ABSTRACT
Creating expressions – the ability to tell one parameter to follow another, stay at a constant value, or create new values as the result of ingenious calculations – is one of the most powerful features in After Effects. Using expressions to temporarily set an animating property to a constant value is a handy tool when the user is trying to sort out a complex animation. Expressions are very flexible, and are especially useful when the user want to set up master/slave relationships between multiple layers – for example, to be able to change one master color, and have it affect several other layers. Expressions are easy to break. After Effects does what it can to make writing expressions easier. The best tool for this is the pick whip, which allows the user to literally connect one property to another. The pick whip tool does what it can to help resolve differences in the number of dimensions between properties.
