A complete IFC model can be exported into CityGML by using the IfcExplorer (FZK internal version).
- select "File-->Export-->CityGML"
- select the Level of Detail and the building elements for the export
- enter the global offset and the elevation
- confirm or change the file name
- confirm input by pressing ok
- IFC building elements are converted into corresponding CityGml entities
- IFC property sets are converted into CityGML generic attributes
- IFC external references are converted into CityGML external references
- the IFC building structure is converted into a set of CityObjectGroups
CityGML model imported into LandXplorer
CityGML model imported into Aristoteles
CityGML model opened in the IFCExplorer
Examples of converted models can be found here