def b_spline_centerline(x_centerline,y_centerline,z_centerline):
"""Give a better fitting of the centerline than the method 'spline_centerline' using b-splines"""
points = [[x_centerline[n],y_centerline[n],z_centerline[n]] for n in range(len(x_centerline))]
nurbs = NURBS(3,1000,points) # for the third argument (number of points), give at least len(z_centerline)
# (len(z_centerline)+500 or 1000 is ok)
P = nurbs.getCourbe3D()
x_centerline_fit=P[0]
y_centerline_fit=P[1]
return x_centerline_fit, y_centerline_fit
