Hyperbolisches Helikoid

x(u,v) = sinh(v) cos(t u)/ (1+cosh(u)cosh(v)) y(u,v) = sinh(v) sin(t u)/ (1+cosh(u)cosh(v)) z(u,v) = cosh(v)sinh(u)/ (1+cosh(u)cosh(v))