Hi Pilou,

> Why primitive 3D cylinder and cone have not control point ?

It's because the end caps are trimmed planes. Control points cannot be turned on for objects that have joined edges where those edges are not natural edges of the underlying surface. Otherwise if points were turned on in these situations, it would be too easy for the surfaces to pull apart and make a gap in what is supposed to be a joined edge.

See the FAQ for some more explanation and illustrations.

There's an illustration in the FAQ answer that shows the kind of gaps that would be easily caused.

You can always turn on control points for an individual surface, so you can use Edit > Separate to break the cylinder into individual surfaces and then you can show points for those.

- Michael