Subdivision Surface Refine and smooth a PolyNURBS surface by adjusting the parameters of its subdivisions. On the ribbon, click the PolyNURBS tab. Click the Subdivision Surface icon. Optional: Enter the number of Iterations. The greater the number of iterations (subdivisions), the smoother the resulting surface. Note: The subdivision computation uses a lot of memory, so be careful not to increase the number of iterations too much. Click the PolyNURBS object. Right-click and mouse through the check mark to exit, or double-right-click. Figure 1. Original cube Figure 2. Iterations factor = 1 Figure 3. Iterations factor = 2