Checking if part is within area boundary

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I wrote a neat demo for this a couple years ago https://devforum.roblox.com/t/area-zoning/19151
Here’s some math that does it without FindPartOnRay

local function PointInPolygon(Point, Polygon)
	local current = Polygon
	local inside = false
	local A = current.Position
	local ax, az = A.X, A.Z
	local px, pz = Point.X, Point.Z
	repeat
		local B = current.Next.Position
		local bx, bz = B.X, B.Z
		if ((az >= pz) ~= (bz >= pz)) and ((px - ax) <= (bx - ax)*(pz - az)/(bz - az)) then
			inside = not inside
		end
		current = current.Next
		A, ax, az = B, bx, bz
	until current == Polygon
	return inside
end

local function CreatePolygonFromPoints(Points)
	local Polygon = {Position = Points[1]}
	local First = Polygon
	for i = 2, #Points do
		Polygon.Next = {Previous = Polygon, Position = Points[i]}
		Polygon = Polygon.Next
	end
	Polygon.Next, First.Previous = First, Polygon
	return First
end

CreatePolygonFromPoints takes a table of Vector3s and returns a “Polygon”, which is a circular doubly linked list of vertices. PointInPolygon takes a point and a polygon and returns whether the point is inside that polygon.

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