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3 In the Hierarchy list, scroll down to the Objects branch and, if necessary,
expand Sphere01 the branch so the sphere's Position track is visible. Click
the Position label to highlight it.
4 In the Hierarchy list, right-click the Position label and then choose Assign
Controller
The Assign Controller dialog opens.
5 Choose Position Expression from the list of controller types, and then
click OK.
The Expression Controller dialog opens.
NOTE You can also open the Expression Controller dialog with Track View
> Controller menu > Properties.
6 Replace the default expression by typing the following position expression
in the Expression field:
[100*cos(360*NT), 100*sin(360*NT), 0]
The expression specifies a circular path for the sphere. NT is a variable
that means normalized time. Movement based on NT happens exactly
once per the active time segment, regardless of how many frames are in
the animation.
7 Click Evaluate.
8 Play the animation. The sphere moves in a circle about the world origin
(0,0,0). The radius of the circular path is 100 units.
Example continued: To change the radius of the circle:
The two 100s in the position expression from the previous procedure specify
the radius. To adjust the radius of the circle's path, create a symbolic variable
to represent the radius. The variable has a constant value that is easy to edit.
1 Reopen Track View and the Expression Controller dialog if necessary.
2 In the Name field of the Expression Controller dialog, type radius Make
sure Scalar is chosen, and then click Create.
The variable name "radius" appears in the Scalars list of the dialog.
3 Click Assign To Constant.
A dialog titled "radius" opens.
4 Enter 150 in the Value field, and then click OK.
Expression Controller | 3157