code: public static int getProjectedIsoDirection (int ax, int ay, int bx, int by)
      {
          return toIsoDirection(DirectionUtil.getDirection(ax, ay, bx, by));
      }
docs: Given two points in screen coordinates, return the isometrically
  projected compass direction that point B lies in from point A.
  
  @param ax the x-position of point A.
  @param ay the y-position of point A.
  @param bx the x-position of point B.
  @param by the y-position of point B.
  
  @return the direction specified as one of the <code>Sprite</code>
  class's direction constants, or <code>DirectionCodes.NONE</code> if
  point B is equivalent to point A.