Hi, I explained myself badly, what I mean is better understood with a reference image that I enclose below and with some sample files.



As you can see the USB plug is exported with Moi3D in Obj and in the export Moi3D, mark the faces edges with sharp attribute, but as regards the conversion to SubD it is an unused attribute and could be used as an expedient case before finding a valid alternative.



And here some shading difference inside the awesome app CAD Assistant for phone that manage several type and conversion and many more features. Here the shading with edge sharp is better to understand the shapes.

https://www.opencascade.com/content/cad-assistant

And I attach the file in obj with marked sharp and no mark..