My friend and colleague Ian Braid, who has died aged 77, was a pioneer in the field of solid modelling. His fundamental work on the 3D modelling of mechanical engineering parts in computer memory was a key technology that has changed the way engineering is practised around the world.

Ian was born in Melbourne and raised on a farm in rural New South Wales. After initial home schooling, he was educated at Scotch college in Melbourne and Melbourne University, where he graduated in mechanical engineering. Soon afterwards he sailed for the UK to join an English Electric graduate apprentice scheme.

He worked on steam turbines for a couple of years but a growing interest in the new-fangled world of computing led him, in 1968, to the Cambridge University computer laboratory. After completing the diploma in computer science he joined the laboratory’s Computer-Aided Design (CAD) Group as a PhD student. His thesis, published under the deceptively simple title Designing With Volumes, described ways of combining simple solid shapes together to build 3D models of mechanical parts. He continued to advance the field of modelling and its application for the next 30 years.

He took over leadership of the CAD Group in 1975, by which time he, together with three colleagues, had set up a company in Cambridge, Shape Data Ltd, to further develop the work of the group commercially. He joined Shape Data full time in 1980. The company released the world’s first commercial solid modeller, Romulus, based on Ian’s work, in 1978.

In 1986 Ian and two other founders left to start a new company, Three-Space Ltd. Here they created a new generation modeller, ACIS, sharing the development with a US company, Spatial Technology. ACIS and a competitive modeller from Shape Data, Parasolid, are both still going strong, the former now owned by Dassault Systèmes and the latter by Siemens. When he began this work in 1969 Ian could have had no idea of how wide-ranging its application would be in the future. Nowadays designs created using solid modellers are used for engineering analyses, parts classification, computer-controlled manufacture including robotics, documentation and many other applications. Modellers enable engineering teams to collaborate internationally via the internet as they can all have access to the same design information.

Ian was a modest man with a gentle manner and a wry sense of humour. In his retirement he was able to devote more time to his music. He was a fine amateur cellist and enjoyed playing in chamber music groups, learning languages and studying geology. He pursued too his interest in family history, tracing the fortunes of his Braid ancestors who had emigrated from Fife to start a new life in Melbourne in 1854 – much as he had done in reverse just over a hundred years later.

Ian is survived by his wife Judith (nee Slater), whom he married in 1973, their children, Jo and Alex, five grandchildren, and his brother, Andrew.