基于嵌入式系统的人工生命动画引擎关键技术研究

传统动画采用关键帧技术,设计出的动画缺乏自主性、情节单一、在一定程度上不能满足用户的需求。因此本文采用基于人工生命的方法,进行动画引擎的设计。考虑到嵌入式系统中硬件性能有限的问题,提出了适应嵌入式系统的人工生命动画新方法,即采用分层算法构建人工生命模型,以提高动画运行速度、运行效率。另外,由于50%的CPU处理时间花费在渲染引擎上面,重点分析了图形渲染中的几个关键技术,并在理论与实践相结合的基础上实现了一个简单的图形渲染引擎。     

Presence and interaction in mixed reality environments

In this paper, we present a simple and robust mixed reality (MR) framework that allows for real-time interaction with virtual humans in mixed reality environments under consistent illumination. We will look at three crucial parts of this system: interaction, animation and global illumination of virtual humans for an integrated and enhanced presence. The interaction system comprises of a dialogue module, which is interfaced with a speech recognition and synthesis system. Next to speech output, the dialogue system generates face and body motions, which are in turn managed by the virtual human animation layer. Our fast animation engine can handle various types of motions, such as normal key-frame animations, or motions that are generated on-the-fly by adapting previously recorded clips. Real-time idle motions are an example of the latter category. All these different motions are generated and blended on-line, resulting in a flexible and realistic animation. Our robust rendering method operates in accordance with the previous animation layer, based on an extended for virtual humans precomputed radiance transfer (PRT) illumination model, resulting in a realistic rendition of such interactive virtual characters in mixed reality environments. Finally, we present a scenario that illustrates the interplay and application of our methods, glued under a unique framework for presence and interaction in MR.     

浅析基于游戏引擎技术的三维动画制作

游戏引擎技术凭借其一系列功能优势,诸如实时渲染、实时修改等,应用于三维动画制作中,可显著缩减渲染周期,提升制作效率,并促进获得高质量的三维动画作品。本文通过阐述游戏引擎的内涵特征,分析游戏引擎的主要功能,对基于游戏引擎技术的三维动画制作展开探讨,旨在为如何促进三维动画制作顺利进行提供一些思路。     

Quaternion calculus as a basic tool in computer graphics

Quaternions, although not well known, provide a fundamental and solid base to describe the orientation of an object or a vector. They are efficient and well suited to solve rotation and orientation problems in computer graphics and animation. This paper describes two new methods for splining quaternions so that they can be used within a keyframe animation system. We also show that quaternions, although up to now solely used for animation purposes, can be used successfully in the field of modelling and rendering and we prove that we can speed up the rendering algorithm by using quaternions.     

A Survey of Real‐Time Crowd Rendering

In this survey we review, classify and compare existing approaches for real‐time crowd rendering. We first overview character animation techniques, as they are highly tied to crowd rendering performance, and then we analyze the state of the art in crowd rendering. We discuss different representations for level‐of‐detail (LoD) rendering of animated characters, including polygon‐based, point‐based, and image‐based techniques, and review different criteria for runtime LoD selection. Besides LoD approaches, we review classic acceleration schemes, such as frustum culling and occlusion culling, and describe how they can be adapted to handle crowds of animated characters. We also discuss specific acceleration techniques for crowd rendering, such as primitive pseudo‐instancing, palette skinning, and dynamic key‐pose caching, which benefit from current graphics hardware. We also address other factors affecting performance and realism of crowds such as lighting, shadowing, clothing and variability. Finally we provide an exhaustive comparison of the most relevant approaches in the field.     

Improving the communication performance of distributed animation rendering using BitTorrent file system

Rendering is a crucial process in the production of computer generated animation movies. It executes a computer program to transform 3D models into series of still images, which will eventually be sequenced into a movie. Due to the size and complexity of 3D models, rendering process becomes a tedious, time-consuming and unproductive task on a single machine. Accordingly, animation rendering is commonly carried out in a distributed computing environment where numerous computers execute in parallel to speedup the rendering process. In accordance with distribution of computing, data dissemination to all computers also needs certain mechanisms which allow large 3D models to be efficiently moved to those distributed computers to ensure the reduction of time and cost in animation production. This paper presents and evaluates BitTorrent file system (BTFS) for improving the communication performance of distributed animation rendering. The BTFS provides an efficient, secure and transparent distributed file system which decouples the applications from complicated communication mechanism. By having data disseminated in a peer-to-peer manner and using local cache, rendering time can be reduced. Its performance comparison with a production-grade 3D animation favorably shows that the BTFS outperforms traditional distributed file systems by more than 3 times in our test configuration.     

Realistic modeling of spectator behavior for soccer videogames with CUDA

Soccer has always been one of the most popular videogame genres. When designing a soccer game, designers tend to focus on the game field and game play due to the limited computational resources, and thus the modelling of virtual spectators is paid less attention. In this study we present a novel approach to the modeling of spectator behavior, which treats each spectator as a unique individual. We also propose an independent software layer for sport-based games that simply obtains the game status from the game engine via a simple messaging protocol and computes the spectator behavior accordingly. The result is returned to the game engine, to be used in the animation and rendering of the spectators. Additionally, we offer a customizable spectator knowledge base with well structured XML to minimize coding efforts, while generating individualized behavior. The employed AI is based on fuzzy inference. In order to overcome additional demand for computing realistic spectator behavior, we use GPU parallel computing with CUDA.     

Perception-based model simplification for motion blur rendering

Motion blur effects are important to motion perception in visual arts, interactive games and animation applications. Usually, such motion blur rendering is quite time consuming, thus blocking the online/interactive use of the effects. Motivated by the human perception in relation to moving objects, this paper presents simplified geometric models that enable to speedup motion blur rendering, which has not been tracked in motion blur rendering specifically. We develop a novel algorithm to simplify models with motion-aware, to preserve the features whose characteristics are perceivable in motion. We deduce the formula to outline the level of detail simplification by the object moving velocity. Using our simplified models, methods for motion blur rendering can achieve the rendering quality as using the original models, and obtain the processing acceleration mostly. The experimental results have shown the effectiveness of our approach, more acceleration with the larger models or faster motion (e.g. for the dragon model with over a million facets, the motion-blur rendering via hierarchical stochastic rasterization is sped up by over 27 times).     

利用OSG三维图形渲染引擎实现的骨骼动画

动态实体模型是虚拟场景的重要组成部分,骨骼动画是表达虚拟场景中动态实体行为的主要技术。提出了一种虚拟场景中三维模型骨骼动画渲染的策略,即采用第三方软件建立三维动画模型,基于Cal3D动画控制机制,使用OSG三维图形渲染引擎对虚拟场景中运动的三维模型进行模拟。在VisForest软件的基础上,集成了骨骼动画渲染方法,解决了动物在虚拟地表上“踏空”的问题,扩展了动态实体在虚拟环境中的行为模拟。以梅花鹿和大象为例,逼真地模拟了动物在虚拟环境中的奔跑和行走的过程,模拟过程中动作衔接比较自然。     

BRDF Representation and Acquisition

Photorealistic rendering of real world environments is important in a range of different areas; including Visual Special effects, Interior/Exterior Modelling, Architectural Modelling, Cultural Heritage, Computer Games and Automotive Design. Currently, rendering systems are able to produce photorealistic simulations of the appearance of many real‐world materials. In the real world, viewer perception of objects depends on the lighting and object/material/surface characteristics, the way a surface interacts with the light and on how the light is reflected, scattered, absorbed by the surface and the impact these characteristics have on material appearance. In order to re‐produce this, it is necessary to understand how materials interact with light. Thus the representation and acquisition of material models has become such an active research area. This survey of the state‐of‐the‐art of BRDF Representation and Acquisition presents an overview of BRDF (Bidirectional Reflectance Distribution Function) models used to represent surface/material reflection characteristics, and describes current acquisition methods for the capture and rendering of photorealistic materials.     

Perception-based fast rendering and antialiasing of walkthroughsequences

We consider accelerated rendering of high quality walkthrough animation sequences along predefined paths. To improve rendering performance, we use a combination of a hybrid ray tracing and image-based rendering (IBR) technique and a novel perception-based antialiasing technique. In our rendering solution, we derive as many pixels as possible using inexpensive IBR techniques without affecting the animation quality. A perception-based spatiotemporal animation quality metric (AQM) is used to automatically guide such a hybrid rendering. The image flow (IF) obtained as a byproduct of the IBR computation is an integral part of the AQM. The final animation quality is enhanced by an efficient spatiotemporal antialiasing which utilizes the IF to perform a motion-compensated filtering. The filter parameters have been tuned using the AQM predictions of animation quality as perceived by the human observer. These parameters adapt locally to the visual pattern velocity     

力/触觉再现中柔性物体可视化物理形变模型研究进展

力/触觉再现技术的出现,为虚拟现实开辟了全新的应用领域,促使基于物理意义的柔性物体形变建模成为一个研究热点.系统地讨论了近年来基于物理意义的柔性物体形变建模方法,分析了基于直接构建的模型、基于连续介质力学的模型和其他相关模型的基本思想和优缺点.对这些建模方法的性能进行了细致的比较,并探讨了柔性物体物理形变建模的未来发展趋势.     

Real‐time Realistic Ocean Lighting using Seamless Transitions from Geometry to BRDF

Realistic animation and rendering of the ocean is an important aspect for simulators, movies and video games. By nature, the ocean is a difficult problem for Computer Graphics: it is a dynamic system, it combines wave trains at all scales, ranging from kilometric to millimetric. Worse, the ocean is usually viewed at several distances, from very close to the viewpoint to the horizon, increasing the multi‐scale issue, and resulting in aliasing problems. The illumination comes from natural light sources (the Sun and the sky dome), is also dynamic, and often underlines the aliasing issues. In this paper, we present a new algorithm for modelling, animation, illumination and rendering of the ocean, in real‐time, at all scales and for all viewing distances. Our algorithm is based on a hierarchical representation, combining geometry, normals and BRDF. For each viewing distance, we compute a simplified version of the geometry, and encode the missing details into the normal and the BRDF, depending on the level of detail required. We then use this hierarchical representation for illumination and rendering. Our algorithm runs in real‐time, and produces highly realistic pictures and animations.     

OGRE引擎中基于BVH的角色动画的实现研究

OGRE是一个被广泛使用的开源三维图形渲染引擎。为了提高角色动画的制作效率,应该减少一些中间转换的环节,本文提出采用解析标准BVH文件的方法:通过结构体函数直接将解析后的数据加载到内存中,利用OGRE引擎对其进行实时渲染。实验结果证明,在OGRE引擎中,解析后的BVH文件的运动数据能够成功驱动模型,并且实现高逼真的3D渲染效果。     

Harmonic rendering for visual coherence on mobile outdoor AR environment

Rapid developments in augmented reality (AR) and related technologies have led to increasing interest in immersive content. AR environments are created by combining virtual 3D models with a real-world video background. It is important to merge these two worlds seamlessly if users are to enjoy AR applications, but, all too often, the illumination and shading of virtual objects is not consider the real world lighting condition or does not match that of nearby real objects. In addition, visual artifacts produced when blending real and virtual objects further limit realism. In this paper, we propose a harmonic rendering technique that minimizes the visual discrepancy between the real and virtual environments to maintain visual coherence in outdoor AR. To do this, we introduce a method of estimating and approximating the Sun’s position and the sunlight direction to estimate the real sunlight intensity, as this is the most significant illumination source in outdoor AR and it provides a more realistic lighting environment for such content, reducing the mismatch between real and virtual objects.

     

基于图象的绘制技术

基于图象绘制技术是实现对虚拟场景建模和实时绘制的新的有效方法,可以克服传统的基于几何绘制方式中建立起初模型的困难和实时绘制计算在的缺陷。本文介绍和分析目前图象绘制技术的一些主要方法,并提出改进途径。     

虚拟环境中化身技术的研究与进展

化身(Avatar)是虚拟环境、系统仿真和数字娱乐等应用中的一项重要技术。首先回顾用户化身的发展历史和定义,然后综述其中的人体建模、实时绘制、角色动画和情感计算等基本技术,介绍代表性算法,并加以比较和总结。在介绍几种典型的应用之后,指出未来的发展方向。     

Animation of deformable models

Although kinematic modelling methods are adequate for describing the shapes of static objects, they are insufficient when it comes to producing realistic animation. Physically based modelling remedies this problem by including forces, masses, strain energies and other physical quantities. The paper describes a system for the animation of deformable models. The system uses physically based modelling methods and approaches from elasticity theory for animating the models. Two different formulations, namely the primal formulation and the hybrid formulation, are implemented so that the user can select the one most suitable for an animation depending on the rigidity of the models. Collision of the models with impenetrable obstacles and constraining of the model points to fixed positions in space are implemented for use in the animations.     

基于Pro／E和3DSMax的缝纫机原理仿真动画制作研究

缝纫机原理仿真动画对缝纫机主要功能零件模型的几何尺寸准确度要求较高．利用Pro/E对缝纫机零部件进行精确建模和装配,将三维模型导入3DS Max中进行材质渲染和动画制作,完成缝纫机原理仿真动画。充分发挥Pro／E和3DS Max软件各自的优势,解决单独使用3DS Max软件在机构动画制作中零件的尺寸和装配不准确的问题,为机构仿真动画制作提供新思路。     

Solid modelling in a virtual reality environment

This paper presents a constraint-based methodology for intuitive and precise solid modelling in a virtual reality (VR) environment. A hierarchically structured and constraint-based data model is developed to support solid modelling in the VR environment. A constraint reasoning engine is also developed to automatically deduce allowable motions for precise constraint-based 3D manipulations. A prototype system of product modelling has been successfully developed, and experimental results demonstrate the advantage of precise solid modelling through constraint-based manipulation in virtual environments.