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
i,j
proportional to
P
i,j
's contribution to
S(u,v)
Set
