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EDITORIAL

For those of you receiving this issue of Computer Graphics Forum at the annual EUROGRAPHICS conference - Welcome to Hamburg. For the unfortunate few who were unable to make it to the annual event - we’re sorry you were not able to be there and are certain, even at the time of writing that you will have missed a great conference. However you will be able to console yourself by spending some time studying the contents of your favourite Journal - Computer Graphics Forum!

In this issue six refereed papers and a technical note combine with three substantial reports to bring a wide range of topics. We are also pleased with the wide geographic spread of the sources of contribu- tions, spanning the globe from China to the US.

The issue starts with the paper by Andreev on the clipping of arbitrary polygons which categorises the existing algorithms, dividing them into those which clip individual polygon edges against the whole clip region and those whch clip the whole polygon against individual boundaries of the clip regon ‘ 1 ~

sequence. Having noted deficiencies of the existing methods the author proceeds to elaborate the first approach to produce an improved version claimed to be capable of coping with all cases.

Hidden surface removal continues to exercise the designers of graphics systems, representing both a major computational step and an opportunity to speed up subsequent operations. As new representations of objects are considered so new methods of processing become appropriate. Heal’s paper investigates the new problems raised by the octree representation of solid objects. Whilst his method is only applicable to some cases it does offer the opportunity to use a culling approach to achieve other speedups.

Another area which whde not novel in intention is only slowly achieving the impact many feel it deserves in graphics is object oriented programming. Hubner and de Lancastre describe work on the application of OOPS to the modeling and specification of user interfaces. Their system allows a user interface to be built interactively from basic building blocks coded in object oriented style. Such a system allows rapid prototyping and dynamic tailoring of the interface, incorporating new or previously defined tools and thus allowing the development of a house style, while still permitting experienced designers the flexibility to provide tailored performance.

Two more contributions in this issue reflect the concern for efficient clipping in 3D graphics systems. The first by Krammer examines further the problems of efficient clipping which avoids the potential singularities of projective transformations. This work overlaps that of Herman and Reviczky (see Com- puter Graphics Forum 7(4)), and the short technical note by Zachrisen comments further on that paper. The issue includes a brief response from Herman. We are pleased when a paper produces a lively inter- change of ideas and would encourage readers who feel moved to comment on the journal contents. Con- tributions are considered for publication with a reply from the authors of the paper.

The paper by PaoluzZi, Rosina and Scopigno proposes a novel highly parallel architecture for the viewing pipeline. They examine three stages in a typical graphics system, starting with the conversion of object data structures into lists of primitives, then the identification of shadows and hidden surface remo- val, and finally examining the lighting models and the stages of rendering. For each stage they consider algorithms and the potential for parallel solutions. They describe why they have opted for a particular parallel architecture and the initial configurations they are using. It will be necessary to wait for the fol- low up paper to see whether theory holds in practice. Watch this space!

The final refereed paper, by Xiangping Chen and Daoning Ying, addresses the task of triangulating an arbitrary polygon. The method they propose copes with all cases of polygons with holes etc. and will be of particular interest to those such as Paoluzzi et al whose graphics engines are tuned to the use of tri- angles as the basic primitives, as well as those with applications in finite element mess generation, reser- voir simulation and similar fields. As this editorial is written within a few weeks of the recent incidents in China we are particularly pleased to be able to include the contribution at this difiicult time for higher education and research in that country and sincerely hope that many contributions can continue to flow

182 Edrtorial

in both directions in the future. Of the three reports the first addresses the issue of GKS-3D / PHIGS compatibihty, analysing each

system in terms of the recently proposed components and frameworks technique for modelling graphics systems. The authors compare the components to deduce the level of compatibility. The problem is of course that the modelling process is by its nature an abstraction from the detail of a system, whereas in dealing with the complex question of compatibility it is often the fine grain detail that produces the prob- lems. The attempt remains valid as an application of components and frameworks in analysing interoper- abihty of graphics standards.

The other reports are both literature surveys. The first is Computer Graphics Forum’s annual listing of published CAD and graphics material, indexed by keyword. The editors are again grateful to Jon Owen for producing this. The second report relates to PHIGS publications, with a brief statement on the con- tents and relevance of many of them. We are grateful to Toby Howard for this contribution and would welcome comments on whether other topics should be surveyed in this way.

Finally we would draw the reader’s attention to the announcement and requests for participants in the various EUROGRAPHICS working groups.

Computer Graphics Forum - Publication Dates

Computer Graphics Forum is published quarterly in March, June, September and December. In practice, members of the Association receive their copies later than these dates. Why?

With the exception of the September issue, publication is scheduled to coincide with the end of the month in question, rather than the start. This is for a number of practical reasons. Publication of the journal takes of the order of 10 weeks from receipt of typeset material by the publisher. The first issue of each volume is typeset in January, to avoid delays with receipt of contributed material arising from the Chnstmas holidays. The June issue is typeset in March. This date is partly chosen to allow the inclusion of papers from the UK Chapter Conference in this issue.

The September issue is scheduled to coincide with the annual conference. in order to include reports of the conference and minutes of the General Assembly in issue 4 of each volume, typesetting is not done until the end of September or early October. Because of delays due to Christmas holidays, it can happen that this issue is published in early January.

The journal is distributed to members from the Central Secretariat in Geneva and transportation of bulk copies to Geneva does take a little time. So members may receive their copies some little time after the end of the month of publication. In the case of the conference issue, members attending the confer- ence receive their copies at the conference. Copies to other members are mailed after the conference. if you want the September issue early, come to the conference!

David Arnold Behr de Ruiter.