Hi Micheal

Thank you for your clear explanation. I understand now.
I actually also try to export to Blender and try Blender to MoI.
Result is the same. No Polygon mesh allowed.
Nevermind, I found MoI can still be a good tool to do task that polygon modeling hard to create.

Just wonder, I heard that MoI and Rhino can Ctrl+V, Crtl+P copy-paste model between these 2 apps without exporting and importing.
Is it possible to copy paste model from MoI to SKP directly for better work flow ?
This should be very useful feature.

Thanks