Degree reduction of ball-control-point Bézier surfaces over triangular domain

The problem of degree reduction of ball-control-point Bezier surfaces over triangular domain was discussed.A method to reduce degree from n to n-m(1≤m≤n-1) was proposed.In the method,the lower-degree ball-control-point Bezier surface was required to enclose the given original surface and the difference between the two surfaces was as small as possible.Some examples were provided to illustrate the method.