Ambiguous cases 7 and 10. The “in” states can either be connected (7 and 10) or disconnected (7b and 10b). Using either the original case or its corresponding “b” state will yield a closed curve. To determine which to use, we calculate the density at the center of the square. If it is “in,” then we assume that the “in” states are linked; otherwise, we assume that the “out” states are linked (the “b” states).