大型网格模型简化和多分辨率技术综述

网格简化和多分辨率绘制是2种对于提高绘制性能非常有效的技术,但对于大型网格模型,这2种技术的设计和实现本身也存在诸多难点.文中综述了大型网格模型简化和多分辨率技术的研究进展,首先分析和比较基于网格分割、基于外存数据结构和基于流式策略的大型网格模型简化方法,然后介绍和比较大型网格模型多分辨率表示的设计、构建和绘制技术.最后总结并展望了该研究领域的发展趋势.     

大型网格模型多分辨率的外存构建与交互绘制

结合多分辨率、网格排布和基于视点的绘制技术,提出一种外存多分辨率构建和绘制算法.采用适应性八叉树对模型的包围盒进行划分,自顶向下构建模型的多分辨率层次结构,较好地保持了原模型的细节分布;并对多分辨率结构中每个节点所包含的三角形片段进行网格排布优化,降低了缓存的平均失效率;在实时绘制时,采用基于视点的细节层次选择策略进行模型的细化;最后通过引入数据预取机制来隐藏磁盘I/O延时,进一步提高绘制性能.实验结果表明,该算法在绘制速度与细节保留上均优于同类MRMM算法.     

分布式并行绘制系统中带宽降低方法的研究

把静态与视点无关网格简化技术和动态与视点相关的网格简化技术结合起来，根据应用领域的要求，采用考虑了离散曲率边折叠算法构造的多分辨率模型，把得到的简化模型提交给与视点相关的网格简化技术处理，在基于联网PC的分布式并行绘制系统中实现模型的渐进传输并进行实时绘制；同时采用几何索引等方式来降低立即模式分布式系统的网络传输数据量，进一步缓解网络带宽压力，增强数据的实时动态交互性。     

视相关地形多分辨率模型在飞行仿真中的应用

对于飞行仿真中海量地形数据,现有的软硬件无法直接对其进行实时连续的绘制,采用视点相关的层次细节模型可以有效地提高实时绘制的性能.该文针对飞行仿真中大地形实时显示问题,对现有的视点相关多分辨率模型算法进行了改进,采用四叉树结构来表示地形,给出了节点的数据结构和构建四叉树的算法;提出了一种新的细节层次选择误差度量标准;实现了视点相关的连续多分辨率地形网格的简化和实时绘制.     

一种基于多区域并行的网格模型简化的两步法

针对三角形网格模型简化中保持细节特征的要求，引入了图像的区域分割原理，提出了一种基于区域生长的网格模型区域分割方法．在此基础之上，提出了一种基于多区域并行的自适应三角网格模型简化的两步法，对于不同的区域采取按照比例进行简化的并行机制．此方法的特点是保持模型细节的基础上，大大地加快了模型的简化速度．另外，还提出了一种基于多区域并行的累进网格模型的实现方法，有效地实现了保持细节特征的多分辨率模型，并实现了具有细节特征的多分辨模型间的层次过渡．经实验证明，该方法能够快速有效地对三角形网格模型进行简化，并具有保持模型的三角形网格密度分布的特点．     

基于混合多细节层次技术的实时绘制算法

细节层次是实时图形生成的一项重要技术.提出一种把视点无关和视点相关两类多细节层次技术结合起来的网格模型实时绘制算法.该算法首先根据应用领域的不同要求或用户给出的误差范围,对模型进行与视点无关的预处理简化,然后把简化后得到的模型用在与视点相关的实时简化算法中.实验表明,这种网格模型简化和绘制算法能在损失很小的屏幕像素误差的前提下大大提高绘制速度.     

保留细节特征的轮廓线远程绘制算法

目前,智能掌上电脑、个人数字助理和智能手机等移动终端因为其便携性和可移动性,越来越多地被应用于分布式虚拟环境中,但是因为移动终端自身的局限性,在移动终端上的3维模型实时绘制问题仍未得到很好的解决。结合多分辨率网格模型和基于轮廓线的远程绘制的优点,提出了一种保留细节特征的轮廓线远程绘制算法。该算法预处理阶段,在原始精细网格模型上提取细节特征线,并进行多分辨率网格模型的预处理;运行时阶段,根据视点、帧率等交互信息使用选取策略对细节特征线进行选取,然后构建合适的多分辨率网格模型,并在该模型上提取出外围轮廓线,最后发送这两种轮廓线到移动终端进行绘制。实验结果表明,该算法在基于轮廓线的远程绘制中较好地保留了模型的细节特征,并保证了在移动终端的实时绘制。     

基于视点的网格模型快速简化算法

在计算机图形学中，经常采用网格模型对物体和场景进行描述，而网格模型的大数据量成为实时绘制的瓶颈。因此，必须对网格模型进行简化，目前的简化算法，主要是以网格模型几何误差的最小化为准则，而忽略了模型的视觉特征。文章提出了一种基于视点的网格模型简化算法，其简化准则是视觉特征的最优化，利用视点相关，建立视点与网格精度的对应关系，对距离视点较近的部分采用较密网格，对距视点较远的部分采用稀疏网格。实验结果表明，该算法能够在保证高度真实感视觉效果的前提下，实现模型较大幅度的简化。     

一种点面混合的复杂三维模型加速绘制方法

在主流个人计算机硬件条件下，为加速百万以上三角面片构成的复杂稠密几何模型的绘制速度，综合基于几何的建模与绘制方法GBMR和基于点的建模与绘制方法PBMR的优点，提出了一种同时使用三角面片和点作为基本单元进行对象建模与绘制的点面混合方法．在预处理阶段，对模型表面进行网格分割，存储子块三角面片和顶点点云数据，同时对顶点点云按顶点重要度排序并序列化为线性结构．在实时绘制阶段，进行视相关的裁剪和背面剔除，不同子块按视点距离分别由三角形或点进行绘制．以上过程充分利用图形处理单元GPU，实现了基于GPU的点面混合的对象连续多分辨率绘制，有效地提高了复杂模型的绘制效率．     

复杂模型的视点依赖简化算法

为了达到在虚拟环境的漫游系统中对复杂模型进行实时绘制的目的，通常采用多层次细节模型来解决这一问题，给出一种即与视点相关又无须对原来的复杂模型进行预处理的网格简化算法，该算法采用精细(refinement)法．每次绘制前都从最粗糙的模型开始，根据视点位置、视方向和模型的每个部分产生的误差，对影响视觉效果大的部分进行细分(subdivision)，逐步产生可显示的模型，实验表明，本文提出的网格简化算法能在对视觉效果影响不大的前提下大大降低需要绘制的三角形数量。     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

Call for Papers The 6^th International Conference on Grid and Cooperative Computing

Recent years have seen rapid advances in various grid-related technologies, middleware, and applications. The GCC conference has become one of the largest scientific events worldwide in grid and cooperative computing. The 6th international conference on grid and cooperative computing (GCC2007) Sponsored by China Computer Federation (CCF),Institute of Computing Technology, Chinese Academy of Sciences (ICT) and Xinjiang University ,and in Cooperation with IEEE Computer Soceity ,is to be held from August 16 to 18, 2007 in Urumchi, Xinjiang, China.     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.     

A pragmatic multi-method investigation of discrepant technological events: Coping,attributions, and ‘accidental’ learning

Discrepant technological events or situations that entail a problem, a misunderstanding or a difficulty with the Information Technology (IT) being employed, are common in the workplace, and can lead to frustration and avoidance behaviors. Little is known, however, about how individuals cope with these events. This paper examines these events by using a multi-method pragmatic approach informed by coping theory. The results of two studies – a critical incident study and an experiment – serve to build and test, respectively, a theoretical model that posits that individuals use a variety of strategies when dealing with these events: they experience negative emotions, make external attributions, and adopt engagement coping strategies directed at solving the event, eventually switching to a disengagement coping strategy when they feel they have no control over the situation. Furthermore, users’ efforts may result in ‘accidental’ learning as they try to overcome the discrepant IT events through engagement coping. The paper ends with a discussion of the results in light of existing literature, future opportunities for research, and implications for practice.     

The Distributed Time-Triggered Simulation Scheme: Core Principles and Supporting Execution Engine

Distributed real-time simulation is a young technology field but its practice is under increasing demands. In recent years the author and his collaborators have been establishing a new approach called the distributed time-triggered simulation (DTS) scheme which is conceptually simple and easy to use but widely applicable. The concept was initiated in the course of developing a new-generation object-oriented real-time programming scheme called the time-triggered message-triggered object (TMO) programming scheme. Some fundamental issues inherent in distributed real-time simulation that were learned during recent experimental studies are discussed along with some approaches for resolving the issues. An execution engine developed to support both the TMOs engaged in control computation and the TMOs engaged in DTS is also discussed along with its possible extensions that will enable significantly larger-scale DTSs.     

Software-Konfigurationsmanagement in großen Softwareprojekten

Zusammenfassung Mit zunehmender Größe der Softwaresysteme verschärfen sich die für die Software-Herstellung typischen Probleme: Beherrschen großer Objektmengen, Erhalten der Systemkonsistenz, Kontrolle der ständigen Änderungseinflüsse und Gewährleisten einer langen Lebensdauer. Die Disziplin Konfigurationsmanagement bildet den methodischen Ansatz, diese Probleme besser zu beherrschen. Software-Konfigurationsmanagement faßt die Herstellung von Softwaresystemen als eine Abfolge von kontrollierten Änderungen an gesicherten Zwischen- und Endergebnissen auf. Dargestellt werden die Objekte und Funktionen des Software-Konfigurationsmanagements sowie die hierfür in großen Software-Projekten benötigten Methoden, Instanzen und Hilfsmittel.     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and     

Editorial:Brain-machine interface(BMI) and cyborg intelligence

正Brain-machine interfaces(BMIs)aim at building a direct communication pathway between the brain and an external device,and represent an area of research where significant progress has been made during the past decade.Based on BMIs,mind information can be read out by neural signals to control     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate