Algorithms for Handling the Fill Area Primitive of GKS

The fill area primitive of GKS (Graphical Kernel System)¹ is one of the more powerful features which differentiates it from earlier device independent graphics software and systems. Its specification is extremely general in the form of a closed boundary, possibly self-intersecting, and whose interior can be filled in a variety of styles. However a complete implementation of this primitive is very complex. It is difficult to find a single graphics workstation incorporating this primitive in hardware or firmware. Most GKS implementations will have to include software for simulating the appearance of this primitive on the commonly available displays and hard-copy graphics devices. Correct and efficient algorithms are necessary for developing this software. Because of the generality many of the existing algorithms are not directly applicable. In this paper we describe:
1. a new algorithm for clipping a fill area polygon, using what we have named as the Bridge Technique.
2. implementation of a plane sweep algorithm, by Nievergelt and Preparata,² for solid filling and hatching, particularly applicable to vector devices.
3. extension of the plane sweep algorithm for filling with any given pattern on raster as well as vector devices.
The algorithms have been designed to work for all special cases as well. In fact they have been implemented having in mind the fill area set primitive of GKS-3D extension.³ All these algorithms have been very successfully implemented in a commercially available GKS implementation, namely indoGKS.     

GKS-9x: Some Implementation Considerations

The Graphical Kernel System (GKS) was published as an ISO standard for computer graphics programming in August 1985. GKS is now undergoing revision in ISO/IEC and at the time of writing the text of the Draft International Standard of GKS-9x was being finalized. This paper presents a way in which a key part of the new functionality in GKS-9x, namely namesets and selection criteria, can be implemented effectively.     

Are PHIGS and GKS Necessainly Incompatible?

The compatiblility issues that are of concern through the graphics industry are particularly serious in the relationship of GKS, GKS-3D, and nowcomer PHICS. The point made in this article is that PHIGS can be brought more into line with the GKS standards, offering a broader range of applications to both sets of users.     

BD-GKS3D图形软件的设计与实现

BD-GKS3D是按图形国际标准GKS-3D(ISO 8805)开发的三维图形支持软件。本文讨论了该软件的设计原则:符合国际标准及尽可能高效率。还讨论了实现的策略,包括二维GKS与三维兼容问题,裁剪与变换,实现环境,图段的数据结构及三维输入等内容。最后对开发BD-GKS3D的工作量、与PHIGS,CGI的关系等作了说明。     

Graphics standards in the GDR

This article outlines implementations and applications of the GKS standard and GKS-3D standard in the German Democratic Republic (GDR). The graphical standardization in the GDR was highly stimulated by becoming a member of the ISO and by the active colaboration of the GDR in the ISO/IEC JTC1/SC24 “Computer Graphics.” Some of the national activities and efforts in this field are illustrated.     

GKS Programming in a PHIGS Environment

GKS is an international standard for the functional interface to 2D graphics, whilst PHIGS is currently an ISO work item for 2D and 3D graphics. In addition, PHIGS allows improved control over structuring graphics data in the system. With a new work item, the upwards compatability from GKS to PHIGS is being called into question. This paper is an attempt to give direction to these discussions by listing the implications of introducing a software layer between a GKS application program and a PHIGS environment on which this application is to be run. It is intended to highlight differences between the systems and to answer questions such as, “How compatible?”, “Is it possible?”, “How much does the software layer have to do?”, etc.     

Guidelines for Determining When to Use GKS and When to Use PHIGS

GKS, GKS-3D, and PHIGS are all approved ISO standards for the application programmer interface. How does a system analyst or programmer decide which standard to use for his application? This paper discusses the range of application requirements likely to be encountered, explores the suitability of GKS and PHIGS for satisfying these requirements, and offers guidelines to aid in the decision process.     

GKS-94: an overview

A revision of the Graphical Kernel System (GKS), the first ISO standard for computer graphics programming, was completed in 1994. This summary of GKS-94 also describes an implementation of part of its new functionality. We have demonstrated that fast selection is possible with GKS-94. Thus, an application can use namesets and selection criteria as its main method of subdivision, selection and creating hierarchy within the application, and performance is acceptable given a reasonable implementation. European organizations are showing interest in implementing GKS-94, and new products are anticipated early in 1996     

At Last an ISO C Binding of GKS

The C⁴ bindings of GKS1 and other semantic computer graphics standards like GKS–3D² and PHIGS³ are long overdue. While GKS was completed in 1985 and GKS–3D² (and PHIGS³) became an international standard in 1988, none of their C bindings could be standardized, for the simple reason that the C language itself was not a standard. Instead, a host of de facto GKS/C bindings⁹ appeared.
This paper will give the flavour of the ISO C binding^5,6 of GKS; the main features will be outlined.
1983 CR Categories: D.3.0,I.3.0,I.3.4.     

Conformance specification in the CGI

The Computer Graphics Interface (CGI) is a developing International Organization for Standardization (ISO) standard proposal¹ that addresses the interface between a virtual graphics device and an implementation of one of the ISO functional standards (namely, Programmer's Hierarchical Interactive Graphics System (PHIGS)², Graphical Kernel System (GKS)³, and Graphical Kernel System for Three Dimensions (GKS-3D)⁴. This paper may interest those who are tracking the development of the CGI and describes a recently introduced method for structuring conformance to provide for a wide diversity of device technology and architecture, while also providing for the spread of functional specification requirements. This scheme involves the definition of a number of standard constituency profiles, and pays particular attention to the needs of GKS and the Computer Graphics Metafile (CGM)⁵ in accessing the virtual device through the CGI. It must be stressed that the CGI is an emerging standard, and has not yet achieved a state of technical stability.     

具有三维图形描述功能的页面描述语言(PostScript-3D)

页面描述语言是一种新型的程序设计语言,具有很强的图形描述功能。PostScript-3D是对PostScript语言的三维扩充,它支持三维观察变换、裁剪、3D路径、隐藏线和隐藏面消除、三维线框图和具有浓淡效应的真实感图形。本文对PostScript-3D的实现技术进行讨论,并把它与GKS-3D进行比较。     

Standards in computer graphics

GKS, which recently became the International Standards Organization (ISO) standard for computer graphics programming, is the first of a set of interlocking graphics standards. This paper outlines the important ideas behind GKS, describes its relationship with other standards and discusses the benefits of standardization.     

GKS-3D: A Three-Dimensional Extension to the Graphical Kernel System

The three-dimensional Graphical Kernel System is designed to provide a basic set of 3D function with hooks for incorporating hidden-line/hidden-surface removal. Every attempt has been made to ensure full compatibility with GKS so that programs can run unmodified in the GKS-3D environment. For effective operation in a 3D environment, GKS-3D provides a full set of viewing operations that can support not only the widely known synthetic camera model but also special viewing models tailored to the application.     

New Methods for Improving the GKS Fill Area Output Primitive

The fill area primitive is one of the most powerful primitives of GKS and its derivatives (GKS-3D, PHIGS etc.). Since its specrfication is extremely general, it is important to explore new approaches to achieve higher performance in its implementation. In this paper fast algorithms are presented for special situations, which can be included, together with appropriate tests, into a complete GKS output pipeline. As a result, a speed improvement With a factor of two may be achieved in important practical cases.     

Parametric Surfaces in PHIGS PLUS: a New Chance for Patterning and Hatching?

The Polygon Fill style PATTERN and HATCH, which are quite successful in 2D graphics standards as GKS¹ and CGI² have proved to be less suitable for 3D graphics standards as GKS-3D³ and PHIGS⁴. However, the emerging standard PHIGS PLUS⁵ offers a unique chance to successfully employ these Interior Styles (under another name and in a slightly different form), because PHIGS PLUS supports a.o. topologically rectangular parametric surfaces In this article it is shown how these Interior Styles could be efficiently applied to curved surfaces in PHIGS PLUS. In addition, the possible interaction between the tessellation method and the patterning is shown.     

GKS-the standard for computer graphics

GKS is about to be ratified as the first international standard for computer graphics. It will provide a unique base on top of which portable graphical applications software can be built. This paper traces the history of GKS and describes its main concepts.     

An Implementation of the Viewing Pipeline in GKS-3D

Following the analysis and evaluation to the viewing pipeline of GKS-3D,a draft proposalof the international standard ofthree-dimensional computer graphics,an implementation of theviewing pipeline is further proposed in the paper and its algorithms are given in detail.Theimplementation is characterized by allowing a possible combination of the view clip andworkstation dip.     

GosiP: A GKS3D Shell for PHIGS

Gosip is an implementation of a GKS-3D level 2c interface to PHIGS. It allows GKS applications to run on PHIGS platforms, offering performance and portability across a wide range of high-performance 3D workstations. Compatibility of the standards is reviewed. A selection of design solutions is given for the problems of error processing, non-retained primitives and attribute management. The concepts of Workstation Display Session and atmbute state are introduced. Some comments are made on implementation dependencies, performance and portability.