检索结果-内蒙古大学图书馆

A heat flow based relaxation scheme for n dimensional discrete hyper surfaces

computerS & graphics-UK 2018年第Apr.期71卷 124-131页

作者： Livesu, Marco CNR IMATI Genoa Italy

We consider the problem of relaxing a discrete (n - 1) dimensional hyper surface defining the boundary between two adjacent n dimensional regions in a discrete segmentation. This problem often occurs in computer graphics and vision, where objects are represented by discrete entities such as pixel/voxel grids or polygonal/polyhedral meshes, and the resulting boundaries often expose a typical jagged behavior. We propose a relaxation scheme that replaces the original boundary with a smoother version of it, defined as the level set of a continuous function. The problem has already been considered in recent years, but current methods are specifically designed to relax curves on triangulated discrete 2-manifolds embedded in R-3, and do not clearly scale to multiple discrete representations or to higher dimensions. Our biggest contribution is a smoothing operator entirely based on three canonical differential operators: namely the Laplacian, gradient and divergence. These operators are ubiquitous in applied mathematics, are available for a variety of discretization choices, and exist in any dimension. To the best of the author's knowledge, this is the first intrinsically dimension-independent method, and can be used to relax curves on 2-manifolds, surfaces in R-3, or even hyper-surfaces in R-n. We demonstrate our method on a variety of discrete entities, spanning from triangular, quadrilateral and polygonal surfaces, to solid tetrahedral meshes. (C) 2018 Elsevier Ltd. All rights reserved.

关键词： Diffusion Smoothing Implicit hyper surfaces Heat flow

来源：评论

学校读者我要写书评

暂无评论

A Multi Patch Warping Approach for Improved Stereo Block Matching 12

A Multi Patch Warping Approach for Improved Stereo Block Mat...

引用

12th International Joint Conference on computer vision, Imaging and computer graphics Theory and Applications (VISIGRAPP)

作者： Muresan, Mircea Paul Nedevschi, Sergiu Danescu, Radu Tech Univ Cluj Napoca Dept Comp Sci Dept Cluj Napoca Romania

ISBN: (纸本)9789897582271

Stereo cameras are a suitable solution for reconstructing the 3D information of the observed scenes, and, because of their low price and ease to set up and operate, they can be used in a wide area of applications, ranging from autonomous driving to advanced driver assistance systems or robotics. Due to the high quality of the results, energy based reconstruction methods like semi global matching have gained a lot of popularity in recent years. The disadvantages of semi global matching are the large memory footprint and the high computational complexity. In contrast, window based matching methods have a lower complexity, and are leaner with respect to the memory consumption. The downside of block matching methods is that they are more error prone, especially on surfaces which are not parallel to the image plane. In this paper we present a novel block matching scheme that improves the quality of local stereo correspondence algorithms. The first contribution of the paper consists in an original method for reliably reconstructing the environment on slanted surfaces. The second contribution consists in the creation of set of local constraints that filter out possible outlier disparity values. The third and final contribution consists in the creation of a refinement technique which improves the resulted disparity map. The proposed stereo correspondence approach has been validated on the KITTI stereo dataset.

关键词： Dense Stereo Block Matching Slanted surfaces Disparity Refinement Binary Descriptors

来源：评论

学校读者我要写书评

暂无评论

A Complex-Valued Field Model for Shape Representation with Applications in computer vision and graphics

A Complex-Valued Field Model for Shape Representation with A...

引用

作者： Corring, John R. University of Florida

学位级别：Ph.D.

Shape processing and analysis is a growing area of research straddling computer vision and computer graphics. Probability density and signed distance representations have become central to the field. While modeling uncertainty about observations and providing a convex representation, probability densities lack geometric precision and often exhibit topological inaccuracies. Signed distances lack the robustness of densities and the geometry of the feature space is very complicated. In this thesis, we develop a parametric model for approximating signed distance functions. This allows us to build up a useful shape representation with accurate topological and geometric data from point and normal estimates. The representation is approximately linear under union of parameters, thus allowing for easy computation and conventional statistical methods to be leveraged for shape processing. We develop an algorithm for registering oriented point-sets that leverages the representation. We compare this algorithm with various contenders in registration. We also develop algorithms for mesh extraction from sparsely scattered oriented points, dimensionality reduction on a collection of shapes, and approximation of distance functions on Riemannian surfaces. Empirical validation of all of the approaches outlined in this work is performed. Theoretical contributions include the description of a family of curves for which the representation converges uniformly, clarification of the regularizing principle on the geometric component of the representation, and an analysis of the asymptotic behavior of the representation with respect to the magnitude variance and frequency variance parameters.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Heat flow based relaxation of n dimensional discrete hyper surfaces

Heat flow based relaxation of n dimensional discrete hyper s...

引用

2017 Italian Chapter Conference - Smart Tools and Apps in computer graphics, STAG 2017

作者： Livesu, Marco CNR IMATI Genoa Italy

ISBN: (纸本)9783038680482

We consider the problem of relaxing a discrete (n − 1) dimensional hyper surface defining the boundary between two adjacent n dimensional regions in a discrete segmentation. This problem often occurs in computer graphics and vision, where objects are represented by discrete entities such as pixel/voxel grids or polygonal/polyhedral meshes. A common approach consists in assigning to each element of the domain a value (or label). Elements sharing the same label belong to the same region, whereas elements with different labels belong to different regions. Segmentation boundaries are therefore only intrinsically defined, and amount to the union of the interfaces between adjacent elements having different label, which tend to be geometrically poor and expose a typical jagged behavior. We propose a relaxation scheme that replaces the original boundary with a smoother version of it, defined as the level set of a continuous function. The problem has already been considered in recent years, but current methods are specifically designed to relax curves on discrete 2-manifolds embedded in R3, and do not clearly scale to multiple discrete representations or to higher dimensions. Our biggest contribution is a smoothing operator that is based only on three canonical differential operators: namely the Laplacian, gradient and divergence. These operators are ubiquitous in applied mathematics, are available for a variety of discretization choices, and exist in any dimension. To the best of the author's knowledge, this is the first intrinsically dimension-independent method, and can be used to relax curves on 2-manifolds, surfaces in R3, or even hyper-surfaces in Rn. As such, not only it is useful to refine the boundaries of discrete segmentations, but also for applications like data mining, where clustering in high dimensional spaces often occur, and the refinement of the clusters' boundaries may be beneficial for classification algorithms. © 2017 The Author(s) Eurographics Proceedin

关键词： Data mining

来源：评论

学校读者我要写书评

暂无评论

Mitre :: Esd Technical Reports :: Esd-Tr-70-202 Information Processing Techniques for Networking and graphics Research Jun70

引用

2016年

[Auto Generated] SECTION I. TECHNICAL SUMMARY 1 SECTION II. INTRODUCTION 3 SECTION iii. TECHNICAL DISCUSSIONS 5 3.1 Three Dimensional curves and surfaces 5 3.2 Iterative Techniques for computer graphics 6 3.3 computer-Assisted Design of Complex Organic Molecular Syntheses 7 3.A SPLOT, A PDP-1 Hard Copy Facility 7 3.5 Music 3 8 3.6 A Tree Manipulator 8 3.7 Curve Fitting 12 3.8 The Synchronous Wheel 13 3.9 A computer graphics System for Non-Standard Characters 14 3.10 Voynich Manuscript 14 3.11 A

关键词： color complex organic computer computer display computer graphics curves dimensional curves display esd-tr-70-202 graphics hard copy harvard information jun70 mitre networking organic molecular program rand tablet surfaces techniques three dimensional todd wipke unclassified security voynich

来源：评论

学校读者我要写书评

暂无评论

Structuring 3D medial skeletons: A comparative study 21

Structuring 3D medial skeletons: A comparative study

引用

21st International Symposium on vision, Modeling and Visualization, VMV 2016

作者： Delame, T. Kustra, J. Telea, A. INRIA France Philips Research Netherlands Institute Johann Bernoulli Univ. of Groningen Netherlands

ISBN: (纸本)9783038680253

Medial skeletons provide an effective alternative to boundary or volumetric representations for applications that focus on shape structure. This capability is provided by the skeletal structure, i.e., the curves and surfaces computed from centers of maximally inscribed balls by a process called structuration. Many several structuration methods exist, all having various challenges in terms of delivering a high-quality medial skeleton. This paper provides a first overview of existing structuration methods. We formally define the skeletal structure by giving its theoretical properties, and use these properties to propose quality criteria for structurations. We next review existing structuration methods and compare them using the established criteria. The obtained insights help both practitioners in choosing a suitable structuration method and researchers in further perfecting such methods. © 2016 The Author(s) Eurographics Proceedings © 2016 The Eurographics Association.

关键词： computer graphics

来源：评论

学校读者我要写书评

暂无评论

Photogrammetric computer vision 1st ed. 2016

引用

丛书名： Geometry and Computing

2016年

作者： Wolfgang Förstner Bernhard P. Wrobel

ISBN: (数字)9783319115504

ISBN: (纸本)9783319115498

This textbook offers a statistical view on the geometry of multiple view analysis, required for camera calibration and orientation and for geometric scene reconstruction based on geometric image features. The authors have backgrounds in geodesy and also long experience with development and research in computer vision, and this is the first book to present a joint approach from the converging fields of photogrammetry and computer vision. Part I of the book provides an introduction to estimation theory, covering aspects such as Bayesian estimation, variance components, and sequential estimation, with a focus on the statistically sound diagnostics of estimation results essential in vision metrology. Part II provides tools for 2D and 3D geometric reasoning using projective geometry. This includes oriented projective geometry and tools for statistically optimal estimation and test of geometric entities and transformations and their relations, tools that are useful also in the context of uncertain reasoning in point clouds. Part iii is devoted to modelling the geometry of single and multiple cameras, addressing calibration and orientation, including statistical evaluation and reconstruction of corresponding scene features and surfaces based on geometric image features. The authors provide algorithms for various geometric computation problems in vision metrology, together with mathematical justifications and statistical analysis, thus enabling thorough evaluations. The chapters are self-contained with numerous figures and exercises, and they are supported by an appendix that explains the basic mathematical notation and a detailed index. The book can serve as the basis for undergraduate and graduate courses in photogrammetry, computer vision, and computer graphics. It is also appropriate for researchers, engineers, and software developers in the photogrammetry and GIS industries, particularly those engaged with statistically based geometric computer vision methods.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Fast parallel solver for the levelset equations on unstructured meshes

引用

CONCURRENCY AND COMPUTATION-PRACTICE & EXPERIENCE 2015年第7期27卷 1639-1657页

作者： Fu, Zhisong Yakovlev, Sergey Kirby, Robert M. Whitaker, Ross T. Univ Utah Sci Comp & Imaging Inst Salt Lake City UT 84112 USA

The levelset method is a numerical technique that tracks the evolution of curves and surfaces governed by a nonlinear partial differential equation (levelset equation). It has applications within various research areas such as physics, chemistry, fluid mechanics, computer vision, and microchip fabrication. Applying the levelset method entails solving a set of nonlinear partial differential equations. This paper presents a parallel algorithm for solving the levelset equations on unstructured 2D and 3D meshes. By taking into account constraints and capabilities of different computing architectures, the method is suitable for both the coarse-grained parallelism found on CPU-based systems and the fine-grained parallelism of modern massively single instruction, multiple data architectures such as graphics processors. In order to solve the levelset equations efficiently, we combine the narrowband scheme with a domain decomposition that is adapted for several different architectures. We also introduce a novel parallelism strategy, which we call hybrid gathering, which allows regular and lock-free computations of local differential operators. Finally, we provide the detailed description of the implementation and data structures for the proposed strategies, as well as performance data for both CPU and graphics processing unit implementations. Copyright (c) 2014 John Wiley & Sons, Ltd.

关键词： levelset equations unstructured meshes parallel computing graphics processing unit

来源：评论

学校读者我要写书评

暂无评论

A geodesic based approach for an accurate and invariant 3D surfaces representation 23

A geodesic based approach for an accurate and invariant 3D s...

引用

23rd International Conference in Central Europe on computer graphics, Visualization and computer vision, WSCG 2015

作者： Jribi, Majdi Ghorbel, Faouzi CRISTAL Laboratory GRIFT research group ENSI La Manouba University La manouba2010 Tunisia

ISBN: (纸本)9788086943664

In this paper, we propose a novel 3D invariant surface representation under the 3D motion group M(3). It is obtained by combining two main representations: the three-polar representation and the one defined by the radial line curves from a starting point. The retained invariant points correspond to the geometrical locations of the intersection between the two last representations. The approximation of the novel surfaces description method on the 3D discrete meshes is studied. Its accuracy for the 3D faces description and retrieval is evaluated in the mean of the Hausdorff shape distance.

关键词： Geodesy

来源：评论

学校读者我要写书评

暂无评论

Characterizing the performance of an image-based recognizer for planar mechanical linkages in textbook graphics and hand-drawn sketches

引用

computerS & graphics-UK 2015年第Nov.期52卷 1-17页

作者： Eicholtz, Matthew Kara, Levent Burak Carnegie Mellon Univ Dept Mech Engn Pittsburgh PA 15213 USA

In this work, we present a computational framework for automatically generating kinematic models of planar mechanical linkages from raw images. The hallmark of our approach is a novel combination of supervised learning methods for detecting mechanical parts (e.g. joints, rigid bodies) with the optimizing power of a multiobjective evolutionary algorithm, which concurrently maximizes image consistency and mechanical feasibility. A rigorous set of experiments was conducted to systematically evaluate the performance of each phase in our framework, comparing various combinations of joint and body detection schemes and feasibility constraints. Precision-recall curves are used to assess object detection performance. For the optimization, in addition to standard accuracy measures such as top-N accuracy, we introduce a new performance metric called user effort ratio that quantifies the amount of user interaction required to correct an inaccurate optimization solution. Current state-of-the-art performance is achieved with (i) one (or a cascade of) support vector machines for joint detection, (ii) foreground extraction to reduce false positives, (iii) supervised body detection using normalized geodesic time, distance, and detected joint confidence, and (iv) feasibility constraints derived from graph theory. The proposed framework generalizes moderately well from textbook graphics to hand-drawn sketches, and user effort ratio results demonstrate the potential power of an interactive system in which simple user interactions complement computer recognition for fast kinematic modeling. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： computer vision Evolutionary multiobjective optimization Image processing Kinematic modeling Object recognition Sketch recognition

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：