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Evaluation for Small Visual Difference Between Conforming Meshes on Strain Field

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Journal of Computer Science & Technology 2009年第1期24卷 65-75页

作者：边哲胡事民 ralph R.martin Department of Computer Science and Technology Tsinghua University School of Computer Science Cardiff UniversityCardiffU.K.

This paper gives a method of quantifying small visual differences between 3D mesh models with conforming topology, based on the theory of strain fields. Strain field is a geometric quantity in elasticity which is used to describe the deformation of elastomer. In this paper we consider the 3D models as objects with elasticity. The further demonstrations are provided： the first is intended to give the reader a visual impression of how our measure works in practice; and the second is to give readers a visual impression of how our measure works in evaluating filter algorithms. Our experiments show that our difference estimates are well correlated with human perception of differences. This work has applications in the evaluation of 3D mesh watermarking, 3D mesh compression reconstruction, and 3D mesh filtering.

关键词： 3D conforming meshes mesh comparison perception strain fields

3D Morphing Using Strain Field Interpolation

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Journal of Computer Science & Technology 2007年第1期22卷 147-155页

作者：严寒冰胡事民 ralph R martin National Computer Network Emergency Response Technical Team/Coordination Center of China Beijing 100029 China Department of Computer Science and Technology Tsinghua University Beijing 100084 China School of Computer Science Cardiff University Cardiff U.K.

In this paper, we present a new technique based on strain fields to carry out 3D shape morphing for applications in computer graphics and related areas. Strain is an important geometric quantity used in mechanics to describe the deformation of objects. We apply it in a novel way to analyze and control deformation in morphing. Using position vector fields, the strain field relating source and target shapes can be obtained. By interpolating this strain field between zero and a final desired value we can obtain the position field for intermediate shapes. This method ensures that the 3D morphing process is smooth. Locally, volumes suffer minimal distortion, and no shape jittering or wobbling happens： other methods do not necessarily have these desirable properties. We also show how to control the method so that changes of shape （in particular, size changes） vary linearly with time.

关键词： morphing strain field interpolation

Livestock detection in aerial images using a fully convolutional network

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Computational Visual Media 2019年第2期5卷 221-228页

作者： Liang Han Pin Tao ralph R.martin Department of Computer Technology and Application Qinghai UniversityXiningChina Department of Computer Science and Technology Tsinghua UniversityBeijingChina School of Computer Science and Informatics Cardiff UniversityCardiffWalesUK

In order to accurately count the number of animals grazing on grassland, we present a livestock detection algorithm using modified versions of U-net and Google Inception-v4 net. This method works well to detect dense and touching instances. We also introduce a dataset for livestock detection in aerial images, consisting of 89 aerial images collected by quadcopter. Each image has resolution of about 3000 ×4000 pixels, and contains livestock with varying shapes,scales, and *** evaluate our method by comparison against Faster RCNN and Yolo-v3 algorithms using our aerial livestock dataset. The average precision of our method is better than Yolo-v3 and is comparable to Faster RCNN.

关键词： livestock detection segmentation classification

Static Scene Illumination Estimation from Videos with Applications

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Journal of Computer Science & Technology 2017年第3期32卷 430-442页

作者： Bin Liu Nun Xu ralph R. martin Department of Computer Science and Technology Tsinghua University Beijing 100084 China School of Computer Science and Informatics Cardiff University Cardiff CF243AA U.K.

We present a system that automatically recovers scene geometry and illumination from a video, providing a basis for various applications. Previous image based illumination estimation methods require either user interaction or external information in the form of a database. We adopt structure-from-motion and multi-view stereo for initial scene reconstruction, and then estimate an environment map represented by spherical harmonics （as these perform better than other bases）. We also demonstrate several video editing applications that exploit the recovered geometry and illumination, including object insertion （e.g., for augmented reality）, shadow detection, and video relighting.

关键词： video processing augmented reality illumination recovery

New advances in visual computing for intelligent processing of visual media and augmented reality

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Science China(Technological Sciences) 2015年第12期58卷 2210-2211页

作者： WANG JuHong ZHANG SongHai martin ralph R. Department of Computer Science and Technology Tsinghua University School of Computer Science & Informatics Cardiff University

Visual imagery constitutes the most important sensory information for *** entire field of acquiring,analyzing and synthesizing visual data by means of computers is called visual *** has an extraordinarily wide range of applications,including for example:industrial quality control,street view and driver assistance systems,robot navigation,multimedia systems,and computer games.

关键词： Augmented reality Intelligent computing

As-Rigid-As-Possible Surface Morphing

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Journal of Computer Science & Technology 2011年第3期26卷 548-557页

作者：刘亚姝严寒冰 ralph R.martin Department of Computer Science Beijing University of Civil Engineering and Architecture National Computer Network Emergency Response Technical Team/Coordination Center of China School of Computer Science Cardiff University

This paper presents a new morphing method based on the ＂as-rigid-as-possible＂ approach. Unlike the original as-rigid-as-possible method, we avoid the need to construct a consistent tetrahedral mesh, but instead require a consistent triangle surface mesh and from it create a tetrahedron for each surface triangle. Our new approach has several significant advantages. It is much easier to create a consistent triangle mesh than to create a consistent tetrahedral mesh. Secondly, the equations arising from our approach can be solved much more efficiently than the corresponding equations for a tetrahedral mesh. Finally, by incorporating the translation vector in the energy functional controlling interpolation, our new method does not need the user to arbitrarily fix any vertex to obtain a solution, allowing artists automatic control of interpolated mesh positions.

关键词： morphing simplex transformation interpolation

Improving Shape from Shading with Interactive Tabu Search

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Journal of Computer Science & Technology 2016年第3期31卷 450-462页

作者： Jing Wu Paul L. Rosin Xianfang Sun ralph R. martin School of Computer Science and Informatics Cardiff University Cardiff CF24 3AA U.K.

Optimisation based shape from shading （SFS） is sensitive to initialization： errors in initialization are a signifi- cant cause of poor overall shape reconstruction. In this paper, we present a method to help overcome this problem by means of user interaction. There are two key elements in our method. Firstly, we extend SFS to consider a set of initializations, rather than to use a single one. Secondly, we efficiently explore this initialization space using a heuristic search method, tabu search, guided by user evaluation of the reconstruction quality. Reconstruction results on both synthetic and real images demonstrate the effectiveness of our method in providing more desirable shape reconstructions.

关键词： shape from shading user interaction tabu search

Harmonic Field Based Volume Model Construction from Triangle Soup

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Journal of Computer Science & Technology 2010年第3期25卷 562-571页

作者：沈超慧张国鑫来煜坤胡事民 ralph R. martin Tsinghua National Laboratory for Information Science and Technology Department of Computer Science and Technology Tsinghua University School of Computer Science Cardiff University

Surface triangle meshes and volume data are two commonly used representations of digital geometry. Converting from triangle meshes to volume data is challenging, since triangle meshes often contain defects such as small holes, internal structures, or self-intersections. In the extreme case, we may be simply presented with a set of arbitrarily connected triangles, a ＂triangle soup＂. This paper presents a novel method to generate volume data represented as an octree from a general 3D triangle soup. Our motivation is the Faraday cage from electrostatics. We consider the input triangles as forming an approximately closed Faraday cage, and set its potential to zero. We then introduce a second conductor surrounding it, and give it a higher constant potential. Due to the electrostatic shielding effect, the resulting electric field approximately lies in that part of space outside the shape implicitly determined by the triangle soup. Unlike previous approaches, our method is insensitive to small holes and internal structures, and is observed to generate volumes with low topological complexity. While our approach is somewhat limited in accuracy by the requirement of filling holes, it is still useful, for example, as a preprocessing step for applications such as mesh repair and skeleton extraction.

关键词： volume model triangle soup harmonic field representation conversion mesh repair

Panorama completion for street views

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Computational Visual Media 2015年第1期1卷 49-57页

作者： Zhe Zhu ralph R.martin Shi-Min Hu TNLIST Department of Computer Science and Technology Tsinghua University School of Computer Science & Informatics Cardiff University

This paper considers panorama images used for street views. Their viewing angle of 360° causes pixels at the top and bottom to appear stretched and warped. Although current image completion algorithms work well, they cannot be directly used in the presence of such distortions found in panoramas of street views. We thus propose a novel approach to complete such 360° panoramas using optimizationbased projection to deal with distortions. Experimental results show that our approach is efficient and provides an improvement over standard image completion algorithms.

关键词： image completion panorama street views structure-rectifying warp