#http://www.mathcurve.com/surfaces/boy/boy.shtml
vertices = D1:100 D2:100
u = from 0 to (PI) D1
v = from 0 to (PI) D2
a = sin(u)
b = cos(u)
c = sin(v)
d = cos(v)
m = sqrt(2)
k = rand2(0.1, 1.4)
t = b/(m - k*sin(2*u)*cos(3*v))
x = t*(b*cos(2*v) + m*a*d)
y = t*(b*sin(2*v) - m*a*c)
z = 3*t*b
