## Direct Manipulation of B-spline Surfaces |

- Based on Bartels and Beatty's technique for curve manipulation
- Suppose we want to move
*S(u,v)*by - Move
*2 x 2*block of control points with most influence over*S(u,v)*.

Call them*P*,_{a,b}*P*,_{a,b+1}*P*,_{a+1,b}*P*_{a+1,b+1} - Find weights
*w*proportional to_{i,j}*P*'s contribution to_{i,j}*S(u,v)* - Set