- May 30, 2003
About NURBS Primitives
NURBS primitives represent a collection of frequently used, predefined curves and surfaces. Maya includes eight NURBS primitives: sphere, cube, cylinder, cone, plane, torus, circle, and square (Figure 3.7).
Figure 3.7 The NURBS primitives are used as starting points for more complex models.
These predefined primitive surfaces are not only time-savers for creating simple objects; you can also use them as a starting point for more detailed shapes. The circle and square primitives are NURBS curves without surfaces attached to them; the other six NURBS primitives are predefined surfaces ready to be placed in the Maya scene or further manipulated.
Each primitive includes a number of attributes that you can set for an object. You can change each primitive's attributes in its Options dialog box before you create an object (Figure 3.8). In addition, most primitives include a construction history that's attached to their surfaces: This is where you can adjust and fine-tune the surface's properties after it's been created (Figure 3.9). The construction-history attributes appear in the Channel Box under each primitive's makeNurb heading. In this chapter, we'll show you how to create NURBS primitives and change some of their attributes (both before and after the object has been created). For more information on construction history, see Chapter 1.
Figure 3.8 A primitive's attributes can be changed in its Options dialog box.
Figure 3.9 The construction history allows you to change an existing surface's attributes.
Creating NURBS primitives
NURBS primitives are found in the Create > NURBS Primitives submenu (Figure 3.10). You create a primitive by selecting the primitive's name from the submenu. You can also create a NURBS primitive through the Hotbox, as described below. And by simply clicking their icons in the Surfaces Shelf, you can quickly create any of the primitive NURBS surfaces (Figure 3.11).
Figure 3.10 NURBS primitives are found in the Create > NURBS Primitives submenu.
Figure 3.11 You can quickly create NURBS primitives by clicking their icons in the Surfaces Shelf.
When you create a primitive surface or curve, Maya will place the object's center point at the origin of the scene (at 0, 0, 0 coordinates). This centers most objects over the y-axis line (so that half of the object is above the axis, and half is below) (Figure 3.12). The exception is the cone, whose center point is at its base. You can create NURBS primitives by following the steps that follow.
Figure 3.12 Maya places the center point of the primitive at the origin of the scene.
To create a NURBS primitive using the main menu:
From the Create menu select the NURBS Primitives submenu.
Select the name of the primitive you want to createin this case, the sphere (Figure 3.13).
Figure 3.13 Select the name of the primitive you want to create from the NURBS Primitives submenu.
The NURBS primitive appears at the origin of the Maya scene (Figure 3.14).
Figure 3.14 The NURBS primitive appears at the origin of the Maya scene (the sphere is shown).
The Hotbox is a great time-saver for creating objects and primitives because you can do so without accessing the main menu. You can display the Hotbox from anywhere within the Maya window, providing even faster access to Maya's menus.
To create a NURBS primitive using the Hotbox:
Hold down spacebar anywhere in the scene to show the Hotbox.
From the Create menu in the Hotbox select the NURBS Primitives submenu.
Select the name of the primitive you want to createin this case, the cube (Figure 3.15).
Figure 3.15 You can use the Hotbox to select the NURBS Primitives submenu (the cube is shown).
The NURBS primitive is created at the origin of the Maya scene (Figure 3.16).
Figure 3.16 The NURBS primitive is created at the origin of the Maya scene (the cube is shown).
Maya's Surfaces Shelf contains shortcut icons for all of the primitive NURBS surfaces (Figure 3.17). By selecting these primitives from the Shelf, you can save yourself the two or three steps required to select the same primitive from the Create menu.
Figure 3.17 The default Shelf in Maya holds shortcut icons for the sphere and cone NURBS primitives.
To create a NURBS primitive using the Shelf:
From the Surfaces Shelf, select the NURBS primitive icon for the object you would like to create (for example, a sphere or cone ).
The primitive is created at the origin of the Maya scene (Figure 3.18).
Figure 3.18 Select the primitive NURBS icon in Shelf 1; here the cone has been chosen.
If the Shelf is not already open, open it by going to the Display menu and selecting UI Elements > Shelf (Figure 3.19).
Figure 3.19 To view the Shelf, select UI Elements > Shelf.
To add primitives or other objects to the Shelf, hold down Shift and Ctrl/Control while selecting the menu item in the main menu. This stores the command you selected from the menu in the Shelf with its currently selected options. Thus, if you were to change the object's attributes in the Options dialog box before adding it to the Shelf, you could have one sphere in the Shelf with an end-sweep angle of 20 and another with an end-sweep angle of 360another way to speed your workflow for commonly used settings.
You can remove items from the Shelf by pressing the middle mouse button while dragging the items to the trash.