基于几何特征的流体动画控制方法

在流体动画中,流体控制是生成可控流体运动的关键技术.为产生视觉逼真、行为可控的流体动画效果,提出一种基于几何特征的流体控制方法.首先通过构建流体形状的时变几何分区,实现对可控流体形状的表达及动态跟踪;在此基础上设计异构控制模型,以增强流体运动控制的灵活性,该模型采用了带约束优化的刚性控制和基于弹簧模型的柔性控制2种方法;最后将异构控制模型与高精度流体物理模型相耦合,生成视觉逼真的可控流体运动效果.实验结果表明,该方法能够在保持流体角色形状的同时产生丰富的流体细节,满足动画师的设计需求.     

基于实例数据分析的多精度网格布料动画

在布料动画领域,细节变形褶皱的快速逼真模拟是一个具有挑战性的问题.多精度网格布料动画技术,在不同变形区域采用不同密度的网格,由此保证布料运动的丰富细节和更高的动画合成效率.已有的研究工作,主要针对多精度网格布料动画的可计算问题,即在动画过程中动态获取顶点或面片曲率,依据手工设定的阈值进行动态迭代精化,而对于有效性问题,即如何预测布料运动趋势并据此合理修改网格精度,未深入研究.针对该问题,在对布料运动过程中弯曲变形特征进行分析的基础上,提出一种基于实例数据分析的多精度网格布料动画方法.首先,选取一段持续的高精度布料动画作为实例数据,分析并提取弯曲变形模式;其次,以弯曲变形模式作为启发信息,结合有效的精化策略以及精化原则,对相应低精度布料模型进行逐层精化,从而构建多精度网格布料几何模型;最后,建立多精度网格各层质点的受力关系,并通过增加边界约束和质量约束,构建可适用于多精度网格的布料动画模型.实验结果显示,文中预构建的多精度网格模型可用于同类相似运动驱动下的布料动画计算,能够在保持较多细节变形的前提下,有效提高计算效率.     

真实感流体实时重建

针对流体重建中存在的实时性差以及重建精度低的问题,提出一种流体三维重建方法.首先利用明暗度恢复形状方法计算流体表面的法向量,使用Stokes波模型计算流体表面高度;然后对重建表面的细节做进一步处理,确定水花点的位置,使用二维正态分布曲面对重建的流体表面进行拟合;最后根据拟合结果生成水花飞溅的效果并映射相应的纹理,从而增强了流体重建的真实感,可以逼真地表现出流体运动状态.实验结果表明,采用该方法进行重建能够保证实时性的要求,重建的流体具有真实感强的特点,可以有效地应用于增强现实技术的研究中.     

一种自适应的粒子水平集算法

在基于物理的流体动画中,准确而高效地跟踪流体运动界面是提高仿真效果的关键.针对传统算法存在耗散大、效率低等问题,提出了一种自适应的粒子水平集算法.通过建立耗散函数估计的重要性采样模型,获取自适应优化规则;然后基于该优化规则,定义窄带上的局部特征尺寸函数和累积变形率,构建采样点分布的随机过程,在此基础上进行流体界面跟踪计算的优化.实验及应用结果表明:该方法能有效利用计算资源,在界面跟踪的精度与效率方面均优于原有方法,能够得到满足需求的仿真效果.     

一种基于混合模型的实时虚拟人服装动画方法

实时服装动画生成技术能够为三维虚拟角色实时地生成逼真的服装动态效果,在游戏娱乐、虚拟服装设计展示等领域有着广泛的应用前景.其难点在于如何建立服装动画计算模型,在实时计算的前提下获得最佳的服装动画生成效果.在对服装模型与人体模型在运动过程中发生的位置冲突(collision,也称碰撞)进行分析的基础上,研究并提出了一种基于混合模型的实时虚拟人服装动画计算模型.首先,根据服装动画样本数据中服装与人体发生位置冲突的信息,对服装与人体的运动相关性进行分析;在此基础上,提出并实现一种新的混合策略,将具有较好服装动态模拟效果的动力学计算模型与具有较高计算效率的几何变形方法进行混合,建立支持实时计算且效率可动态控制的服装动画计算模型.实验结果表明,该计算模型能够实时地生成具有较好视觉逼真性的服装动画.     

基于可视外壳的cage 生成

借助cage 作为代理几何来处理高精度复杂模型,正成为计算机动画与几何造型中的一种重要方法.目前,已有的cage 生成算法尚缺乏普适性,很大程度上依赖于几何的表示和模型的复杂度.因此,提出一种基于可视外壳的cage 生成算法.通过逆向模拟计算机视觉领域可视外壳的生成过程获取cage,以实现cage 生成与几何表示和模型复杂度无关的目标.实验结果表明,该方法易于实现且效率高.     

基于形状特征与变形保持的动态模型简化

提出了一种基于形状特征与变形区域保持的动态表面多分辨率模型生成方法.该方法使用了基于形状特征的二次误差度量来计算边折叠代价,可以较好的保持模型表面特征.在计算整个变形动画中累加的边折叠代价时,加入相邻帧之间的变形程度信息,以保持变形程度较大区域的细节特征.最后基于整体的边折叠顺序,对每一帧模型进行细微的调整,以得到视觉失真最小的简化网格.文中方法的效率较高,易于实现,并且可以在变形网格的任意帧上生成高质量的、保持良好细节特征的简化模型.     

基于申威1621的高精度点积算法实现与优化

点积函数是BLAS库中的一级基础函数,其被科学计算等领域广泛调用.由于浮点计算会引入舍入误差,现有BLAS库中双精度点积函数不足以满足某些应用领域的精度要求,因此需要高精度算法来实现更精确可靠的计算.在本文中,面向国产申威1621平台,在现有的BLAS库的基础上,新增高精度点积函数的实现接口,来满足应用的高精度需求.同时,对于高精度点积算法运用循环展开、访存优化、指令重排等优化策略,实现汇编级手工优化.实验结果显示,文中高精度点积算法的计算结果精度,近似达到了双精度点积的两倍,有效提升了原始算法精度.同时,在保证精度提升的基础上,文中优化后的高精度点积函数相比未优化前,平均性能加速比达到了1.61.     

复杂场景流固耦合的高效模拟

大规模复杂流体场景的高效交互模拟技术在灾难仿真、虚拟现实和影视特效制作等领域都有重要的应用价值.针对现有基于物理的流体算法大多只适于尺度较小的场景,难以有效地模拟复杂流体大场景中流固耦合时的固体破碎效果的问题,提出一种复杂场景的固液耦合高效模拟方法.首先提出一种基于流体隐式粒子法和散度为零的SPH法相混合的计算框架,在确保流体物理属性的同时充分利用细粒度的隐式粒子来丰富流体运动细节,提高场景模拟的真实感;然后采用一种多维度的流固耦合分合计算策略来进一步提高流固耦合效率;为实现流体冲击下的固体破碎效果,采用一种物理与几何相混合的破碎方法:以基于断裂力学中的应变能密度模型来确定固体破碎时碎片的分布,采用基于几何的质心Voronoi方法快速生成碎片,最终实现百万量级粒子参与的复杂流体场景的交互模拟,以及高速流体冲击下的固体破碎效果的高效模拟.     

多精度混合弹性变形及其交互模拟

固体的弹性变形模拟作为计算机物理动画领域的重要内容,如何在保证模拟真实感的同时尽可能地提高计算效率以满足交互应用,一直是其研究难点.为此,提出一种多精度混合弹性变形模型来高效地模拟固体的弹性变形及其交互.该模型通过对物体计算空间进行物理和几何区域的用户自定义比例划分,并混合处理交界面处计算结点,实现2种变形区域的稳定耦合;利用虚拟顶点算法对物理变形区域进行稳定和光滑的虚拟切割模拟;提出自适应边界粒子采样的固流耦合算法模拟固流交互.实验结果表明,文中模型通过调整2种区域计算结点的比例,控制和调整弹性变形模拟的效率和精度,可以满足虚实交互和固流交互模拟中稳定和高效的性能需求.     

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     

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.     

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。