STEP open shell importing as independent surfaces?

Rhino Rhino for Mac
1

Hi,
A customer reported (and I’ve been able to verify with the macOS version of Rhino 7) that STEP faces in the format open shell / shell based surface model / manifold surface shape representation imports each face as an independent surface, whereas STEP faces set up as closed shell / manifold solid brep / advanced brep shape representation are created as a solid. (In both cases this is with the “join surfaces” option turned off.)

Is this the intended behavior? Is there a way to format open shell faces so that they automatically import as one object into Rhino 3D? I don’t seem to have any difficultly using openNURBS to create the exact equivalent of the STEP open shell object as a single object in a 3dm file and then load it into Rhino that way…

2

open_shell.stp (9.6 KB)
open_shell.3dm (16.9 KB)
brep.stp (9.3 KB)

3

Turning off Join Surfaces tells the importer to import everything as individual surfaces. The ones from the same shape rep are probably grouped or blocked together, whether open or closed shell. Check the Join Surfaces box and you should get what you expect.