Thanks for your reply. But maybe the definition of this control point is different between us.
For rational B-splines, if we have a general 3D control points, it will be P(x, y, z, w), where x, y, z are 3D coordinates, and w is its relative weight. When we calculate in function, we will use Pw(x/w, y/w, z/w). If it’s irrational, w is 1, and we will have P(x, y, z), which is generally used in function.
However, if I have additional dimension, like stress s11, we will have new control point P0(w, y, z, s11, w). Similarly, for irrational case, we will have a new control point like P0(x, y, z, s11). This is what I mean, a 4D control point.
It’s just put additional dimension for control point when we calculate interpolation point. Each Lagrangian interpolated point will have its 3D coordinate value and an additional dimension value, like stress, or even more dimensions.
Hope this would be clear for you.