检索结果-内蒙古大学图书馆

Single-knot wavelets for non-uniform B-splines

COMPUTER AIDED GEOMETRIC DESIGN 2005年第9期22卷 849-864页

作者： Bertram, M TU Kaiserslautern Kaiserslautern Germany

We propose a flexible and efficient wavelet construction for non-uniform B-spline curves and surfaces. The method allows to remove knots in arbitrary order minimizing the displacement of control points when a knot is re-inserted. Geometric detail subtracted from a shape by knot removal is represented by an associated wavelet coefficient replacing one of the control points at a coarser level of detail. From the hierarchy of wavelet coefficients, perfect reconstruction of the original shape is obtained. Both knot removal and insertion have local impact. Wavelet synthesis and analysis are both computed in linear time, based on the lifting scheme for biorthogonal wavelets. The method is perfectly suited for multiresolution surface editing, progressive transmission, and compression of spline curves and surfaces. (c) 2005 Elsevier B.V. All rights reserved.

关键词： multiresolution modeling hierarchical splines wavelet lifting

来源：评论

学校读者我要写书评

暂无评论

CyberWalk: A web-based distributed virtual walkthrough environment

引用

IEEE TRANSACTIONS ON MULTIMEDIA 2003年第4期5卷 503-515页

作者： Chim, J Lau, RWH Leong, HV Si, A Hong Kong Polytech Univ Dept Comp Hong Kong Hong Kong Peoples R China City Univ Hong Kong Dept Comp Sci & Comp Engn & Informat Technol Kowloon Hong Kong Peoples R China Oracle Corp Redwood Shores CA 94065 USA

A distributed virtual walkthrough environment allows users connected to the geometry server to walk through a specific place of interest, without having to travel physically. This place of interest may be a virtual museum, virtual library or virtual university. There are two basic approaches to distribute the virtual environment from the geometry server to the clients, complete replication and on-demand transmission. Although the on-demand transmission approach saves waiting time and optimizes network usage, many technical issues need to be addressed in order for the system to be interactive. CyberWalk is a web-based distributed virtual walkthrough system developed based on the on-demand transmission approach. It achieves the necessary performance with a multiresolution caching mechanism. First, it reduces the model transmission and rendering times by employing a progressive multiresolution modeling technique. Second, it reduces the Internet response time by providing a caching and prefetching mechanism. Third, it allows a client to continue to operate, at least partially, when the Internet is disconnected. The caching mechanism of CyberWalk tries to maintain at least a minimum resolution of the object models in order to provide at least a coarse view of the objects to the viewer. All these features allow CyberWalk to provide sufficient interactivity to the user for virtual walkthrough over the Internet environment. In this paper, we demonstrate the design and implementation of CyberWalk. We investigate the effectiveness of the multiresolution caching mechanism of CyberWalk in supporting virtual walkthrough applications in the Internet environment through numerous experiments, both on the simulation system and on the prototype system.

关键词： distributed virtual environments model prefetching multiresolution caching multiresolution modeling virtual walkthrough

来源：评论

学校读者我要写书评

暂无评论

Confetti: Object-space point blending and splatting

引用

IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS 2004年第5期10卷 598-608页

作者： Pajarola, R Sainz, M Guidotti, P Univ Calif Irvine Dept Comp Sci Irvine CA 92697 USA Univ Calif Irvine Dept Math Irvine CA 92697 USA

In this paper, we present Confetti, a novel point-based rendering approach based on object-space point interpolation of densely sampled surfaces. We introduce the concept of a transformation-invariant covariance matrix of a set of points which can efficiently be used to determine splat sizes in a multiresolution point hierarchy. We also analyze continuous point interpolation in object-space and we define a new class of parameterized blending kernels as well as a normalization procedure to achieve smooth blending. Furthermore, we present a hardware accelerated rendering algorithm based on texture mapping and alpha-blending as well as programmable vertex and pixel-shaders.

关键词： point-based rendering multiresolution modeling level-of-detail hardware accelerated blending

来源：评论

学校读者我要写书评

暂无评论

View-dependent pruning for real-time rendering of trees

引用

COMPUTERS & GRAPHICS-UK 2011年第2期35卷 364-374页

作者： Gumbau, Jesus Chover, Miguel Remolar, Inmaculada Rebollo, Cristina Univ Jaume 1 Inst New Imaging Technol Castellon de La Plana Spain

The main problem in the real-time rendering of vegetation is the massive amount of primitives to be rendered. These primitives are needed to fully describe the geometry of the plants. However, some of them are not visible depending on the location of the viewer. This work focuses on this fact to interactively reduce the amount of geometry needed to represent the foliage through a view-dependent multiresolution scheme. Following a camera-dependent criterion, the less visible parts of the foliage are detected in real time, and rendered with a decreased level of detail for improving efficiency. This fact considerably reduces the extraction and the visualization time of the geometry that represents the foliage. The novelty of the presented method is that its design is oriented to being efficient on massively parallel architectures, such as the graphics processing unit. Moreover, we introduce a new management system for efficiently handling level of detail objects in order to improve performance for forest scenes. (C) 2010 Elsevier Ltd. All rights reserved.

关键词： Vegetable species Real-time rendering multiresolution modeling Hardware oriented

来源：评论

学校读者我要写书评

暂无评论

An In-Network Querying Framework for Wireless Sensor Networks

引用

IEEE TRANSACTIONS ON PARALLEL AND DISTRIBUTED SYSTEMS 2009年第8期20卷 1202-1215页

作者： Demirbas, Murat Lu, Xuming Singla, Puneet SUNY Buffalo Dept Comp Sci & Engn Buffalo NY 14260 USA SUNY Buffalo Dept Mech & Aerosp Engn Buffalo NY 14260 USA

In contrast to traditional wireless sensor network (WSN) applications that perform only data collection and aggregation, the new generation of information processing applications such as pursuit-evasion games, tracking, evacuation, and disaster relief applications require in-network information storage and querying. Due to the resource limitations of WSNs, it is challenging to implement in-network querying in a distributed, lightweight, resilient, and energy-efficient manner. We address these challenges by exploiting location information and the geometry of the network and propose an in-network querying framework, namely, the Distributed Quad-Tree (DQT). DQT is distance sensitive for querying of an event: the cost of answering a query for an event is at most a constant factor (2 root 2 in our case) of the distance "d" to the event. DQT construction is local and does not require any communication. Moreover, due to its minimalist infrastructure and stateless nature, DQT shows graceful resilience to node failures and topology changes. Since event-based querying is inherently limited to the anticipated types of inquiries, we further extend our framework to achieve complex range-based querying. To this end, we use a multiresolution algorithm, which is optimal with respect to least square errors that models the data in a decentralized way. Our model-based scheme answers queries with approximate values accompanied by certainty levels with increased resolution at lower layers of the DQT hierarchy. Our analysis and experiments show that our framework achieves distance sensitivity and resiliency for event-based querying, as well as greatly reduces the cost of complex range querying.

关键词： Distributed Quad-Tree distance-sensitive in-network querying multiresolution modeling wireless sensor networks

来源：评论

学校读者我要写书评

暂无评论

Volume and Normal Field Based Simplification of Polygonal Models

引用

JOURNAL OF INFORMATION SCIENCE AND ENGINEERING 2013年第2期29卷 267-279页

作者： Hussain, Muhammad King Saud Univ Coll Comp & Informat Sci Dept Comp Sci Riyadh 11451 Saudi Arabia

In automatic decimation of polygonal models, the measure of geometric fidelity plays the key role. Among the existing measures, volume based error measure results in better quality approximations whereas the one based on normal field variation better preserves salient features. We exploit both volume and normal field to develop a more reliable and efficient two phase greedy algorithm. In the first phase, the priority of each vertex is defined using the normal field variation across its one-ring neighborhood. In the second phase, the desired number of vertices is removed according to their priorities. Once a vertex is a candidate for removal, it is eliminated by collapsing an outgoing half-edge that is selected by using the measure of geometric fidelity based on volume loss. Subjective and objective comparisons validate that the proposed algorithm not only has better speed-quality trade-off but also consumes less memory space and keeps visually important features even after drastic simplification in a better way than the similar state-of-the-art best algorithms. This method is useful for applications where computing coordinates and/or attributes other than those attached to the original vertices is not allowed by the application and the focus is on both speed and quality of LODs.

关键词： polygonal models polygonal simplification LOD modeling multiresolution modeling half-edge-collapse

来源：评论

学校读者我要写书评

暂无评论

Compressed progressive meshes (vol 6, pg 79, 2000)

引用

IEEE TRANSACTIONS ON VISUALIZATION AND COMPUTER GRAPHICS 2000年第2期6卷 190-192页

作者： Pajarola, R Rossignac, J Information and Computer Science Department University of California Irvine Graphics Visualization and Usablity Center Georgia Institute of Technology

Most systems that support visual interaction with 3D models use shape representations based on triangle meshes. The size of these representations imposes limits on applications for which complex 3D models must be accessed remotely. Techniques for simplifying and compressing 3D models reduce the transmission time. multiresolution formats provide quick access to a crude model and then refine it progressively. Unfortunately, compared to the best nonprogressive compression methods, previously proposed progressive refinement techniques impose a significant overhead when the full resolution model must be downloaded. The CPM (Compressed Progressive Meshes) approach proposed here eliminates this overhead. It uses a new technique, which refines the topology of the mesh in batches, which each increase the number of vertices by up to 50 percent. Less than an amortized total of 4 bits per triangle encode where and how the topological refinements should be applied. We estimate the position of new vertices from the positions of their topological neighbors in the less refined mesh using a new estimator that leads to representations of vertex coordinates that are 50 percent more compact than previously reported progressive geometry compression techniques.

关键词： Triangle mesh compression Progressive Meshes multiresolution modeling Geometry Compression

来源：评论

学校读者我要写书评

暂无评论

A Multiscale Approach for Geologically and Flow Consistent modeling

引用

TRANSPORT IN POROUS MEDIA 2018年第1期124卷 237-261页

作者： Tahmasebi, Pejman Kamrava, Serveh Univ Wyoming Dept Petr Engn Laramie WY 82071 USA

Subsurface geological models are usually constructed on high-resolution grids in a way that various complexities and heterogeneities are depicted properly. Such models, however, cannot be used directly in the current flow simulators, as they are tied with high computational cost. Thus, using upscaling, by which one can produce flow consistent models that can alleviate the computational burden of flow simulators, is inevitable. Although the upscaling methods are able to reproduce the flow responses, they might not retain the initial geological assumptions. The reservoir models are initially constructed on uniform and high-resolution grids and then, if necessary, are upscaled to be used for flow simulations. A subsurface modeling approach that not only preserves the geological heterogeneity but also provides models that can be used, straight or with a small level of upscaling, in the flow simulators is desirable. In this paper, a new multiresolution method based on (1) the importance of conditioning well data and (2) being geologically and flow consistent is presented. This method discretizes the initial model into several regions based on the available data. Then, the initial assumed geological model is converted into, for example, various high- and low-resolution models. Next, the high-resolution model is used for regions with high-quality data (e.g., well locations), while the low-resolution model is used for the remaining areas. Finally, the patterns of these areas are interlocked, which result in a multiresolution geologically and flow consistent subsurface model. The accuracy of this method is demonstrated using two-phase flow simulation on four complex subsurface systems. The results indicate that the same flow responses, in a much less time, are reproduced using the multiscale models. The speed-up factor gained using the proposed method is also several orders of magnitude.

关键词： Two-phase flow multiresolution modeling Geological model SPE-10 Data assimilation

来源：评论

学校读者我要写书评

暂无评论

Control of polygonal mesh resolution for 3-D computer vision

GRAPHICAL MODELS AND IMAGE PROCESSING

引用

GRAPHICAL MODELS AND IMAGE PROCESSING 1998年第4期60卷 261-285页

作者： Johnson, AE Hebert, M CALTECH Jet Prop Lab Pasadena CA 91109 USA Carnegie Mellon Univ Inst Robot Pittsburgh PA 15213 USA

A common representation in 3-D computer vision is the polygonal surface mesh because meshes can model objects of arbitrary shape and are easily constructed from sensed 3-D data. The resolution of a surface mesh is the overall spacing between vertices that comprise the mesh. Because sensed 3-D points are often unevenly distributed, the resolution of a surface mesh is often poorly defined. We present an algorithm that transforms a mesh with an uneven spacing between vertices into a mesh with a more even spacing between vertices, thus improving its definition of resolution, In addition, we show how the algorithm can be used to control the resolution of surface meshes, making them amenable to multiresolution approaches in computer vision. The structure of our algorithm is modeled on iterative mesh simplification algorithms common in computer graphics;however, the individual steps in our algorithm are designed specifically to control mesh resolution. An even spacing between vertices is generated by applying a sequence of local edge operations that promote uniform edge lengths while preserving mesh shape. To account for polyhedral objects, we introduce an accurate shape change measure that permits edge operations along sharp creases. By locally bounding the total change in mesh shape, drastic changes in global shape are prevented. We show results from many 3-D sensing domains including computed tomography, range imaging, and digital elevation map construction. (C) 1998 Academic Press.

关键词： polygonal mesh surface simplification multiresolution modeling shape approximation 3-D computer vision

来源：评论

学校读者我要写书评

暂无评论

Visualizer:: a mesh visualization system using view-dependent refinement

引用

COMPUTERS & GRAPHICS-UK 2002年第3期26卷 491-503页

作者： Güdükbay, U Arikan, O Özgüç, B Bilkent Univ Dept Comp Engn TR-06533 Bilkent Turkey Univ Calif Berkeley Dept Elect Engn & Comp Sci Comp Sci Div Berkeley CA 94720 USA

Arbitrary triangle mesh is a collection of 3D triangles without any shape or boundary restrictions, Progressive mesh (PM) is a multiresolution representation that defines continuous level of detail approximations for arbitrary triangle meshes. PM representation of a mesh can be processed to obtain a mesh approximation between the original and the base (simplified) mesh. Furthermore, PM can be refined in a view-dependent fashion to obtain a simpler mesh within a perceptual image quality. In this paper, we introduce an adaptation and improvements in our implementation for view-dependent refinement of progressive meshes. Essentially, we use a similar approach to Hoppe's framework (ACM Comput. Graphics, Proceedings of SIGGRAPH'97, August 1997, pp. 189-198) for view-dependent refinement with a different algorithm for constructing PM representation. Our method is simple to implement and fast enough to achieve interactive frame rates for moderately complex models (models containing hundreds of thousands of polygons) on a machine with polygon rendering hardware. Moreover, our implementation allows changes to topology and achieves a simpler and sometimes more realistic refinements. (C) 2002 Elsevier Science Ltd. All rights reserved.

关键词： view-dependent refinement multiresolution modeling progressive mesh mesh visualization

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：