RoIs is kept as small as possible by exploiting a polygon-based RoI representation. Span arithmetic on a multiresolution grid is used to support the redundancy-free transmission of overlapping RoIs.

关键词： Image coding Image communication Shape Arithmetic Wavelet coefficients computer science computer graphics Computed tomography Bit rate Lapping

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Vickrey prices and shortest paths: what is an edge worth?

Vickrey prices and shortest paths: what is an edge worth?

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IEEE International Conference on Cluster Computing

作者： J. Hershberger S. Suri Mentor Graphics Corporation Wilsonville OR USA Computer Science Department University of California Santa Barbara CA USA

We solve a shortest path problem that is motivated by recent interest in pricing networks or other computational resources. Informally, how much is an edge in a network worth to a user who wants to send data between two nodes along a shortest path? If the network is a decentralized entity, such as the Internet, in which multiple self-interested agents own different parts of the network, then auction-based pricing seems appropriate. A celebrated result from auction theory shows that the use of Vickrey pricing motivates the owners of the network resources to bid truthfully. In Vickrey's scheme, each agent is compensated in proportion to the marginal utility he brings to the auction. In the context of shortest path routing, an edge's utility is the value by which it lowers the length of the shortest path, i.e., the difference between the shortest path lengths with and without the edge. Our problem is to compute these marginal values for all the edges of the network efficiently. The naive method requires solving the single-source shortest path problem up to n times, for an n-node network. We show that the Vickrey prices for all the edges can be computed in the same asymptotic time complexity as one single-source shortest path problem. This solves an open problem posed by N. Nisan and A. Ronen (1999).

关键词： Protocols Shortest path problem Pricing computer networks computer science Internet IP networks computer graphics Operations research Application software

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