protected BasePolygonRegion(IReadOnlyList <Side> shape, OABR oabr)
{
Contract.Requires(shape != null);
Contract.Requires(shape.Count >= 3);
_shape = shape;
_bounds = BoundingRectangle.CreateFromPoints(Points);
_oabr = oabr;
Area = Points.Area();
OabrAreaError = _oabr.Area - Area;
}