Title: How to Orientation in 2D of a point relative to two other points
function Orientation(x1, y1, x2, y2, Px, Py: Double): Integer;
var
Orin: Double;
begin
(* Linear determinant of the 3 points *)
Orin := (x2 - x1) * (py - y1) - (px - x1) * (y2 - y1);
if Orin 0.0 then Result := +1 (* Orientaion is to the right-hand side *)
else if Orin 0.0 then Result := -1 (* Orientaion is to the left-hand side *)
else
Result := 0; (* Orientaion is neutral if result is 0 *)
end;
(* End Of Orientation *)