def get_body_jacp(self, name, np.ndarray[double, ndim=1, mode="c"] jacp = None):
        id = self._model.body_name2id(name)
        if jacp is None:
            jacp = np.zeros(3 * self._model.nv)
        cdef double * jacp_view = &jacp[0]
        mj_jacBody(self._model.ptr, self.ptr, jacp_view, NULL, id)
        return jacp

    def get_body_jacr(self, name, np.ndarray[double, ndim=1, mode="c"] jacr = None):
        id = self._model.body_name2id(name)
        if jacr is None:
            jacr = np.zeros(3 * self._model.nv)
        cdef double * jacr_view = &jacr[0]
        mj_jacBody(self._model.ptr, self.ptr, NULL, jacr_view, id)
        return jacr

    def get_body_xvelp(self, name):
        id = self._model.body_name2id(name)
        jacp = self.get_body_jacp(name).reshape((3, self._model.nv))
        xvelp = np.dot(jacp, self.qvel)
        return xvelp

    def get_body_xvelr(self, name):
        id = self._model.body_name2id(name)
        jacr = self.get_body_jacr(name).reshape((3, self._model.nv))
        xvelr = np.dot(jacr, self.qvel)
        return xvelr