code: public Vector3D getVertex(int index) {
          tmpV.setX(cornerX.get(index));
          tmpV.setY(cornerY.get(index));
          tmpV.setZ(cornerZ.get(index));
          calcG();
          return tmpV;
      }
docs: Gets the corner of Polygon.
  
  @param index The index number of the corner.
  @return The coordinates of the corner.