一种支持大规模多种精度地形的实时绘制算法

为加强大规模地形数据的表现能力,通常采用地形叠加或地形编辑等方法在局部地形数据上构建更高精度的细节模型.因而如何将大规模地形数据与具有高精度的细节数据进行实时融合与绘制成为一个迫切需要解决的问题.基于Geometry Clipmap方法对这一问题开展研究,给出了一种支持大规模多种精度地形的实时绘制算法.在预处理阶段,对大规模地形数据采用clipmap结构进行组织,对细节数据使用mipmap结构进行组织;在运行阶段,重点针对clipmap更新所引起的不同种精度数据间特有的"F"形空洞进行分析和处理,使用过渡带结构对空洞区域进行修补,并对修补后的顶点进行了平滑处理.实验结果表明,该方法有效解决了"F"形空洞并支持大规模地形及细节数据的实时绘制.     

基于Geometry Clipmap的三维地形可视化研究

随着数字科技的广泛应用和信息化普及的逐渐深入,实现地形的三维可视化的重要性日渐彰显。但目前的普通PC内存容量无法容纳海量的几何数据和纹理数据。为解决这个问题并提高绘制的效率,采用Geometry Clipmap算法绘制地形,充分利用GPU以提高绘制效率,通过顶点纹理获取各顶点高程值。同时,简化了三角形条带的组织方式,使用简化的视锥体裁剪方法和动态确定绘制层数方法减少需要绘制的顶点数。根据特定层结构,提出数据更新的新方法(二进制定位法)减少视点移动时各帧的数据更新量。实验结果表明,该方法使用很少的内存完成大规模地形绘制,且取得了较高的帧率,漫游流畅,保证了地形的真实感,能满足大规模地形实时可视化的要求。     

基于四叉树分割的连续LOD漫游地形绘制

针对大规模地形数据访问量大、场景渲染消耗内存大、实时渲染效率低的问题,提出了一种基于四叉树分割的连续LOD(层次细节)地形绘制方案,实现了多分辨率地形的快速绘制.视见体裁剪算法判断次数少,并结合四叉树分割过程,快速地对地形数据进行裁剪.采用与视点和地形粗糙度相关的分割评价系统,在预处理阶段对地形粗糙度误差进行计算,提升了地形实时绘制的速度:同时对分割标志位按位存储,使得内存占有率大幅减少.通过分割低分辨率节点边的方式,消除了节点间裂缝.算法运行效果良好,在普通PC机上即可达到较高的帧频率和较好的漫游效果.     

大规模地形无缝漫游技术研究*

针对大规模地形动态漫游提出实现流程和算法框架,基于分层分块地形LOD组织存储策略完成数据预处理,绘制阶段提出视点相关的地形调度和简化算法,利用多线程处理机制进行地形块裁剪和内外存数据交换,借助GPU硬件实现场景加速绘制算法,并提出分块地形和纹理数据的无缝拼接策略。真实数据实验的算法比较和性能测试结果表明,该方法具有支持数据量大,绘制效率高、实用性强等特点。     

基于GPGPU的海量山地地形数据的实时绘制算法

针对山地地形海量数据的特点,基于GPU的Geometrical Clipmap算法,应用简化的工作流程,结合GPGPU技术,采用了一种更为合理的高程数据组织交换模式,通过引入高程误差数据巧妙地解决不同分辨率之间的裂缝问题,并对高分辨率的遥感影像作为地形纹理的实现方法加以补充,进而实现可应用于虚拟现实系统的海量地形数据的实时可视化.     

基于Geometry Clipmap算法的大规模地形可视化研究

大规模地形可视化一直是实时计算机图形学的研究瓶颈,归因于地形数据的海量性与实时计算机图形学的实时性之间的矛盾。基于Geometry Clipmap算法提出一个扩展的大规模地形实时渲染的解决方案,在高效地利用现代图形学硬件的同时,有效地减少批次渲染的三角形面片数量。在使用合适的数据调度算法之后,使无限大小地形的实时漫游成为可能。     

大规模地形的LOD生成算法研究

为了实时地绘制大规模地形数据,提出了一种改进的实时连续LOD生成算法.该算法采用分块分层的思想,首先将大规模高程数据进行分块,然后对块中数据按照分辨率的大小分层存储.根据视点位置和网格空间对象误差的关系建立基于四叉树的LOD模型,从而提高了大规模地形的绘制效率.使用该方法描述了太湖流域的地形,取得了良好的绘制效果.     

基于LOD的自适应无裂缝地形渲染

提出了一种新型三角形簇作为GPU的图元绘制单元,结合LOD技术实现了自适应的无裂缝地形渲染.该三角形簇,称为N-簇,分为8种基本类型,不同尺寸和位置的地形网格块都可以通过这8种基本类型进行缩放和平移得到.采用二叉树数据结构组织N-簇,每个二叉树节点对应一种N-簇,同时存储了N-簇的缩放及平移.结合八边形误差算法进行场景LOD的构建,避免了不同LOD层次间过滤产生的T-连接.由于大规模地形的高程数据量及纹理数据量非常庞大,不能一次性载入内存,采用四叉树数据结构分块组织高程数据和纹理数据,在程序运行时进行数据块的动态加载.实验结果表明,N-簇提高了地形三角形网格的绘制效率,同时,整个算法能自适应地进行无裂缝地形渲染,并能满足大规模地形场景实时绘制的要求.     

基于Mipmap的大规模地形绘制算法与仿真

研究大规模地形与纹理数据动态可视化算法与仿真问题。针对大规模地形与纹理数据动态可视化实时显示难题,提出一种基于Mipmap的大规模地形动态绘制算法,实现模型数据库组织与管理的高效性、场景调度的实时性,以北京市地形数据为仿真模型,实现大规模地形与纹理数据动态可视化算法与实时仿真。上述算法在Mipmap技术的基础上,首先利用双线性内插算法把离散的原始数据生成规则网格DEM,然后采用四叉树结构的LOD算法简化海量地形和纹理数据,最后使用四队列分页调度、基于视域的LRU算法释放内存、多线程并行处理的场景优化策略来进行动态调度和绘制。结合OSG和Open GL渲染引擎,将基于Mipmap的大规模地形绘制算法应用在北京市地形绘制中,仿真结果表明,上述算法比传统的CLOD地形瓦片绘制算法,具有更快的渲染绘制速率,并且能够快速绘制北京市地形数据和在不同场景下进行快速浏览。     

大规模地形真三维可视化系统设计与实现*

对已有算法进行了综合及改进,对地形绘制中的四叉树剖分控制、DEM分块、纹理自动分块、地形数据的数据库存储、视见体剪裁、误差控制、裂缝拼接等方面进行了深入研究,提出了改进方法,并结合OpenGL立体显示技术,基于微机平台实现了一个简洁、快速的大规模真三维立体地形实时绘制原型系统,达到了很好的效果.实验结果表明,该算法实现简单、内存开销较少、CPU耗费小,具有较低的时间、空间开销,适于大规模地形的真三维实时可视化.     

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.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.