Extraordinary patches:parametrization S An extraordinary patchS can be partitioned into an infinite sequence of uniform bicubic B-spline patches{S,1,m=1,2,3 Partition the unit square into tiles {),k1,m=1,2,3 Stam's parametrization: S(u,=S(u,)=S(G(u,叨 Transformation t maps the tile onto the unit square Extraordinary patches: parametrization  An extraordinary patch can be partitioned into an infinite sequence of uniform bicubic B-spline patches  Partition the unit square into tiles  Stam’s parametrization: ◼ Transformation maps the tile onto the unit square { }, 1, 1, 2,3 k m S k m  = S  { }, 1, 1, 2,3 k m   = k m ( , ) ( , ) ( ( , )) k m k k k m m m u v u v t u v  S S S = = k m t k  m 1 S2 2 S2 1 S1 2 S1 2 S3 1 S3