I was using"https://github.com/tum-gis/ifc-to-citygml3" to write GML3.0. the w.pace is designed to write BldgConstructiveElement so I changed it into wall /floor surface. I can see the converted wall on visual preview but it is not writing it. any id

Hi @bizab093​. The GitHub link that you provided is for the purpose of testing CityGML 3 and it is not meant to support CityGML 2. The example uses the GML writer in FME, not the CityGML writer. You will need a different workflow for CityGML 2. A colleague provided some examples for you to explore. For IFC to CityGML2 you could take a look at the GeoBIM benchmark and Indoor Pilot examples from last week's CityGML webinar.

You could also check out our tutorials from our knowledge base. Best of luck, let us know if these help you out.