I have an NPC that follows the player around. I want it to keep track and update 'Cover Positions' if things get bad.

I am walking through a village all of the buildings have mesh colliers on them. I want my NPC to create an array of all the different buildings within a 10 by 10 unit box around the NPC to flee to.

I tried using indie{RAIN} but felt restricted by it so I decided to create my own sensor. I started with a trigger box collider and simple script to detect collisions:

 void OnCollissionEnter(Collision other){
         if(other.transform.tag == "building"){
             Debug.Log (other.gameObject.name);    
         }
     }

this however does not detect collisions. I was wondering if anyone had tried to do something like this and how they achieved it( ideas not actual working game object or code). I want to figure this out on my own I just want an idea of where to go. Also please no RAIN stuff, already tried didn't like.

thanks again