Monotonicity of rectilinear geodesics in d-space (extended abstract)

Let B be any finite set of pairwise-disjoint, axes-parallel boxes in Euclidean &space. Our main theorem is that for any two points s, t not in the interior o;’ l?, there exists a coordinate direction @such that every rectilinear B-avoiding shortest path is monotone along@ The key concept in the proof is an appropriate notion of pyramids.