Apple Shake 4 - Manual (Page 78)

78 Chapter 1 An Overview of the Shake User Interface
Using Expressions in Parameters
An expression is any non-numeric entry, such as a variable or a mathematical
calculation. Any parameter can use an expression. Some expressions, such as time, are
extremely simple. When you type the expression variable “time” into a value field,
Shake returns the numeric value of the current playhead position. For example, if the
playhead (in the Time Bar) is parked at frame 1, typing “time” into a value field returns a
value of 1 in that field.
Entering an expression consisting of any letter (whether valid or not) activates a plus
sign (+) to the left of the parameter name. To edit a parameter’s expression, click the
plus sign to open an expression field underneath.
If the parameter has an expression and you make an adjustment to that parameter’s
slider, the expression is removed in favor of your numerical change. If the parameter is
animated, however, these special expressions are recognized by Shake and are not
removed when the slider is adjusted. For more information on animating parameters,
see Chapter 10, “
Parameter Animation and the Curve Editor ,” on page 291.
Note: You can also remove an expression by right-clicking the field and selecting Clear
Expression from the shortcut menu.
You can modify expressions in various ways:
• To load or save an expression, use the right-click menu.
• To create extra sliders to build complex expressions (and still allow interactive input),
right-click the field and select Create Local Variable. To remove a local variable, right-
click and select Delete Local Variable.
For a lesson on using local variables and expressions, see Tutorial 4, “Working With
Expressions,” in the Shake 4 Tutorials.
For a list of mathematical expressions and variables, see Chapter 30, “ Installing and
Creating Macros ,” on page 905.