Fussy Navmesh Generation... why?

[frozenfire2]

Was wondering why are navmesh in UDKs fussy and I can't quite understand the lines/colours of the generated mesh.


Below are 2 setups. one works and one does not ( which means the AI manage to pathfind ). exactly same mesh.
The right side one utilizes another pylon with re-cast disabled.

http://udn.epicgames.com/Three/Navig...Debugging.html
Navmesh Path Debugging page doesn't seems to make sense, there are no mention of what the blue lines ( crosses ? ) are for?
It also doesn't mention why it's it's building it in a weird way.


Can someone tell me why is the right one working and the left doesn't. ?

[Jetfire]

The blue lines indicate the pawn can cross that edge. Note how the blue lines approach the walls up to pawn radius or so. In one image, not all edges towards your destination have a blue line, so they arent traversable because you made it too narrow.

[frozenfire2]

I also thought the size was the issue too at first, unfortunately it wasn't. I tested on much narrower path and it still builds in a different setup.
Notice the left picture. despite the narrow-ness. the meshes on the right side still has the blue line, while the left side of the mesh which is the same narrowness connected to the larger meshes apparently doesn't have the blue lines.

Is there anyway I can get it to build better or force it to be connected?