Catmull-Clark Variant of Doo-Sabin Subdivision Repeated averaging [Stam 2001,Zorin and Schroder 2001]: ■Linear subdivision: E,=B,+P+小 ■Dual averaging: E=R+E-1+B+) =（2+4 P++P+1+P)t∑ Z Huang.G Wang Non-Uniform Recursive Doo-Sabin Surfaces (NURDSes) Catmull-Clark Variant of Doo-Sabin Subdivision Repeated averaging [Stam 2001, Zorin and Schröder 2001]: Linear subdivision: Ei = 1 2 (Pi + Pi+1), F = 1 n Xn−1 j=0 Pj Dual averaging: Pi = 1 4 (Pi + Ei−1 + Ei + F) = (1 2 + 1 4n )Pi + (1 8 + 1 4n )(Pi+1 + Pi−1) + 1 4n X |i−j|>1 Pj . Z Huang, G Wang Non-Uniform Recursive Doo-Sabin Surfaces (NURDSes)