Trust me, that depends on your implementation I'm making an RTS, and if I relied on a regular grid for the nodes I'd be in serious trouble (just too many nodes to consider on that scale; too slow). I have a dynamic node system where visibility between nodes is recalculated whenever a building/obstacle is created or destroyed, and each obstacle has nodes attached to its corners so that the nodes always mark out the best path. Each node knows its children and the cost of getting there.

It's a bit more effort, though!

Jibb