I use KeyShot with MoI and the two programs play very well together. Output as OBJ and use Quads & Triangles as Michael recommends.

Just make sure you have assigned a unique color (Style) to each surface or solid where you want to assign a unique KeyShot material. The Style names you assign in MoI will come across into the KeyShot Scene Parts Tree, making it very easy to assign materials, show/hide parts, etc.

Ed