Hi Andy, yeah in general you won't be able to apply sub-d smoothing to meshes that you generate with MoI. That's because sub-d smoothing requires a particular arrangement and topology of polygons and edges - you can't just apply sub-d to any mesh and get good results, it has to be specifically constructed for sub-d. Usually the method to do that is to construct the mesh by hand in a sub-d modeling program rather than trying to use an automatic conversion mechanism, or there are re-topology tools you can use to assist you in creating a sub-d specific topology from a general mesh.

But why are you trying to apply sub-d smooth to an already smooth model anyway? The picture you show has fillets in it so the edges are already rounded. Once you have the model in the form that you want it like that you don't need to apply sub-d smoothing on top of the already existing smoothing, just directly render it.

For transfer from MoI into Modo, I would definitely recommend LWO format and not 3DS - just make sure in the export options for the MoI v3 beta to set the Vertex normals style for the LWO output to be "Lightwave v10" style, and not actually Modo style, since Modo switched how they interpret vertex normals with version 601 to be the same as LightWave v10.

.3ds is a very old antiquated format, it has various 16-bit era limitations in it on the size of a single mesh and worse yet does not allow for transfer of vertex normals for getting the best quality smooth shading to come over like you will get with LWO or OBJ transfers. Also .3ds only supports triangle polygons and not n-gons so that's another limitation that you will run into if you use .3ds format. Usually you should only use .3ds as a kind of last resort, avoid it if at all possible.

- Michael