A quick note - Modo 203 doesn't seem to properly handle any type of editing operation on a mesh with vertex normals, even flipping.

It will just flip the face orientations but the vertex normals will remain unaltered, this will cause shading problems with the face and vertex normals pointing in opposite directions.

If you export a closed solid from MoI, MoI will do some work to automatically orient normals towards the "outside" direction of the solid. But if you export open surfaces, there won't be any automatic orientation. Due to the Modo flipping bug, you won't be able to flip it properly in Modo so to render it properly you will need to turn on double-sided rendering for the render material.

I think I will tune this up so that open meshes will get a double-sided material set on them by default on export from MoI.

I still haven't seen if there is a way in Modo 203 to throw out vertex normals and return to auto-generated ones... If that was possible that would also fix the problem but at the cost of returning to less smooth shading.

- Michael