Here are a few things to keep in mind when working with surfaces.
Optimizing Display and Interaction
As you manipulate objects and play back animation, you may notice that surface objects are displayed in coarse mode. This is an option that allows for faster interaction.
You can toggle Use Coarse Step by Default for Interaction/Playback in your Display preferences. You must restart Softimage before this change takes effect.
You can also set the Step value to Coarse, Medium, or Full during Interaction and Playback for Selected Objects and Unselected Objects in individual 3D views or all open 3D views at once.
For more information, see Setting Display Options [Interface and Tools].
As an alternative to using multiknot curves, you can create sharp ridges in cubic NURBS surfaces by placing control points so that the hulls intersect themselves. Be careful not to place the points too far apart or the surface will contain a loop.
Autodesk Softimage v.7.5