The hyperbolic space $\mathbb{H}^3$, has a boundary $\mathbb{CP}^1$.

A ideal tetrahedron in $\mathbb{H}^3$, is a tetrahedron, where the four vertices are on the boundary $\mathbb{CP}^1$. 

The four vertices of the tetrahedron may be parametrized by four complex numbers $z_1, z_2, z_3, z_4$.

What is the surface of this ideal tetrahedron, as function of $z_1, z_2, z_3, z_4$?