Steiner points can only occur at wide reflex vertices of P .
3 Polygon Reductions Consider the unique polygon P 0 inside P containing the terminals Z such that its perimeter is as short as possible. 3 Polygon Reductions Consider a unique polygon P 0 inside P containing the terminals Z, and such that its perimeter is as short as possible. P 0 is sometimes referred to as the geodesic convex hull for its polygon and its terminals. The shortest loop enclosing a set and contained in the interior of a polygon is the relative convex hull of the set. We compute Euclidean shortest loops in section 5.