Additional images: Anaglyph, Parallel Stereo
A classical result from algebraic geometry says that on every smooth cubic surface there are 27 lines (possibly complex). Clebsch Cubic is a surface with 3-fold symmetry that has all 27 real lines. Its function is:
81*(x^3 + y^3 + z^3) - 189*(x^2*y + x^2*z + y^2*x + y^2*z + z^2*x + z^2*y) + 54*(x*y*z) + 126*(x*y + x*z + y*z) - 9*(x^2 + y^2 + z^2) - 9*(x + y + z) + 1
Above: another view of the Clebsch cubic, showing its 3-fold symmetry.
See also: ImplicitSurfaces.pdf