Computer graphics and displays

A review is given of recent developments in computer graphics, with emphasis on displays. The principles of refresh, storage and raster-scan technologies are outlined, followed by an examination of developments in intelligent raster graphics terminals, displays for 3D computer graphics, and the emergence of powerful personal graphics workstations. Colour hardcopy is needed to complement today's colour raster displays, and ink-jet and electrostatic devices are described. A summary is given of the current status of international standards for computer graphics, and the paper concludes by pointing out some likely areas for future development.     

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.     

Raster graphics display technology: a review

Performance and technologies of monochrome and polychromatic raster CRT visual display units are reviewed. For computer graphics, image quality is affected most by parameters such as size, resolution, luminance, contrast ratio, geometric distortion, flicker and video bandwidth. For polychromatic displays, chromaticity and convergence are also important parameters. Comparisons of 480 mm VDUs show that monochrome untis are less expensive and have better performance except for the use of colour to discriminate between different entities on the screen. Some typical graphics processor output head architectures are reviewed together with trends in display technology.     

On developing a GKS driver architecture for raster workstations

The use of raster graphics devices needs adapting to graphics applications. The first graphics standard, the Graphics Kernel System GKS, defines a logical interface on an application and device independent level. The workstation driver maps the logical GKS functions to device functions. First some special raster device facilities are outlined and then it is shown how to use them within the driver. To reduce the amount of driver implementations a common driver concept is sought here, especially for raster devices.     

An image processing approach to computer graphics

Computer graphics was conceived as, and remains for the most part, a line-drawing phenomenon. The cautious management of display lists or of in-line vector generators has captured most of the attention of researchers in computer graphics. Cathode ray tubes with randomly positionable beams have served as the primary medium for this research and development.The underlying position of this paper is that the future of computer graphics does not lie in ‘vectored’ displays but in raster scan television, conceivably as we know it in our homes. This posture is motivated by arguments of cost and compatibility, but the most salient motivation comes in view of the ubiquitous nature of raster scan display technologies.This paper explains a way to implement an image processing approach to computer graphics, one that is conceptually straightforward and, in terms of hardware, fairly easy to design. A device is being built that encompases as much as is known about raster scan, multi-bit per point displays. The work described is conducted, principally, to produce a multi-bit per point graphics output device that dynamically shares its image storage with the memory space of an expanded mini-computer.     

IDECAP Interactive Pictorial Information System for Demographic and Environmental Planning Applications

IDECAP is a database type information system. It is different from regular database systems as the information is mainly presented via thematic maps displayed on a graphics screen. Retrieval of information is usually achieved by means of graphical interaction with these images. The system utilizes interaction techniques and systems software from interactive computer graphics, using vector graphic and colour raster graphic stations for output. The present databank contains data based on grids and polygonal data. The system is being applied, but not restricted, to the Dutch 1971 Census data and the 1978 land use data. It allows the mapping of grid variables against a topographic background. Areas of interest can be investigated in detail by zooming in on a window drawn on the graphics screen by the user. Maps can be adjusted by user-definable class distributions shown in the form of histograms with standard deviations.     

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.     

Low cost computer graphics in engineering education

The Apple II is a personal computer which provides 6 color, raster graphics via a 280 h × 192 v frame buffer. A user-programmable MOS Technology 6502 CPU addresses 48 K bytes of RAM, 12 K of ROM. and 4 K of memory-mapped I/O. This system has been evaluated in a variety of applications for which one normally assumes higher resolution, higher cost graphics devices are needed.Examples were drawn from computer aided design, color microfilm previewing, cartography, and aircraft synthesis. The results were encouraging: low resolution raster scan graphics is surprisingly effective for a wide range of applications. As a result, a computer graphics laboratory, with a cluster of 10 Apples as its nucleus, was formed and has been functioning successfully for 4 terms.     

一种新的基于链码的填充算法

将计算机图形学的栅栏填充算法移植到链码的填充算法中，发展出了一种新的基于链码的填充算法。利用边界Freeman链码，定义了一种新的边界点分类方法，通过对边界上的左右端点到栅栏间的像素取补填充该区域，算法能填充任意复杂图像区域，不需要辅助内存空间和标记边界色。与现有的算法进行了对比实验，实验表明该文提供的算法对于图像具有填充速度快、效率高等优点。     

The raster graphics approach in mapping

Graphics hardware technology is expanding from pen plotters and vector screens to raster. The decade for outstanding advancements in raster output devices, in terms of greater resolution, more colors and greatly reduced costs, is upon us.

Ever since the first graphic output devices were developed, discussion as to whether the raster or vector technique is better has occupied computer graphics analysts. There are problems which are easier to solve in one system, but almost impossible to attack in the other. For example, high-precision engineering drafting consists mainly of short line segments, an operation very cumbersome for a raster structure, but simple with the vector technique. On the other hand, solid shaded areas, colored lines of varying thickness and satellite image processing are impossible with vector systems, but natural for a raster display.

Recent years developments have concentrated on devices which do not draw straight lines, but instead use a matrix of dots to build up the picture. This method is the raster technique.     

VIPER: a general-purpose digital image-processing system applied to video microscopy

This paper describes VIPER, the video image-processing system Erlangen. It consists of a general purpose microcomputer, commercially available image-processing hardware modules connected directly to the computer, video input/output-modules such as a TV camera, video recorders and monitors, and a software package. The modular structure and the capabilities of this system are explained. The software is user-friendly, menu-driven and performs image acquisition, transfers, greyscale processing, arithmetics, logical operations, filtering display, colour assignment, graphics, and a couple of management functions. More than 100 image-processing functions are implemented. They are available either by typing a key or by a simple call to the function-subroutine library in application programs. Examples are supplied in the area of biomedical research, e.g. in in-vivo microscopy.     

Book Reviews

The second edition of the Newman and Sproull's book is a welcome sight. A much more comprehensive text includes discussions of the work done in computer graphics since the first edition. For example, the new edition reflects the recent burgeoning of raster graphics techniques by devoting substantially larger sections to the subject. Discussion of software system construction is also a major consideration in the volume, likewise reflecting one of the major current concerns in the field of computer graphics.     

Analyzing and comparing the performance of two real-time playback systems

A technique used in animated computer graphics involves the use of real-time playback. This method is used when it is not possible to display frames of display code in real-time. Instead, frames are compiled in advance at non realtime rates, saved in secondary storage, and played back at desired realtime speeds. The basic design and operation of two such systems will be considered. The more powerful of the two is built upon an Evans and Sutherland picture System I and utilizes animated vector graphics. The other playback system is built upon a Terak micro computer display and represents an example of rudimentary raster graphics animation. The synchronization, buffering, blocking and man-machine interfaces of both systems are detailed thus spotlighting their operational behavior. A comparison of the two systems show: that similarities in the logical organization of each system exist; that both systems are input bound; and both require their image files to be built on other computer systems. The differences in the performance of the two systems can be attributed to technological differences between the two systems; the retrieval rates of their respective disk subsystems; and differences in the intent and purpose behind the design of each machine. The systems are demonstrated by applying them to chemical modeling. It is determined that playback is a useful technique for examining complicated sequential situations or for providing the concise and convenient representation of large amounts of data.     

Unified sun and sky illumination for shadows under trees

Assume that the sun, sky, and clouds are represented as a raster image on a plane at infinity, and the shadows of a tree canopy are represented as a raster transparency mask on a canopy plane. Then the illumination on the ground is the correlation of these two rasters, which can be rapidly computed by fast Fourier transform techniques.     

Topology in Raster and Vector Representation

Egenhofer's nine-intersection, well-known for vector representations, is defined here on a raster, using a hybrid raster model, and then systematically transformed to yield functions which can be used in a convolution operation applied to a regular raster representation. Applying functions, the hybrid raster elements need not be stored. It becomes thus possible to determine the topological relation of two regions, given in raster representation, with the same reasoning as in vector representations. This contributes to the merging of raster and vector operations. It demonstrates how the same conceptual operations can be used for both representations, thus hiding in one more instance the difference between them.     

An approach to the formal specification of computer graphics systems

This paper discusses the approach to formal specification of computer graphics systems developed by the ANSI X3H3 committee (Computer Graphics Programming Languages) in the United States. ANSI's specification philosophy aims to gradually replace existing informal English language specifications with more formal ones without sacrificing the readibility and usefulness of standards documents. The specification techniques used are derived from those presently employed in the specification of computer communication protocols and the specification of software systems, not those used for the specification of programming languages. The specifications consist of three parts: the interface between both graphics and the host language and graphics and the graphical display device, the structure of the graphics system, and the functions that are performed by the graphics system. The specifications are based on abstract data types. These data types, together with the operations which can be performed on them, are used to describe the structure and functions of the graphics system. Using these techniques, X3H3 has developed a complete formal specification for a minimal graphics system. Extracts from this specification are included here.     

Crystal gazing in computer graphics

We, the people, are in the midst of the age of the computer. We are at the beginning of the age of computer graphics. This article will crystal gaze upon a few of the areas of life which are beginning to be and soon will be very affected by computer graphics. Topics vary from homes and cities; hardware and animation; Congress and business; and architecture and drafting to art. These show that the future uses of computer graphics are limited only by the imagination.

Underlying the whole gamut is the theme that computer graphics must be user oriented! The application user must not be required to know anything about computers or their languages or how to manipulate complex mathematics!