Separating semantics from rendering: a scene graph based architecture for graphics applications

A large number of rendering and graphics applications developed in research and industry are based on scene graphs. Traditionally, scene graphs encapsulate the hierarchical structure of a complete 3D scene, and combine both semantic and rendering aspects. In this paper, we propose a clean separation of the semantic and rendering parts of the scene graph. This leads to a generally applicable architecture for graphics applications that is loosely based on the well-known Model-View-Controller (MVC) design pattern for separating the user interface and computation parts of an application. We explore the benefits of this new design for various rendering and modeling tasks, such as rendering dynamic scenes, out-of-core rendering of large scenes, generation of geometry for trees and vegetation, and multi-view rendering. Finally, we show some of the implementation details that have been solved in the process of using this software architecture in a large framework for rapid development of visualization and rendering applications.     

The Convergence of Graphics and Imaging

Over twenty years ago a SIGGRAPH panel session addressed the convergence of computer graphics and image processing. At that time the emphasis was on low-level operations such as filtering to avoid anti-aliasing, and related psycho-physics issues. More recently, Graphics and Imaging are converging at a higher level as we move toward blending the synthetic world of computer-generated images with the real world of computer-captured images. In this talk we describe several research directions that relate to this convergence, and illustrate with specific examples of work at MERL – A Mitsubishi Electric Research Laboratory. These research directions are: Analyzing images of the human face to determine identity and orientation and ultimately to reconstruct the shape of the face. Reconstruction of static and dynamic 3D geometries from 2D images separated in time or space: here the objective is to take multiple images of a real-world scene and recreate the 3D geometry of the scene. If objects in the scene are moving, then the objective is extracting the dynamic geometry. Once the geometry has been reconstructed, editing and relighting of the scene becomes possible. Display of 3D scalar fields (also known as volume graphics) concerns 3D as opposed to 2D images, such as CT and MRI scans. These scans can be thought of as 3D images in that they are point samples of a 3D scalar field, just as a computer-captured image is a point sample of a 2D sample field. The objective of volume graphics is to create and display the 3D geometries that underly 3D images. An inexpensive yet real-time (30 fps for a 256 x 256 x 256 image) implementation of Pfister and Kaufman's Cube-4 rendering architecture will be described.     

Web-Based Remote Renderingwith IBRAC (Image-Based Rendering Acceleration and Compression)

Recent advances in Internet and computer graphics stimulate intensive use and development of 3D graphics on the World Wide Web. To increase efficiency of systems using 3D graphics on the web, the presented method utilizes previously rendered and transmitted images to accelerate the rendering and compression of new synthetic scene images. The algorithm employs ray casting and epipolar constraints to exploit spatial and temporal coherence between the current and previously rendered images. The reprojection of color and visibility data accelerates the computation of new images. The rendering method intrinsically computes a residual image, based on a user specified error tolerance that balances image quality against computation time and bandwidth. Encoding and decoding uses the same algorithm, so the transmitted residual image consists only of significant data without addresses or offsets. We measure rendering speed-ups of four to seven without visible degradation. Compression ratios per frame are a factor of two to ten better than MPEG2 in our test cases. There is no transmission of 3D scene data to delay the first image. The efficiency of the server and client generally increases with scene complexity or data size since the rendering time is predominantly a function of image size. This approach is attractive for remote rendering applications such as web-based scientific visualization where a client system may be a relatively low-performance machine and limited network bandwidth makes transmission of large 3D data impractical.     

Real-time rendering in curved spaces

A hypersphere surface provides a finite 3D world in which the user can fly freely without encountering boundaries, while hyperbolic space provides a spacious environment. The algorithm for rendering a scene in a hypersphere is identical to the standard algorithm for rendering a scene in ordinary flat 3D space. Indeed, the computations are so similar that off-the-shelf 3D graphics cards, when fed the correct matrices, will do real-time animations in a hypersphere just as easily and as quickly as they do in flat space.     

The Open Inventor Toolkit and the PREMO Standard

PREMO is an emerging international standard for the presentations of multimedia objects including computer graphics. Open Inventor™ is a commercially available "de facto" standard for interactive computer graphics packaged as a library of objects. In this paper, we consider whether the concepts and objects of PREMO are sufficient to represent a professional quality system, such as Open Inventor.
By comparing PREMO with Open Inventor, we hope to show that PREMO's computer graphics environment model and event model can properly describe Open Inventor's rendering action and event model. The scene graph is very important in Open Inventor. Most Open Inventor functions rely on various operations over scene graphs. The construction, edition and traversal of the scene graphs are implemented as a set of newly defined PREMO objects. Graphics rendering, event handling and scene graphs constitute the fundamental parts of Open Inventor, other Open Inventor functionalities can be constructed from these. We conclude that since these three fundamental parts of Open Inventor can be properly modelled and implemented by means of PREMO, that the concepts and objects of PREMO are sufficient to represent Open Inventor.     

基于可编程图形硬件的实时阴影算法及实现

阴影在增强三维场景真实感方面起着非常重要的作用。随着计算机图形硬件的发展,利用可编程图形硬件加速并提高渲染效果已经成为主要发展趋势。基于当前可编程图形硬件技术,针对目前shadow maps算法存在的问题,提出了一种根据场景特征程序自动生成合适偏移量的实时的阴影生成算法,该算法很好的改善了阴影渲染效果,防止了走样。最后给出了算法基于GLSL着色语言的实现代码。     

The Java 3D API and virtual reality

Java programmers can quickly and easily define graphics programs using Java 3D's scene graph classes. An expanded view model lets applications seamlessly operate in a variety of single- and multiple-display, nonhead-tracked and head-tracked, display environments. This view model relies on the flexible InputDevice interface that Java 3D provides to remove most of the vagaries of hardware trackers     

基于X3D的动态交互式虚拟社区技术研究

三维虚拟社区具有强大的功能和广泛的商业价值,是虚拟现实技术的应用之一。X3D是新一代互联网3D图形规范,为构建基于Web的3D应用提供了解决方案。本文从虚拟场景建模、动态交互的实现技术和虚拟场景优化三个方面讨论基于X3D构建动态交互式虚拟社区的技术。     

Graphing in depth: perspectives on the use of three-dimensional graphs to represent lower-dimensional data

Embellishing simple graphs by adding perspective, 'the 3D look, has become increasingly commonplace with the ready availability of graphics software. However, the effect of adding such decorative depth on the comprehension and recall of the graph's message has received little attention. The present study evaluated performance on such common graphical formats as line graphs, bar charts and pie charts constructed with and without the 3D look. When subjects were asked to make relative magnitude estimations, only the 3D line graphs resulted in reliable performance decrements. Likewise, information presented in 3D line graphs was remembered less accurately than information presented in 2D line graphs. For the estimation of global trends, both 3D line graphs and bar charts were used more quickly than 2D formats, but this speed was obtained at the expense of accuracy. For a trend classification task involving more focused processing, 3D line graphs and bar charts were associated with an overall performance decrement when compared with their 2D counterparts. Finally, the use of 3D designs, in addition to modifying performance, may influence the attitudes formed by subjects toward the information presented in the graphs.     

基于OpenGL的空战飞机三维飞行轨迹显示

开放图形程序库 Open GL是一种快速、高质量的 3D图形软件 ,用 Open GL与 MFC相结合开发 3D图形 ,可以实现优势互补。概述了 Open GL的特点和实现原理 ,结合空战仿真的需要 ,用 Open GL编写三维飞行轨迹显示程序 ,可以显示飞机的三维飞行轨迹 ,并能实现视点漫游、轨迹上特定点飞行数据读取     

Graphing in depth: perspectives on the use of three-dimensional graphs to represent lower-dimensional data

Abstract

Embellishing simple graphs by adding perspective, 'the 3D look, has become increasingly commonplace with the ready availability of graphics software. However, the effect of adding such decorative depth on the comprehension and recall of the graph's message has received little attention. The present study evaluated performance on such common graphical formats as line graphs, bar charts and pie charts constructed with and without the 3D look. When subjects were asked to make relative magnitude estimations, only the 3D line graphs resulted in reliable performance decrements. Likewise, information presented in 3D line graphs was remembered less accurately than information presented in 2D line graphs. For the estimation of global trends, both 3D line graphs and bar charts were used more quickly than 2D formats, but this speed was obtained at the expense of accuracy. For a trend classification task involving more focused processing, 3D line graphs and bar charts were associated with an overall performance decrement when compared with their 2D counterparts. Finally, the use of 3D designs, in addition to modifying performance, may influence the attitudes formed by subjects toward the information presented in the graphs.     

一种基于模型方法的三维数字影像生成系统

虚拟现实（ＶＲ）已成为计算机图形学中的一个重要分支,它作为一种新兴媒体,从八十年代末开始受到普遍关注,并已在多个领域发挥出色。本文主要介绍一种基于模型的３Ｄ数字影像生成系统。通过多路摄像机记录真实世界中的人物或情景,并提取数字信息,结合标准的计算机图形方法重现原始的三维景物。     

SVG的3D实现

针对SVG在3D图形的描述与绘制上存在局限性的问题,提出了一种SVG的3D实现方法;详细介绍了SVG的2D坐标系到3D坐标系的转换原理,给出了转换到3D坐标系后的SVG-3D图形的绘制与操控流程,并以在3D场景中绘制一个正立方体和圆球体为例,介绍了在HTML页面中采用JavaScript创建3D场景和绘制与操控这2个图形的实现。     

Three‐dimensional interaction and autostereoscopic display system using gesture recognition

We propose a 3D interaction and autostereoscopic display system that use gesture recognition, which can manipulate virtual objects in the scene directly by hand gestures and can display objects in 3D stereoscopy. The system consists of a gesture recognition and manipulation part as well as an autostereoscopic display as an interactive display part. To manipulate the 3D virtual scene, a gesture recognition algorithm is proposed, which use spatial‐temporal sequences of feature vectors to match predefined gestures. To get smooth 3D visualization, we utilize the programmable graphics pipeline in graphic processing unit to accelerate data processing. We develop a prototype system for 3D virtual exhibition. The prototype system reaches frame rates of 60 fps and operates efficiently with a mean recognition accuracy of 90%.     

矢量图形技术与X3D的应用

对当前Web图形技术应用面临的问题进行了探讨，分析了矢量图形的优势与SVG技术得以广泛应用的原因。指出在现有的文件格式与标准优势基础上新标准制定的必要性，对X3D体系结构的特点、浏览器结构及Web应用进行了探讨，在功能上同VRML97进行了比较，最后基于X3D-Edit给出了三维场景模型实例。     

实时三维图形平台BH_GRAPH

BH_GRAPH是一个面向视景仿真类应用系统开发人员、支持实时三维图形开发与运行的基础软件平台．它提供可扩展的软件体系结构、标准化的场景管理机制、高效率的场景处理方法、方便易用的应用程序接口,为三维图形应用系统的快速开发、高效运行提供完整的技术支撑．BH_GRAPH主要由三维视景绘制引擎、三维对象建模工具、三维场景布置工具以及一系列关键技术构成．概要介绍了BH—GRAPH各主要组成部分的软件结构、基本功能和技术特点．     

GRASP—A 3D graphics system for Pascal users

This paper describes a 3D graphics package ‘GRASP’ implemented in Pascal language and interfaced with the Pascal compiler developed for the DEC PDP-10 machine, by Urs Amman et al. GRASP supports storage tube and raster scan graphics terminals and pen plotters. The package is incorporated as a set of standard procedures into the enhanced Pascal compiler. The various features of the package are presented here and a comparison is made vis-a-vis the other existing 3D graphics packages. GRASP is simple to use and provides a valuable tool for the development of application programs written in Pascal and requiring a graphics capability.     

GPU在复杂场景的阴影绘制中的应用

通过有效利用图形硬件的图形处理单元（GPU）的运算能力和可编程性，将人量计算从CPU分离出来。在GPU上采用顶点和片元程序进行阴影计算，从而加速复杂场景阴影绘制。选择图像空间阴影算法进行GPU加速绘制。用Cg图形编程语言和OpenGL实现了算法的绘制过程，能够满足通用的复杂3D场景应用的需要，达到满意的实时绘制效果。