I often get STEP files from CATIA users that contains assembly information without the actual parts.
From reading the file in Notepad it seems the file has the parts name and their position/orientation but not the actual geometry. I guess it’s a setting they have to check while creating the STEP file and it’s not our problem… But it would be nice if Rhino told us what happened, right now it says the file was successfully read and that the assembly is contained in a block.
I think it should warn us with a message like: "No geometry created. File contains unavailable links to the following part(s): xxxx1.catpart, xxxx2.catpart, etc."
I can send an example STEP file in private if needed.