def sphere(ndiv=6):
"""Create a triangulated spherical surface.
A high quality approximation of a spherical surface is constructed as
follows. First an icosahedron is constructed. Its triangular facets are
subdivided by dividing all edges in `ndiv` parts. The resulting mesh is
then projected on a sphere with unit radius. The higher `ndiv` is taken,
the better the approximation. `ndiv=1` results in an icosahedron.
Returns:
A TriSurface, representing a triangulated approximation of a
spherical surface with radius 1 and center at the origin.
"""
from elements import Icosa
from plugins.trisurface import TriSurface
M = TriSurface(Icosa.vertices,Icosa.faces)
M = M.subdivide(ndiv).fuse()
M = M.projectOnSphere()
return M
