Hi Leonard, I'm glad that you have it solved now.

So the problem is that the curves that were created in Cinema4D are not actually smooth curves at all, they are instead just a sequence of line segments.

There are enough little line segments so that it kind of looks like it is a smooth curve when it really isn't.

If you zoom in to examine them and turn on some points and move them slightly you will be able to see that more clearly.

I think Cinema4D is mostly focused on polygon modeling and not on actual true spline curve drawing, so that's probably why they generate a curve that is actually more like polygons, just made up of lines instead of smooth pieces.

Once you extrude something in MoI that is made up of a bunch of little lines, it generates a bunch of little planes in the extruded part rather than a smooth extruded surface.

So you're probably better off drawing the curve from the beginning in MoI rather than drawing it in Cinema4D for something where you want to produce a smooth surface when it is turned into a surface in MoI.

- Michael