Geometrical Modellers for HEP

Physics applications such as reconstruction, visualisation, simulation and event viewing make wide use of geometrical information about the detector. Historically, these programmes have been written inside HEP because it was difficult to find products that met the necessary criteria. With the recent developments of geometrical modelling, very high quality codes are now available that can be efficiently used to transport particles in very complicated setups. This talk will review the results obtained with one of these codes on a typical HEP application.