层次结构导向下的动画角色模型分割与标记

对三维角色模型进行语义化检索与重组的前提是进行准确的分割和标记。本文针对游戏与影视中应用广泛的三维角色模型,提出了一种基于结构先验知识的角色部件分割和标记方法。总结了动画角色模型的一般性结构规则,并形式化为可以指导分割的层次化知识表达;采用区域生长法逐层剥离模型部件,在此规则下进行末端检测与边界判断,同时对部件进行语义标记。在两足与四足角色模型上进行测试,与其它可标记的角色模型分割方法相比,本方法具有更好的部件化结果,以及对动画角色有良好的扩展性。     

面向自定义格式的动画角色数据转换工具

为了充分利用常用建模软件里动画角色数据信息,进行动画角色算法的 研究,开发了动画角色数据转换工具。该转换工具包括导出模块和导入模块。其中导出模块 通过对3ds max 动画角色数据结构的分析,采用max SDK 进行二次开发,将3ds max 中的 数据导出到用于存储动画角色信息的自定义格式的文件中,便于使用者通过导出的文件数据 进行动画角色网格与运动数据融合等方面的算法研究;导入模块通过max SDK 读取自定义 文件中的数据进行动画角色的导入重建,便于使用者在3ds max 里对经过算法操作后的动画 角色进行观察。动画角色数据转换工具大大减轻了研究人员的负担,使研究人员可以对最本 质的动画角色数据进行算法研究,而不用考虑对数据的重建渲染等。     

骨骼蒙皮动画中网格优化的研究与实现

在骨骼蒙皮动画中需要处理大量的网格三角形,而在很多骨骼蒙皮动画的应用中都需要很高的动画实时性,为了提高骨骼蒙皮动画的实时性,对网格的优化是其中一项重要的工作.本文提出了一种优化网格的方法,并予以实现.     

附着贴图的3维角色模型融合方法

现有的3维模型融合均是立足于模型的几何网格信息,需要大量的顶点来提升融合效果。然而在目前的游戏与动画中,角色3维模型一般使用低精度模型,而以贴图来表现模型细节。因此针对低模角色网格顶点稀疏以及贴图特征,提出简单调和映射和均平面的思想简化网格连接,提高网格融合效率;其次采用基于仿射变换的贴图合成方法完成网格模型融合后的新贴图生成问题,进而完成角色模型的无缝融合。针对本文的方法以及3维模型设计制作的业务流程,建立人机交互的3维模型融合应用系统,实现高效率的3维模型融合与贴图合成。实验结果表明,该方法能够快速有效地完成动画和游戏中角色模型的融合,形成逼真度较高的新角色,为动画和游戏应用增添乐趣。     

骨骼蒙皮动画中网格优化的研究与实现

在骨骼蒙皮动画中需要处理大量的网格三角形，而在很多骨骼蒙皮动画的应用中都需要很高的动画实时性，为了提高骨骼蒙皮动画的实时性，对网格的优化是其中一项重要的工作。该文提出了一种优化网格的方法，并予以实现。     

基于凸壳与有向包围盒的骨架提取方法

为获取三维模型的几何及拓扑信息,提出一种基于凸壳与有向包围盒(OBB)的线性骨架提取方法.首先将三维网格模型进行分割生成多个子网格模型;然后对各子网格中的点集求取凸壳作为该子网格点集的近似,由凸壳顶点的形心构成原始骨架点;再用OBB进行重叠计算求出相交点集,以生成关节骨架点;最后对原始骨架点与关节骨架点进行连接,经冗余检测后形成完整骨架.实验结果表明,该方法快速、有效,提取出的骨架能保证连通性与中心性且能很好地提取关节骨架点,为蒙皮关节动画、模型形状分析等提供有效信息.     

基于角色几何碰撞体估计的实时服装仿真

提出了一种快速处理三维服装仿真中角色与服装碰撞的方法.该方法能够满足交互式实时仿真环境的需求.在预处理阶段,根据蒙皮动画的特点,将角色的几何形状以球和简化凸包等简单碰撞体进行估计.在实时模拟阶段,这些碰撞体跟随骨架运动并代替角色模型网格完成与虚拟服装之间的碰撞处理.此外,为了能够快速计算碰撞响应信息,该方法还利用外围映射机制进一步开发了相交测试的空间局部性.实验结果表明,应用该方法可以有效避免衣片与角色模型之间的相互穿透,同时大幅度地减少碰撞处理计算量.实时仿真系统对于复杂服装网格仍然保持了较高的模拟帧速率.     

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。     

三维图形引擎中骨骼蒙皮动画的一种实现方法*

提出了三维图形引擎中骨骼蒙皮动画的一种实现方法,即将现有的关节动画与单一网格动画相结合,利用骨架的继承变换和顶点混合技术使骨骼蒙皮动画平滑逼真。实验表明该方法有良好的显示效果,并具有较好的实时性,且占用的存储空间不大,能够满足当前三维图形引擎对动画技术的要求。     

实时三维人体卡通运动的设计与实现

为了实现虚拟角色的三维卡通运动,提出一种结合卡通滤波与骨骼模型自动绑定的实时生成算法.首先运用高斯拉普拉斯算子对捕获的运动数据进行滤波,然后用热量平衡的原理来自动绑定给定的人体模型,最后将滤波后的运动数据加载到绑定好的模型中,生成卡通化的夸张的动画序列.为了避免出现"collapse"和"candy wrapper"等走样现象,采用了SBS算法对网格进行变形.运动捕获数据滤波与蒙皮过程均使用GPU进行了加速.实验结果表明,运用该算法生成的动画效果满足动画法则,网格变形后表面光滑,用户交互简单.     

多角色与虚拟场景的运动融合

在基于运动捕获的计算机动画中,已提出的各种运动编辑的方法大都针对单个角色运动进行处理,而且角色的运动多数是事先规划好的,缺乏对外界环境变化的响应能力.为了提高角色对环境的感知、响应能力以及角色间的自主协同能力,提出将多个结构化环境下捕获的单角色运动融合到同一个非结构化虚拟环境下的"运动融合"的新概念和方法,并根据运动决策、运动协调、运动求解和运动执行的体系结构对运动规划、多角色协同、离散运动模式决策和连续运动姿势生成等关键问题进行了深入研究.实验结果表明,提出的方法能够真正有效地实现同一场景下角色与场景协调的运动融合.动画角色的高自主性和运动捕获数据的高重用性使得提出的方法在计算机动画和游戏中具有普遍的应用价值.     

Automatic Conversion of Mesh Animations into Skeleton-based Animations

Recently, it has become increasingly popular to represent animations not by means of a classical skeleton‐based model, but in the form of deforming mesh sequences. The reason for this new trend is that novel mesh deformation methods as well as new surface based scene capture techniques offer a great level of flexibility during animation creation. Unfortunately, the resulting scene representation is less compact than skeletal ones and there is not yet a rich toolbox available which enables easy post‐processing and modification of mesh animations. To bridge this gap between the mesh‐based and the skeletal paradigm, we propose a new method that automatically extracts a plausible kinematic skeleton, skeletal motion parameters, as well as surface skinning weights from arbitrary mesh animations. By this means, deforming mesh sequences can be fully‐automatically transformed into fullyrigged virtual subjects. The original input can then be quickly rendered based on the new compact bone and skin representation, and it can be easily modified using the full repertoire of already existing animation tools.     

Local Volume Preservation for Skinned Characters

Generating plausible deformations of a character skin within the standard production pipeline is a challenge. This paper presents a volume preservation method dedicated to skinned characters. As usual, the character is defined by a skin mesh at some rest pose and an animation skeleton. At each animation step, skin deformations are first computed using standard SSD. Our method corrects the result using a set of local deformations which model the fold‐over‐free, constant volume behavior of soft tissues. This is done geometrically, without the need of any physically‐based simulation. To make the method easily applicable, we also provide automatic ways to extract the local regions where volume is to be preserved and to compute adequate skinning weights, both based on the character's morphology.     

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．     

Reusing view-dependent animation

In this paper we present techniques for reusing view-dependent animation. First, we provide a framework for representing view-dependent animations. We formulate the concept of a view space, which is the space formed by the key views and their associated character poses. Tracing a path on the view space generates the corresponding view-dependent animation in real time. We then demonstrate that the framework can be used to synthesize new stylized animations by reusing view-dependent animations. We present three types of novel reuse techniques. In the first we show how to animate multiple characters from the same view space. Next, we show how to animate multiple characters from multiple view spaces. We use this technique to animate a crowd of characters. Finally, we draw inspiration from cubist paintings and create their view-dependent analogues by using different cameras to control different body parts of the same character.     

Optimized keyframe extraction for 3D character animations

In this paper, we propose a new method to automatically extract keyframes from animation sequences. Our method can be applied equally to both skeletal and mesh animations. It uses animation saliency computed on the original data to help select the group of keyframes that can reconstruct the input animation with less perception error. For computational efficiency, we perform nonlinear dimension reduction using locally linear embedding and then carry out the optimal search in much lower‐dimensional space. With this approach, reconstruction of the animation from the extracted keyframes shows much better results as compared with earlier approaches. Copyright © 2012 John Wiley & Sons, Ltd.     

Animation‐Aware Quadrangulation

Geometric meshes that model animated characters must be designed while taking into account the deformations that the shape will undergo during animation. We analyze an input sequence of meshes with point‐to‐point correspondence, and we automatically produce a quadrangular mesh that fits well the input animation. We first analyze the local deformation that the surface undergoes at each point, and we initialize a cross field that remains as aligned as possible to the principal directions of deformation throughout the sequence. We then smooth this cross field based on an energy that uses a weighted combination of the initial field and the local amount of stretch. Finally, we compute a field‐aligned quadrangulation with an off‐the‐shelf method. Our technique is fast and very simple to implement, and it significantly improves the quality of the output quad mesh and its suitability for character animation, compared to creating the quad mesh based on a single pose. We present experimental results and comparisons with a state‐of‐the‐art quadrangulation method, on both sequences from 3D scanning and synthetic sequences obtained by a rough animation of a triangulated model.     

数据驱动的大规模水面动画合成方法

为了生成大规模且细节丰富的水面动画,提出了一种数据驱动的合成方法。整个 合成分为两大部分：基于视频的水面重建和三角网格拼接。首先简化了线性近似的影调恢复形 状(SFS)方法,针对满足朗伯表面假设的室外大规模水面进行重建,并根据时间和空间的连续性 进行了一系列优化处理。然后提出一种针对三角网格序列的拼接方法,根据距离最小原则对重 建的表面序列进行采样,将采样结果融合得到无缝的表面。利用以上方法,对四类水面的视频 进行重建与拼接,结果表明,合成出的水面具有较高的真实感,在规模与细节之间取得了较好 的平衡,该方法可以方便地生成满足用户需求的大规模水面动画。     

Aura Mesh: Motion Retargeting to Preserve the Spatial Relationships between Skinned Characters

Applying motion‐capture data to multi‐person interaction between virtual characters is challenging because one needs to preserve the interaction semantics while also satisfying the general requirements of motion retargeting, such as preventing penetration and preserving naturalness. An efficient means of representing interaction semantics is by defining the spatial relationships between the body parts of characters. However, existing methods consider only the character skeleton and thus are not suitable for capturing skin‐level spatial relationships. This paper proposes a novel method for retargeting interaction motions with respect to character skins. Specifically, we introduce the aura mesh, which is a volumetric mesh that surrounds a character's skin. The spatial relationships between two characters are computed from the overlap of the skin mesh of one character and the aura mesh of the other, and then the interaction motion retargeting is achieved by preserving the spatial relationships as much as possible while satisfying other constraints. We show the effectiveness of our method through a number of experiments.     

一种网格融合算法

快速建模是三维游戏动画领域的重要技术,从已有模型经过修改、编辑、融合构建出新的模型是一种高效的建模方法.本文提出了一种网格模型融合算法,该算法首先将需要的部分网格从源模型上交互剪切下来,并将其配准对齐;然后将两网格模型转化成点模型表示,并将点模型转化成RBF隐函数表示;再对两隐函数进行布尔运算;最后将布尔运算生的隐函数曲面在两网格接合区域进行三角形化,得到最终的网格模型.算法定义了隐函数曲面的影响区域,有效控制融合过渡.采用边界扩展的三角形化方法,保留了融合区域以外源模型的特征.实验结果表明,本文算法具有很好的网格融合结果,可用于游戏动画中快速造型.