Hi Tom, it's possible for Rhino to store various kinds of data in 3DM files, like NURBS objects, spotlights, annotation text, polygon mesh objects, etc...

MoI only deals with NURBS data itself and so MoI will only read that one kind of object from 3DM files, not any of those other various things.

In this case the objects in your particular 3DM file are polygon mesh objects, they're made up of a kind of data that has a big pile of little planar facets instead of large smooth NURBS surfaces. MoI does not work on that kind of data, so there isn't really any good way to transfer that whole ring into MoI, it's just not the kind of data that MoI works with itself at modeling time.

From the polygon structure of the file (which you can see if you open that 3DM file in Rhino instead of MoI), it looks like probably the ring was originally a NURBS model which has now been converted into polygons. In order to bring it into MoI you would want to get that original CAD model, not this version which has been converted into polygon data.

Hope that helps explain what you are seeing in this case,

- Michael