The Virtual Geometry Model (VGM) has been developed as a generalization of the existing convertors roottog4, g4toxml provided within Geant4 VMC , when new directions: g4toroot, roottoxml were asked by users. Instead of adding other bilateral converters and multiplying the implementations, the abstract layer to geometry has been defined and the geometry models have been "mapped" to this generalized scheme. Once this is done, the geometry objects in different models can be handled in the same way.

In the VGM, abstract interfaces to geometry objects and an abstract factory for geometry construction, import and export are introduced. The interfaces to geometry objects were defined with the intention to be suitable for desription of "geant-like" geometries with a hierarchical volume structure.