GameMaker Anyway to "map out" an existing boundary

[Rydon_Star]

I have an action game that has the player wandering around big rooms, like any zelda or final fantasy 16 bit game, which have invisible boundaries that the player cannot go beyond, pretty standard.

I then have a battle system, which when activated, will move the camera to a certain position, and that single position is now the "battle field." I built invisible objects that surround the player and enemies when a battle is initiated and they cannot move beyond the screen because of this, once the battle is over, the boundary is destroyed, all good. BUT, I have these rooms, that are do not always have a rectangular area that is large enough for a battle, meaning, there might be a wall on one side that is "inside" the battle rectangle, or part of a river or creek might be running through the battle area, etc.

So, my question is, is there any function or "easy" way for GM to find and map all the existing boundaries that the player and enemies cannot cross into? Is there anyway I can have GM find these invisible objects and be able to map out an area that the players/enemies cannot go beyond?

I appreciate any input or help on this.

Thanks