func get_nurbs_xmat(nurbs *gm.Nurbs, ibasis []int) (xmat [][]float64) { nd := nurbs.Gnd() xmat = utl.DblsAlloc(nd, len(ibasis)) for k, l := range ibasis { q := nurbs.GetQl(l) for j := 0; j < nd; j++ { xmat[j][k] = q[j] } } return }