#http://www.mathcurve.com/surfaces/helicoidcercle/helicoidcercle.shtml

vertices = D1:72 D2:1200

u = from 0 to (2*PI) D1
v = from 0 to (36*PI) D2

a = 1
h = 1/(2*PI)

x = a*cos(u)*cos(v)
z = a*cos(u)*sin(v)
y = b*sin(u) + h*v