B-Spline Surface

A B-Spline Surface is a Surface defined using Boundary Curves (similarly as a Quadrangle). However, for this type of Surface, one needs to also define additional matrix of N*N internal nodes, which allows one to curve the inside of a Surface. One needs to define a number of internal nodes N and an order of the Surface Spline. Internal nodes are created automatically when a B-Spline Surface is defined. Their coordinates can be subsequently edited.