Applied Geometry:Discrete Differential Calculus for Graphics

Geometry has been extensively studied for centuries, almost exclusively from a differential point of view. However, with the advent of the digital age, the interest directed to smooth surfaces has now partially shifted due to the growing importance of discrete geometry. From 3D surfaces in graphics to higher dimensional manifolds in mechanics, computational sciences must deal with sampled geometric data on a daily basis‐hence our interest in Applied Geometry. In this talk we cover different aspects of Applied Geometry. First, we discuss the problem of Shape Approximation, where an initial surface is accurately discretized (i.e., remeshed) using anisotropic elements through error minimization. Second, once we have a discrete geometry to work with, we briefly show how to develop a full‐ blown discrete calculus on such discrete manifolds, allowing us to manipulate functions, vector fields, or even tensors while preserving the fundamental structures and invariants of the differential case. We will emphasize the applicability of our discrete variational approach to geometry by showing results on surface parameterization, smoothing, and remeshing, as well as virtual actors and thin‐shell simulation. Joint work with: Pierre Alliez (INRIA), David Cohen‐Steiner (Duke U.), Eitan Grinspun (NYU), Anil Hirani (Caltech), Jerrold E. Marsden (Caltech), Mark Meyer (Pixar), Fred Pighin (USC), Peter Schröder (Caltech), Yiying Tong (USC).     

Colour Raster Operations

We propose a form of three-input BitBlt/RasterOp which is useful for pictures constructed in a colour-mapped form as well as in true colour. The model used for this is that of a piece of potentially multicoloured paper on which the picture appears as ink marks. Computationally simple range testing operations can be applied to the source and destination regions to produce many useful effects, some of which we demonstrate. The resulting operations are primitives which can be used to construct more complex operations.     

High Performance Colour Displays for Computer Graphics*

High-performance computer graphics displays for CAD utilize the Shadow-Mask CRT (SMCRT). Factors affecting colour-display quality and ergonomics include beam-to-beam convergence, beamspot profile, resolution, brightness, mask pitch, and image linearity. This paper briefly covers the results of recent experiments on eye fatique and vision. In particular, the effects of beam-to-beam misconvergence and poor spot performance in colour displays. Extensive discussion is given on beam-to-beam misconvergence: What it is, how it is corrected in different SMCRT types, and state-of-the-art techniques for controlling it. Emphasis is given to the digital-processor based convergence system employing feedback (autoconvergence). Also included are considerations given to selection of CRT types for high-performance graphics. CRTs are available with dot, slot, or line screens. There are also inline and delta configuration electron guns. Each combination of screen and gun offers tradeoffs in quality, performance, and cost.     

Overlap Operations and Raster Graphics

This paper outlines the development of a volume and surfaces modelling system for use with raster graphic displays. The ideas are presented in a historical framework to make the reasoning behind the design decisions clear and to indicate the main influences which have guided the work. There are two outcomes of importance: a language form for defining volumes and surfaces; and hardware to convert this representation directly into a display. The hardware provides hidden-line or hidden-area removal as a display primitive which, in an appropriate implementation, can be fast enough to support a range of real-time display applications. Linked to this hidden-line, hidden-area removal facility is an ability to provide interference tests for objects that are being moved around in a scene. Again there appears to be a hierarchy of applications ranging in complexity from interactive volume editing to robot control and vision systems. The new facilities complement existing point and line based display operations, on which most current displays' hardware is based. A good case is emerging for integrating the two approaches into a single hardware implementation for CAD workstations and for simulator display systems.     

Colour Graphics and te Fifth Generation Workstation

If we accept the above idiosyncratic views, what kind of architecture will the fifth generation machine offer to graphics users? We would hope to see high quality colour raster graphics, tightly coupled to a sophisticated processor but in its own address space. It should allow for pictures much larger than the screen and also at higher resolution. The local disk must be organized to handle the large amounts of data which picture manipulation on this scale calls for. Disk and main memory must have support for manipulation of two dimensional arrays of pixel data and the filing system and its utilities must reflect this. Response is more important than ever. The software to be built on to this hardware is still a matter for conjecture and depends on whether a particular combination of hardware and language family can be packaged to give clear performance advantages. However a real-time style operating system is essential. Timescales for suitable architectures seem quite short, around two or three years, with software developing beyond that. Certainly such a machine will contain far more graphical software in the operating system than any before and ought to satisfy a wide range of raster graphics applications.     

微计算机控制的多画面交互式彩色图形系统

本文阐述一个低成本、应用灵活的交互式彩色图形系统.它包含一个用于画面前后台显示处理的多画面存贮管理部件,具有彩色图形、字符、伪彩色图象和动画四种显示模式.系统的交互功能(例如图象/图形的输入,修改与画面编辑等)由系统软件和一个易于扩充的图形命令语言定义,因此可望该系统能在多方面获得应用.     

Vector Ordering and Morphological Operations for Colour Image Processing: Fundamentals and Applications

: The extension of concepts of greyscale morphology to colour image processing requires the use of a proper ordering of vectors (colours) and the definitions of infimum and supremum operators in an appropriate colour space. In this paper, a new approach to colour image morphology is proposed. It is based on a new ordering of vectors in the HSV colour space that is partial ordering. The proposed approach is hue preserving, and it is not a component-wise technique. Its basic characteristic is that it is compatible to the standard greyscale morphology: its fundamental and secondary operations possess the same basic properties as their greyscale counterparts, and furthermore, it is identical to greyscale morphology when it is applied to greyscale images. Examples that illustrate the application of the defined operations to colour images are provided. Moreover, the usefulness of the new method in various colour image processing applications, such as colour image edge detection, object recognition, vector top-hat filtering and skeleton extraction, is demonstrated. Received: 14 July 2000, Received in revised form: 24 April 2001, Accepted: 19 June 2001     

A Calculus for Cryptographic Protocols: The Spi Calculus

We introduce the spi calculus, an extension of the pi calculus designed for describing and analyzing cryptographic protocols. We show how to use the spi calculus, particularly for studying authentication protocols. The pi calculus (without extension) suffices for some abstract protocols; the spi calculus enables us to consider cryptographic issues in more detail. We represent protocols as processes in the spi calculus and state their security properties in terms of coarse-grained notions of protocol equivalence.     

Computer Graphics: The Need for Graphics Design Part One

Graphics design and computer graphics should be inseparable partners, not virtual strangers. This is the first of two articles examining the relationship between the two fields.     

Computer Graphics: The Need for Graphics Design Part Two

The best use of color and design requires an experienced graphics designer. But even engineers and businessmen can improve the appearance of their information displays.     

National's Advanced Graphics Chip Set for High-Performance Graphics

To reinforce the growth of computer graphics, hardware architectures must be developed to support the rapid growth in display resolution that will occur in the next few years. The architectures must allow a high degree of application independence without requiring significant changes in the overhead software interface. The hardware architecture must be expandable, again avoiding significant software changes. Finally, the architecture must be implemented in VLSI for reasons of cost and speed. This article will describe a graphics hardware architecture that meets these criteria.     

Scheme: A Interpreter for Extended Lambda Calculus

Inspired by ACTORS [7, 17], we have implemented an interpreter for a LISP-like language, SCHEME, based on the lambda calculus [2], but extended for side effects, multiprocessing, and process synchronization. The purpose of this implementation is tutorial. We wish to: 1.alleviate the confusion caused by Micro-PLANNER, CONNIVER, etc., by clarifying the embedding of non-recursive control structures in a recursive host language like LISP. 2.explain how to use these control structures, independent of such issues as pattern matching and data base manipulation. 3.have a simple concrete experimental domain for certain issues of programming semantics and style. This paper is organized into sections. The first section is a short reference manual containing specifications for all the unusual features of SCHEME. Next, we present a sequence of programming examples which illustrate various programming styles, and how to use them. This will raise certain issues of semantics which we will try to clarify with lambda calculus in the third section. In the fourth section we will give a general discussion of the issues facing an implementor of an interpreter for a language based on lambda calculus. Finally, we will present a completely annotated interpreter for SCHEME, written in MacLISP [13], to acquaint programmers with the tricks of the trade of implementing non-recursive control structures in a recursive language like LISP.This report describes research done at the Artificial Intelligence Laboratory of the Massachusetts Institute of Technology. Support for the laboratory's artificial intelligence research is provided in part by the Advanced Research Projects Agency of the Department of Defense under Office of Naval Research contract N00014-75-C-0643.     

DSS中图形系统的设计研究

图形技术是进行DSS人机接口设计的一个重要方面。本文给出了在DSS开发和研制过程中常用图形的种类(统计图、地形图、象形图、图标、汉字图形);有重点地阐述了在微型计算机支撑下,这些图形的设计方法和技巧;对于在不同软件环境下,如何应用本图形系统,作出了详细的论述。本图形系统在DSS的研究范围内具有一定的通用性。