Cross Cap
A self intersecting, single sided surface!
Graphics by Paul Bourke
December 1995
Source Code

Equations
x = cos(u) * sin(2*v)
y = sin(u) * sin(2*v)
z = cos(v) * cos(v)  cos(u) * cos(u) * sin(v) * sin(v)
0 <= u <= 2
and 0 <= v <= / 2
Implicit surface
4 (x^{4} + x^{2} y^{2} +
x^{2} z^{2} + x^{2} z)
+ y^{4} + y^{2} z^{2}  y^{2} = 0
