基于线型草图的多源3维动画传输

为了对3维动画进行鲁棒地传输,提出了一种基于线型草图的3维动画传输方法,该方法可以把多个源网格的动画传输到一个目标网格。该方法由以下几个步骤组成:(1)使用线型草图在源网格和目标网格间建立映射;(2)使用差分均值坐标(differential mean value coordinates),根据源动画来变形目标网格;(3)对齐各部分变形后的目标网格,通过求解最小化约束函数,以获取光滑的目标网格,从而生成目标动画的关键帧;(4)对由步骤(3)产生的结果进行插值,即可产生完整的目标对象的3维动画。通过对上述几个方面的深入研究,以及将这些成果集成在原型系统中的结果表明,该方法具有以下特点:①既不需要源网格和目标网格有相同的顶点数和三角面片数,也不需要有类似的拓扑信息;②源动画既可以是3维的,也可以是2维视频或Flash;③目标对象可以是无结构化的点云数据。实践表明,该方法直观易用,可以生成逼真的3维动画。最后通过从狗、猫、蛇、人体的3维动画与2维车轮视频的合成来产生复杂的马车动画,对该方法进行了验证。另外,原型系统还通过产生其他几个例子来进一步验证其通用性和鲁棒性。     

基于均值坐标的三维动画传输

为了重用已有动画资源,提出一种基于均值坐标的三维动画传输方法．首先使用标记点在源网格和相应的目标网格间建立映射,然后采用均值坐标,根据源网格的动画来变形相应的目标网格．该方法不需要源网格和目标网格有相同的顶点数和三角面片数,也不需要有类似的拓扑信息．     

利用Laplace-Beltrami形状空间的基于样例材料的快速仿真方法

物理仿真中当仿真对象与样例具有不同拓扑结构时,现有采用Laplace-Beltrami算子在表面网格上构建形状插值空间的基于样例仿真方法,在重建其欧氏空间表示时会有精度和效率损失.为克服上述问题,提出一种高效地利用Laplace-Beltrami形状空间的基于样例的仿真方法.首先,提出基于有限元形函数离散化方法的Laplace-Beltrami算子在体网格上计算特征函数,该特征函数重建后直接获得体网格位移,避免了近似的投影过程;其次在特征函数构成的形状空间中采用简化的线性插值来计算目标形状,提高了仿真效率;最后依据目标形状计算出的样例引导力,在有限元仿真框架下实现基于样例材料的形变体仿真方法.实验结果表明,该方法可以获得与已有方法相似的仿真结果,并具有更高的仿真效率.     

图象Morphing过程中的控制

本文研究了图象渐变动画技术,重点讨论了基于网格的二维图象渐变技术.本文提出一种图象渐变的过程控制方法,这种控制方法用一个控制序列对图象渐变过程进行控制,该序列用于网格变换时,可以控制源图象和目标图象分别在中间帧图象中所占的比例;用于颜色混合时,可以去掉中间帧图象上的一些不良效果.另外,本文用Java语言实现了基于网格的二维图象渐变动画和动画过程控制,取得了较好的渐变效果.     

时空一致的动态纹理地图快速生成

为了获得真实的动态重建体验,需要在重建几何的基础上进一步重建颜色信息,并高效地进行数据编码传输.为此提出一种面向动态三维重建的纹理地图序列快速生成方法.首先基于动态三维重建的基准网格序列的几何相似特性快速生成相邻帧网格的三角面对应关系,然后根据该对应关系使用一种基于网格块的优化方法得到网格序列的一致性分割结果,最后结合网格序列的一致性分割结果及网格前后帧的三角面对应关系,快速生成具有时空一致性的纹理地图序列.实验结果表明,在真实动态重建场景下,使用H.264对由该方法生成的一致性纹理地图序列进行无损视频编码时可以降低约50%的比特率,使用有损编码可以降低70%～80%的比特率.     

个性化虚拟化妆效果迁移

为克服当前虚拟化妆迁移中只能迁移单一化妆效果的问题,提出一种个性化虚拟化妆迁移方法.给定目标图像与多(单)个化妆后的样例图像,首先对脸部进行区域分类,将样例对象脸部与目标对象脸部进行匹配;然后通过二尺度分解技术获得脸部结构层、纹理层及色彩层,并使用梯度域技术修复样例对象纹理层,去除样例的脸部瑕疵;最后将每个子区域的化妆信息迁移至目标对象的对应区域,并无缝融合区域间的信息.实验结果表明,该方法不仅可以快速生成高质量的基于多个化妆样例的个性化虚拟化妆效果,同时具有和谐克隆的特性,可以获得良好的图像和谐克隆结果.     

人脸动画关键点最优化算法

Thin-shell变形算法基于一组控制点的位移计算所有顶点的位移,不同的控制点集合会得到不同的重构结果.为了使该变形算法更精确地重构人脸表情动画,基于该算法,提出一种最优控制点计算方法.首先将计算人脸变形最优控制点问题建模,以最小化thin-shell变形算法的重构误差为目标,提出一种自适应前后向贪婪策略学习最优化控制点,称为人脸动画关键点;通过引入边界约束、对称性约束以及多分辨率性,使得所提出的关键点具有通用性.实验结果证明,所提出的人脸动画关键点方法在仿真数据和真实数据上可以有效地获取关键控制点和重构人脸动画.     

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.     

基于手绘轮廓的3维服饰模型生成

为了满足虚拟角色交互式服饰设计的需要,提出了一种基于手绘轮廓的3维服饰模型生成方法,该方法的主要特点在于以下3个方面：一是通过限定距离场的方向(仅考虑z轴方向)来建立3维人体模型的参考模型,从而简化了距离场计算;二是利用手绘服饰轮廓与人体投影轮廓间的相对位置关系来生成服饰网格,以实现2维草图向3维服饰的有效映射;三是根据服饰网格点与人体模型上网格点间的对应关系来生成3维服饰模型,确保了服饰宽松部分的有效生成。实验结果表明,该方法能够从2维服饰轮廓实时生成符合人体表面形状的3维服饰模型。     

基于NURBS权因子调整的FFD直接操作

FFD（Free-Form Deformation）是计算机动画和变形中最重要的方法之一。FFD的直接操作为变形提供了更直观更方便的控制手段。该文用约束优化方法，通过调整张量积网格控制点对应的权因子，解决基于NURBS的FFD直接操作问题，给出了变形物体在单点约束下FFD直接操作的解，使变形后的物体通过给定的目标点。该方法计算简便，易于实现。文中给出的变形实例也表明，变形结果比较自然。     

Accurate visible speech synthesis based on concatenating variable length motion capture data

We present a novel approach to synthesizing accurate visible speech based on searching and concatenating optimal variable-length units in a large corpus of motion capture data. Based on a set of visual prototypes selected on a source face and a corresponding set designated for a target face, we propose a machine learning technique to automatically map the facial motions observed on the source face to the target face. In order to model the long distance coarticulation effects in visible speech, a large-scale corpus that covers the most common syllables in English was collected, annotated and analyzed. For any input text, a search algorithm to locate the optimal sequences of concatenated units for synthesis is described. A new algorithm to adapt lip motions from a generic 3D face model to a specific 3D face model is also proposed. A complete, end-to-end visible speech animation system is implemented based on the approach. This system is currently used in more than 60 kindergartens through third grade classrooms to teach students to read using a lifelike conversational animated agent. To evaluate the quality of the visible speech produced by the animation system, both subjective evaluation and objective evaluation are conducted. The evaluation results show that the proposed approach is accurate and powerful for visible speech synthesis.     

HandPuppet3D: Motion capture and analysis for character animation

Motion capture is a technique of digitally recording the movements of real entities, usually humans. It was originally developed as an analysis tool in biomechanics research, but has grown increasingly important as a source of motion data for computer animation. In this context it has been widely used for both cinema and video games. Hand motion capture and tracking in particular has received a lot of attention because of its critical role in the design of new Human Computer Interaction methods and gesture analysis. One of the main difficulties is the capture of human hand motion. This paper gives an overview of ongoing research “HandPuppet3D” being carried out in collaboration with an animation studio to employ computer vision techniques to develop a prototype desktop system and associated animation process that will allow an animator to control 3D character animation through the use of hand gestures. The eventual goal of the project is to support existing practice by providing a softer, more intuitive, user interface for the animator that improves the productivity of the animation workflow and the quality of the resulting animations. To help achieve this goal the focus has been placed on developing a prototype camera based desktop gesture capture system to capture hand gestures and interpret them in order to generate and control the animation of 3D character models. This will allow an animator to control 3D character animation through the capture and interpretation of hand gestures. Methods will be discussed for motion tracking and capture in 3D animation and in particular that of hand motion tracking and capture. HandPuppet3D aims to enable gesture capture with interpretation of the captured gestures and control of the target 3D animation software. This involves development and testing of a motion analysis system built from algorithms recently developed. We review current software and research methods available in this area and describe our current work.     

Interactive motion mapping for real‐time character control

It is now possible to capture the 3D motion of the human body on consumer hardware and to puppet in real time skeleton‐based virtual characters. However, many characters do not have humanoid skeletons. Characters such as spiders and caterpillars do not have boned skeletons at all, and these characters have very different shapes and motions. In general, character control under arbitrary shape and motion transformations is unsolved ‐ how might these motions be mapped? We control characters with a method which avoids the rigging‐skinning pipeline — source and target characters do not have skeletons or rigs. We use interactively‐defined sparse pose correspondences to learn a mapping between arbitrary 3D point source sequences and mesh target sequences. Then, we puppet the target character in real time. We demonstrate the versatility of our method through results on diverse virtual characters with different input motion controllers. Our method provides a fast, flexible, and intuitive interface for arbitrary motion mapping which provides new ways to control characters for real‐time animation.     

基于WebGL的3D动画实时播放系统

由于受到网络带宽及三维动画数据量过大等因素的影响,三维动画如果要在网络上一次性传输往往需要花费比较长的时间.这不仅影响了动画播放的实时性,同时,传输过程中数据的不完整也会造成动画播放不流畅.通过对基于WebGL的三维动画实时播放关键技术的研究,提出模型文件预加载、文件压缩传输等方法,在有限带宽的条件下将三维动画内容实时传输到用户端,利用WebGL技术实现三维模型的创建和渲染,并在此基础上实现三维动画实时播放,使用户能够直接通过浏览器进行观看,或参与到场景交互中.     

Shape exploration of 3D heterogeneous models based on cages

Shape exploration of 3D heterogeneous models is essential for special effects in 3D animation and games. As heterogeneous models have different numbers of vertices and different topological structures,the mapping between source and target model may be ambiguous for deformation transfer. We propose a new framework for heterogeneous model shape exploration based on cages, which provides a feasible and fast solution to this open problem. Using a public cage as an intermediate medium, the deformation of the source models can be denoted as the position changing of the cage. When applying the cage change to the target model, rough deformation transfer can be achieved. After an optimization and interpolation to generate the explored shape of the heterogeneous target model, animation can be acquired. Our method is not only suitable for triangle meshes, but also for quadrilateral meshes or any other type of meshes. We demonstrate the validity of our scheme by a series of shape exploration experiments with different models.     

手机3D动画中基于导演知识库的摄像机规划

基于全过程计算机辅助动画自动生成技术构建的手机3D动画自动生成系统的最终目标是实现短信内容自动动画化.摄像机规划作为传达动画主题的直接方式,是手机3D动画自动生成系统的关键环节,并已经在系统中建立了完整的定性和定量规划流程.本文在现有相关理论研究的基础上,归纳总结摄影领域的通用性规则,利用语义网本体语言构建摄像机导演知识库,并基于导演知识库完成了摄像机定性规划的两层规则推导,最终实现手机3D动画自动生成系统中摄像机规划的自动生成.     

基于梯形阴影映射技术的平截头体交汇算法

阴影映射是在三维计算机图形中加入阴影的过程,在三维动画中有广泛的应用,但该算法容易产生走样,使用一种基于梯形阴影映射的平截头体交汇算法,对阴影映射进行了反走样处理。实验表明,该方法对于阴影映射分辨率和它们之间平滑过渡的总体能够有很好的把握和控制,能够生成高质量的阴影。     

圆弧路径法，一种新的多边形变形方法

二维形状变形技术在二维角色动画、模式匹配、几何造型、虚拟现实、工业模拟、科学计算可视化等领域有着重要的应用。本文提出了一种顶点路径圆弧法的二维形状变形新方法。该算法通过控制关键帧多边形顶点按照一条特殊的圆弧曲线路径进行运动，实现二维形状变形。通过许多实例的测试表明，该算法效果良好：不仅可以保持首末关键帧形状的共同特征，而且中间插值形状变化自然平滑。同时，我们的方法易于用户交互控制；容易推广到高维情形；计算量较小、能达到系统实时的要求。