Ambiguous Cell with Two Sharp Features

This graph shows all possible configurations when you have two sharp features inside an ambiguous cell. Seven have a diagonal connection, seven don't, and two are impossible. Luckily this can be condensed into a much smaller graph.

The letters represent point-below-line relationships that can exist inside the cell, of which there are four. The Marching Squares 3 tutorial has the full story.

http://catlikecoding.com/unity/tutorials/marching-squares-3/