Mirroring and Subdivs

When you're making symmetrical models, you can use the Mirror command to copy and flip the subdiv surface. This takes a few more steps than with polygons because you can't mirror a subdiv surface directly.

To mirror a subdiv surface:

1.	Choose Create > Subdiv Primitives > Cube.
2.	Right-click the cube, and select Polygon from the marking menu.
3.	Right-click the cube, and select Face from the marking menu.
4.	Select and delete the faces from the right side ( Figure 9.31 ). Figure 9.31. Select four faces on one side of the cube. The subdiv surface is now open on one end ( Figure 9.32 ). Figure 9.32. The deleted faces create an open-ended subdiv surface.
5.	Select the subdiv surface, and then select the box next to Mirror in the Subdiv Surfaces menu. The Subdiv Mirror Options dialog box opens ( Figure 9.33 ). Figure 9.33. For Mirror, choose X in the Subdiv Mirror Options dialog box.
6.	Select X to mirror the object across that axis, and click Apply. A flipped copy of the surface is created ( Figure 9.34 ). Figure 9.34. The mirrored subdiv surface.

When your model is made up of many separate pieces, you can use the Attach command to join them as one piece. However, any edges you attach must have the same number of vertices.

To attach two subdiv surfaces:

1.	Arrange the surfaces from the previous task, "To mirror a subdiv surface," so that their openings are near one another ( Figure 9.35 ). Figure 9.35. Place the openings of the surfaces you want to attach near one another.
2.	Select both surfaces, and make sure you're in standard mode.
3.	From the Subdiv Surfaces menu, select the box next to Attach. The Subdiv Attach Options dialog box opens ( Figure 9.36 ). Figure 9.36. Set the Threshold to 5 in the Subdiv Attach Options dialog box.
4.	Set the Threshold amount to 5 to close the gap between the surfaces.
5.	Click Apply. The two surfaces become one surface ( Figure 9.37 ). Figure 9.37. The attached subdiv surface.

Tip

• Subdiv operations like Attach only work in standard mode. When you're in poly proxy mode, Maya doesn't consider your object to be a subdiv surface (although it provides subdiv options in the marking menu).