Generalizing bicubic splines for modeling and IGA with irregular layout ?
Bi-3 tensor-product splines are complemented by bi-4 splines near irregular points. The vertices of the irregular quad mesh serve as spline-like control points. The resulting surfaces have a good distribution of highlight lines. The resulting surfaces have a increased smoothness and reproduction at irregular points.
geometric continuity extraordinary point iso-geometric analysis guide surface biquartic spline surface