How to check if its around npc utilizing raycasting?

Hello devs!

I’m trying to remake l4d2’s survivor bot system but i’ve stumbled into a problem.

I made my raycasting work that only zombies on the front of the survivor can be shot but, They don’t really notice it due to only noticing front.

What i wan’t to do (which i’m in a trouble on making) is to create a circular sight that does not collide with walls, To make sure it is around the survivor itself.

I really need help because this is one of the most difficult projects i’ve ever worked on.