The degree elevation formula for ball Bezier curve is given,and it is proved that the(union) of ball control point converges to the original ball Bezier curve as the degree is elevated incessantly.

• 给出球域B ez ier曲线的升阶公式；并证明在不断升阶的过程中球域控制顶点的并集收敛到原球域B ez ier曲线.