3D geometry and 3D materials are complex objects. Therefore, a 1:1 translation of one representation of 3D scenes to another is almost always impossible. All of GroIMP's geometry can be exported to POV-Ray, however, some objects like NURBS surfaces have to be exported as triangle meshes because POV-Ray does not support them directly. This leads to quite big POV-Ray file sizes.
The export of GroIMP's materials to POV-Ray is even more restricted. For some material definitions, it is not possible to export all of their parts to POV-Ray, so POV-Ray's output may look different from what you would expect. Manual postprocessing of exported POV-Ray-scenes may be necessary.