MAYA for Windows and MacIntosh

NURBS curves, surfaces, and primitives are an important part of Maya modeling. You can use NURBS objects to produce long, smooth surfaces (such as car hoods) or sharp, angular surfaces (such as stop signs). NURBS objects make it possible for you to adjust the look of a surface by manipulating just a few weighted control points (Figure 3.4).

Each of the NURBS curves and surfaces has an associated degree that controls the smoothness of the NURBS object. A surface degree of 1, or a setting of linear, will produce a straight connection between each control point, creating a very angular surface (Figure 3.5). As you raise the degree of the NURBS object, you create a smoother curve and surface (Figure 3.6). The higher the degree of the curve, the more points are needed to define it. For more about NURBS degrees, see Chapter 7, "NURBS Curves and surfaces." NURBS, or nonuniform rational B-spline, describes objects whose shapes are defined by mathematical equations. Luckily for us, Maya takes care of most of the math behind the scenes. B-spline refers to the underlying curve that defines all NURBS objects. When creating a NURBS object, you use multiple curves to produce a wire representation of the surface's appearance. After using curves to lay down the shape of the surface, you add a skin atop the curves to create the final surface: This process of creating a surface that extends from one curve to the next is called lofting (Figure 3.7).

You can break down NURBS objects into separate components that work together to define the shape of the NURBS object. Components include (among others) CVs (control vertices), edit points, and hullseach of which can be manipulated to sculpt the surface or define the curves' shapes. (You can manipulate components together or separately to change the shape of an object.) For more information on NURBS components, see Chapter 7.