To Automatically Regenerate Surfaces
Surfaces automatically regenerate during editing. To set the curve regeneration options, perform the following actions:
1. Click 
Style > > 
Preferences. The Style Preferences dialog box opens.
Style > > Preferences. The Style Preferences dialog box opens.2. Under Auto regenerate, select one or more of the following check boxes:
◦ To automatically generate only the wireframe surfaces, select Surfaces.
◦ To automatically generate both wireframe and shaded surfaces, select Shaded surfaces.
Surfaces generate automatically if you edit any of the following items:
• The curves that are used to create a surface.
 | If the edited curves do not form a valid closed boundary, the surface does not regenerate. You must resolve this by editing the curves so as to form a valid surface boundary and clicking  Regenerate All. |
• The internal curves of a surface. Any COSs and dependent children are also updated so as to lie on the regenerated surface.