Pathing

Alrighty,

I have a ground model for, obviously, the ground of my map. This is easier than skinning the terrain. The poly count seems to be fine, and when playing in game there is no problem viewing it. Now what I want to do is make it so the units walk on it, Ive done this once before, but have been unsuccesful now (5 months later).

Do I have to make a pathing map? And if so, how do I define the ups and downs of the terrain? Or is there a easier way using a modifier?

Model in: 3ds Max 5.2

Bump.