### Kuen's Surface

This is one of the more complicated of the surfaces of constant negative curvature.
Parametric form :

x=2*(cos(u)+u*sin(u))*sin(v)/(1+u*u*sin(v)*sin(v))
y=2*(sin(u)-u*cos(u))*sin(v)/(1+u*u*sin(v)*sin(v))
z=log(tan(v/2))+2*cos(v)/(1+u*u*sin(v)*sin(v))

Try these values.

u = {-4, 4}, v = 0.05, pi-0.05

Here is the PoV3-source I used

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