Modeling detector geometries in Geant4

The Geometry modeler in Geant4 (a software toolkit for the simulation of the interactions of particles with matter) has been designed to offer to a generic user the ability to describe the geometrical structure of a detector in a very natural way, and allowing an efficient propagation of particles in the geometrical detector model. Advanced techniques for optimizing tracking in the geometrical model have been seriously taken into consideration in the design, both in order to optimize the run-time performance and reduce the physical memory consumption when dealing with complex geometrical setups. The major concepts of geometry modeling in the Geant4 toolkit are here reviewed, with a special focus on the more recent features introduced in the last releases of the software. (6 refs).