Constraints can also be satisfied by gradient descent on a potential
surface representing their lack of satisfaction
(Sects. 4.2 and 5.2).
However, a problem with relaxation techniques is that they may get
trapped in local minima.
One way to avoid this is to do the relaxation on a
multiresolution representation of the potential function.
At low resolution, local minima will tend to be averaged
away, so relaxation on a low-resolution representation will
tend to move toward the global minimum.
By gradually increasing the resolution, the system can be
allowed to settle into a more accurate representation of the
global minimum.
This can be accomplished, for example, by gradually activating the
higher frequency bands of a Gabor or wavelet representation of the
potential surface.