Datasheet

Navigating the 3D Space n 17
Restricting to Axes
When you rotate, translate, or scale, you often want to restrict the operation to a par-
ticular axis or to fix one axis while operating in the other two. To select an axis to rotate,
scale, or translate along, press X, Y, or Z after pressing the R, S, or G key. This restricts the
operation to the global axis. Press the axis key twice to restrict the operation along the
object’s local corresponding axis. To scale or translate along a plane, press Shift and the
key corresponding to the axis you do not want changed. For example, to scale an object
along its x- and y-axes, press S followed by Shift+Z.
Pivot Point
The pivot point is the point around which rotations are calculated, and it is also used as
a reference point for scaling. You can choose the point to use as your reference point in
the drop-down menu shown in Figure 1.11. The default, Median Point, is a point calcu-
lated to be in the center of your entire selection. If you have multiple objects selected, the
median point is somewhere in between them all. You can choose to have objects rotate
independently around their own centers, around the active object, around the 3D cur-
sor, or around the center of the object’s bounding box. The default median point pivot,
which you can set with the Shift+comma hotkey, is the most commonly used, but in this
book you will occasionally switch the pivot point to be the 3D cursor for specific purposes,
which you can set with the keyboard period key.
Object Centers
Every object has a center. The center is the point around which the object rotates by
default, and the location of the center is considered to be the location of the object. When
you translate and rotate in Object mode, the actions are carried out on the entire object.
However, in Edit mode, you can move the 3D portion of the object (for example, in the
case of a Mesh object, by selecting and moving the entire mesh in Edit mode) without
moving the center. When you do a lot of editing, this can easily happen and cause poorly
placed centers that can cause unexpected behavior with objects. You can set the origin
either by using the Tool Shelf button or by using the hotkey Shift+Ctrl+Alt+C over the
3D viewport region, which will open a menu of options for setting the origin.
Parenting
Parenting is an important way to create relationships between objects (and some other
entities). You will use parenting often in modeling, animating, and texturing. When
one object is parented to another, you can refer to the first object as the child and the sec-
ond object as the parent. In this case, the child object’s movements are all considered only
in relation to the parent. When you translate, rotate, or scale the parent object, you do
Figure 1.10
The manipulator
selection buttons
Figure 1.11
Pivot selection
drop-down menu
427378c01.indd 17 3/19/11 1:45:08 PM