Sorry about the late reply. I've been out of town for a week and a half.But there
is one polygon with shape of letter L, which gives me a lot of problems:
the shape of polygon is something like this:
The problem is that the above polygon is 'concave' which gives FSDS
trouble. If you split it into two polygons, one using points 1,2,3,6
and the other using points 6,3,4,5 you should have no trouble.