def get_transformation_matrix(self, theta):
        """ Computes the homogeneous transformation matrix for this link. """
        ct = numpy.cos(theta + self.theta)
        st = numpy.sin(theta + self.theta)
        ca = numpy.cos(self.alpha)
        sa = numpy.sin(self.alpha)

        return numpy.matrix(((ct, -st * ca, st * sa, self.a * ct),
                             (st, ct * ca, -ct * sa, self.a * st),
                             (0, sa, ca, self.d),
                             (0, 0, 0, 1)))
Computes the homogeneous transformation matrix for this link.