def METHOD_NAME(self, pars, axis):
    uk = nm.unique(self.knots[axis])
    indices = nm.searchsorted(uk[1:], pars)
    ref_coors = nm.empty_like(pars)
    for ii in range(len(uk) - 1):
        ispan = nm.where(indices == ii)[0]
        pp = pars[ispan]
        ref_coors[ispan] = (pp - uk[ii]) / (uk[ii+1] - uk[ii])
    return uk, indices, ref_coors