A
quartic surface that looks like a rounded
cube in its simplest form, but gets more funky as the
variables a, b, and c get further away from
zero (see:
Tooth Surface). The equation for Goursat's Surface is as follows:
x4 + y4 + z4 + a(x2 + y2 + z2) + b(x2 + y2 + z2) + c = 0