Thanks to flight% who answered my first question
I did the trick to convert NURBS (any surface) to mesh. It is OK. But the result is not OK.
I tried with a simple intersection : I made 2 planes (meshes) and I do “intersect” … and as far as I know the intersection should be a 3D line, but in blender I have 2 parts of my planes ? how can it be ? What must I do to obtain a 3D curve by intersection of 2 surfaces ?
Or anyway if blender returns a surface (part of the 2 planes) how can I extract the border only ?
Thank you by advance