Feature matching and affine transformation for 2D cell animation

This paper presents an application for feature matching and affine transformation in computer graphics. The study case considered is 2D cell animation, which is still a labor-intensive process in current cartoon film production. One key problem in automating 2D cell animation in inbetween frame generation. The objective of our work is to investigate how to automatically generate inbetweening from pairs of hand-drawn 2D key frames. Our technique first establishes the correspondence of feature points and then estimates the affine transformation between each pair of 2D key frames. The inbetween frames are then automatically generated by interpolation.     

A model for the three-dimensional reconstruction and animation of the human heart

This paper presents a strategy for the production of a computer-generated film showing the complete motion of a human heart. The model for construction and animation is discussed. The heart is decomposed into different parts; each part is considered as a subactor of the heart which is viewed as the main actor. The left ventricle simulation is emphasized, because it is based on medical measures. The atrium simulation is based on beta-spline surfaces and blood volume considerations.     

Performance‐driven animation of hand‐drawn cartoon faces

We present a novel performance‐driven approach to animating cartoon faces starting from pure 2D drawings. A 3D approximate facial model automatically built from front and side view master frames of character drawings is introduced to enable the animated cartoon faces to be viewed from angles different from that in the input video. The expressive mappings are built by artificial neural network (ANN) trained from the examples of the real face in the video and the cartoon facial drawings in the facial expression graph for a specific character. The learned mapping model makes the resultant facial animation to properly get the desired expressiveness, instead of a mere reproduction of the facial actions in the input video sequence. Furthermore, the lit sphere, capturing the lighting in the painting artwork of faces, is utilized to color the cartoon faces in terms of the 3D approximate facial model, reinforcing the hand‐drawn appearance of the resulting facial animation. We made a series of comparative experiments to test the effectiveness of our method by recreating the facial expression in the commercial animation. The comparison results clearly demonstrate the superiority of our method not only in generating high quality cartoon‐style facial expressions, but also in speeding up the animation production of cartoon faces. Copyright © 2011 John Wiley & Sons, Ltd.     

Towards an integrated view of 3-D computer animation

To automate character animation and extend it to 3-D we need to create and manipulate three-dimensional models of articulated figures as well as the worlds they will inhabit.Abstraction andadaptive motion are key mechanisms for dealing with thedegrees of freedom problem, which refers to the sheer volume of control information necessary for coordinating the motion of an articulated figure when the number of links is large. A three level hierarchy of control modes for animation is proposed:guiding, animator-level, andtask-level systems. Guiding is best suited for specifiying fine details but unsuited for controlling complex motion. Animatorlevel programming is powerful but difficult. Task-level systems give us facile control over complex motions and tasks by trading off explicit control over the details of motion. The integration of the three control levels is discussed.     

Facial animation retargeting and control based on a human appearance space

Expressive facial animations are essential to enhance the realism and the credibility of virtual characters. Parameter‐based animation methods offer a precise control over facial configurations while performance‐based animation benefits from the naturalness of captured human motion. In this paper, we propose an animation system that gathers the advantages of both approaches. By analyzing a database of facial motion, we create the human appearance space. The appearance space provides a coherent and continuous parameterization of human facial movements, while encapsulating the coherence of real facial deformations. We present a method to optimally construct an analogous appearance face for a synthetic character. The link between both appearance spaces makes it possible to retarget facial animation on a synthetic face from a video source. Moreover, the topological characteristics of the appearance space allow us to detect the principal variation patterns of a face and automatically reorganize them on a low‐dimensional control space. The control space acts as an interactive user‐interface to manipulate the facial expressions of any synthetic face. This interface makes it simple and intuitive to generate still facial configurations for keyframe animation, as well as complete temporal sequences of facial movements. The resulting animations combine the flexibility of a parameter‐based system and the realism of real human motion. Copyright © 2010 John Wiley & Sons, Ltd.     

Human body animation: a survey

A survey of human body animation is presented dealing with its geometrical representation, motion control techniques and rendering. A classification of human body animation systems is presented according to different criteria.The human body movement notations are described and the different existing geometric models of the body and the face are analised and compared.The body and face control motion techniques are presented and discussed, as well as human body motion in its environment. Finally, the different problems of human body rendering are presented.     

一种草图动画工具的设计与实现

针对当前计算机在中小学课堂应用中采用静态幻灯片模式对学生缺乏吸引力、教学效率不高等不足,以及现有的动画制作工具对于大部分教师难以使用的问题,探讨了基于运动轨迹的动画制作方法、草图动画中的动作协调,以及形变算法在草图动画中的应用等问题,实现了一个草图动画制作工具。该草图动画制作工具支持平移、旋转、放缩等草图动画中常用的动作方式。基于运动轨迹的动画制作方法和简洁的用户界面使得设置动作像绘制物体一样简单。使用形变动画作为轨迹动画的补充方式,可制作出更加生动的动画。老师使用该工具可以快捷方便地制作出自己的动画。     

Virtual human animation in natural language visualisation

Simulation motion of Virtual Reality (VR) objects and humans has experienced important developments in the last decade. However, realistic virtual human animation generation remains a major challenge, even if applications are numerous, from VR games to medical training. This paper proposes different methods for animating virtual humans, including blending simultaneous animations of various temporal relations with multiple animation channels, minimal visemes for lip synchronisation, and space sites of virtual human and 3D object models for object grasping and manipulation. We present our work in our natural language visualisation (animation) system, CONFUCIUS, and describe how the proposed approaches are employed in CONFUCIUS’ animation engine.     

An object-oriented architecture for a computer animation system

This paper describes the architecture, capabilities and implementation of The Clockworks, an object-oriented computer animation system encompassing a wide variety of modeling, image synthesis, animation, programming and simulation capabilities in a single integrated environment. The object-oriented features of The Clockworks are implemented in portable C under UNIX using a programming discipline. These features include objects with methods and instance variables, class hierarchies, inheritance, instantiation and message passing.     

Virtual marionettes: a system and paradigm for real-time 3D animation

This paper describes a computer graphics system that enables users to define virtual marionette puppets, operate them using relatively simple hardware input devices, and display the scene from a given viewpoint on the computer screen. This computerized marionette theater has the potential to become a computer game for children, an interaction tool over the Internet, enabling the creation of simultaneously viewed and operated marionette show by users on the World Wide Web, and, most importantly, a versatile and efficient professional animation system.     

计算机动画技术发展研究

本文将国内外计算机动画发挥情况进行了对比,并介绍了目前计算机动画技术发挥在那的现状。     

Design and animation of volume density functions

This paper describes the design and animation of volume density functions for creating images containing gases, solid textures and hypertextures. The development of functions for producing images and animations of gases is explained in detail. Procedures for modelling the geometry of various gases are described. Next, animation techniques for volume density functions are described and examples of the animation of these functions are presented, including steam rising from a teacup, wind effects, marble forming, and gas and liquid flow into an opening in a wall. Solid spaces are introduced as a unifying approach to describing and animating object attributes.     

一种卡通动画中人物头发运动生成技术研究

介绍了一种新的卡通动画中人物头发运动的混合技术,使动画师们能方便地创作出有吸引力和可控性的头发运动效果,而不需要手工对头发运动表现过程进行逐帧绘制,仅设置好所需的一些关键帧画面。该技术方法演示如何根据给出的手绘卡通人物角色动作配以相应的头发运动效果。这种方法的新颖之处是,既不是简单地插入关键帧来获得头发运动效果,也不是通过物理模拟的方式来生成头发飘逸的动画,而是从动画师预先准备好的少量的作为关键帧草图的头发运动效果,建立物理模拟动画数据库,根据此数据库中头发的运动效果来创建出特定头发运动动画。此方法生成的头发动画分两个阶段完成,首先是在数据库中搜索对应的运动效果画面,然后顺利连接;其次数据库序列的关键帧之间的过渡帧由在动画中运用转移函数生成的插值补充,以实现流畅的头发飘逸动画。     

A simple approximation to rigid body dynamics for computer animation

Recently, the dynamics of linked articulated rigid bodies has become a valuable tool for making realistic three-dimensional computer animations. An exact treatment of rigid body dynamics, however, is based on rather non-intuitive results from classical mechanics (e.g. the Euler equations for rotating bodies) and it relies heavily on sophisticated numerical schemes to solve (large) sets of coupled non-linear algebraic and differential equations. As a result, articulated rigid bodies are not yet supported by most real-time animation systems. This paper discusses an approach to rigid body dynamics which is based on (both conceptually and algorithmically much simpler) point mechanics; this gives rise to an asymptotically exact numerical scheme (NSI) which is useful in the context of real-time animation, provided that the number of degrees of freedom of the simulated system is not too large. Based on NSI, a second scheme (NS2) is derived which is useful for approximating the motions of linked articulated rigid bodies; NS2 turns out to be sufficiently fast to give at least qualitative results in real-time simulation. In general, the algorithm NS2 is not necessarily (asymptotically) exact, but a quantitative analysis shows that in the absence of reaction forces it conserves angular momentum.     

基于运动捕获数据的虚拟人动画研究

随着三维游戏等行业对计算机动画制作需求的增加,在三维动画制作软件中人工调整虚拟人动作的工作方式已经不再适合现在的计算机动画制作。运动捕获技术是直接记录物体的运动数据并将其用于生成计算机动画,具有高效率、所生成的动画真实感强等优点,因而获得了广泛应用。提出了一种利用运动捕获数据来生成动画的方法,基于运动捕获得到的数据建立并驱动三维骨架模型,从而产生骨架的运动,形成动画。该方法可以充分利用现有的大量运动捕获数据,因此具有较大的应用前景。     

Flash动画设计与传统动画设计的特点比较研究

随着现如今的经济水平的不断提高和发展，人们对于生活品质当中的追求不仅仅停留在物质的层面上，更多地开始关注精神文化方面的享受。动画是人们精神世界中不可忽视的重要组成部分，传统动画凭借其细腻的风格，开辟了我国动画事业的第一战场，也推动了flash动画的发展，但二者之中存在着许多特点方面的差异性。     

Perceptual validity in animation of human motion

The crucial concept of modeling and synthesis/control of human motion (including face and body) for animation has been widely studied and explored in the literature. In this regard, the audience's perception of generated or recorded animation scenes is of critical importance. In this paper, we explore and conceptualize the general notions that need to be taken into account for human motion to maintain perceptual accuracy. We propose a paradigm called Perceptual Validity composed of four major components, which are discussed in detail. The model is concerned with different aspects of the scene such as correct illustration of the stimuli, context, and local/global relations of various visual cues present in human motion. Satisfying all the proposed principles, based on the literature, seems compulsory and vital for synthesis of perceptually valid animation scenes of human motion. We investigate the relative significance of the different components of the paradigm using feedback from expert animators and conduct a case study on one of the components of the paradigm. For further evaluation and exploration, Disney's principles of animation are discussed and compared against our proposed paradigm. We argue that while there are significant parallels and overlaps, our model is only focused on and more inclusive towards human motion and can therefore provide a valuable set of guidelines for animators in the field of character animation. Copyright © 2015 John Wiley & Sons, Ltd.