Ian Stroud has worked with solid modelling since 1977 and has a number of unique insights into how CAD systems work, which are shared in this book. Ian Stroud started work in the first research group in boundary representation solid modelling, headed by Ian Braid. He was responsible for developing the first versions of many operations used in CAD systems today. In 1980 he moved to Sweden to continue work on generalising models, an idea of Professor Torsten Kjellberg. Ian Stroud was responsible for making the ideas work and developed many of the data structure elements, the basic techniques and system philosophy behind these. Techniques used in modern systems, such as thickening sheet models, shelling and wire-frame extrusion, originate from him. He has continued to look at different aspects of modelling which will help system users to be more efficient in their work when they eventually arrive in commercial systems. Ian Stroud is also knowledgeable about many other modelling aspects, such as features, which underpin efficient communication between application areas. He also teaches a course on Computer-Aided Engineering for Master's level students for which many of the exercises in this book were developed.