Autodesk AUTOCAD 2006 Command Reference Manual page 877

Regen
Regenerates the polygon mesh.
Exit
Exits Edit Vertex mode.
Smooth Surface
Fits a smooth surface. The SURFTYPE system variable controls the type of
surface this option fits. The types of surfaces include quadratic B-spline, cubic
B-spline, and Bezier.
original polygon
Desmooth
Restores the original control-point polygon mesh.
Mclose
Closes the M-direction polylines if the polygon mesh is open in the M direction.
closed M direction
Mopen
Opens the M-direction polylines if the polygon mesh is closed in the M
direction.
Nclose
Closes the N-direction polylines if the polygon mesh is open in the N direction.
quadratic
cubic B-spline
B-spline
Bezier
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