def point( parameter )
      Util3D.check_arg_type(::Array, parameter )
      # TODO Argument check
      return self.vertices[0]*parameter[0] + self.vertices[1]*parameter[1] + self.vertices[2]*parameter[2]
    end
def point( parameter )
      Util3D.check_arg_type(::Array, parameter )
      # TODO Argument check
      return self.vertices[0]*parameter[0] + self.vertices[1]*parameter[1] + self.vertices[2]*parameter[2]
    end
[Input]
  _parameter_ should be three element Array of Numeric.
 [Output]
  return point on triangle at parameter position as Vector3.