This optional process can also be applied to the generalization process. Defocusing spreads each shoal depth over an area defined by the horizontal error. The process uses an ellipsoid of rotation around each node with the horizontal error as the semi-major axis. Nodes within the ellipse are adjusted up to the surface of the ellipse.
In the following image, the webbed surface overlaying a surface represents the generalized area after defocusing has taken place. The shoals are preserved, but without the sharply defined detail of the original surface.