Hello and thank you for posting.
FNAF is such an iconic awesome game. I managed to find a relatively short method of accomplishing you goals for the short term. As stated by bumbumgoesnuts, they opted to use a cone mesh that detects overlap events.
Another related subject are Environment Queries. Though it is a lot more in-depth in AI, it is great reading material for starting performant AI in the future.
I hope the provided information assists you in your development.