Modify > Convert > Subdiv to NURBS

Specifies what happens to the source object after conversion.

Deletes the original object, leaving only the original transform node. To maintain the scene hierarchy, maya keeps the original transform node and makes the resulting NURBS patches children of it.

These options keep the original object. If you have construction history turned on, you can still edit the original subdivision surface to change the resulting NURBS patches. With Hide, the original is hidden from view. If you later want to display and edit the original, select it in the Outliner and choose Display > Show > Show Selection.

Instead of NURBS, you can choose to create a Bezier surface by turning on the Beziers option. You can export Beziers surfaces for use with some game engines.

If you perform operations from the Edit NURBS menu, such as inserting an isoparm, the surface will switch from Bezier to NURBS. To switch back to Bezier, use Edit NURBS > Rebuild Surfaces.