A normalized basis for quintic Powell–Sabin splines

We construct a suitable normalized B-spline representation for C2-continuous quintic Powell–Sabin splines. The basis functions have a local support, they are nonnegative, and they form a partition of unity. The construction is based on the determination of a set of triangles that must contain a specific set of points. We are able to define control points and cubic control polynomials which are tangent to the spline surface. We also show how to compute the Bézier control net of such a spline in a stable way.