8

Expression Controller 317
The name "boxposn" is displayed in the Vec tors
list in the lower-left part of the dialog.
Variable names are case sensitive; the variable
name should be lower case.
4. Click Assign to Controller.
The Track View Pick dia log 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 B ox01 and then click OK.
6. In the Expression field, add boxposn as an
offset:
[radius * cos(360*NT), radius * s in(360*NT),
0]+b oxposn.
7. Click Evalu ate, and then click Close.
Play the animation again. The sphere m oves
in a circle around the box and follows the box
wherever it moves.
Inter face
Tip: You can resize the dialog by dragging an edge
or a corner.
Create Variables group
Name—Contains the variable.
Scalar —Selects the type of variable to create.
Vector—Selects the type of variable to create.
Cr e a te —Creates the variable.
You must enter a name and specify a type before
clicking Create.
Delete—Select a variable in the Scalar or Vector
list, then click to delete it.
Variable Pa rameters group
Tick Offset—Contains an offset value.
A t ick is 1/4800 of a second. If a var iable has a
non-zero tick offset, that value is added to the
current time.
Expression group
Type an expression in the Expression box.
The expression must be a va lid mathematical
expression. The result is either a three-value vector
for a vector expression (position, scale, or point3)
orascalarvalueforafloatexpression.
Description group
Type text in this group to document an expression.
For example, you can describe user-defined
variables.
Function l ist—Displays a list of Expression
controller functions.
In the list, p, q, and r represent sca lar values or
scalar expressions; V a nd W represent vector
values or vector expressions.
Save—Saves an expression. Expressions are saved
as files with a .
xpr file name extension.
Loa d—Loads an expression.
A saved expression does not save variable
definitions or va lues. After loading the expression,
you need to redefine them.
Debug—Displays the Expression Debug window.
This window shows the values of all variables,
and the value of the expression. When you