A Constraint-Based Reasoning Framework for Behavioural Animation

Behaviour is a reflection of a reasoning process that must deal with constraints imposed by an external environment, internal knowledge and physical structure. This paper proposes a framework for behavioural animation that is based on the next generation of object-oriented, constraint-based expert systems technology, and applies a control structure of knowledge agents and knowledge units to determine the behaviour of objects to be animated. Knowledge agents are responsible for planning, plan implementation and information extraction from the environment. The activity of an agent is dependent on the knowledge units ascribed to them by the animator. The interaction between agents and knowledge units is resolved by the reasoning engine, and thus, influences the eventual motion displayed. An example given is NSAIL, a pilot implementation using the model-based ECHIDNA constraint logic programming shell. With this approach, the motion for a sailing scenario and other behavioural domains can be specified at a high level through the characterization of the knowledge agents.     

时空人脸表情动画编辑

为了提高计算机合成人脸表情动画的后期制作效率,提出一种基于时空的人脸表情动画编辑方法.首先使用基于拉普拉斯的网格变形技术将用户的编辑效果在空间域传播到整个人脸模型,很好地保留了中性人脸模型的几何细节特征,从而提高合成表情的真实感;然后使用高斯函数将用户编辑效果在时间域传播到邻近表情序列,保持人脸表情动画的平滑过渡,所合成人脸表情动画与初始给定数据保持一致.该方法为用户提供了人脸表情动画编辑的局部控制,可由用户指定编辑的影响范围,使得编辑效果在指定范围内自然传播.实验结果表明,文中方法所合成人脸表情动画自然、真实,有效地提高了数据驱动人脸表情动画的编辑效率.     

Consistency techniques for continuous constraints

We consider constraint satisfaction problems with variables in continuous, numerical domains. Contrary to most existing techniques, which focus on computing one single optimal solution, we address the problem of computing a compact representation of the space of all solutions admitted by the constraints. In particular, we show how globally consistent (also called decomposable) labelings of a constraint satisfaction problem can be computed.Our approach is based on approximating regions of feasible solutions by 2 ^k -trees, a representation commonly used in computer vision and image processing. We give simple and stable algorithms for computing labelings with arbitrary degrees of consistency. The algorithms can process constraints and solution spaces of arbitrary complexity, but with a fixed maximal resolution.Previous work has shown that when constraints are convex and binary, path-consistency is sufficient to ensure global consistency. We show that for continuous domains, this result can be generalized to ternary and in fact arbitrary n-ary constraints using the concept of (3,2)-relational consistency. This leads to polynomial-time algorithms for computing globally consistent labelings for a large class of constraint satisfaction problems with continuous variables.     

Fuzzy Constraint-Based Agent Negotiation

Conflicts between two or more parties arise for various reasons and perspectives. Thus, resolution of conflicts frequently relies on some form of negotiation. This paper presents a general problem-solving framework for modeling multi-issue multilateral negotiation using fuzzy constraints. Agent negotiation is formulated as a distributed fuzzy constraint satisfaction problem (DPCSP). Fuzzy constrains are thus used to naturally represent each agent's desires involving imprecision and human conceptualization, particularly when lexical imprecision and subjective matters are concerned. On the other hand, based on fuzzy constraint-based problem-solving, our approach enables an agent not only to systematically relax fuzzy constraints to generate a proposal, but also to employ fuzzy similarity to select the alternative that is subject to its acceptability by the opponents. This task of problem-solving is to reach an agreement that benefits all agents with a high satisfaction degree of fuzzy constraints, and move towards the deal more quickly since their search focuses only on the feasible solution space. An application to multilateral negotiation of a travel planning is provided to demonstrate the usefulness and effectiveness of our framework.     

基于运动传播和Isomap分析的三维人脸动画编辑与合成

提出一种三维人脸动画数据编辑与合成的有效方法,使用户可以在三维人脸模型上选定控制点,并在二维平面上指定表情动作的约束条件.根据人脸动画数据训练一个先验概率模型,将较少的用户约束传播到人脸网格的其他部分,从而生成完整生动的人脸表情;通过Isomap学习算法对三维人脸动画知识进行建模,并结合用户指定的关键帧拟合高维曲面上的平滑测地线,以自动合成新的人脸动画序列.实验结果表明,该方法可以直观地对人脸动画的生成进行交互式控制,并能生成较为逼真的表情动画.     

人脸表情动画

人脸表情动画是计算机动画研究的一个重要分支．它有着十分广泛的应用前景。本文评述了国内外人脸表情动画方法和技术研究现状，提出了进一步需要解决的问题。并针对真人脸表情点提取难题给出了一个有效的特别的解决方案。     

视频驱动的语义表情基动画方法

为了重用视频内容中的表情信息,提出一种语义表情构造与语义表情参数优化方法.首先从带有噪声的稀疏特征点中定义出人脸表情的语义信息;然后在语义表情空间中优化求解出最优表情参数,以提高人脸动画的真实感.该方法既不需要标定相机参数,也不需要预先建立表演者的3D人脸模型及其表情基,因此除了可用于网络视频的表情重用,也可用于开发实时在线的网络社交等应用.实验结果表明,对于头部摆动的俯仰角和侧角在[?15?,15?]范围内的原始视频,文中方法能够实时合成稳定、逼真的表情动画.     

视频驱动人脸动画合成

描述了一种实时的视频驱动的人脸动画合成系统.通过该系统,用户只要在摄像头前面表演各种脸部动作,就可以控制虚拟人脸的表情.首先,建立一个基于肌肉的三维人脸模型,并使用肌肉激励参数控制人脸形变.为提高人脸动画的真实感,将口轮匝肌分解为外圈和内圈两部分,同时建立脸部形变与下颌转动的关系.然后,使用一种实时的特征点跟踪算法跟踪视频中人脸的特征点.最后,将视频跟踪结果转换为肌肉激励参数以驱动人脸动画.实验结果表明,该系统能实时运行,合成的动画也具有较强真实感.与大部分现有的视频驱动的人脸动画方法相比,该系统不需要使用脸部标志和三维扫描设备,极大地方便了用户使用.     

A Constraint-Based Interactive Train Rescheduling Tool

In this paper, we report the design and implementation of a constraint-based interactive train rescheduling tool, a project in collaboration with the International Institute for Software Technology, United Nations University (UNU/IIST), Macau. We formulate train rescheduling as constraint satisfaction and describe a constraint propagation approach for tackling the problem. Algorithms for timetable verification and train rescheduling are designed under a coherent framework. Formal correctness properties of the rescheduling algorithm are established. We define two optimality criteria for rescheduling that correspond to minimizing the number of station visits affected and passenger delay respectively. Two heuristics are then proposed to speed up and direct the search towards optimal solutions. The feasibility of our proposed algorithms and heuristics are confirmed with experimentation using real-life data.     

支持表情细节的语音驱动人脸动画

针对语音驱动人脸动画中如何生成随语音运动自然呈现的眨眼、抬眉等表情细节以增强虚拟环境的沉浸感的问题,提出一种可以合成表情细节的语音驱动人脸动画方法.该方法分为训练与合成2个阶段.在训练阶段,首先对富有表情的三维人脸语音运动捕获数据特征进行重采样处理,降低训练数据量以提升训练效率,然后运用隐马尔可夫模型(HMM)学习表情人脸语音运动和同步语音的关系,同时统计经过训练的HMM在训练数据集上的合成余量;在合成阶段,首先使用经过训练的HMM从新语音特征中推断与之匹配的表情人脸动画,在此基础上,根据训练阶段计算的合成余量增加表情细节.实验结果表明,文中方法比已有方法计算效率高,合成的表情细节通过了用户评价验证.     

具有真实感的三维人脸动画

具有真实感的三维人脸模型的构造和动画是计算机图形学领域中一个重要的研究课题.如何在三维人脸模型上实时地模拟人脸的运动,产生具有真实感的人脸表情和动作,是其中的一个难点.提出一种实时的三维人脸动画方法,该方法将人脸模型划分成若干个运动相对独立的功能区,然后使用提出的基于加权狄里克利自由变形DFFD(Dirichlet free-form deformation)和刚体运动模拟的混合技术模拟功能区的运动.同时,通过交叉的运动控制点模拟功能区之间运动的相互影响.在该方法中,人脸模型的运动通过移动控制点来驱动.为了简化人脸模型的驱动,提出了基于MPEG-4中脸部动画参数FAP(facial animation parameters)流和基于肌肉模型的两种高层驱动方法.这两种方法不但具有较高的真实感,而且具有良好的计算性能,能实时模拟真实人脸的表情和动作.     

语音驱动人脸唇形动画的实现

提出了一种实现语音直接驱动人脸唇形动画的新方法。结合人脸唇部运动机理，建立了与唇部运动相关肌肉拉伸和下颌转动的唇形物理模型，对输入的语音信号进行分析和提取其与唇部运动相关的特征参数，并直接将其映射到唇形物理模型的控制参数上，驱动唇形动画变形，实现输入语音和唇形动画的实时同步。仿真实验结果表明，该方法有效实现了语音和唇形的实时同步，唇形动画效果更接近自然，真实感更强。且该唇形物理模型独立于人脸几何模型，可广泛应用于各类人脸唇形动画的语音驱动，具有良好的普适性和可扩展性。     

Icola — Incremental Constraint-Based Graphics for Visualization

Visualization is valuable in monitoring and debugging programs. The goal of the Wand research project at the University of Saskatchewan is to provide both a framework and tools for rapid development of visualization aids for logic programming languages. The ICOLA (Incremental Constraint-based Object Layout Algorithm) system is the newest graphics facility within Wand. ICOLA positions graphical objects according to object declarations and constraints specifying relative positional relationships among the objects. Three important features of ICOLA are that it is capable of creating reasonable pictures from highly under-constrained specifications, it uses an incremental constraint solution algorithm and hence generates those pictures efficiently, and it supports incremental (i.e. progressive) insertions and deletions of objects and constraints. The ability of the incremental algorithm to support such deletions is particularly noteworthy. This paper describes: PDI, the language supported by ICOLA; the incremental constraint solution algorithm itself; a successful implementation in Prolog and C; and results of a performance evaluation of the implementation.     

Colouration Issues in Computer Generated Facial Animation

In everyday interactions with one another we use the face for recognising people and for communicating with them. Despite the considerable amount of research into computer generated facial animation, one particular aspect, that of the colouration of the face appears to have been neglected. In this paper we address issues pertinent to the use of colour for both modelling the appearance of the face and for enhancing communication during facial expression and animation. Colouration is an integral part of the face, which helps in the recognition of faces as well as in the interpretation of the often subtle signals emitted by the human face.     

基于物理模型的人脸表情动画技术研究

用计算机建立人脸表情动画是当前计算机图形学研究领域的一个富有挑战性的课题，该文在总结了国内外有关该课题研究方法的基础上，提出了一种基于物理模型的人脸表情画生成算法，并依该算法计和开发了一个实际的人脸表情动画系统HUFACE。该算法将人的脸部模拟为一个弹性体，为使计算简化，又将人脸表面依其生理特性分为八个子块，脸部表情所产生的五官动作模拟为弹性体的形变，并建立相应的弹性形变模型，当脸部表情引起脸部各子块形变时，每个子块上的各点将发生位移，于是利用该模型计算这些点的位移量，由此获得表情动画中的每一帧画面，由于脸部动作由该形变模型控制，且计算简单，速度快，因此不需存储表情动画中的各个画面，提高了系统的效率，实验结果表明，由HUFACE系统生成的人脸表情真实，自然。     

An Analysis of Arithmetic Constraints on Integer Intervals

Arithmetic constraints on integer intervals are supported in many constraint programming systems. We study here a number of approaches to implement constraint propagation for these constraints. To describe them we introduce integer interval arithmetic. Each approach is explained using appropriate proof rules that reduce the variable domains. We compare these approaches using a set of benchmarks. For the most promising approach we provide results that characterize the effect of constraint propagation. The work of the second author was supported by NWO, The Netherlands Organization for Scientific Research, under project number 612.069.003.     

面向普通用户的3D虚拟人脸动画

为合成真实感人脸动画,提出一种实时的基于单摄像头的3D虚拟人脸动画方法.首先根据用户的单张正面人脸图像重建用户的3D人脸模型,并基于该人脸模型合成姿态、光照和表情变化的人脸图像,利用这些图像训练特定用户的局部纹理模型;然后使用摄像头拍摄人脸视频,利用特定用户的局部纹理模型跟踪人脸特征点;最后由跟踪结果和3D关键形状估计Blendshape系数,通过Blendshape模型合成的人脸动画.实验结果表明,该方法能实时合成真实感3D人脸动画,且只需要一个普通的摄像头,非常适合普通用户使用.     

与语速相关的人脸语音动画合成及其评估

为了有效地合成人脸语音动画,根据对唇区肌肉收缩力与语速关系的分析,以及在对皮肤肌肉组织的粘弹性力学进行研究的基础上,提出了一种新的基于不同语速的唇动模型,并将其应用在了汉语人脸语音动画系统中。该模型根据获得的肌肉收缩力与语速的关系,并通过对皮肤肌肉组织的粘弹性分析,首先得到了语速、唇动速度与唇动位移三者之间的关系,并建立了不同语速下的唇动模型;然后通过这个唇动模型合成了不同语速状态下的具有较高自然度和个性化的人脸语音动画;最后,通过设计感知学评估实验,对合成的语音动画的效果和可理解性进行了评估。实验结果表明,该模型可以合成较高可接受性和可理解性的不同语速状态下的人脸语音动画。     

改进Wav2Lip的文本音频驱动人脸动画生成

为了提高中文唇音同步人脸动画视频的真实性, 本文提出一种基于改进Wav2Lip模型的文本音频驱动人脸动画生成技术. 首先, 构建了一个中文唇音同步数据集, 使用该数据集来预训练唇部判别器, 使其判别中文唇音同步人脸动画更加准确. 然后, 在Wav2Lip模型中, 引入文本特征, 提升唇音时间同步性从而提高人脸动画视频的真实性. 本文模型综合提取到的文本信息、音频信息和说话人面部信息, 在预训练的唇部判别器和视频质量判别器的监督下, 生成高真实感的唇音同步人脸动画视频. 与ATVGnet模型和Wav2Lip模型的对比实验表明, 本文模型生成的唇音同步人脸动画视频提升了唇形和音频之间的同步性, 提高了人脸动画视频整体的真实感. 本文成果为当前人脸动画生成需求提供一种解决方案.     

基于语音驱动的三维人脸动画技术综述

随着三维数字虚拟人的发展,语音驱动三维人脸动画技术已经成为虚拟人交互的重要研究热点之一.其关键技术在于语音-视觉映射模型的建立以及三维人脸动画的合成.首先分析了音-视素匹配法和音-视觉参数映射两类方法的特点;之后阐述了目前三维人脸模型的建立方法,并依据三维人脸模型的表示方法不同,分析了不同运动控制方法的优缺点;然后阐述了语音驱动三维人脸动画的主观评价和客观评价方法;最后总结了语音驱动三维人脸动画技术的未来发展方向.