Bézier AwardTitle SMAI. Braid, A. Grayer and C. Lang

Ian Braid, Alan Grayer and Charles Lang, the 2008 Pierre Bézier Award Recipients

This group of three people made many fundamental contributions to practical solid modelling, and their work has had a profound influence on today’s commercial solid modelling systems. They commenced working together in the CAD Group at the Computer Laboratory, Cambridge University. The Group was set up by Charles Lang under Prof. Maurice Wilkes’ direction in 1965 to undertake research on tools for building mechanical CAD/CAM systems, with an emphasis on software system components, computer graphics and computational geometry. Initial experiments in solid modelling were made in 1969. Also in 1969 Ian Braid joined the Group where, under Charles Lang’s supervision, he developed the BUILD boundary representation modeller, the most advanced such system of its day. Whereas other systems used faceting to avoid the problems of calculating intersections between non-planar surfaces, the BUILD team tackled such problems head-on. Ian was awarded his PhD in 1973.

Alan Grayer joined the group in 1971 and, also under Charles’ supervision, developed algorithms for the automatic machining of prismatic parts modelled in BUILD. These were machined on a model making machine, built by the Group in 1971 following an inspirational visit to Bézier at Renault in Paris. Alan was awarded his PhD in 1977. Ian then developed a completely new solid modeller, BUILD 2, which was a significant advance as it made a clear separation of geometry and topology in both its data structures and algorithms. This made it possible to implement generalised boolean operations and to systematically extend the geometric coverage and the functionality of the modeller with operations such as blending. Subsequently other PhD theses supervised by Ian and based on the BUILD modellers included Dimensions and Tolerances (Hillyard 1978), Feature Recognition (Kyprianou 1980), Automatic 2D and 3D Mesh Generation (Wördenweber 1982) and Surface Intersections (Solomon 1986). These theses were some of the earliest contributions to solid modelling and to applications.

In 1974 Alan, Ian and Charles, together with another member of the CAD Group, Peter Veenman, formed Shape Data Ltd. Peter Veenman was the first employee while Alan, Ian and Charles remained in the CAD Group at that time, joining the company later. At Shape Data they developed the ROMULUS modeller, based on the ideas of the BUILD modellers, but engineered as a commercial product written in Fortran. The first license to a customer was in 1978. ROMULUS was a kernel modeller designed for building into CAD/CAM systems. Of the several ROMULUS-based systems that emerged HP’s ME30 system was the most widely used. Shape Data was acquired by Evans & Sutherland in 1981 and in 1985 commenced the development of Parasolid as a successor to ROMULUS. A specific area of specialized development undertaken was the creation (under contract to CAM-I) of the Applications Interface Specification (1980), intended as a standardized API for solid modellers.

At the end of 1985 Alan, Ian and Charles left Shape Data to form Three-Space Ltd which developed ACIS, a totally new solid modeller, together with Spatial Technology, Inc. They worked intensively on generalising models to include wires, sheets, solids, cells, and both manifold and non-manifold objects; adding new geometric types for curves and surfaces; blending techniques; local operations; toleranced models; and particularly the software architecture of the modellers and the precision of numerical calculations. The ACIS business was acquired from Spatial Technology by Dassault Systčme in 2000. Any commercial CAD system using ACIS or Parasolid as its kernel owes a large part of its success to the work of Ian, Alan and Charles and their many colleagues over a period of more than thirty years. ACIS was also found to be an invaluable research tool by many university research projects.

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