DR. JAN HADENFELD
		Extension to sets of Bézier- and B-Spline Surfaces If one B-spline surface was a set of Bézier- or B-spline surfaces then the same problems which we had with curves do occur. Fairing without changing the method, the resulting patches are smooth but not the whole surface. Two possible solutions are given for this problem: remove as much as possible knots (see [5]) or use an extended functional. One proposal for this new functional is $${F = (1-\lambda) \int \!\!\! \int_A {\bf X}_{uu}^2 + 2\;{\bf X}_{uv}^2 + {\bf X}_{vv}^2 \;du\,dv}$$ $$\;\;\;\;\;\;+ \lambda \displaystyle \sum \limits_{ \begin{array}{c} \scriptstyl... ...tyle \partial \widetilde{\bf X}(u_i^+,v_j)}{\displaystyle \partial u} \right)^2$$ (44) $$\;\;\;\;\;\;+ \lambda\;\;\;\; \displaystyle \sum \limits_{i=k-1}^{m+1} \display... ...rtial \widetilde{\bf X}(u_i,v_j^+)}{\displaystyle \partial v} \right)^2 \;\;\;,$$ which is also a mixture of energy and continuity minimization. As for curves, the solution of minimizing this functional can be splitted into an energy and continuity one, which should not be given here.