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pacific conference on computer graphics and applications

作者： T. Kim M.C. Lin Department of Computer Science University of North Carolina Chapel Hill USA

We present a physically-based method for animating and rendering lightning and other electric arcs. For the simulation, we present the dielectric breakdown model, an elegant formulation of electrical pattern formation. We then extend the model to animate a sustained, 'dancing' electrical arc, by using a simplified Helmholtz equation for propagating electromagnetic waves. For rendering, we use a convolution kernel to produce results competitive with Monte Carlo ray tracing. Lastly, we present user parameters for manipulation of the simulation patterns.

关键词： Animation Lightning Dielectric breakdown Pattern formation Electromagnetic modeling Equations Electromagnetic propagation Optical propagation Electromagnetic scattering Convolution

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Wavelet based 3D compression with fast random access for very large volume data

Wavelet based 3D compression with fast random access for ver...

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pacific conference on computer graphics and applications

作者： F.F. Rodler Department of Computer Science Brics University of Aarhus Denmark

In this paper we propose a wavelet based method for compressing volumetric data with little loss in quality allowing fast random access to individual voxels within the volume. Such a method is important since storing and visualising very large volumes impose heavy demands on internal memory and external storage facilities, a problem not likely to become less in the future, making it accessible only to users with huge and expensive computers. Experimental results on the CT dataset of the Visible Human have shown that our method provides very high compression rates with fairly fast random access.

关键词： Image coding Humans Computed tomography Magnetic resonance imaging computer science Birth disorders Transform coding Shape Data visualization Electronic switching systems

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A method to generate wet and broken-up animal fur

A method to generate wet and broken-up animal fur

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pacific conference on computer graphics and applications

作者： A. Bruderlin Sony Pictures Imageworks Culver CA USA

This paper describes part of the pipeline which we have implemented for the creation of hair and fur for the upcoming motion picture "Stuart Little". In particular, we discuss the two effects of producing wet fur and broken-up dry fur. We assume that our animal models consist of a connected set of NURBS patches, which define the skin onto which the individual hairs are placed. A wet fur look is achieved by clumping together of neighboring hairs within certain clumping areas on the skin. The definition of these clumping areas can be either static or animated, the latter to simulate spouts of water hitting parts of the fur coat, making it increasingly wet. A broken-up fur look is generated by breaking of hairs along certain fur-tracks on the skin.

关键词： Animals Hair Skin Spline Surface topography Surface reconstruction Pipelines Animation Motion pictures Rendering (computer graphics)

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A method of human short hair modeling and real time animation

A method of human short hair modeling and real time animatio...

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pacific conference on computer graphics and applications

作者： Yang Guang Huang Zhiyong Volume Interactions Singapore Department of Computer Science School of Computing National University of Singapore Singapore

ISBN: (纸本)0769517846

This paper describes a method of human short hair modeling and real time animation. A method is proposed to model short hair. First, a hair style model is derived from a scalp model interactively. The hair model is then derived automatically from the hair style and scalp models. Texture mapping is applied to the hair model for a better visual effect. For animation, a method is proposed based on an approximation of the accurate physically-based hair model, from which 3D morphing key shapes are derived. Intermediate shapes are then computed by applying 3D morphing. We have implemented it and compared the results with real hair. The visual quality and frame rate are satisfactory for real time applications.

关键词： Humans Hair Animation Shape Scalp Visual effects Strips Fluid dynamics computer science Deformable models

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Spatial Matching of Animated Meshes

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computer graphics FORUM 2016年第7期35卷 21-32页

作者： Seo, H. Cordier, F. Univ Strasbourg ICube Strasbourg France Univ Haute Alsace LMIA Mulhouse France

This paper presents a new technique which makes use of deformation and motion properties between animated meshes for finding their spatial correspondences. Given a pair of animated meshes exhibiting a semantically similar motion, we compute a sparse set of feature points on each mesh and compute spatial correspondences among them so that points with similar motion behavior are put in correspondence. At the core of our technique is our new, dynamic feature descriptor named AnimHOG, which encodes local deformation characteristics. AnimHOG is ob-tained by computing the gradient of a scalar field inside the spatiotemporal neighborhood of a point of interest, where the scalar values are obtained from the deformation characteristic associated with each vertex and at each frame. The final matching has been formulated as a discreet optimization problem that finds the matching of each feature point on the source mesh so that the descriptor similarity between the corresponding feature pairs as well as compatibility and consistency as measured across the pairs of correspondences are maximized. Consequently, reliable correspondences can be found even among the meshes of very different shape, as long as their motions are similar. We demonstrate the performance of our technique by showing the good quality of matching results we obtained on a number of animated mesh pairs.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.5 [computer graphics]: Computational Geometry and Object Modeling—Geometric algorithms, languages, and systems I.3.6 [computer graphics]: Methodology and Techniques—graphics data structures and data types I.3.7 [computer graphics]: Three-Dimensional graphics and Realism—Animation

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Eigenanalysis and continuity of non-uniform Doo-Sabin surfaces

Eigenanalysis and continuity of non-uniform Doo-Sabin surfac...

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pacific conference on computer graphics and applications

作者： Kaihuai Qin Huawei Wang Department of Computer Science & Technology Tsinghua University Beijing China

In computer graphics and computer-aided geometric design, more and more subdivision schemes are being extensively used for free-form surfaces of arbitrary topology. The convergence and continuity analyses of uniform subdivision surfaces have been performed very well, but it is very difficult to prove the convergence and the continuity properties of non-uniform recursive subdivision surfaces (NURSSes, for short) because the subdivision matrix varies at each iteration step. This restricts widespread use of NURSSes, although NURSSes have a lot of advantages over uniform subdivision surfaces. In this paper, the concept of equivalent knot spacing is presented. A new technique for eigenanalysis, convergence and continuity analyses of non-uniform Doo-Sabin surfaces is proposed. Also, an interesting and important fact is found that the subdivision process of nonuniform Doo-Sabin surfaces may diverge sometime.

关键词： Convergence Topology Spline Algorithm design and analysis computer science Surface topography Surface reconstruction Electrical capacitance tomography Performance analysis Clothing

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Towards Digital Refocusing from a Single Photograph

Towards Digital Refocusing from a Single Photograph

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pacific conference on computer graphics and applications

作者： Yosuke Bando Tomoyuki Nishita TOSHIBA Corporation

This paper explores an image processing method for synthesizing refocused images from a single input photograph containing some defocus blur. First, we restore a sharp image by estimating and removing spatially-variant defocus blur in an input photograph. To do this, we propose a local blur estimation method able to handle abrupt blur changes at depth discontinuities in a scene, and we also present an efficient blur removal method that significantly speeds up the existing deconvolution algorithm. Once a sharp image is restored, refocused images can be interactively created by adding different defocus blur to it based on the estimated blur, so that users can intuitively change focus and depth-of-field of the input photograph. Although information available from a single photograph is highly insufficient for fully correct refocusing, the results show that visually plausible refocused images can be obtained.

关键词： Image restoration Focusing Digital cameras computer graphics Image processing Layout Deconvolution Lenses Application software Optical arrays

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Local injectivity conditions of 2D and 3D uniform cubic B-spline functions

Local injectivity conditions of 2D and 3D uniform cubic B-sp...

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pacific conference on computer graphics and applications

作者： Yongchoel Choi Seungyong Lee Department of Computer Science and Engineering Pohang University of Science and Technology Pohang South Korea

Uniform cubic B-spline functions have been used for mapping functions in various areas such as image warping and morphing, 3D deformation, and volume morphing. The injectivity (one-to-one property) of a mapping function is important to obtain good results in these areas. We consider the local injectivity conditions of 2D and 3D uniform cubic B-spline functions. We propose a geometric interpretation of the local injectivity of a uniform cubic B-spline function, with which 2D and 3D cases can be handled in a similar way. Based on the geometric interpretation, we present sufficient conditions for the local injectivity that are represented in terms of control point displacements. These sufficient conditions are simple and easy to check and will be useful to guarantee the injectivity of mapping functions in application areas.

关键词： Spline Lattices Electrical capacitance tomography computer science Reactive power computer graphics World Wide Web Sufficient conditions

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Progressive geometry compression for meshes

Progressive geometry compression for meshes

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pacific conference on computer graphics and applications

作者： Xinguo Liu Hujun Bao PhengAnn Heng TienTsin Wong Hanqiu Sun Qunsheng Peng State Key Laboratory of CAD&CG University of Zhejiang China Department of Computer Science and Engineering Chinese University of Hong Kong Hong Kong China

ISBN: (纸本)0769508685

A novel progressive geometry compression scheme is presented in this paper. In this scheme, a mesh is represented as a base mesh followed by some groups of vertex split operations using an improved simplification method in which each level of the mesh can be refined into the next level by carrying out a group of vertex split operations in any order. Consequently, the progressive mesh (PM) representation can be effectively encoded by permuting the vertex split operations in each group. Meanwhile, a geometry predictor using the Laplacian operator is designed to predict each new vertex position using its neighbours. The correction is quantized and encoded using a Huffman coding scheme. Experimental results show that our algorithm obtains higher compression ratios than previous work. It is very suitable for the progressive transmission of geometric models over the Internet.

关键词： Solid modeling Computational geometry Internet Information geometry computer science Laplace equations Huffman coding computer graphics Application software Bandwidth

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Segmentation of 3D meshes through spectral clustering

Segmentation of 3D meshes through spectral clustering

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pacific conference on computer graphics and applications

作者： Rong Liu Hao Zhang GrUVi Lab School of Computing Science Simon Fraser University Burnaby BC Canada

ISBN: (纸本)0769522483

We formulate and apply spectral clustering to 3D mesh segmentation for the first time and report our preliminary findings. Given a set of mesh faces, an affinity matrix which encodes the likelihood of each pair of faces belonging to the same group is first constructed. Spectral methods then use selected eigenvectors of the affinity matrix or its closely related graph Laplacian to obtain data representations that can be more easily clustered. We develop an algorithm that favors segmentation along concave regions, which is inspired by human perception. Our algorithm is theoretically sound, efficient, simple to implement, andean achieve high-quality segmentation results on 3D meshes.

关键词： Image segmentation Clustering algorithms Shape control Humans Object recognition Application software Geometry computer graphics Laplace equations Pervasive computing

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