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EDITORIAL

Volume 8(2) of Computer Graphics Forum brings the usual crop of refereed papers along with the papers from the EG(UK) conference. This means that the issue is rather larger than normal with a total of eleven papers, spanning a wide variety of interesting topics. The issue begins with two papers on software engineering for graphics, both of them touchng on functional programming and formal methods, particularly for datatypes. The paper by Lakshminarasimhan and Srivas provides an approach to the formal specification and classification of Hidden Surface Elimination Algorithms, using OBJ and LOBJ. This includes an interesting transformation of the Z-buffer algorithm in order to derive equivalent algorithms for application on parallel architectures. As a potentially practical application of formal specification techniques this seems a particularly positive attempt to promote the use of such techniques in computer graphics. In addition in addressing the complex area of algorithm generation for parallel architectures (all to often considered the purview of individually tailored designs) the authors must encourage the view that effort spent on such ‘one-off solutions might be as well apllied to the generation of formally specified tools for automating the exercise, particularly in applications sensitive to algorithms known to be correct.

Parsons, in another paper oriented towards software engineering, examines the application of the functional programming language Miranda to graphics software, and in particular the usefulness of Miranda laws in providing self-checking and adjusting datatypes. This allows for example the self- compressing image representation. The approach obviously has wider application (particularly in the area of automated consistency checking in CAD applications), although similar ideas in other languages seem to have been slow in gaining widespread acceptance and usage.

Until such time as the formal tools are established there remains a need for individual problems in many areas. The paper by Theoharis and Page examines parallel implementations of the Sutherland- Hodgman polygon clipping algorithm comparing formulations for MIMD and SIMD architectures in the forms of an INMOS Transputer system and a AMT Distributed Array Processor and the authors highlight some interesting design decisions which need to be made in exploiting the different forms of parallelism.

The EUROGRAPHICS(UK) conference this year took place in Manchester, where a small but enthusiastic conference was presented with six of the papers submitted to the conference for refereeing. These papers were part of a conference programme which included an impressive demonstration of the exchange of CGM files between systems from a number of manufacturers. We hope to include a report on the conference in the next issue. The first paper in this issue addresses the needs for the provision of wider ranges of line rendering styles as part of the revisions of graphics standards. These issues have already been raised at the Eurographics workshop on the revision of GKS, but Gossling illustrates an application-oriented justification for the approach and makes a concrete suggestion for how the provision should be made. There remain questions arising from the conversion of what is usually thought of as a one-dimensional primitive into an area primitive and the implications of this when included in a GKS-3D environment for example, but the paper makes some interesting suggestions which could be developed further.

The paper by Plummer and Penna on mass market applications of real time 3D graphics concen- trates on a kitchen planning application where the authors’ systems gives the designer an opportunity to explore the visual effects of particular kitchen layouts. No provision of ergonomic analysis aids is made and such analysis would be an interesting continuation of work provided the system could continue to work in real time. The existing system was demonstrated at the conference and won the Ken Brodlie prize for the best paper.

The paper by John and Willis is on the control of animation sequences and uses graphical techniques to allow the designer of the animation sequence to control such effects as acceleration of motion along given paths. Somewhat unusually the conference included for the first time as far as we are aware a sub- mitted paper based on overseas work. Perez-Cavarez and Rannou report another area of application for animation techniques, although in this case the animation is rather more concerned with simulation than the design of artistic sequences of pictures.

Both of the other EG(UK) papers address the part of the graphics system responsible for manipula- tions of graphic data at the display level. Rush and Milne’s paper picks up the theme of parallelism by developing the earlier work of Arabnia and Oliver on transputer based display operations (see Computer Graphics Forum 8(1) for the most recent paper of their series). In the current paper the operations inves- tigated are the rotation of images where the responsibility for handling a n image has been distributed between a number of transputers arranged in a ring. The authors present results analysing the efficiency of the multiprocessor system.

The final submitted paper at the conference was the paper by Smith and Leitch who presented a novel method for the incremental display of single valued functions. The method is a natural progression of techniques originating in the work of Bresenham on incremental line drawing algorithms although as the shapes to be displayed become more complex the methods will of course only address the subset of applications which require those shapes.

The first invited paper from the EUROGRAPHICS(UK) Conference is by N. Magnenat-Thalmann and D. Thalmann who have had a lasting impact on the software support of animation systems. The topic of this paper is “The Problematics of Human Prototyping and Animation”. This is obviously an extremely complex area and the conference could not have hoped to get a more experienced team to address the ‘problematics’. I t is somehow comforting to know that the problems of simulating humans is not trivial and still some way from perfection. There is an interesting philosophical question as to whether achievement of perfect simulation will then be self defeating since not only will there be no further problem to solve, but also the artistic licence of animators is likely to require introduction of dis- tinctive features in order to differentiate their work from conventional photography. Perhaps the next range of problems will need to address simulation of personality! In the meantime the simulations presented are very recognizable as caricatures of specific individuals.

The second invited paper was given by the EUROGRAPHICS(UK) chairman Anne Mumford, who set the scene for the C G M demonstration which took place as part of the exhibition.

This then is the second issue of Volume 8. We would draw our readers’ attention to the cover com- petition, which is formally announced in this issue, with a relatively short time to the closing date. We look forward to receiving your submissions.

David Arnold Behr de Ruiter