基于卷积曲面的几何造型方法

卷积曲面是一种很有潜力的隐式曲面造型方法。由于卷积的可叠加性质,使得其生成的曲面很光滑,不会产生凸包和裂缝。卷积曲面造型是基于骨架的,其骨架可以是曲线或曲面,也可以以物体轮廓线为骨架原型来获取所需要的物体造型。在卷积造型的过程中,通过对骨架加权可以精细地控制结果曲面的形状。在介绍了卷积曲面造型的各类方法后,分析了其特点和发展方向。     

Construction of Blending Surfaces

Surface blending is very important in geometric modeling and is widely used in product design and manufacturig. This paper has a comprehensive discussion in surface blending with constant/variable radil, including the generation of rolling-ball blending between a curve and a surface, rolling-ball blending between two surfaces at a given contact curve, sliding-circle blending between two surfaces, etc. All those algorithms developed have been put into the commercial CAD/CAE/CAM software system-CAXA-ME and greatly enhanced its modeling ability     

Creating and Rendering Convolution Surfaces

Implicit surfaces obtained by convolution of multi-dimensional primitives with some potential function, are a generalisation of popular implicit surface models: blobs, metaballs and soft objects. These models differ in their choice of potential function but agree upon the use of underlying modelling primitives, namely, points. In this paper a method is described for modelling and rendering implicit surfaces built upon an expanded set of skeletal primitives: points, line segments, polygons, arcs and planes. An analytical solution to the convolution is described. This solution offers a more accurate and robust representation of the resultant implicit surface than previous methods. An algorithm for ray-tracing the surfaces formed through convolution of any combination of these primitives is also outlined.     

用分片代数曲面构造管道曲面的过渡曲面

借助围绕一个顶点处代数曲面的光滑拼接条件,提出并研究了用分片代数曲面构造三通管道的过渡曲面问题。首先对空间区域进行适当的剖分以确定分片代数曲面的定义区域。然后,通过求解一个线性方程组来构造出光滑拼接的分片代数曲面,同时还了在代数曲面片的Ｂ－Ｂ表示下,Ｂｅｚｉｅｒ纵标对过渡曲面的形状的局部控制问题。结果表明,用分片代数曲面构造过渡曲面不仅可以降低曲面的次数,而且更有利于曲面形状的控制。     

三次B样条曲线骨架卷积曲面造型

提出一种基于B样条曲线降阶的三次B样条曲线骨架卷积曲面造型方法．首先通过顶点扰动降阶方法把三次B样条曲线骨架（C^1连续）降阶为C^1连续的二次B样条,然后应用二次B样条曲线骨架的卷积曲面势函数计算方法得到三次B样条曲线骨架的势函数．     

光顺过渡面的热传导方程--能量优化构造方法

首先运用热传导方程、初值条件和带有固定边界的边值条件,建立过渡面的偏微分方程模型.再对方程像空间中的曲面簇,采用关于时间t的曲面能量表达式作为曲面光顺准则,建立起满足热传导方程的光顺过渡面的优化构造模型,即带有固定边界的光顺过渡面的热传导方程-能量优化构造模型,此模型的解即为满足连续性和光顺性要求的过渡面.数值实验表明这种光顺过渡面的构造方法是可行与有效的.     

Simulating the structure and dynamics of human hair: Modelling,rendering and animation

We develop and present a new approach to modelling the characteristics of human hair, considering not only its structure, but also the control of its motion and a technique for rendering it in a realistic form. The approach includes a system for interactively defining the global positioning of the strands of hair on the head. Special attention is paid to the self shadowing of the hair. A mass/spring/hinge system is used to control a single strand's position and orientation. We demonstrate that this approach results in a believable rendition of the hair and its dynamics.     

几何偏微分方程和离散曲面设计

使用若干个几何本质的曲率驱动的偏微分方程来构造符合指定C0或C1边界条件的三边曲面片和四边曲面片,这些方程的数值解由所涉及的微分几何算子的离散化来得到,微分几何算子的离散化则源于参数逼近.所构造的曲面片满足某些特定的几何偏微分方程,故具有理想的形状,将这些曲面片组装起来便构造出复杂的几何模型.通过反复的子分和演化,得到几何模型的多尺度表示.     

基于Metaball的曲面约束变形模型及应用

结合曲面变形技术和Metaball原理,提出了基于Metaball的曲面约束变形模型,将Metaball的势函数表达曲面变形的约束,用它去作用于待变形曲面,通过调整Metaball势函数的约束中心、作用半径、偏移等参数控制曲面的预期变形效果,利用骨架卷积获得平坦光滑的曲面.讨论了约束关系、单个约束的影响、控制约束的相互影响等问题,并举例说明了这个模型的机理和应用.     

Highly stylised animation

In this paper we argue for our NPAR system as an effective 2D alternative to most NPR research, which is focused on frame coherent stylised rendering of 3D models. Our approach gives a highly stylised look to images without the support of 3D models. Nevertheless, they still behave as though they are animated by drawing, which they are. First, a stylised brush tool is used to freely draw extreme poses of characters. Each character is built of 2D drawn brush strokes which are manually grouped into layers. Each layer is assigned its place in a drawing hierarchy called a hierarchical display model (HDM). Next, multiple HDMs are created for the same character, each corresponding to a specific view. A collection of HDMs essentially reintroduces some correspondence information to the 2D drawings needed for inbetweening and, in effect, eliminates the need for a true 3D model. Once the models are composed the animator starts by defining keyframes from extreme poses in time. Next, brush stroke trajectories defined by the keyframe HDMs are inbetweened automatically across intermediate frames. Finally, each HDM of each generated inbetween frame is traversed and all elements are drawn one on another from back to front. Our techniques support highly rendered styles which are particularly difficult to animate by traditional means including the ‘airbrushed’, scraperboard, watercolour, Gouache, ‘ink-wash’, pastel, and the ‘crayon’ styles. In addition, we describe the data path to be followed to create highly stylised animations by incorporating real footage. We believe our system offers a new fresh perspective on computer-aided animation production and associated tools.     

基于Maya的人物动画研究

为了对二维图像实现人物动画,对人物图像进行轮廓提取、贴图,给模型添加骨骼并进行骨骼绑定,最后进行人物动画模拟。实验结果表明,基于Maya的人物动画能够以较高真实度生成人物动画。     

Automated generation of control skeletons for use in animation

Published online: 15 March 2002     

融入剪纸文化的骨骼动画教学创新设计

针对多媒体技术及应用课程的重难点骨骼动画教学,提出将剪纸文化融入骨骼动画教学的创新改革方案。以成果导向教育为引导,以学生发展为中心,从课前、课中和课后介绍融入剪纸文化的骨骼动画教学创新改革,提升学生的计算机应用能力,培养学生传承创新剪纸文化,实现用现代数字媒体技术弘扬中华优秀传统文化。     

A new implicit blending technique for volumetric modelling

Current implicit blending techniques are mostly designed for use in surface modelling, where only boundaries of the object defined by the implicit primitives are important. In contrast, in volumetric implicit modelling the interior of the object is also significant, which requires different and more suitable techniques for combining implicit primitives. In this paper, we first discuss irregularities that occur using the current techniques. Then, a new technique for blending implicit primitives, especially appropriate in volumetric modelling (e.g., cloud modelling), is introduced. It overcomes these abnormalities and gives us better results than current techniques.     

基于结式的曲面拼接与三维造型

针对很多几何造型是带有约束条件的曲面拼接问题,在线性连续同伦的基础上提出了利用非线性同伦连续计算拼接曲面以进行三维造型的方法。首先,根据得到的截面(切片)的位置及其曲线方程确定插值点并得到插值多项式;其次,将此插值多项式作为非线性连续同伦映射函数并分别代入主曲面和辅助曲面的多项式方程得到过渡曲面的方程;然后,仅将插值变元作为变元而主、辅助曲面方程的变元作为参数,利用Sylvester结式消去过渡方程中的变元得到关于主曲面的拼接方程即造型曲面。利用该方法能实现带有控制点的曲面造型以及多曲面约束的几何造型,而且它可以确定造型过程中的中间形状及中间形状的位置,从而更加具有实用性。     

基于球B样条的3D人物角色建模与动画

提出一种新的人物角色的快速建模和动画的方法.通过使用球B样条实现以骨架为基础自动构建角色模型以及数据驱动的角色动画生成方法.给定人物角色骨架后,依据人体测量学根据骨骼长度计算出关节点处的半径.通过插值关节点以及半径生成球B样条曲线曲面表示的角色模型.根据所获取的运动数据(来自运动捕获),通过更新控制顶点来更新角色模型,从而实现角色的实时动画.     

NURBS曲面G~1光滑拼接算法

非均匀有理Ｂ样条（ＮＵＲＢＳ）曲线、曲面造型方法，是当前ＣＡＤ／ＣＡＭ领域研究热点之一，大量的基于ＮＵＲＢＳ的实用造型系统得到发展。对ＮＵＲＢＳ而言，虽然具有参数连续性，但为了实用需要，仍需构造具有一定光滑程度的合成曲面，满足局部设计和修改的目的。本文给出了实用的具有二次公共边界曲线的ＮＵＲＢＳ曲面片Ｇ１光滑拼接条件，得到了相应控制顶点、权系数的具体算法；对于一个已知ＮＵＲＢＳ曲面，构造另一个ＮＵＲＢＳ曲面，使其达到Ｇ１拼接是简单易行的。     

Introducing blending operations in feature models

We describe the implementation of a blending facility in the context of a feature modelling system where solid and feature-based modelling operations can be utilized in parallel during the design process of a part. The definition of blends can be done in a graphical user interface by selecting edges to be blended. Feature recognition of blends facilitates the definition process of blends. Alternatively, a special feature editor can be used to add blends to the feature model. The particular implementation style chosen gives rise to aflexible and easy-to-use modelling tool.