Our goal 89 To derive a bound on the distance between a Loop patch s(v,w)and its limit triangleF(v,) as ma|S,n）-F(v.w)s B(n)M M:the second order norm of the control mesh of s B(n):a constant only depends on valence n Our goal To derive a bound on the distance between a Loop patch and its limit triangle as „ : the second order norm of the control mesh of „ : a constant only depends on valence n S(, ) v w F(, ) v w (, ) max ( , ) ( , ) ( ) v w vw vw nM β ∈Ω S F− ≤ M S β ( ) n