Hi Pilou, I am glad that this worked for you but just keep in mind that NURBS solids are not really designed to be made up of many thousands of little faceted pieces like that, so you may run into problems like extremely large file sizes and operations taking a long long time, things like that.

It's something that you could use for special circumstances but in general you would be better off keeping data like that as polygons rather than trying to turn it into NURBS.

- Michael