How would I make my npc view objects below head level?

I was working on my stealth system and I’ve realized npcs can not see below their head’s level. For example if a player is down sone stairs, but is clearly in sight, the guard will not see anything.

I currently use a vector dotproduct and a raycast

I’m looking for an idea since I can’t really figure it out.

Now do not understand me wrong but you can also alternatively make a zone and use raycast to detect if there’s an obstacle in the way. If there is not, the guard will be able to see down these stairs by checking if someone is in the zone.

Hope that helped, SwedishRaptor.