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AHT Bézier Curves and NUAHT B-Spline Curves

Journal of computer Science & Technology 2007年第4期22卷 597-607页

作者：徐岗汪国昭 Institute of Computer Graphics and Image Processing Zhejiang University Department of Mathematics Zhejiang University

In this paper, we present two new unified mathematics models of conics and polynomial curves, called algebraic hyperbolic trigonometric （ AHT） Bezier curves and non-uniform algebraic hyperbolic trigonometric （ NUAHT） B-spline curves of order n, which are generated over the space span{sin t, cos t, sinh t, cosh t, 1, t,..., t^n-5}, n 7〉 5. The two kinds of curves share most of the properties as those of the Bezier curves and B-spline curves in polynomial space. In particular, they can represent exactly some remarkable transcendental curves such as the helix, the cycloid and the catenary. The subdivision formulae of these new kinds of curves are also given. The generations of the tensor product surfaces are straightforward. Using the new mathematics models, we present the control mesh representations of two classes of minimal surfaces.

关键词： CAD/CAM AHT Bezier curve NUAHT B-spline curves transcendental curves

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Relation among C-curve characterization diagrams

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第10期8卷 1663-1670页

作者： CAO Juan WANG Guo-zhao Institute of Computer Graphics and Image Processing Department of Mathematics Zhejiang University Hangzhou 310027 China

As three control points are fixed and the fourth control point varies, the planar cubic C-curve may take on a loop, a cusp, or zero to two inflection points, depending on the position of the moving point. The plane can, therefore, be partitioned into regions labelled according to the characterization of the curve when the fourth point is in each region. This partitioned plane is called a "characterization diagram". By moving one of the control points but fixing the rest, one can induce different characterization diagrams. In this paper, we investigate the relation among all different characterization diagrams of cubic C-curves based on the singularity conditions proposed by Yang and Wang (2004). We conclude that, no matter what the C-curve type is or which control point varies, the characterization diagrams can be obtained by cutting a common 3D characterization space with a corresponding plane.

关键词： Spline C-curve Characterization diagram Singularity

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Design and implementation of a virtual demonstration system for furniture

Design and implementation of a virtual demonstration system ...

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China-Ireland International Conference on Information and Communications Technologies, CIICT 2007

作者： Wang, Yigang Ye, Lexiao Ding, Jianhao Institute of Computer Graphics and Image Processing Hangzhou Dianzi University Hangzhou 310018 China

ISBN: (纸本)9780863418273

This paper designs and implements a virtual demonstration system for furniture. First, in order to let users virtually dispose furniture, showing the best effect of furniture in the virtual environment, we model different series of a company's furniture and common houses, and create panoramic pictures and transition videos with 3D Max and image processing tools, realizing walkthrough of the furnished house. Secondly, our system adopts Open Scene Graph(OSG)platform to realize virtual demonstration of the furniture. Users can add?delete and move the 3D furniture in the virtual houses. Third, the system supports furniture demonstration in a real house. Users can import the photos of their own houses, and then dispose the selected furniture on these photos, to see the whole effect of furniture in their own real houses. The experiment result shows that the system makes customers be personally on the scene and can boost up users' purchase desire.

关键词： Houses

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Design and implementation of a collaborative 3D design system

Design and implementation of a collaborative 3D design syste...

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China-Ireland International Conference on Information and Communications Technologies, CIICT 2007

作者： Wang, Yigang Huang, Pengcheng Institute of Computer Graphics and Image Processing Hangzhou Dianzi University Hangzhou Zhejiang Province 310018 China

ISBN: (纸本)9780863418273

The team design becomes increasingly important to future manufacturing industry. This paper focus on the key issues of collaborative 3D design system through Internet or Intranet in CSCW(computer Support for Cooperative Work). In the paper, we propose our solutions of concurrency control tactics, collaboration aware, multi-mode communications network management, synchronous real-time protection in a collaborative 3D design system. Based on Open Source Projects-Open CASCADE and Adaptive Communication Environment (ACE), we implement our collaborative 3D design system, and experiments show our system can meet the requirements of some 3D cooperative modeling design applications.

关键词： Intranets

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House layout and furnishing using VR technologies

House layout and furnishing using VR technologies

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China-Ireland International Conference on Information and Communications Technologies, CIICT 2007

作者： Ding, Jianhao Wang, Yigang Institute of Computer Graphics and Image Processing Hangzhou Dianzi University Hangzhou 310018 Zhejiang Province China

ISBN: (纸本)9780863418273

This paper presents some new virtual reality methods for house layout and furnishing to realize interactive high realistic presentation of a furnished house. Virtual houses and furniture are built from actual schedule drawing data by 3D-modeling technology. This paper mainly proposes four ways of demonstrating virtual house on Internet, including indoor virtual tour, fix-position panorama browse, interactively indoor touring and globe view of house layout. Taking advantage of these ways, customers can navigate in the virtual house environment through Internet, observing the layout of houses from different angles and performing some interactive actions to show house style clearly.

关键词： Virtual reality

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Uniform algebraic-trigonometric spline curves

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Journal of Information and Computational Science 2007年第2期4卷 463-474页

作者： Chen, Wenyu Wang, Guozhao Institute of Computer Graphics and Image Processing Department of Mathematics Zhejiang University Hangzhou 310027 China

Based on the space spanned by {1, t, , tn-5, sint, cost, t sin t, t cos t}, (n≥5), this paper presents a new kind of uniform splines. These splines are called uniform algebraic-trigonometric splines, which share most of the properties as those of the B-splines in the polynomial space. Such splines can encompass conical solenoids, involutes of circles and some other transcendent curves. The subdivision scheme of this new kind of curves is given, and it is verified to be convergent. The subdivision scheme is equal to a series of linear subdividing process, which followed the V.D. property and the convexity preserving property of the splines.

关键词： Splines

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Sparse MRF appearance models for fast anatomical structure localisation

Sparse MRF appearance models for fast anatomical structure l...

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2007 18th British Machine Vision Conference, BMVC 2007

作者： Donner, René Mičušsík, Branislav Langs, Georg Bischof, Horst Institute for Computer Graphics and Vision Graz University of Technology Austria Pattern Recognition and Image Processing Group Vienna University of Technology Austria GALEN Group Laboratoire de Mathématiques Appliquées Aux Systèmes Ecole Centrale de Paris France

ISBN: (纸本)1901725340

image segmentation methods like active shape models, active appearance models or snakes require an initialisation that guarantees a considerable overlap with the object to be segmented. In this paper we present an approach that localises anatomical structures in a global manner by means of Markov Random Fields (MRF). It does not need initialisation, but finds the most plausible match of the query structure in the image. It provides for precise, reliable and fast detection of the structure and can serve as initialisation for more detailed segmentation steps. Sparse MRF Appearance Models (SAMs) encode a priori information about the geometric configurations of interest points, local features at these points and local features along the edges of adjacent points. This information is used to formulate a Markov Random Field and the mapping of the modeled object (e.g. a sequence of vertebrae) to the query image interest points is performed by the MAX-SUM algorithm. The local image information is captured by novel symmetry-based interest points and local descriptors derived from Gradient Vector Flow. Experimental results are reported for two data-sets showing the applicability to complex medical data.

关键词： image segmentation

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Local Structure Detection with Orientation-invariant Radial Configuration

Local Structure Detection with Orientation-invariant Radial ...

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Conference on computer Vision and Pattern Recognition (CVPR)

作者： Lech Szumilas Rene Donner Georg Langs Allan Hanbury Pattern Recognition and Image Processing Group University of Technology Vienna Vienna Austria Institute for Computer Graphics and Vision Graz University of Technology Graz Austria

Local image descriptors have proved themselves as useful tools for many computer vision tasks such as matching points between multiple images of a scene and object recognition. Current descriptors, such as SIFT, are designed to match image features with unique local neighborhoods. However, the interest point detectors used with SIFT often fail to select perceptible local structures in the image, and the SIFT descriptor does not directly encode the local neighborhood shape. In this paper we propose a symmetry based interest point detector and radial local structure descriptor which consistently captures the majority of basic local image structures and provides a geometrical description of the structure boundaries. This approach concentrates on the extraction of shape properties in image patches, which are an intuitive way to represent local appearance for matching and classification. We explore the specificity and sensitivity of this local descriptor in the context of classification of natural patterns. The implications of the performance comparison with standard approaches like SIFT are discussed.

关键词： Detectors Shape computer vision Layout Object recognition

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A comparision of Model-based methods for knee cartilage segmentation

A comparision of Model-based methods for knee cartilage segm...

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2nd International Conference on computer Vision Theory and Applications, VISAPP 2007

作者： Cheong, J. Faggian, N. Langs, G. Suter, D. Cicuttini, F. Dept. of Electrical Dept. of Computer Systems Engineering Monash University Australia Clayton School of Information Technology Monash University Australia Institute for Computer Graphics and Vision Graz University of Technology Austria Pattern Recognition and Image Processing Group Vienna University of Technology Austria Dept. of Epidemiology Dept. of Preventive Medicine Monash University Australia

Osteoarthritis is a chronic and crippling disease affecting an increasing number of people each year. With no known cure, it is expected to reach epidemic proportions in the near future. Accurate segmentation of knee cartilage from magnetic resonance imaging (MRI) scans facilitates the measurement of cartilage volume present in a patient's knee, thus enabling medical clinicians to detect the onset of osteoarthritis and also crucially, to study its effects. This paper compares four model-based segmentation methods popular for medical data segmentation, namely Active Shape Models (ASM) (Cootes et al., 1995), Active Appearance Models (AAM) (Cootes et al., 2001), Patch-based Active Appearance Models (PAAM) (Faggian et al., 2006), and Active Feature Models (AFM) (Langs et al., 2006). A comprehensive analysis of how accurately these methods segment human tibial cartilage is presented. The results obtained were benchmarked against the current "gold standard" (cartilage segmented manually by trained clinicians) and indicate that modeling local texture features around each landmark provides the best results for segmenting human tibial cartilage.

关键词： Medical imaging

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Motion Analysis of Endovascular Stent-Grafts by MDL Based Registration

Motion Analysis of Endovascular Stent-Grafts by MDL Based Re...

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International Conference on computer Vision (ICCV)

作者： Georg Langs Nikos Paragios Rene Donner Pascal Desgranges Alain Rahmouni Hicham Kobeiter GALEN Group Laboratoire de Mathématiques Appliquées aux Systàmes Ecole Centrale de Paris France Institute for Computer Graphics and Vision Graz University of Technology Austria Pattern Recognition and Image Processing Group University of Technology Vienna Austria University of Paris XII Paris France

The endovascular repair of a traumatic rupture of the thoracic aorta - that would otherwise lead to the death of the patient - is performed by delivering a stent-graft into the vessel at the rupture location. The age range of the affected patients is large and the stent-graft will stay in the body for the remaining life. The technique is relatively new, and no experience with regard to long-term effects, and durability exists. To predict long-term complications, such as ruptures or destructive interactions with surrounding tissue during the life of the patient, it is important to understand the - rather intense and constant - movement of the stent- graft during the cardiac cycle. A computed tomography with heart gating (gated CT) acquires sequences that show the region of the stent-graft at different time points. We analyze the motion of stent-grafts with a model based approach. Stent-grafts are represented as sparse sets of axis points extracted from the gated CT, and motion patterns are captured by a minimum description length based group-wise registration of the stent-graft at different time points. No parameterization or a priori definition of the topology is necessary, and highly variable elasticity properties in the data volume can by accounted for by the sparse statistical model, that captures correlations and motion components of the stent-graft. We report results for deformation models and registration accuracy for 5 patients.

关键词： Motion analysis Computed tomography Biomedical imaging Heart Buildings computer graphics Pattern recognition image processing Hospitals Data mining

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