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
HPs 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.