Hi Mike,

> Maybe what I need to ask for is a way to remove control points.

That could be possible, but there are some complications - the number of knots and control points are related, so if you remove a control point you also have to remove a knot as well and then you have to decide do you want the other control points to shift in position or do you want the other control points to stay where they were which instead could make the surface kind of mutate strangely in shape with a shifted knot vector.

If you want to do a lot of surface control point manipulation, sub-d modeling tends to be a better tool for that...

- Michael