Surface smoothing (fairing) is available for B-spline surfaces. This modeling operator is implemented following the paper by [Kallay, 1993]. The purpose of this operator is to move the control points of a B-surface attempting to minimize its approximate bending energy. The boundary control points are usually constrained to be in a fixed position so that any deformation of a surface does not violate its boundaries (hence the faired surface is not a trivial plane for any values of the fairing coefficient). The following picture illustrates the unfaired (top) and faired (bottom) surface for a certain value of fairing coefficient.