Creating Primatives and Text in Maya 4.5
As premade geometry sets that simplify the creation of more complex shapes, primitives are the building blocks of 3D modeling. To understand this, just take a look at the objects around you: Everything in nature, no matter how complex, can be broken down into a few primitive shapessomething you can do right now with the objects in front of you. Is the object you're looking at built around many cylinders like a metal chair, or is it a squashed cube like a door or a wall? Many objects combine a number of different primitives. Take, for example, the bicycle: Its wheels combine a cylinder (for each spoke) and a slim torus (which defines the tires' shape). Likewise, you can use a number of primitives to create a detailed face from a simple sphere, or employ just a few well-placed cubes to construct a building.
Because they can be manipulated in a variety of ways, primitives have become an important part of Maya and other 3D programs. NURBS primitives can speed workflow because the curves have already been drawn and, in many cases, have been replaced with surface geometry. You can stretch, cut, scale, translate, trim, and rebuild them, making them essential to your workflow and great time-savers as well.
Maya includes three primary types of primitives: NURBS, polygons, and subdivisions. To help you understand which type is appropriate for the task at hand, this chapter takes a close look at NURBS (Figure 3.1) and polygons (Figure 3.2), explaining the strengths and weaknesses of each. Subdivisions, a more advanced topic, are covered in detail in Chapter 8.
Figure 3.1 The NURBS primitives (top to bottom): sphere, cube, cylinder, cone, plane, torus, circle, and square.
Figure 3.2 The Polygon primitives (top to bottom): sphere, cube, cylinder, cone, plane, and torus.
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 3.3).
Figure 3.3 NURBS surfaces are changed using weighted control points.
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 3.4). As you raise the degree of the NURBS object, you create a smoother curve and surface (Figure 3.5). The higher the degree of the curve, the more points are needed to define it. For more about NURBS degrees, see Chapter 7.
Figure 3.4 A surface with a degree of 1, or setting of linear.
Figure 3.5 A surface with a higher degree will appear smoother.
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 3.6).
Figure 3.6 The top object has curves only; the bottom object has curves plus a skin.
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.