A General Framework for the 2-Contact Case
Polygonal regions P and P’ satisfy P’ P and each vertex-edge rectangle for P, V, and E is a vertex-edge rectangle for P’, V’, and E’.
For every vertex v V’ and every edge e E’: if any point q interior(e) is rectangularly visible from v inside P’, then all of e is rectangularly visible from v.
If vertex v V’ and a point q E’ are rectangularly visible with respect to vertices(P’), then v and q are rectangularly visible with respect to P’.
Given vertically separated, y-monotone chains V, E of P, “orthogonalize” them
: reduce to the Largest Empty Corner Rectangle (LECR) problem