A second order Voronoi Diagram is defined as:
$V(p_i,p_j)=\{x / \forall k \neq i,j : d(x,p_i)\leq d(x,p_k) \wedge d(x,p_j)\leq d(x,p_k) \}$ with $p_i \neq p_j$.
The question is: how can I characterize the pair of points $p_i,p_j$ such that $V(p_i,p_j)$ is bounded.
In first order Vornoi Diagram was quite simple: just looking if the point remains to the convex hull of the set of points. But in the secon order I cannot find a proper solution.