2009

The radius variable is now 150.
Next you'll use the new variable in the expression.
Example continued: To replace the literal value with the variable name:
1 In the Expression field, change 100 to radius in both places. The
expression should now look like this:
[ radius*cos(360*NT), radius*sin(360*NT), 0]
2 Click Evaluate.
3 Play the animation. The sphere moves in a circle about the world origin
(0,0,0). The radius of the circular path is 150 units.
Example continued: To make the sphere rotate about a box:
1 Create a box about 40 units square, and animate its position over three
or four keyframes.
2 Select the sphere.
3 In the Name field of the Expression Controller dialog, enter boxposn.
Choose Vector, and then click Create.
The name "boxposn" is displayed in the Vectors list in the lower-left area
of the dialog.
Variable names are case sensitive; the variable name should be lower case.
4 Click Assign to Controller.
The Track View Pick dialog is displayed. It shows the object hierarchy as
it appears in the left side of Track View-Dope Sheet.
5 In the Hierarchy list, highlight the Position controller for Box01 and then
click OK.
6 In the Expression field, add boxposn as an offset:
[radius * cos(360*NT), radius * sin(360*NT), 0]+boxposn.
7 Click Evaluate, and then click Close.
Play the animation again. The sphere moves in a circle around the box
and follows the box wherever it moves.
3158 | Chapter 15 Animation