Hi @007fkj,

Can you check that you when you first add the CityGML writer that you have the Feature Definition Type set to Copy From Reader?

This means that the writer will look at the reader's schema and offer you a selection of writer feature types from the IFC schema. You can then select which feature types you wish to write out. In the screenshot below the [rac_basic_sample_project.... is just the name of my reader, so you can ignore that.

If that setting isn't showing the feature types that you're looking for, check what LOD your IFC is and inspect the reader in the Data Inspector to see what feature types are available to you. I noticed in LOD1 IFC when reading it in, I do get fewer feature types available to me since it contains less data:

Screenshots are taken from this tutorial workspace, with a more basic example of the IFC to CityGML tutorial, and a more advanced one available which might be helpful resources for you. I believe this webinar also touches on IFC to CityGML (the intermediate one). Depending on what level of detail you are working with this can be a more involved workspace than some other translations that you could start with. I'd also like to mention if you are new to FME that we also have free training courses like an FME Basic Training that could help if you're interested in taking a look at that.

Happy FME'ing!