Maya 2012 Tutorial
How to Create a Maya Boundary Object
Boundary objects are defined by a series of CV or EP curves. In this example we will add four curves to the workspace. The curves define the shape and contour of the newly created Nurbs object.
Select the CV Curve Tool (Create > CV Curve Tool) and activate the Snap to Grids feature. In the side view, draw a curved line that snaps to the y-axis on the top and bottom. This is line A.
In the top view, draw a line to define the object's profile as seen from the top. The end points should snap to the x axis. This is line B.
Move line A so the bottom end point lines up with one of line B's end points.
Select line A and duplicate (Edit > Duplicate). Move the duplicate to the other end of line B.
Select line B and duplicate (Edit > Duplicate). Move the duplicate to the other end of line A.
Select all four lines and choose Surfaces > Boundary.
In the Boundary options, leave Common End Points to Optional. By selecting Required, all end points must line up. Output Geometry should be set to Nurbs.
Changing the Patch Density
If you are planning to attach this surface to another Nurbs object and need to alter the patch density to match the other object, choose Edit Nurbs > Rebuild Surfaces.
Resetting Boundary Settings
Whenever you create a Boundary object, a new object is created based on the last time the tool was used. To reset the Boundary tool to the default values, open it's options and choose Edit > Reset Settings.
Creating Boundary Polygon Patches
The Boundary tool is also helpful in creating polygon surface objects. For instance, to create a car fender made of quads, you could draw a series of Linear CV Curves to define the fender. In the Boundary options select Polygons and Tessellation Method: Control Points. Provided the two end curves have an identical point count, and the top and bottom are also equal, the resulting surface should be a clean polygon quad object.