ISBELOWPLANE Test whether a point is below or above a plane.

   BELOW = isBelowPlane(POINT, PLANE)
   where POINT is given as coordinate row vector [XP YP ZP], and PLANE is
   given as a row containing initial point and 2 direction vectors, 
   return TRUE if POINT lie below PLANE.

   Example
   isBelowPlane([1 1 1], createPlane([1 2 3], [1 1 1]))
   ans =
       1
   isBelowPlane([3 3 3], createPlane([1 2 3], [1 1 1]))
   ans =
       0

   See also
   planes3d, points3d, linePosition3d, planePosition

 ------
 Author: David Legland
 e-mail: david.legland@grignon.inra.fr
 Created: 2007-01-05
 Copyright 2007 INRA - BIA PV Nantes - MIAJ Jouy-en-Josas.

Package: matgeom