Control mesh of a Loop patch 89 Assume:the initial control mesh has been subdivided at least once Each triangle face contains at most one extraordinary point The control mesh of a Loop patch s of valence n consists of n+6 control points 叶兴 {P,:i=1,2,,n+6} Control mesh of a Loop patch P1:the only extraordinary of valence n point of valence n Control mesh of a Loop patch Assume: the initial control mesh has been subdivided at least once „ Each triangle face contains at most one extraordinary point The control mesh of a Loop patch of valence consists of n+6 control points „ P 1: the only extraordinary point of valence n S Control mesh of a Loop patch of valence n { Pi : 1,2, , 6 = + i n … } n