Title: Signed Volume in 3D?
function Signed(x1, y1, z1, x2, y2, z2, x3, y3, z3, Px, Py, Pz: Double): Double;
var
Px1, Px2, Px3: Double;
Py1, Py2, Py3: Double;
Pz1, Pz2, Pz3: Double;
begin
Px1 := x1 - px;
Px2 := x2 - px;
Px3 := x3 - px;
Py1 := y1 - py;
Py2 := y2 - py;
Py3 := y3 - py;
Pz1 := z1 - pz;
Pz2 := z2 - pz;
Pz3 := z3 - pz;
Result := Px1 * (Py2 * Pz3 - Pz2 * Py3) +
Px2 * (Py3 * Pz1 - Pz3 * Py1) +
Px3 * (Py1 * Pz2 - Pz1 * Py2);
end;
(* End Of Signed *)