Parabolic cyclide:
_FxGraph3D (a/2)*(2*v*v + b*(1-u*u-v*v))/(1+u*u+v*v);(a*u)*(v*v+b)/(1+u*u+v*v);(a*v)*(1+u*u-b)/(1+u*u+v*v);-10;10;-10;10;50;50;1;0.5;1;UV

Network works at this density.
Open circles show up in v mode, or u mode.
The u and v in the parametric equation range over +/- infinity, so the circles are not closed.
The open circles could be replaced with 3 point circles, and lofted...


Parabola1:
_FxGraph3D u*u;0;sqrt(2)*u;-3.536;3.536;0;1;20;0;1;0;1;UV

Parabola2:
_FxGraph3D 0.5 - 0.5*u*u;-u;0;-5;5;0;1;20;0;1;0;1;UV

The parametric formulas for the two parabolas were mathematically manipulated to match the two standard formula formats.

- Brian

Formulas from Wikipedia and:
http://www.math-only-math.com/parametric-equations-of-a-parabola.html