Hi Jan - re: minimal surface,

> The plug-in itself seems to work with quadrangles, at least visually. The triangulation seen
> in the render happened - also visually - after exporting the file.

From what you showed there it does seem to use some amount of quads but not 100% only quads - look near the boundaries of the surface and you can see a lot of them are sliced off, those ones are not quads but instead n-gons.

So you don't have a totally restricted "all quad" topology there - because of that there isn't really an automatic way to transfer from a generalized polygon mesh like that to the totally uniform MxN grid of points that a NURBS surface requires for its control polygon net.


> Maybe I can find a way to somehow re-model the surface back to MoI
> to go further from there.

If you can convert it to OBJ format, you could then use the OBJ to 3DM wireframe converter here:
http://moi3d.com/resources#Obj23dmWireframe_converter

That will convert the edges of that polygon mesh data into lines in a 3DM file, and then that 3DM file can be loaded into MoI, and you'll then have the wireframe of that model which you could use to as a snapping guide when drawing some new curves.

But just in general polygon mesh geometry like you have generated there is a pretty different form of data than NURBS geometry.

Polygon mesh data is made up of a lot of little facet pieces. NURBS geometry is made up of larger smooth spline surfaces.

It is possible to convert a broad smooth NURBS surface into polygons by dicing the surface up into little flat pieces - MoI will do that for you if you export to a polygon mesh format like OBJ, LWO, STL, SKP, ... Think of this step as similar to how you can take apples and smash them up into little bits to make applesauce.

But if you are starting with already diced up data (the faceted polygon mesh type data) and want to convert it back into big NURBS surfaces, that's basically the equivalent of wanting to start with applesauce and trying to reconstruct full apples back from the smashed up applesauce - a difficult task...

- Michael