OpenRoads/OpenSite can only apply Feature Definition to Meshes, not solids.

This would make it possible for advanced modeling with solids elements for BIM use. Feature Definition play a huge role when using the Export to IFC tool.

If the solid has no FD, then it will be exported without a name. Converting them to mesh is a solution, but solids tend to work much better with other softwares.

File size in mind, the same element in Mesh can be 10x bigger than as a solid.