Graphics Programs Reference
In-Depth Information
The Scale Constraint
A
scale constraint
attaches the source's Scale attributes to the target's Scale attributes.
Select the target object(s) first, and then Shift+click the source object. In the Animation
menu, choose Constrain
➔
Scale
r
.
The Offset parameter allows you to set a scale offset in any axis. Otherwise, the source
assumes the exact scale of the target. The source uses the average of the scales of multiple
targets. Figure 9.54 shows the cone's scale matching the target sphere.
The scale constraint is good for matching the sizes of objects. For example, if an air
hose is inflating a string of balloons, constraining the balloons to one target saves you the
hassle of animating all their Scale attributes in unison. If a cartoon character's eyes are
bugging out at something, you can scale-constrain one to the other so that both bug out
in the same time and proportion.
The Aim Constraint
The
aim constraint
adjusts the source's rotations so that the source always points to the
target object. Select the target object(s) first, and then Shift+click the source object. In
the Animation menu, choose Constrain
➔
Aim
r
.
The aim constraint has more options than the other constraints because you need to
specify which axis of the source is to point to the target. You do so using the Aim Vector
and Up Vector settings.
The Aim Vector setting specifies which axis of the source is the “front” and points to
the target. In the cone and sphere examples, you set the Aim Vector of the cone to (0,1,0)
to make the
Y
-axis the front so that the cone's point aims at the sphere. If Aim Vector is
set to (1,0,0), for example, the cone's side points to the sphere. Figure 9.55 shows the cone
pointing to the sphere with an Aim Vector setting of (0,1,0).
Figure 9.54
The cone now
matches the
sphere's scale.
Figure 9.55
The cone aiming at
the sphere
