This is an animation of the equi-valued surfaces of the field f(x,y,z) =
(x^{2}+y^{2}+z^{2}+a^{2})
/ (x^{2}+4y^{2})
for a = 1 and f in the range [-0.5,1.5]. The animation contain some quadratic surfaces:

- f < 1/4 - Ellipsoid
- f = 1/4 - Elliptic Cylinder
- 1/4 < f < 1 - Hyperbolic Paraboloid
- f = 1 - 'Hyperbolic plane'
- f > 1 - Hyperboloid of Two Sheets

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