(6-4-18-1)
��T= .
其中, = n - k + 1。由于当节点的重复度增加1时, 曲线在节点处的连续性就减少1次, 因此为了保证升一阶后相邻曲线段的连续性不变, 应在tk-1至tn+1之间插入一些节点[10], 使tk-1tn+1之间的节点的重复度分别增加1。另外, 在节点矢量的两端分别各增加一个节点, 使节点矢量变为:
.
于是, 根据定理1, 可以给出一条B样条曲线升阶的算法:
算法6.2
for (i=k to k+s-1 by 1) Insert Knot ti into the curve;
�j = -1;
��for (i=k-1 to n+s by mj+1)
��if (i == k-1) Start = 0;
��else Start = k - mj ;
��for (v=Start to k by 1)
��j = j + 1;
��= 0;
��for (u=0 to k-1 by 1) = + V i-k+1+u;
��endfor
endfor