Originally Posted by
Dragon Knight Of Rhun
Not really. There is two 180 degree arcs as Jwolf said, the rear arc and the front arc. If the formation charges from the rear arc u attack from the rear, if the formation attacks where these two arcs meet its at the side, the front arc at the the front.
I don't think which way the model is facing at the time of the charge is arbitrary at all. You just use your senses to see which it is. For a monster not to ever be able to be charged from the rear is a ridiculous notion.