 Command entry:
Command entry: 
 Modify panel 

 Select a NURBS object. 

 Modifier stack display 

 Surface sub-object level 

 Select an independent CV surface sub-object. 

 CV Surface rollout 

 Rebuild button
            
 The Rebuild button for CV surfaces opens this dialog. It lets you specify how to rebuild the surface. Rebuilding the surface
            can change its appearance.
         
          
            Interface
            
  - Tolerance
- 
                   
                     Rebuilds the surface according to accuracy. The lower the Tolerance value, the more accurate the rebuild. Increasing Tolerance
                        enables the surface to be rebuilt using fewer CVs.
                      
 
- Number
- 
                   
                     (The default.) Lets you alter the number of CVs in the surface. Number in U specifies the number in the U dimension, and Number
                        in V specifies the number in the V dimension. These values default to the numbers that already exist in the surface.
                      
 
- Preview
- 
                   
                     When on (the default), your changes are previewed in viewports.