You can twist hemisphere along x and y axis. Try rx=-1.0 (and let ry=1.0 as default), it will make a saddle. #!BPY import bpy import math def vert(n,rx,ry): yield (0.0, 0.0, 1.0) for k in range(1, n+1): theta = float(k)*math.pi/2.0/float(n…