How to create a SplineSurface with curved edges?

Hi, I would like to create a surface that looks like a part of the side surface of a cylinder using SplineSurface. Here is my code with a rectangle surface that I would like to curve:

from netgen.csg import *
from ngsolve import *

base = Plane(Pnt(0, 0, 0), Vec(0, 0, 1))
surface = SplineSurface(base)

pts = [(-0.5, -0.5, 0), (-0.5, 0.5, 0), (0.5, 0.5, 0), (0.5, -0.5, 0)]
p1, p2, p3, p4 = [surface.AddPoint(*p) for p in pts]

surface.AddSegment(p1, p2)
surface.AddSegment(p2, p3)
surface.AddSegment(p3, p4)
surface.AddSegment(p4, p1)

geo = CSGeometry()
geo.Add(Sphere(Pnt(0, 0, 0), 1))
mesh = Mesh(geo.GenerateMesh(maxh=0.5))


This should be possible using the occ interface. We fixed the meshing of free faces there in recent commits so try the master or nightly build

Best Christopher