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EDITORIAL

As Computer Graphcs Forum moves into the 90’s the most striking change our readers will already have noticed - the new cover. We are very pleased with this and hope you will agree with our view.

This issue contains five refereed papers and an interesting survey article. The first paper, by Miente Bakker discusses the potential for inclusion of more effective 3D pattern and hatch styles into the proposed PHIGS PLUS system. He proposes the use of these styles with parametrically defined surfaces and shows how this could be incorporated in a usable and useful way.

A second standards-related paper, “An Approach to Hierarchical Input Devices” by Duce, van Liere and ten Hagen, is the latest in a series which has applied formal specification techniques to the definition of aspects of international standards, in order to demonstrate how more rigorous definitions can be achieved and encourage the application of these techniques to international standards projects. In this paper the authors apply the notions of Hoare’s CSP notation to the definition of hierarchically defined input devices. This extends earlier work on the GKS input model and allows the construction of input devices from more elementary components leading to devices where inputs are potentially gen- erated not directly, but from the triggering of more simple component input devices. In this respect the approach anticipates some of the discussions around the five year revision of the GKS standard (although the changes which arise from the five year review are a long way from being agreed - even in natural language!). They demonstrate the approach by inventing a bicycle input device formulated from frame wheels and spokes - although the deliberate inclusion of spokes in the operations seems to us rather risky. The authors conclude that the combinators of CSP provide a very natural way of split- ting a complex structure into a number of simple subcomponents and describing the behaviour of the whole structure in terms of the behaviour of the subcomponents.

The paper by Barbic and Spegel describes a language they have defined for the description of geometric configurations. Their long term objective is the definition of a language and system to allow the simple manipulation of configurations in ways which properly use the accompanying phenomena such as the invariance of descriptions within the properties of the connection types, etc. The current version of the language provides for the basic notions such as operations, relations and fragments, but the authors recognise that future versions will require considerably greater descriptive power to allow convenient control of configurations. Such additional features will include control of hierarchy of coor- dinate systems and operations on motions of subgroups.

Milanese also addresses the area of modelling systems with constraints and defines a declarative language, KAAMOZ, for CAD-CAM modelling using type denotations. This language is designed to protect the topological constraints built into models and handle the inheritance of such constraints in building complex models from simple subcomponents. The language is in effect an evolution of Prolog with private modelling structures and modularization. The result allows the language to be interfaced to relational or deductive data bases.

Finally in the refereed section Durand and Faguy present a method of using B-spline interpolation to provide rational zooming of bit mapped images. This improves the quality of zoomed images and, with order 3 B-splines, the authors have been able to produce excellent results with scaling coefficients up to 4. The technique can also be used when higher pseudo-resolutions are required in order to pro- vide output on larger scale film recorders (35 and 70 mm). The paper also includes a description of parallel operation of the algorithm over a local area network containing several similar workstations. The authors conclude that a software tool of the type described is an essential component of any 2D animation system based on scan-and-paint methods.

The reports section contains a very interesting contribution from Martin Prime, who has been con- ducting a current product review of UIMS tools. He begins by highltghting the difficulties of even defining even the term UIMS and then gives a range of the metrics on which he feels UIMS products can be compared. The report then reviews seven products against the criteria developed.

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Computer Graphcs Forum 9(1) concludes with the normal sections of EUROGRAPHICS busi- ness and announcements. We hope you find this issue an interesting and appropriate start to the new decade.

David Arnold Behr de Ruiter