#http://www.mathcurve.com/surfaces/astroidal/astroidal.shtml
vertices = D1:100 D2:100
u = from 0 to (2*PI) D1
v = from (-PI*0.5) to (PI*0.5) D2
a = 10
x = a*pow(cos(u)*cos(v), 3)
y = a*pow(sin(v), 3)
z = a*pow(sin(u)*cos(v), 3)
