The area VO is defined via the border line, i.e. you define the border line as the polygonal chain defined by a sequence of points within a plane.
Another important remark is that the sequence of the points defining the border is important, i.e.
the polygonal chains defined by the sequence of the points 1, 2, 3, 4 and 1, 4, 3, 2 are different.
For the release 2.0 we restrict ourselves to regions that are simple polygons, i.e. regions which do not contain holes and are enclosed by a single closed polygonal chain that does not intersect itself.
Each simple closed simple closed polygonal chain defines two regions, the interior and the exterior region. Our simple polygon is the interior region, the closed polygonal chain surrounding a simple polygon must have clockwise orientation.