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A Skeleton-Based Approach for Consistent Segmentation Transfer

JOURNAL OF INFORMATION SCIENCE AND ENGINEERING 2014年第4期30卷 1053-1070页

作者： Wong, Sai-Keung Yang, Jau-An Ho, Tan-Chi Chuang, Jung-Hong Natl Chiao Tung Univ Dept Comp Sci Hsinchu 300 Taiwan

We present a skeleton-based approach for mapping consistently a segmentation of a source mesh to a target mesh. The source and target meshes are semantically similar but their geometries may be different. We assume that the segmentation of the source mesh and the skeleton correspondence between the meshes are provided. Our method first establishes the skeleton-boundary correspondence and then performs the boundary transfer procedure. The skeleton-boundary correspondence is useful for computing approximately the target boundaries. The boundary transfer procedure aims to produce the segment boundaries of the target mesh such that their geometric details are consistent to the ones of the corresponding source segment boundaries. We have applied our method for various models and compared with the state-of-the-art techniques. Our method computes segment boundaries of the target mesh which are similar to the ones of the source mesh.

关键词： segmentation transfer skeleton correspondence consistent segmentation geometric algorithms skeleton-boundary correspondence

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Sets of Globally Optimal Stream Surfaces for Flow Visualization

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COMPUTER GRAPHICS FORUM 2014年第3期33卷 1-10页

作者： Schulze, M. Esturo, J. Martinez Guenther, T. Roessl, C. Seidel, H. -P. Weinkauf, T. Theisel, H. Univ Magdeburg D-39106 Magdeburg Germany

Stream surfaces are a well-studied and widely used tool for the visualization of 3D flow fields. Usually, stream surface seeding is carried out manually in time-consuming trial and error procedures. Only recently automatic selection methods were proposed. Local methods support the selection of a set of stream surfaces, but, contrary to global selection methods, they evaluate only the quality of the seeding lines but not the quality of the whole stream surfaces. Global methods, on the other hand, only support the selection of a single optimal stream surface until now. However, for certain flow fields a single stream surface is not sufficient to represent all flow features. In our work, we overcome this limitation by introducing a global selection technique for a set of stream surfaces. All selected surfaces optimize global stream surface quality measures and are guaranteed to be mutually distant, such that they can convey different flow features. Our approach is an efficient extension of the most recent global selection method for single stream surfaces. We illustrate its effectiveness on a number of analytical and simulated flow fields and analyze the quality of the results in a user study.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling&mdash geometric algorithms languages and systems

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Remeshing-assisted Optimization for Locally Injective Mappings

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COMPUTER GRAPHICS FORUM 2014年第5期33卷 269-279页

作者： Jin, Y. Huang, J. Tong, R. Zhejiang Univ State Key Lab CAD & CG Hangzhou Zhejiang Peoples R China Zhejiang Univ Artificial Intelligence Inst Hangzhou Zhejiang Peoples R China Zhejiang Univ Cyber Innovat Joint Res Ctr Hangzhou Zhejiang Peoples R China

Constructing locally injective mappings for 2D triangular meshes is vital in applications such as deformations. In such a highly constrained optimization, the prescribed tessellation may impose strong restriction on the solution. As a consequence, the feasible region may be too small to contain an ideal solution, which leads to problems of slow convergence, poor solution, or even that no solution can be found. We propose to integrate adaptive remeshing into interior point method to solve this issue. We update the vertex positions via a parameter-free relaxation enhanced geometry optimization, and then use edge-flip operations to reduce the residual and keep a reasonable condition number for better convergence. For more robustness, when the iteration of interior point method terminates but leaves the positional constraints unsatisfied, we estimate the edges in the current tessellation that block vertices moving based on the convergence information of the optimization, and then split neighboring edges to break the restriction. The results show that our method has better performance than the solely geometric optimization approaches, especially for extreme deformations.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.5 [Computer Graphics] Computational Geometry and Object Modeling&mdash geometric algorithms languages and systems

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Pose partitioning for multi-resolution segmentation of arbitrary mesh animations

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COMPUTER GRAPHICS FORUM 2014年第2期33卷 293-302页

作者： Vasilakis, Andreas A. Fudos, Ioannis Univ Ioannina Dept Comp Sci & Engn GR-45110 Ioannina Greece

We present a complete approach to efficiently deriving a varying level-of-detail segmentation of arbitrary animated objects. An over-segmentation is built by combining sets of initial segments computed for each input pose, followed by a fast progressive simplification which aims at preserving rigid segments. The final segmentation result can be efficiently adjusted for cases where pose editing is performed or new poses are added at arbitrary positions in the mesh animation sequence. A smooth view of pose-to-pose segmentation transitions is offered by merging the partitioning of the current pose with that of the next pose. A perceptually friendly visualization scheme is also introduced for propagating segment colors between consecutive poses. We report on the efficiency and quality of our framework as compared to previous methods under a variety of skeletal and highly deformable mesh animations.

关键词： Categories and Subject Descriptors (according to ACM CCS): I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling&mdash geometric algorithms languages and systems I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism&mdash Animation

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Pattern-Based Quadrangulation for N-Sided Patches

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COMPUTER GRAPHICS FORUM 2014年第5期33卷 177-184页

作者： Takayama, Kenshi Panozzo, Daniele Sorkine-Hornung, Olga Swiss Fed Inst Technol Zurich Switzerland

We propose an algorithm to quadrangulate an N-sided patch (2 <= N <= 6) with prescribed numbers of edge subdivisions at its boundary. Our algorithm is guaranteed to succeed for arbitrary valid input, which is proved using a canonical simplification of the input and a small set of topological patterns that are sufficient for supporting all possible cases. Our algorithm produces solutions with minimal number of irregular vertices by default, but it also allows the user to choose other feasible solutions by solving a set of small integer linear programs. We demonstrate the effectiveness of our algorithm by integrating it into a sketch-based quad remeshing system. A reference C++ implementation of our algorithm is provided as a supplementary material.

关键词： Categories and Subject Descriptors (according to ACM CCS) I.3.3 [Computer Graphics]: Computational Geometry and Object Modeling&mdash geometric algorithms languages and systems

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Efficient triangulation of Poisson-disk sampled point sets

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VISUAL COMPUTER 2014年第6-8期30卷 773-785页

作者： Guo, Jianwei Yan, Dong-Ming Bao, Guanbo Dong, Weiming Zhang, Xiaopeng Wonka, Peter Chinese Acad Sci Inst Automat LIAMA NLPR Beijing Peoples R China King Abdullah Univ Sci & Technol Visual Comp Ctr Thuwal Saudi Arabia

In this paper, we present a simple yet efficient algorithm for triangulating a 2D input domain containing a Poisson-disk sampled point set. The proposed algorithm combines a regular grid and a discrete clustering approach to speedup the triangulation. Moreover, our triangulation algorithm is flexible and performs well on more general point sets such as adaptive, non-maximal Poisson-disk sets. The experimental results demonstrate that our algorithm is robust for a wide range of input domains and achieves significant performance improvement compared to the current state-of-the-art approaches.

关键词： Triangulation Poisson-disk sampling geometric algorithms

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Hierarchical structures for collision checking between virtual characters

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COMPUTER ANIMATION AND VIRTUAL WORLDS 2014年第3-4期25卷 333-342页

作者： Stuevel, Sybren A. Magnenat-Thalmann, Nadia Thalmann, Daniel Egges, Arjan van der Stappen, A. Frank Univ Utrecht VHTLab Dept Informat & Comp Sci Utrecht Netherlands Univ Utrecht VHTLab Utrecht Netherlands Nanyang Technol Univ Inst Media Innovat Singapore 639798 Singapore

Simulating a crowded scene like a busy shopping street requires tight packing of virtual characters. In such cases, collisions are likely to occur, and the choice in collision detection shape will influence how characters are allowed to intermingle. Full collision detection is too expensive for crowds, so simplifications are needed. The most common simplification, the fixed-width, pose-independent cylinder, does not allow intermingling of characters, as it will either cause too much empty space between characters or undetected penetrations. As a possible solution to this problem, we introduce the bounding cylinder hierarchy (BCH), a bounding volume hierarchy that uses vertical cylinders as bounding shapes. Because the BCH is a generalization of the single cylinder, we expect that this representation can be easily integrated with existing crowd simulation systems. We compare our BCH with commonly used collision shapes, namely the single cylinder and oriented bounding box tree, in terms of query time, construction time, and represented volume. To get an indication of possible crowd densities, we investigate how close characters can be before collision is detected and finally propose a critical maximum depth for the BCH. Copyright (c) 2014 John Wiley & Sons, Ltd.

关键词： collision detection hierarchical data structure geometric algorithms shape approximation

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Efficient triangulation of Poisson-disk sampled point sets

Efficient triangulation of Poisson-disk sampled point sets

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31st CGI conference

关键词： Triangulation Poisson-disk sampling geometric algorithms

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An Approximation Algorithm for the Continuous k-Medians Problem in a Convex Polygon

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INFORMS JOURNAL ON COMPUTING 2014年第2期26卷 280-289页

作者： Carlsson, John Gunnar Jia, Fan Li, Ying Univ Minnesota Dept Ind & Syst Engn Minneapolis MN 55455 USA

We give a fast and simple factor 2.74 approximation algorithm for the problem of choosing the k medians of the continuum of demand points defined by a convex polygon C. Our algorithm first surrounds the input region with a bounding box, then subdivides the bounding box into subregions with equal area. Simulation results on the convex hulls of the 50 states in the United States show that the practical performance of our algorithm is within 10% of the optimal solution in the vast majority of cases.

关键词： approximation algorithms geometric algorithms continuous location theory

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Fast and accurate evaluation of regularized Boolean operations on triangulated solids

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COMPUTER-AIDED DESIGN 2013年第3期45卷 705-716页

作者： Feito, F. R. Ogayar, C. J. Segura, R. J. Rivero, M. L. Univ Jaen Dept Comp Sci EPS Jaen Jaen 23071 Spain Univ Jaen Dept Comp Sci EUP Linares Jaen 23700 Spain

In this paper we present a robust and accurate method for evaluating regularized Boolean operations on triangulated solids. It allows the exact evaluation of the regularized union, intersection, difference and symmetric difference simultaneously. Moreover, this approach is simpler than other methods, including those that provide an approximate evaluation or only a rendering of the result. It is based on a simple data structure and on the use of an octree which facilitates the division of the geometry into subsets for distribution among several threads, and accelerates the spatial queries needed during the process. This method is designed to be used in a multithreaded environment and it can also be implemented using an out-of-core approach. We also present some experimental results, and a comparison with other systems that also provide an exact evaluation of the Boolean operations. (C) 2012 Elsevier Ltd. All rights reserved.

关键词： Boundary representations geometric algorithms Boolean operations Triangular meshes

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