三维动画技术与三维虚拟技术的研究

目前三维图形技术主要包括两大类：三维动画技术和三维虚拟技术。该文的目的是研究两种技术的开发原理，并通过对两种技术的对比，进一步说明了三维虚拟仿真技术在实时性、交互性方面的优势。该文首先介绍了三维动画技术的应用原理、开发步骤，重点阐述了三维虚拟技术中的实时显示技术和交互技术，给出了虚拟仿真应用的开发方法及基于两种技术的应用实例，并对两种技术在实时性、交互性、时间性和三维建模效果等方面作了比较，最后展望三维虚拟技术的发展方向。     

基于OpenGL的飞行实时三维动画仿真

在飞行模拟训练器中,显示系统是其重要组成部分.为全面、直观并且实时地反映飞行仿真计算机得到的仿真数据,则采用三维动画方式来制作这个显示系统.文章讨论了使用开放图形库(OpenGL)结合Visual C 6.0开发平台及MFC框架,构建基于OpenGL的飞行实时三维动画仿真系统的方法,并利用从串行口接收来的实时数据实现实时仿真.实验证明,该系统仿真效果好,运行正确、可靠、实时性好.     

Animated simulation graphics for a manufacturing conveyor system

Computer simulation is an important aid for designing manufacturing systems. Computer graphics is an extremely effective medium for communication between man and computer. Because animated simulation graphics is a field whose time has come, the study described herein uses a combination of computer simulation and computer graphics in the designing of a complex manufacturing conveyor system.     

Reality Augmentation for Medical Procedures: System Architecture, Single Camera Marker Tracking, and System Evaluation

Augmented Reality is an emerging technology that seeks to enhance a user’s view by overlaying graphical information. We developed a prototype AR system geared for medical applications. It is built around a stereoscopic head-mounted display of the video-see-through variety. The newest generation of this prototype system exhibits high performance on a standard PC platform. Stereoscopic video images are augmented with medical graphics in real-time at 30 frames per second and with XGA (1024× 768) resolution. The system provides a compelling AR perception: the graphics appears firmly anchored in the scene—there is no time lag between video and graphics or any apparent jitter of the graphics. With the head-mounted display, the user has a natural and direct access to understanding the 3D structure of the scene, based on both stereo and kinetic depth cues. In the present paper, we describe in detail the architecture and several features of the AR prototype system. Head tracking is accomplished with a single-camera system, with the dedicated tracker camera placed on the head-mounted display. This configuration is the foundation of achieving a high-accuracy graphics overlay. We are now exploring the use of the prototype system for a variety of medical applications. This paper gives an overview over the pre-clinical tests that we have performed for interventional guidance. Overall, the feedback has been very positive and encouraging, and we are continuing to work towards realizing the clinical potential of the technology.     

A computer graphics course for the two cultures

The subject of computer graphics offers a special educational opportunity for bringing together students from the two cultures of the arts/humanities and of the sciences/technologies. The author describes a computer graphics course with this approach. Several important problems arise because of students' varying backgrounds in programming and their expectations, the lack of suitable texts, and the lack of suitably-oriented computer graphics centers. The course schedule is composed of lectures, discussions of readings, and workshops in a computer graphics facility. The hardware and software basis of the course is flexible. Students complete an assigned initial project, a final project of their choice, and are responsible for documenting their project visually and verbally before the close of the semester. Student performance and evaluation of the course suggest this cross-cultural approach is a valid, worthwhile experiment to introduce the structure and significance of computer graphics imagery and computer graphics display systems.     

Cultural differences on attention and perceived usability: Investigating color combinations of animated graphics

This experimental study investigates the effects of animated graphic colors on attention and perceived usability of users from two cultural groups, American and Thai. The experiment employs a three-way split-plot design with one between-subjects factor and two repeated-measures factors. The between-subjects factor contains two cultural groups, American and Thai. The two repeated-measures variables are a banner background color factor with six levels and a banner font color factor with two levels. Participants search for target words from text on Web pages that contain three animated banner graphics. The findings lead to the conclusion that users across cultures tend to ignore animated banner graphics when they look for specific information on highly informative Web pages. This study also suggests influences of culture on overall performance, overall retention, and overall self-reports on usability, regardless of differences in banner color combinations. Moreover, cultural differences on the self-report of attention drawing are also revealed in each banner color usage, except yellow banners with white text. This study does not aim at exploring superiority of participants between cultures. Rather, it attempts to explore some possible cultural differences in interacting with a computer interface that could facilitate cognition and perception of users from different cultural groups.     

A formalization for the specification and systematic generation of computer graphics systems

A formalization of graphical processes in computer graphics systems is presented in terms of functions and their system of axioms. The concept of the viewing pipeline is formalized as operation sequence which is a sequential composition of graphical elementary operations. The formalization includes two kinds of operation sequences which are used as the formal specifications of graphics systems and display devices. In order to generate a graphics system using a display device, we introduced the concept of functionality-preserving transformation of operation sequences in terms of various types of commutations among primitive operations. A type of transformation, which is called extraction, plays a central role in the generation algorithm.     

计算机动画关键帧插补技术综述

对计算机辅助动画制作过程中关键帧的插补技术进行了研究。线性插值法通过给定的起始帧和结束帧对应点之间的直线距离算出中间插值帧。移动点约束条件插补法利用随时间空间变化的曲线与彩体上的点相关联，来控制关键帧上对应控制点的轨迹以厦动态特征。骨架插补法是将图形抽象成骨架，然后进行插补。     

Multiscale and local search methods for real time region tracking with particle filters: local search driven by adaptive scale estimation on GPUs

Tracking systems are important in computervision, with applications in surveillance, human computer interaction, etc. Consumer graphics processing units (GPUs) have experienced an extraordinary evolution in both computing performance and programmability, leading to greater use of the GPU for non-rendering applications. In this work we propose a real-time object tracking algorithm, based on the hybridization of particle filtering (PF) and a multi-scale local search (MSLS) algorithm, presented for both CPU and GPU architectures. The developed system provides successful results in precise tracking of single and multiple targets in monocular video, operating in real-time at 70 frames per second for 640 × 480 video resolutions on the GPU, up to 1,100% faster than the CPU version of the algorithm.     

Techniques for Animation on Microcomputers

Animation is a powerful visualization aid and it has applications not only in the traditional areas of cartoons and fiction movies but also in the study of a wide variety of natural and simulated phenomena. Currently, there is growing interest in the study of animated algorithms and data structures particularly due to the availability of cheaper and more powerful microcomputers. Computer animation may use complex graphics systems and therefore the quality and speed of the graphics display are extremely important. Various techniques for animation on microcomputers are examined and it is shown that Scrolling techniques can be successfully applied for realistic animation in many application areas. Macintosh implementations of "animated algorithms" are used to illustrate the effectiveness of the method.     

一个基于映射曲面形式的二维网格采样数据场可视化方法

本文提出了一种基于映射曲面形式的三维可视化方法,较传统的高度场表示所采用的双三次曲面表示法,实现了采样数据点的高精度可视化表现.而且,与同类方法相比,本方法具有灵活性高,能够适于多种应用,并且执行效率高的特点.同时讨论了如何利用OpenGL图象接口的实现问题.在分析了该方法特点的基础上,给出了一个应用实例.     

Telidon graphics and applications

Telidon is essentially a computer graphics code which is very effective as the presentation level protocol for videotex, for which it was originally developed, teletext and other consumer- and business-oriented information systems. Its use of geometric primitives rather than the mosaic characters of its predecessors permits efficient digital storage and rapid transmission of detailed graphics. Display terminals can be built to display the images with different degrees of detail to suit the application.     

A Graphics System Architecture for Interactive Application-Specific Display Functions

Interactive computer graphics display requirements have generally been met is one of two ways: by highly specialized systems designed for a particular application, or, more frequently, by devices with a limited set of display functions common to a wide range of applications. A third alternative, presented here, is to use a high-performance, general-purpose display architecture to provide both common and application-specific graphics functions. A sampling data display to solid modeling, shows that significant improvements in interactivity can be obtained by microprogramming such a machine.     

Are autostereograms useful for computer graphics and scientific visualization

Autostereograms are images that can be observed as “flat” 2D pictures or as a display of 3D objects without any extra apparatus. More than one million copies of books on this subject have been sold recently, but are autostereograms useful for computer graphics and scientific visualization? This short note provides some assistance for easily designing still and animated autostereograms, and tries to encourage reader involvement in finding new scientific applications.     

Measuring cognitive load in test items: static graphics versus animated graphics

The majority of multimedia learning studies focus on the use of graphics in learning process but very few of them examine the role of graphics in testing students' knowledge. This study investigates the use of static graphics versus animated graphics in a computer‐based English achievement test from a cognitive load theory perspective. Three hundred and three 7th‐grade students were randomly split into two groups and given the test questions either with static graphics or with animated graphics accompanied with text. Students' response time, response accuracy, self‐reported ratings on cognitive load and secondary task approach were used to measure their cognitive load. Findings revealed that animating graphics increased the response time and secondary task scores of the students but did not have any significant effect on their test success. Furthermore, no difference was observed in self‐reported cognitive loads. The relationship between the four different cognitive load measures was also examined in the study. No direct relation was found between self‐reported ratings and secondary task scores. On the other hand, self‐ratings and response accuracy were found to be more sensitive to intrinsic cognitive load, whereas response time and secondary task measures were found to be more sensitive to extraneous cognitive load in our testing environment.     

Computer Graphics and Man-Machine Interactions

During the past 10 years, there has been a considerable growth of interest in the problems of applying computer graphics techniques to practical use. This interest has created an increasing need for the applications of theoretical computer graphics methods to software and hardware systems that are cost-effective as well as user-oriented. A number of books have been published on the subject of computer graphics, and some rather cost-effective graphics devices have been designed and built for practical use. The latter has mainly been the result of microminiaturization technology of the last five years. Microprocessors, microcomputers, and microprogrammability have helped considerably in making cost-effective display devices a reality, the intelligence of such devices being limited only by the capability of the microprocessors. Applications of computer graphics have steadily increased in such areas as engineering, design, education, medicine/biomedicine, chemistry, business, analysis, computer-aided design, management, structural design, simulation, and communication.     

Dynamic 3D modelling for architectural design

A graphics design system employing 2D input and display devices (such as the pen and tablet and the calligraphic CRT) to input, edit, and view 3D objects representing landscapes and architectural structures in realtime is discussed. Landscape is entered via a procedure that uses an inking algorithm to obtain 2D data defining the site's contours and additional available interactive devices to obtain the contour heights. Extrusion techniques and compound transformations are used to generate volumes from facial elements input via a suite of rubberband algorithms that take advantage of the graphics hardware. Dynamic menus, displayed transformation parameter values and extensive editing features facilitate user interaction. Architectural studies of complex structures built by combining basic architectural units input using extrusion techniques are presented.     

Real-time optimal adaptation for planetary geometry and texture: 4-8 tile hierarchies

The real-time display of huge geometry and imagery databases involves view-dependent approximations, typically through the use of precomputed hierarchies that are selectively refined at runtime. A classic motivating problem is terrain visualization in which planetary databases involving billions of elevation and color values are displayed on PC graphics hardware at high frame rates. This paper introduces a new diamond data structure for the basic selective-refinement processing, which is a streamlined method of representing the well-known hierarchies of right triangles that have enjoyed much success in real-time, view-dependent terrain display. Regular-grid tiles are proposed as the payload data per diamond for both geometry and texture. The use of 4-8 grid refinement and coarsening schemes allows level-of-detail transitions that are twice as gradual as traditional quadtree-based hierarchies, as well as very high-quality low-pass filtering compared to subsampling-based hierarchies. An out-of-core storage organization is introduced based on Sierpinski indices per diamond, along with a tile preprocessing framework based on fine-to-coarse, same-level, and coarse-to-fine gathering operations. To attain optimal frame-to-frame coherence and processing-order priorities, dual split and merge queues are developed similar to the realtime optimally adapting meshes (ROAM) algorithm, as well as an adaptation of the ROAM frustum culling technique. Example applications of lake-detection and procedural terrain generation demonstrate the flexibility of the tile processing framework.     

Controlled Metamorphosis Between Skeleton‐Driven Animated Polyhedral Meshes of Arbitrary Topologies

Enabling animators to smoothly transform between animated meshes of differing topologies is a long‐standing problem in geometric modelling and computer animation. In this paper, we propose a new hybrid approach built upon the advantages of scalar field‐based models (often called implicit surfaces) which can easily change their topology by changing their defining scalar field. Given two meshes, animated by their rigging‐skeletons, we associate each mesh with its own approximating implicit surface. This implicit surface moves synchronously with the mesh. The shape‐metamorphosis process is performed in several steps: first, we collapse the two meshes to their corresponding approximating implicit surfaces, then we transform between the two implicit surfaces and finally we inverse transition from the resulting metamorphosed implicit surface to the target mesh. The examples presented in this paper demonstrating the results of the proposed technique were implemented using an in‐house plug‐in for Maya?.