that does make sense, alot.
lets say that the river and the ground are on level 1.0 and the bridge is on 2.0. does it matter if part of the ground that is set for 1.0, like a hill. goes heigher then the bridge that is at 2.0. ????
so in short, does the ground need to be for 1.0 and 2.0 in the map editor because part of it is higher then 2.0???