Hi rd, also you mentioned:

> I tried using .step and .stl;

These are very different file formats - STEP is meant to contain NURBS data and if you try to export polygon mesh data out from Rhino into STEP format you will get an empty file since the STEP format is not intended to contain that kind of model data.

STL on the other hand only contains polygon mesh data - so you can export a polygon mesh file out from Rhino with that, but you cannot read an STL file into MoI since MoI only imports NURBS data and not polygonal type model data. MoI can generate an STL file at export time at which point it will break NURBS surfaces up into little triangle facets, but it won't read that kind of data into MoI to work with at model time - MoI only works with NURBS surface/solid data at modeling time.

- Michael