Hi @jaircasti thanks for asking. At this point I don't think there is a way to write out geometries as a cell in DGN without the cell first being defined in the cell library (users please correct me if I'm wrong). There is an idea here which you can vote on to have this functionality added. Someone might have a workaround for this problem though.
Hi @jaircasti,
FME's Microstation writer is currently quite limited in its surface writing. If you are opening the output file in Microstation, I would recommend writing instead with FME's AutoCAD RealDWG writer. This has much better support for 3D surfaces and solids, and DWG files can be opened and edited natively in Microstation.
Thanks Dave, it is exactly what I need. I transformed from gdb to AutoCAD RealDWG and I opened in MicroStation and every building is a cell. In addition to this, I opened the AutoCAD RealDWG in Microstation and I saved as DGN V8 and it worked, but I think keeping as AutoCAD RealDWG is working for what I need.
Thanks Dave for your help.