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12th International Conference on Computer-Aided Design and Computer Graphics, CAD/Graphics 2011

作者： Hu, Kai-Mo Wang, Bin Yuan, Bin Yong, Jun-Hai School of Software Tsinghua University Beijing 100084 China Department of Computer Science and Technology Tsinghua University Beijing 100084 China Key Laboratory for Information System Security Ministry of Education Beijing 100084 China Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China

ISBN: (纸本)9780769544977

Selecting the best views for 3D objects is useful for many applications. However, with the existing methods applied in CAD models, the results neither exhibit the 3D structures of the models fairly nor conform to human's browsing habits. In this paper, we present a robust method to generate the canonical views of CAD models, and the above problem is solved by considering the geometry and visual salient features simultaneously. We first demonstrate that for a CAD model, the three coordinate axes can be approximately determined by the scaled normals of its faces, such that the pose can be robustly normalized. A graph-based algorithm is also designed to accelerate the searching process. Then, a convex hull based method is applied to infer the upright orientation. Finally, four isometric views are selected as candidates, and the one whose depth image owns the most visual features is selected. Experiments on the Engineering Shape Benchmark (ESB) show that the views generated by our method are pleasant, informative and representative. We also apply our method in the calculation of model rectilinearity, and the results demonstrate its high performance. © 2011 IEEE.

关键词： Computer aided design

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Multi-resolution mesh fitting by B-spline surfaces for reverse engineering

Multi-resolution mesh fitting by B-spline surfaces for rever...

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12th International Conference on Computer-Aided Design and Computer Graphics, CAD/Graphics 2011

作者： Zhang, Sen Li, Zhigang Zhang, Hui Yong, Junhai School of Software Tsinghua University Beijing 100084 China Department of Computer Science and Technology Tsinghua University Beijing 100084 China Key Laboratory for Information System Security Ministry of Education Beijing 100084 China Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China

ISBN: (纸本)9780769544977

This paper presents a new multi-resolution mesh fitting algorithm, extending the adaptive patch-based fitting scheme where each underlying quadrilateral is recursively subdivided into four sub-patches. In this paper, the G1 continuity constraints, which mainly consist of perpendicular constraints and twist compatibility constraints, are deduced for B-spline patches. In order to construct a unique B-spline patch for each quadrilateral, the mesh vertices are applied in a least-square approximation, and the energy functions associated with a patch are minimized. In contrast to the original algorithm, this paper fits the mesh into B-spline patches instead of Bézier patches with G1 continuity. The B-spline patches make the algorithm have more free control points to be used for optimizing the shape of the quadrilateral patches to achieve higher flexible patch control and less recursive times. © 2011 IEEE.

关键词： Reverse engineering

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An optimal color mapping strategy based on energy minimization for time-varying data

An optimal color mapping strategy based on energy minimizati...

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12th International Conference on Computer-Aided Design and Computer Graphics, CAD/Graphics 2011

作者： Peng, Yi Dong, Jie Chen, Li Chu, Haiyang Yong, Junhai School of Software Tsinghua University Beijing 100084 China Department of Computer Science and Technology Tsinghua University Beijing 100084 China Key Laboratory for Information System Security Ministry of Education Beijing 100084 China Tsinghua National Laboratory for Information Science and Technology Beijing 100084 China

ISBN: (纸本)9780769544977

Color mapping plays a critical role in visualization of time-varying data and also sets a challenge for researchers due to the consistency of mapping and great changes in time-varying data. In order to solve this problem and generate feature-prominent animation, we present a two phase optimization technique using bilateral filtering and global energy functions. In the first phase, for each time step, we use a weighted mapping function which combines linear mapping and feature histogram. In the second phase, an optimization function taking global color mapping and minimum color difference into consideration is designed. So users can clearly distinguish between data in variable time steps and easily understand the corresponding relationships between different structures. The experiments' results show that our method can achieve high quality visualization for both static and time-varying data. © 2011 IEEE.

关键词： Visualization

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Rough set approach for attributes selection of traditional Malay musical instruments sounds classification

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2nd International Conference on Ubiquitous Computing and Multimedia Applications, UCMA 2011

作者： Senan, Norhalina Ibrahim, Rosziati Mohd Nawi, Nazri Yanto, Iwan Tri Riyadi Herawan, Tutut Faculty of Information Technology and Multimedia Universiti Tun Hussein Onn Malaysia Johor Malaysia Department of Mathematics Universitas Ahmad Dahlan Yogyakarta Indonesia Faculty of Computer System and Software Engineering Universiti Malaysia Pahang Malaysia

ISBN: (纸本)9783642209970

Feature selection has become very important research in musical instruments sounds for handling the problem of 'curse of dimensionality'. In literature, various feature selection techniques have been applied in this domain focusing on Western musical instruments sounds. However, study on feature selection using rough sets of non-Western musical instruments sounds including Malay Traditional musical instruments is inadequate and still needs an intensive research. Thus, in this paper, an alternative feature selection technique using rough set theory based on Maximum Degree of dependency of Attributes (MDA) technique proposed by [8] for Traditional Malay musical instruments sounds is proposed. The modeling process comprises eight phases: data acquisition, sound editing, data representation, feature extraction, data discretization, data cleansing, feature selection using proposed technique and feature validation via classification. The results show that the highest classification accuracy of 99.82% was achieved from the best 17 features with 1-NN classifier. © 2011 Springer-Verlag.

关键词： Rough set theory

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Improved stochastic progressive photon mapping with Metropolis sampling

Improved stochastic progressive photon mapping with Metropol...

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Eurographics Symposium on Rendering 2011

作者： Chen, Jiating Wang, Bin Yong, Jun-Hai School of Software Tsinghua University Beijing China Department of Computer Science and Technology Tsinghua University Beijing China Key Laboratory for Information System Security Ministry of Education of China Beijing China Tsinghua National Laboratory for Information Science and Technology Beijing China

This paper presents an improvement to the stochastic progressive photon mapping (SPPM), a method for robustly simulating complex global illumination with distributed ray tracing effects. Normally, similar to photon mapping and other particle tracing algorithms, SPPM would become inefficient when the photons are poorly distributed. An inordinate amount of photons are required to reduce the error caused by noise and bias to acceptable levels. In order to optimize the distribution of photons, we propose an extension of SPPM with a Metropolis-Hastings algorithm, effectively exploiting local coherence among the light paths that contribute to the rendered image. A well-designed scalar contribution function is introduced as our Metropolis sampling strategy, targeting at specific parts of image areas with large error to improve the efficiency of the radiance estimator. Experimental results demonstrate that the new Metropolis sampling based approach maintains the robustness of the standard SPPM method, while significantly improving the rendering efficiency for a wide range of scenes with complex lighting. © 2011 The Author(s).

关键词： Photons

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The Modelling and Verification of PLC Program Based on Interactive Theorem Proving Tool COQ

The Modelling and Verification of PLC Program Based on Inter...

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2011 International Conference on Computer Science and information technology(ICCSIT 2011)

作者： Litian Xiao Mengyuan Li Ming Gu Jiaguang Sun National Laboratory for Information Science and Technology Key Laboratory for Information System Security Ministry of EducationDepartment of Computer Science and Technology School of Software Tsinghua University Beijing Special Engineering Design and Research Institute National Laboratory for Information Science and Technology Key Laboratory for Information System Security Ministry of Education Department of Computer Science and Technology School of Software Tsinghua University

COQ is an interactive theorem proving tool. The paper abstractly describes the feature of COQ, the architecture and working modes of PLC program with the example of typical PLC. It also introduces the first-order logic syntax and semantics of Intuitionistic Logic. It briefly introduces the main Gallina language syntax elements, the corresponding use methods and main theorem proving tactic on COQ. The work has modeled kernel data type and basic statements and and the denotational semantics of PLC program with Gallina. It has given the correctness proof of PLC program based on theorem proving, i.e. based on semantics function the relationship of configuration between the before codes execution and the after is proved. The main purpose is to prove whether a PLC program satisfies certain nature within a scan period.

关键词： PLC Program, Embedded system, Verification, Denotational Semantics, Theorem Proving, COQ

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Converting sectional views to three orthographic views to reconstruct 3D models

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Computer-Aided Design and Applications 2011年第4期8卷 571-582页

作者： Ding, Fengqing Zhang, Hui Wen, Yamei School of Software Tsinghua University China Tsinghua National Laboratory for Information Science and Technology China Department of Computer Science and Technology Tsinghua University China Key Laboratory for Information System Security Ministry of Education

Compared with the CSG-based approach, the Brep-based approach has several advantages to construct 3D models from 2D engineering drawings, such as the structure is simpler and the domain of objects that can be handled is wider. However, this approach cannot handle sectional views directly. In this paper, a new method of converting sectional views to three orthographic views is presented. Firstly, the views which have the same projection direction are merged into one view. If the number of views is two, then a new view will be added according to the coordinate relations. Secondly, elements which have been omitted in sectional views are recovered according to the matching information of the existing edges. Finally, the existing Brepbased approach is used to reconstruct the 3D models. The algorithm can handle full sections, broken-out sections, offset sections as well as two orthographic views. The algorithm has been validated by experiments. © 2011 CAD Solutions, LLC.

关键词： Three dimensional computer graphics

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A multi-objective evolutionary algorithm for minimal visual coverage path problem in raster Terrain

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ICIC Express Letters 2011年第7期5卷 2299-2304页

作者： Li, Jie Zheng, Chang Wen Hu, Xiaohui Department of Electronic Engineering and Information Science University of Science and Technology of China Hefei 230026 China National Key Laboratory of Integrated Information System Technology Institute of Software Chinese Academy of Sciences Beijing 100190 China

Minimal visual coverage path problem has wide applications, such as selecting the marching route and searching the smuggler's path. Average horizon of a path, which is the ratio of its visual coverage to its length, can be used to measure how covert a path is. If there are loops in a path, the path is meaningless though its average horizon is small due to its infinite length. A compromise is to modify the objective of minimal average horizon as the ratio of the length to the invisible region of the path where minimal length and minimal view shed can be satisfied simultaneously. However, the modified objective is not completely equivalent with average horizon. This study treats two elements of average horizon as two objectives and presents a multi-objective evolutionary algorithm for the minimal path visual coverage problem with single objective. By multiobjectivizating as well as the proper chromosome structure and effective operators, the method presented is superior to the simulated annealing algorithm and the evolutionary algorithm for single objective with respect to both higher quality of the solution and less computation time.

关键词： Evolutionary algorithms

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A linear algorithm for pseudo recognition in 3D reconstruction

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Computer-Aided Design and Applications 2011年第6期8卷 827-839页

作者： Li, Qi Zhang, Hui School of Software Tsinghua University China Department of Computer Science and Technology Tsinghua University China Key Laboratory for Information System Security Ministry of Education China Tsinghua National Laboratory for Information Science and Technology China

Pseudo recognition is essential to reconstruct correct 3D models from engineering drawings. This paper proposes a novel linear algorithm to recognize pseudo elements based on the existence of non-manifold edges. First, mini face loops are defined to construct correct face loops and avoid overlapped loops, which previous loop construction methods would always result in when pseudo elements exist. Then, suspect faces whose all boundary edges are non-manifold edges, are defined to reduce the searching space of the algorithm for pseudo recognition, thus the algorithm can achieve linear time complexity. The algorithm is applicable for wireframe models including planes and basic conicoid surfaces. Experimental results are provided to demonstrate the algorithm. © 2011 CAD Solutions.

关键词： Three dimensional computer graphics

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A hypervolume based approach for minimal visual coverage shortest path

A hypervolume based approach for minimal visual coverage sho...

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Congress on Evolutionary Computation

作者： Jie Li Changwen Zheng Xiaohui Hu Department of Electronic Engineering and Information Science University of Science and Technology Hefei China National Key Laboratory of Integrated Information System Technology Institute of Software Chinese Academy and Sciences Beijing China

In this paper, the minimal visual coverage shortest path in raster terrain is studied with the proposal of a hypervolume contribution based multiobjective evolutionary approach. The main feature of the presented method is that all individuals in the population are periodically replaced by the selected non-dominated candidates in the archive based on hypervolume contribution, besides the well designed evolutionary operators and some popular techniques such as dominated relation and archive. Our algorithm may obtain well distributed Pareto set approximation efficiently, which is superior to the implementations based on the framework of NSGA-II and SMS EMOA with respect to the hypervolume.

关键词： Visualization Biological cells Approximation methods Evolutionary computation Tin Optimization Approximation algorithms

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