About NURBS Objects

NURBS object creation is a Maya strongpoint because of the precise control it affords you over the final surface. There are two types of NURBS objects: curves and surfaces.

NURBS curves have three main components: control vertices (CVs), edit points, and hulls (Figure 7.2). You use these components to create and edit curves in different ways. As you grow familiar with creating NURBS curves, you'll likely come to prefer one component to the others, making it your primary editing method.

Figure 7.2. NURBS components are used to easily and quickly change the shape of an existing curve or surface.

In addition to CVs, edit points, and hulls, NURBS surfaces have the following more advanced components: isoparms and surface patches (Figure 7.3). Both of these components are uneditable pieces of the NURBS surface. You can edit any NURBS surface that was created from a curve (for example, a revolved surface) by editing components of the original curve or by editing the surface's components directly. When a surface is created from one or more curves, it remains linked to that curve through a history connection. Thus, when you modify a curve, you're also editing the surface.

Figure 7.3. NURBS surface components are used to manipulate the shape and composition of the surface.

Each NURBS component (edit point, CV, and so on) can be displayed and edited both individually (Figure 7.4; edit points are shown) and with other components (Figure 7.5; edit points and hulls are shown). NURBS curves are an integral part of NURBS modeling because they help you create and edit surfaces. This chapter will provide the foundation you need to control the look of NURBS curves and surfaces.

Figure 7.4. Surface edit points can be shown by themselves to make selection and editing easier. You can select each component by clicking its icon, in this case a small x.

Figure 7.5. Maya lets you show or hide as many components as you want to view at any given time. This helps you narrow down your selection while still getting a good idea of what the object's other components look like.

Tip

• You'll find it useful to keep your construction history on when modeling with NURBS. Doing so lets you make adjustments to your surfaces much more easily and often prevents the need to re-create pieces of geometry. Without history, the NURBS object workflow feels rigid and unforgiving.

NURBS Modeling Strategy

NURBS models usually consist of many separate NURBS surfaces, all working together to form the semblance of a continuous surface. This can be a tricky process, because all of these surfaces rely on each other, and your surface construction order can affect your workflow efficiency. Also, the number and direction of your curves and surface components can be important in matching or joining your surfaces.

Luckily, Maya offers many tools to tackle these tasks. When you look over these tools as they're covered in the chapter, keep in mind the following tips: When you first begin working on an object, you may find it easiest to start by laying down all the obvious contour curves and then move on to creating the largest or most important components. Fine-tuning the blends between your components is the last piece of the process.

Try to preserve any curve you make, so that you can use it later if you need to make a new surface. To keep your workflow as simple as possible, use layers to store sets of curves, and be careful when naming your curves and groups. As you get more experienced with the NURBS workflow, you can start deleting curves and finalizing pieces of geometry as you go.

NURBS modeling is akin to building frames to lay your surfaces across. This process, referred to as edge-based modeling, can be difficult to master. If you have a hard time with a particular object using NURBS modeling, you may find modeling polygons or subdivision surfaces to be more intuitive. Because you can convert any geometry typeincluding NURBSto polygons, a variety of techniques may suit you.