Polygons with Parallel Opposite Sides
  In this paper we consider planar polygons with parallel opposite sides. This type of polygons can be regarded as discretizations of closed convex planar curves by taking tangent lines at samples with pairwise parallel tangents. For this class of polygons, we define discrete versions of the area evolute, central symmetry set, equidistants and area parallels and show that they behave quite similarly to their smooth counterparts. 
Marcos Craizer, Ralph C. Teixeira and Moacyr A. H. B. da Silva
math.DG