Skinny River Crossings

[PeteMichaud]

There's a problem with the pathfinder ignoring the cost of river crossings when the rivers are skinny:

1. The pathfinder can move to any of the 8 surrounding pixels (ie. it can move diagonally)
2. The water map can have rivers that are a single pixel wide, and if the river has a diagonal section, the pixels from the river create a "gap" that the pathfinder can pass through diagonally, as if the river isn't there at all.

Consider:

One option is to try to fix this, so it conforms to the naive expectations, even though it's not really a bug in the sense that the pixels don't intrinsically represent a continuous river of water, just that that square area is predominantly water.

Another option is to not fix it, let the it be just a square of water that the pathfinder is dumb about. The recommendation would be to use slightly fatter rivers, to avoid skinny diagonals.