Evaluation of Standard Graphics Packages

In order to compare the quality of different implementations of GKS, the ISO0 standard for computer graphics, an evaluation method for GKS implementations is presented. It is based upon several groups of criteria. One group of criteria is concerned with performance, by which we understand here the memory requirements and time requirements for programs using GKS functions. A program that measures the performance of GKS packages is presented. Results of this evaluation method with several commercially available GKS implementations are described in summary. A checklist for evaluation of standard graphics packages is added as an appendix.     

GKS certification—An overview

The rapid emergence of GKS implementations indicates the widespread acceptance of GKS as an international standard for computer graphics. It is essential however if the interests of the standard are to be preserved, that there be a feasible means of validating GKS implementations to ensure that adherence to the standard is maintained. This paper describes an overall methodology for GKS certification, and outlines in more detail the validation of data returned by GKS to an application program. Validation of output generated by GKS is discussed in general terms in this paper, and in more detail in other papers in this issue.     

Functional conformance testing of graphics software using a configurable reference system

This paper introduces a scheme for conformance checking of GKS implementations with the given GKS standard specification[1] based on functional black box testing. Specific testing problems caused by the nature of graphics systems and a solution are presented. Thereby emphasis is laid on a software generation technique which allows to configure reference implementations from a suitable specification of GKS. The reference implementation is used to produce correct reference data the contents and formats of which are adjusted for the particular candidate implementation.     

The evolution of standards for computer graphics

Although work towards international standards for computer graphics was started in 1976, it is in the last 2 years that real agreement and progress have been achieved. The first target, the functional specification of a graphics system, is satisfied by the graphical kernel system (GKS), which is now being processed as an International Organization for Standardization (ISO) draft international standard. GKS provides a reference model for two-dimensional graphics and an agreed vocabulary of terms covering the field. Many implementations of GKS as a package are now being produced. In addition to such a functional specification, two forms of communication are appropriate for graphics: a metafile and a virtual device interface. ISO is now reviewing a proposal for a metafile standard developed by the American National Standards Institute and closely related to GKS. Standards for a graphics virtual device interface and for three-dimensional graphics systems are also being actively developed. All these efforts and their interrelationships are described and examined.     

On Implementing Parallel GKS

This report investigates the problems involved in implementing the GKS 2D graphics standard in Occam. Whilst some of the detail is language specific, similar problems arise with implementations in any parallel system and the paper therefore has wider relevance. The main problems were found to be the lack of data types in Occam, parallel calls to the GKS implementation (which assumes a sequential command stream) and implementing a truly parallel GKS kernel. None of these problems appears to be insuperable, particularly if a preprocessor is used to overcome the potential communication and network conflicts which are possible in a parallel graphic system.     

ADA† and NIL: Two Concurrent Languages for GKS

The Graphical Kernel System (GKS) has become an international standard in graphics programming and attempts are now being made to integrate it with multiprocessing, possibly in distributed systems. It is therefore necessary to consider new programming languages able to support distributed implementations of GKS. Among them, Ada and Nil are considered here, since they are particularly suitable for concurrent programming. They are compared and evaluated in those specific tools which may provide data safety, system reconfigurability, and availability to distributed programming. The structural philosophies of the two languages are emphasized and reconfigurable implementation schemata for GKS in both of them are then suggested.     

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.     

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.     

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.     

A verifier for checking the conformance of programs with the GKS standard

A software development tool is introduced which allows to check the corrections of programs using the Graphical Kernel System (GKS). Such graphical application programs are checked whether their use of GKS functions is syntactically correct and conforms with semantic rules given by the GKS definition. Like the PFORT verifier for FORTRAN programs, this tool greatly reduces development time for GKS programs.     

Some Aspects of Binding GKS to C++

Aspects of a prototype binding of GKS to the C++ programming language are presented. The binding makes use of classes and derived classes to define GKS concepts such as segments and workstations. Operator overloading is used for some GKS Functions.     

A Multi-Microprocessor GKS Workstation

Implementers of graphical application sytems hesitate to interface their applications to the GKS standard not only because GKS functionality seems to be less suffcient for a particular application but also because the use of GKS-as it is offered in portable software implementions-uaually means a loss of system performance. This article describes an installation of GKS on a multi-microprocessor that is based on functional distribution principles as well as on the object-oriented distribution of a graphics system. The main concepts and advantages of a GKS workstation using more than one processing unit with at least one output pipeline are described. The flexibility of this approach opens a perspective view to a GKS workststion that is configurable to application requirements.     

Formal Specification in the Revision of GKS: An Illustrative Example

The first ISO/IEC standard for computer graphics, the Graphical Kernel System (GKS) was published in August 1985. In accordance with ISO/IEC procedures, GKS is now being reviewed and revised. This paper describes how formal specification techniques are being used by the authors to analyse key parts of proposals being made for changes to the framework of GKS to bring the standard into line with the requirements of applications and the operating environment likely to be found in the mid-1990's.     

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.     

3D extension to GKS

The Graphical Kernel System GKS has [1] been established as the first standard in the field of Computer Graphics covering two-dimensional (2D) graphics. Now work is going on to develop standards in related areas. One important effort is the extension of GKS for three-dimensional (3D) graphics. This paper will briefly overview the history of standardization efforts with respect to 3D graphics and then report the current activities of various national and international standardization bodies for extending GKS to 3D. Then the paper will concentrate on GKS-3D [2], a proposal for a 3D extension of GKS which is developed by the Dutch standardization committee NNI in close collaboration with the International Organization for Standardization ISO/TC97/SC21/WG2. Technical work is expected to finish in 1985. Scope and purpose of this future 3D standard and goals of the design are given and the functionality of the 3D extension is described in some detail. As technical work on GKS-3D is going on, changes may occur to the standard document. The major issues will be surveyed and trends will be sketched.     

Filling Complex Polygons by Region-Fill Methods on Raster Graphics Terminals

A method is described for filling polygons according to the GKS Fill Area definition on terminals that provide only region-filling capabilities. The advantages and disadvantages of using this algorithm in GKS device drivers are considered.     

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.     

The GKS Input Model in Manifold

This paper describes the specification of the GKS input model in M anifold . The aim of the work reported in this paper was two-fold: first, to review the communication patterns implied by the GKS input model, and second, to evaluate the suitability of the M anifold language as a tool for defining complex dynamic interaction patterns that are common in non-trivial user interfaces.
The GKS input model is also adopted by all more recent ISO graphics standard documents. A more formal scrutiny of the inter-communication of the components of this model, excluding the implementation details of their functionality, is instructive in itself. It can reveal directions for improvement of its shortcomings and for generalization of its strengths for the ongoing effort to define the functionality of future graphics packages.
M anifold is a language for describing inter-process communications. Processes in M anifold communicate by means of buffered communication links called streams and by reacting to events raised asynchronously by other processes. Our experience shows that M anifold is a promising tool for describing systems of cooperating parallel processes. Our M anifold specification of the GKS input model offers a very flexible way to structure user defined logical input devices. Furthermore, it is simple and modular enough to allow easy extensions to include more functionality by local modifications. As such, it can serve as a basis for possible extensions and enhancements envisioned for future graphics packages.
1987 CR Categories: C.1.2, C.1.3, C.2.m, D.1.3, F.1.2, I.1.3, I.3.6, I.3.4.
1885 Mathematical Subject Classification: 68N99, 68Q10,68U05.