2010

Table Of Contents
Expressions
Introduction
Expressions are program-like instructions you create to control keyable attributes
over time. Expressions can be comprised of mathematical equations, conditional
statements, or MEL
commands.
Expressions offer an alternative to difficult keyframing tasks similar to Set Driven
Key. With Set Driven Key, attribute relationships can be set up and are defined
using animation curves. Unlike Set Driven Key, an expression does not use an
animation curve to define the animation of the attribute but calculates the
attribute values over time from the formula defined in the expression.
Although you can create an expression to animate attributes for any purpose,
theyre ideal for attributes that you want to change incrementally, randomly,
or rhythmically over time.
It is possible to create custom attributes for objects and control them in
conjunction with expressions. It is not possible to mix expressions with other
animation techniques for the same attribute on an object (keyframing, path
animation, set driven key).
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