How to make a view for a NPC?

So simple, I’m trying to make a SWAT game where you see from above and move units by clicking.

So I want you to only be able to see what the units are seeing
Basically, make a triangle where the SWAT guy is looking. Revealing wherever he is looking.
However, people cannot look through walls. So neither can swat.
If you don’t quite understand, tell me.

What things have you tried: I tried to do the glass glitch but it doesn’t look natural.