UGRAF3: A graphic system for process and modelling

The development and fabrication of VLSI circuits calls for permanent advances in the design and technology of these devices. Here important parameters are collected by process and device modelling. The incoming data are processed with the help of computer graphics. The GKS3D implementation UGRAF3, its application, and the relations to the international standardization process are described.     

Something to smile about: 3D graphics are revolutionizing oralhealth care

Computer graphics and all the computer-aided drawing and manufacturing (CAD/CAM), scanning, and imaging technology is changing dentistry. Invisalign is a technology that straightens adult teeth using a series of clear, plastic, nearly invisible aligners. Though proprietary CAD/CAM software that does 3D modeling, the company creates the fixtures for orthodontists. For dental implants dentists make a study cast of the area where the abutment will be placed. They then scan the cast into the computer using a 3D optical scanner, creating a 3D point cloud. Technicians create a polygonal surface from the point cloud. They use proprietary software to virtually assemble the digital teeth data with an unmodified (or template) version of their product. This template is a 3D model of an ideally shaped dental abutment. The computer generates the tool path and sends it to the milling machines that create the titanium abutment. Maxillofacial surgery repairs physical malformations resulting from disease, injury, burns, birth defects, or aging. In these cases, a maxillofacial surgeon must make changes that often include removing bone and replacing it with modeled implants. A surgeon uses computer graphics to solve these problems in his practice. The common thread among the examples of oral health care techniques discussed is the CAD/CAM software they use from Raindrop Geomagic     

Geometric Properties of Ribs and Fans of a Bezier Curve

Ribs and fans are interesting geometric entities that are derived from a given Béezier curve or surface based on the recent theory of rib and fan decomposition. In this paper, we present some of new geometric properties of ribs and fans for a Béezier curve including composite fans, rib-invariant deformation, and fan-continuity in subdivision. We also give some examples for the presented properties. A preliminary version of this paper appeared in Proc. the 1st Korea-China Joint Conference on Geometric and Visual Computing. Joo-Haeng Lee received his B.S., M.S., and Ph.D. degrees in computer science from POSTECH, Korea, in 1994, 1996 and 1999, respectively. He joined ETRI (Electronics and Telecommunications Research Institute), Korea in 1999, and is currently a senior researcher at Digital Contents Division. His research interests include geometric modeling and processing algorithms for computer graphics, CAD, and robotics. Hyungjun Park is a professor of industrial engineering at Chosun University, Korea. He received his B.S., M.S., and Ph.D. degrees in industrial engineering from POSTECH, Korea, in 1991, 1993, and 1996, respectively. From 1996 to 2001, he worked as a senior researcher at Samsung Electronics, Korea. His current research interests include geometric modeling, computational geometry, reverse engineering, bio-medical engineering, virtual prototyping, and CAD/CAM.     

A Type of Triangular Ball Surface and its Properties

A new type of bivariate generalized Ball basis function on a triangle is presented for free-form surface design.Some properties of the basis function are given,then degree elevation,recursive evaluation and some other properties of the generalized Ball surfaces are also derived.It is shown that the proposed recursive evaluation algorithm is more efficient than those of the old surfaces.     

Generation of Discrete Bicubic G^1 B-Spline Ship Hullform Surfaces from a Given Curve Network Using Virtual Iso-Parametric Curves

We propose a method that automatically generates discrete bicubic G^1 continuous B-spline surfaces that interpolate the curve network of a ship huliform.First,the curves in the network are classified into two types;boundary curves and ＂reference curves＂,The boundary curves correspond to a set of rectangular（or triangular）topological type that can be representes with tensot-product （or degenerate）B-spline surface patches.Next,in the interior of the patches,surface fitting points and cross boundary derivatives are estimated from the reference curves by constructing ＂virtual＂isoparametric curves.Finally,a discrete G^1 continuous B-spline surface is gencrated by a surface fitting algorithm.Several smooth ship hullform surfaces generated from curve networks corresponding to actual ship hullforms demonstrate the quality of the method.     

An Application of Computer Graphics and Networks to Anatomic Model and Prosthesis Manufacturing

Computer graphics has now matured in medical applications from 2D and 3D presentations for diagnosis and the planning of surgery and therapy to become the key step in making hand-held models of custom prostheses. The system described here delivers 3D shape information to create skeletal models, plan corrective surgery, and directly manufacture prostheses. Implants and anatomic models are manufactured using computed tomography (CT) image data and a system to generate Instructions for numerically controlled machines. The system combines clinical imaging, an algorithm for 3D edge detection, computer communications, and computer-aided and manufacturing (CAD/CAM). This integration of technologies brings recent advances in computer-aided design and manufacturing to the local community CT scanning clinic in a cost-effective manner. Via computer communications, several hundred remote medical imaging centers can have their CT scanners connected on-line to CAD/CAM facilities that one could not support alone. Operators of the remote CT scanners bear only the cost of computer communications equipment to being their patients this service. We use the clinical course of several patients in whom prostheses have been implanted to describe this technology.     

二次样条插值研究

样条技术在计算机辅助设计,计算机辅助制造,和计算机图形系统得到了广泛应用。分析了二次样条函数插值的条件,分5种边值条件给出了二次样条插值的求解方法,最后给出实例验证求解方法。     

三维造型设计与工程图学的有效融合

随着计算机软硬件技术的普及和飞速发展以及制造业对二维计算机绘图以及三维设计造型技术日益增长的需求,在工程图学教学中有效地融入二维计算机绘图以及三维设计造型技术已显得尤为重要。论文介绍了北京理工大学在工程图学和三维造型创新设计方面“外挂式、分段式和融合式”三种模式的教学改革实践,并着重对如何将三维造型设计与工程图学有效地融合进行了论述。     

Displays on Display

This realistic yet fantastical image of the new Boeing 767 jet airliner was produced by Digital Effects, Inc., as part of a computer graphics animated television commercial for All Nippon Airways in Japan. Animator Alan Green obtained the CAD/CAM database for the 707, which, incidentally, is the first commercial airliner designed entirely on a computer, and entered the database into Digital's IBM 4341. A DECPDP-11/34 was also used for image processing, and the final result was transferred to film using a Dicomed D48C film recorder.     

Theories for graphics processors in TIPS-1

This paper describes the theoretical aspects of graphics processors in CAD/CAM system TIPS-1. As one of the man-machine interfaces in the CAD/CAM field, computer graphics plays an important role. And this field, computer graphics involves not only image processing with shaded pictures produced by raster scan displays but also sectional and/or perspective view drawing picture by line drawing display. By using TIPS-1 graphics processors, we can get both raster scan and line drawing pictures for the same of modeled 3-D geometry. The following items are considered as the necessary conditions for developing graphics processors.

• • To develop geometric modeling theory.

• • To develop generative geometry pattern processing theory.

• • To implement problem-oriented graphics routines based on above conditions.

How to complete these conditions is described with several figures and graphic outputs.     

A Unified, Object-Oriented Graphics System and Software Architecture for Visualising CAD/CAM Presentations

Most object-oriented graphics systems (OOGS) either support general purpose graphics capabilities (drawing editors, ray tracing, etc.), or have targeted specific areas of computer graphics, for example, interface building, animation, and visualisation. However, the key concept in CAD/CAM graphics systems is that of presentations—pictures that convey information about products or parts of products. CAD/CAM graphics systems that create and manipulate presentations have specific graphical requirements that have not been addressed by existing OOGS. These requirements include the support of CAD/CAM concepts such as drawings, views and view-specific graphics, and layers, and the ability to allow external geometric modelers to be linked into the presentation. We describe an object-oriented presentation architecture that allows the application to describe the structure of the CAD/CAM presentation. This architecture provides a unified interface to drawings, views, layers and entities, and allows linkage to models created with an external geometric modeler, while isolating applications from details of the underlying traditional graphics rendering systems. It is our hope that this architecture provide the foundation for the architecture of next generation OOGS. We also present an implementation of this architecture and compare it to other OOGS.     

由二维正投影重建三维实体算法的评述

近二十年来，由二维正投影视图重建三维实体已成为计算机视觉和ＣＡＤ／ＣＡＭ两个不同领域共同关心的一个研究课题。本文综述了１９７３－１９９１期间发表的１４种算法。文中评述了诸算法的特点，并给出了一个汇总表。     

Computer Graphics: The Next 20 Years

Industry spokesmen speculate on the future computer graphics market, talk about financing, predict changes in CAD/CAM, and propose possible new products.     

CATC — A Computer Aided Tolerance Control system

Computer utilization in manufacturing systems is increasing at a rapid rate. Developments thus far have been disjointed. Much work needs to be done in the area of integrating computer aided design and computer aided manufacturing (CAD/CAM). Tolerance control is an important component in the integration of CAD and CAM. Selection of design tolerances affects the build-ability of a product. The selection of manufacturing processes and sequence of processes affects process tolerance stacking. Unexamined process tolerance stacking leads to scrap and rework. A computer aided tolerance control (CATC) system is presented in this paper. This system is based on the tolerance chart technique. The CATC system is interactive and uses computer graphics for information display. The system can be used for computer aided process planning (CAPP) and for CAD/CAM integration.     

Computer-aided robot modeling,programming and simulation

The use of interactive computer graphics for simulation and off line programming provides a powerful tool in implementing robots. This capability essentially became available with the CAD/CAM system.This paper will present the theory of robot modeling and simulation techniques. An overview of CAD/CAM system in robotic application, such as robot off-line programming, simulation and workcell layout will also be represented.     

性能驱动总体布线的关键技术及研究进展

在计算机软件领域,超大规模集成电路技术的迅猛发展迫切需要高性能CAD工具——电子设计自动化(EDA)软件工具的支持.与物理设计相关的CAD技术称为布图设计,总体布线是布图设计中一个极为重要的环节.目前,在深亚微米、超深亚微米工艺下的超大规模、甚大规模集成电路设计中,性能驱动总体布线算法已成为布图设计中的一个国际研究热点.针对这一热点,分析了性能驱动总体布线算法研究中亟待解决的关键技术,并详细阐述了国内外的重要相关研究工作进展情况.     

Robust uniform triangulation algorithm for computer aided design

This paper presents a new robust uniform triangulation algorithm that can be used in CAD/CAM systems to generate and visualize geometry of 3D models. Typically, in CAD/CAM systems 3D geometry consists of 3D surfaces presented by the parametric equations (e.g. surface of revolution, NURBS surfaces) which are defined on a two dimensional domain. Conventional triangulation algorithms (e.g. ear clipping, Voronoi-Delaunay triangulation) do not provide desired quality and high level of accuracy (challenging tasks) for 3D geometry. The approach developed in this paper combines lattice tessellation and conventional triangulation techniques and allows CAD/CAM systems to obtain the required surface quality and accuracy. The algorithm uses a Cartesian lattice to divide the parametric domain into adjacent rectangular cells. These cells are used to generate polygons that are further triangulated to obtain accurate surface representation. The algorithm allows users to control the triangle distribution intensity by adjusting the lattice density. Once triangulated, the 3D model can be used not only for rendering but also in various manufacturing and design applications. The approach presented in this paper can be used to triangulate any parametric surface given in S(u,v) form, e.g. NURBS surfaces, surfaces of revolution, and produces good quality triangulation which can be used in CAD/CAM and computer graphics applications.     

Lower Bound Estimation of Hardware Resources for Scheduling in High-Level Synthesis

In high-level synthesis of VLSI circuits,good lower bound prediction can efficiently narrow down the large space of possible designs.Previous approaches predict the lower bound by relaxing or even ignoring the precedence constraints of the data flow graph (DFG),and result in inaccuracy of the lower bound.The loop folding and conditional branch were also not considered,In this paper,a new stepwise refinement algorithm is proposed.which takes consideration of precedence constraints of the DFG to estimate the lower bound of hardware resources under time constratints,Processing techniques to handle multi-cycle,chaining,pipelining,as well as loop folding and mutual exclusion among conditional branches are also incorporated in the algorithm.Experimental results show that the algorithm can produce a very tight and close to optimal lower bound in reasonable computation time.     

虚拟现实软件系统开发方法研究

虚拟现实技术是一门综合性技术,涉及计算机图形学、多媒体技术、人机交互和人工智能等多个领域,在教育、医疗、娱乐、军事等众多领域有非常广泛的应用。所有这些技术和应用最终都要靠计算机软件来实现,这就使得虚拟现实系统的软件变得十分庞大和复杂,涉及许多多媒体数据。传统软件开发方法和程序设计技术侧重于处理文本数据,显然不能满足开发虚拟现实软件的需要。试图以所在团队研发成功的PAR方法和PAR平台为基础,根据虚拟现实软件系统的特征,探寻虚拟现实软件系统开发的新方法,进一步扩充和完善PAR平台中已有多媒体处理技术、形式化建模技术和C#等高级语言程序自动生成系统。     

Scene graphs in the new millennium

Hardware 3D graphics accelerators will be ubiquitous in the new millennium. The great majority of 3D graphics programs will, almost exclusively, use scene graphs. Rarely will graphics programs use immediate mode-if at all-and then only for very special effects, and scene graphs will grow to support new modalities such as sound and haptics. Outrageous? Probably. Predicting the future is never easy. By looking at where we are today and analyzing technology trends, these predictions may seem even more outrageous, outrageously mundane. The author considers how graphics technologies, hardware and software, are evolving at exponential rates