proc/InConeByDir(atom/ref, facing_dir, atom/target, fov = 90)
	var/dx = target.x - ref.x
	var/dy = target.y - ref.y
	if(!dx && !dy)
		return TRUE

	//This can be done more efficiently with a couple of quick lists, but:
	var/cx = (facing_dir & EAST)	? 1 : ((facing_dir & WEST)	? -1 : 0)
	var/cy = (facing_dir & NORTH)	? 1 : ((facing_dir & SOUTH)	? -1 : 0)
	if(!cx && !cy)
		return TRUE

	//use dot product to compare angles
	return (dx * cx + dy * cy) >= cos(fov / 2) * sqrt((dx * dx + dy * dy) * (cx * cx + cy * cy))

/mob/proc/UpdateFOV()
	for(var/mob/M in ohearers(world.view + 1, src))
		if(M.loc != loc && InConeByDir(src, turn(dir, 180), M, fov))
			if(client)
				client.images += M.hider
		else
			if(client)
				client.images -= M.hider


/mob/proc/UpdateOtherFOV()
	for(var/mob/M in ohearers(world.view, src))
		if(loc != M.loc && InConeByDir(M, turn(M.dir, 180), src, M.fov))
			if(M.client)
				M.client.images |= hider
		else
			if(M.client)
				M.client.images -= hider