In This Chapter

Now that you've modeled with polygons and SubDs in Chapters 5, "Modeling with Polygons," through 7, "More Subdivision Surfaces Modeling," it's time to learn the third modeling technique used in many 3D modeling programs: NURBS. Modeling fundamentals are the basis for everything you create in Maya. Whether you're creating an entire world, a character, or a simple doughnut, the first step is to sculpt in virtual space each object that appears in your project. In 3D computer graphics, modeling is the process of creating object surfaces, and nothing could be closer to that basic definition than creating patches in NURBS.

This chapter helps you understand the basics of NURBS modeling techniques in Maya and gives you some guidelines for the approach you should take with different types of objects. By understanding the principles of NURBS modeling, you can create lighter and more efficient models that are easier to manipulate and faster to render. Maya offers so many features and capabilities with NURBS modeling that you will never get bored!

Here are some of the concepts and techniques covered in this chapter:

• NURBS modeling basics Learn to construct 3D models from primitive objects, such as spheres and cubes, and learn to manipulate the parts of those objects.

• Choosing a modeling technique Compare the strengths and weakness of different modeling techniques to decide which method will give you the effect you want.

• Putting it together Walk step by step through this chapter's tutorial creating the basics of a long trench coat in a variation of the style worn in The Matrix.

• Using curves to create complex surfaces You can connect, spin, or extrude curves in many ways to model complex surfaces.

• Snapping You can snap elements (such as control vertices) or objects to any NURBS-based control vertex, edge, or curve for precise placement.

• Rebuilding You can re-create NURBS surfaces with more or fewer divisions to retain the current shape and to add or remove detail in specific areas.

• Attaching versus stitching If you have a background in polygonal modeling, you might expect an enclosed mesh. Although some pieces of a NURBS model might fit that definition, most complex models are stitched together with seams.

Key Terms

node The basic building block of Maya, it's a place to store information and related actions. A simple object might be made up of its creation history (or shape node), and its transform is a different but connected node. The variables set in a node are called attributes, and a node's attributes can be connected to other nodes to create a network, or web, of nodes. When you work with Maya, behind the scenes it's creating, connecting, evaluating, and eliminating nodes.

NURBS Non-Uniform Rational Bezier Splines, the term for modeling 2D or 3D shapes with curves.

spline A curved line with its curvature dictated by control points.

surface direction A NURBS surface always has a top side and a bottom side that give you the surface direction, defined in U and V coordinates. Similarly, curves have a direction. Trouble can occur when the direction is flipped, but there are tools included to change the direction easily, before problems with the mesh occur.

normal, surface normal Because objects are made up of surfaces that are always infinitely thin sheets, one side is defined as "out" and the flip side is defined as "in." The "out" side is where the surface normal points out. Think of a surface normal as a ray that emanates perpendicularly from the object's surface.

edit point A point that lies on a curve or surface, displayed as a small x in Maya. You create a shape by creating sequential edit points. Moving these points changes the shape of the curve or surface.

control vertex (CV) A NURBS control point that defines the shape of a curve or surface. CVs often float somewhere in space, seemingly tugging on the fabric of the NURBS surface.

isoparms The curves that define the surface topology of a NURBS object. These NURBS "dividers" create the surface as a sheet, with U and V directions that make up the sheet.

span The part of a curve between two edit points. Spans are not directly edited; they "react" to changes you make to the edit points.

hull A visualization enhancement in which the CVs are connected with lines to yield a kind of imaginary cage that shows the CV influence across a surface.

multiplicity A factor specific to each point on a curve that determines its strength or hardness how "pointy" the curve can be.

pivot point The designated center point of an object or a curve, which rotates or scales around that center point. You'll notice this technique used in several chapters, so a hotkey has been added specifically for its use.

Hotkeys to Memorize

spacebar hold Hotbox

up arrow Selects the entire group when a group member has been selected (the group node is the parent of all the member nodes, and the up arrow is used to pick the parent).

Ctrl+z Undo.

F8 Toggle Component/Object mode, exit Component editing mode of NURBS objects.

Insert Adjust pivot point toggle.

Ctrl+g Group selected objects.

Ctrl+c Places the pivot at the center of the selected object.

g Repeat last action.

x (with Move) Snap to grid.

c (with Move) Snap to edges or curves.

v (with Move) Snap to vertices.