直接体绘制技术在地质体三维可视化中的应用研究*

将直接体绘制技术应用于地质体三维可视化,首先对原始钻孔数据进行插值、网格化等预处理得到满足直接体绘制需要的规则体数据,从而建立反映地层分布的地质体三维标量数据场;然后用直接体绘制技术绘制三维地质体,避免了体元建模方法中在对地质体进行剖切等操作时必须要解决的剖面与体元之间复杂的判断求交等过程。采用该方法实现了对某地区地质体的三维可视化。     

Fast Volume Rendering and Data Classification Using Multiresolution in Min‐Max Octrees

Large‐sized volume datasets have recently become commonplace and users are now demanding that volume‐rendering techniques to visualise such data provide acceptable results on relatively modest computing platforms. The widespread use of the Internet for the transmission and/or rendering of volume data is also exerting increasing demands on software providers. Multiresolution can address these issues in an elegant way. One of the fastest volume‐rendering alrogithms is that proposed by Lacroute & Levoy ¹ , which is based on shear‐warp factorisation and min‐max octrees (MMOs). Unfortunately, since an MMO captures only a single resolution of a volume dataset, this method is unsuitable for rendering datasets in a multiresolution form. This paper adapts the above algorithm to multiresolution volume rendering to enable near‐real‐time interaction to take place on a standard PC. It also permits the user to modify classification functions and/or resolution during rendering with no significant loss of rendering speed. A newly‐developed data structure based on the MMO is employed, the multiresolution min‐max octree, M ³ O, which captures the spatial coherence for datasets at all resolutions. Speed is enhanced by the use of multiresolution opacity transfer functions for rapidly determining and discarding transparent dataset regions. Some experimental results on sample volume datasets are presented.     

Tools for constructing pseudo-3D space on the WWW using images

Recently, due to advancements in virtual reality and computer graphics technologies, a virtual space that looks as real as a real space has been constructed. Accordingly, there are many studies that employ virtual spaces to support human communication and remote working. Until now, the virtual space employed by these studies has been composed of geometric models. Since the real space is very large and there are a lot of objects in the real world, the cost of modeling the real space is very high. In our previous paper,¹⁰⁾ we proposed a method for building a virtual space using image data, named theimage based non-rendering (IBNR), in order to cut down the cost. In this paper, we explain the design and implementation of the tools which we implemented to construct virtual spaces based on IBNR. With these tools, it is easy to construct and renew a large-scaled virtual space based on the real space. Takefumi Ogawa: He received his B.E. and M.E. degrees in Information Systems Engineering from Osaka University, Osaka, Japan, in 1997 and 1999, respectively. Currently, he is a Research Associate of the Infomedia Education Division, Cybermedia Center, Osaka University. He is a member of IEEE, IEICE, IPSJ, and VRSJ. His research interests include virtual reality systems and augmented reality systems. Masahiko Tsukamoto, Ph.D.: He received his B.E., M.E., and Dr.E. degrees from Kyoto University, Kyoto, Japan, in 1987, 1989, and 1994, respectively. From 1989 to February 1995, he was a research engineer of Sharp Corporation. Since March 1995, he has been an Assistant Professor in the Department of Information Systems Engineering of Osaka University and since October 1996, he has been an Associate Professor at the same department. He is a member of seven learned societies, including ACM and IEEE. His current research interests include database systems, knowledge-base systems, and distributed computing systems.     

虚拟内窥镜技术的研究与实现

虚拟内窥镜是用计算机处理CT或MRI获取的三维医学数据,以获得类似用标准内窥镜观察病人内脏过程观察效果的一种诊断的新方法。在广泛研究虚拟内窥镜技术的基础上,我们开发了一个小型的基于面绘制的虚拟内窥镜系统,实现了漫游过程的交互功能和动画回放,在虚拟内窥镜技术的实现上做了有益的尝试。     

MAX渲染算法光线跟踪与光能传递的分析对比

光线跟踪（Raytracer）与光能传递（Radiosity）渲染是3D设计软件中常用的渲染方法,时场景使用光线跟踪与光能传递渲染可以生成十分逼真的光影效果。但两种渲染算法都需要进行大量复杂的运算,尤其是光能传递时计算机系统的性能要．求很高,时硬件平台的运算速度和能力都有很苛刻的要求。     

The computer game industry: Current state of play

The computer games industry suffers from a no-longer justified reputation for chaotic and unprofessional software development. This paper describes the current state of the evolving art of games software, and then outlines the precise areas of technique of current interest for development, and research purposes.     

GPU‐Based Spherical Light Field Rendering with Per‐Fragment Depth Correction

Image‐based rendering techniques are a powerful alternative to traditional polygon‐based computer graphics. This paper presents a novel light field rendering technique which performs per‐pixel depth correction of rays for high‐quality reconstruction. Our technique stores combined RGB and depth values in a parabolic 2D texture for every light field sample acquired at discrete positions on a uniform spherical setup. Image synthesis is implemented on the GPU as a fragment program which extracts the correct image information from adjacent cameras for each fragment by applying per‐pixel depth correction of rays. We show that the presented image‐based rendering technique provides a significant improvement compared to previous approaches. We explain two different rendering implementations which make use of a uniform parametrisation to minimise disparity problems and ensure full six degrees of freedom for virtual view synthesis. While one rendering algorithm implements an iterative refinement approach for rendering light fields with per pixel depth correction, the other approach employs a raycaster, which provides superior rendering quality at moderate frame rates. GPU based per‐fragment depth correction of rays, used in both implementations, helps reducing ghosting artifacts to a non‐noticeable amount and provides a rendering technique that performs without exhaustive pre‐processing for 3D object reconstruction and without real‐time ray‐object intersection calculations at rendering time.     

基于PC系统平台实现快速体绘制技术

体绘制技术可将难于理解的三维数据场转化成直观的图像，作为一种最具前景的科学计算可视化技术在医学影像方面有着极强的实用意义。由于体绘制算法需要强大的计算能力，在通常的PC系统上难以实现满足交互式应用的绘制速度，因此阻碍了其普及。研究PC系统上的快速体绘制技术，无疑具有重要的意义．本文使用Shear-warp的体绘制算法，并利用Intel公司的SSE2扩展指令对整个绘制过程进行加速，实现了基于中高档桌面PC系统平台的快速体绘制应用。     

基于"色彩控制圆"的彩色分形图绘制方法

传统的分形图形绘制算法中，大多使用迭代次数来控制绘制颜色，使绘出的分形色彩单调。本文提出了“色彩控制圆”的概念，通过将迭代点到坐标原点的“距离”映射到“色彩控制圆”的方法，来控制分形绘制的颜色选择。合理地配置“色彩控制圆”与某(些)种色彩的对应关系，就可使绘出的分形图层次分明，具有一定的凹凸感，     

基于NPR技术的建筑CAD系统

介绍了E—CAD，一个模拟钢笔画绘制生成建筑场景以及设计图纸的CAD系统，以及系统中实现的一种参数化过程纹理描述语言。从系统的角度具体阐释了为了支持NPR绘制，系统在内核的选择、开发、实体造型、系统框架、渲染体系结构、控制流程和显示模块方面相应的设计和实现。