vertices = D1:100 D2:100
u = from (-3*PI) to (3*PI) D1
v = from 0 to (4*PI) D2

w = sin(v);

o = 0.1

x = u*in_range(v, 0, 2*PI) + cot(u)*w*in_range(v, 2*PI + o, 4*PI) 
y = u*in_range(v, 2*PI, 4*PI) + cot(u)*w*in_range(v, 0, 2*PI - o) 

x = limit(x, -3*PI, 3*PI)
y = limit(y, -3*PI, 3*PI)

u = u*2
v = v*2
