After Effects Expression Elements Reference - Adobe AFTER EFFECTS CS3 PROFESSIONAL User Manual

Expression time
Time within an expression is always in composition time (not layer time) and is measured in seconds. The default
time for any expression is the current composition time at which the expression is being evaluated. The following
expressions both use the default composition time and return the same values:
thisComp.layer(1).position
thisComp.layer(1).position.valueAtTime(time)
To use a relative time, add an incremental time value to the
seconds before the current time, use the following expression:
thisComp.layer(1).position.valueAtTime(time-5)
Default time references to properties in nested compositions use the original default composition time, not
remapped time. However, if you use the
For example, if the source of a layer in the parent composition is a nested composition, and in the parent composition
you have remapped time, when you access the position values of a layer in the nested composition with the following
expression, the position values use the composition's default time:
comp("nested composition").layer(1).position
However, if you access layer 1 using the
thisComp.layer("nested composition").source.layer(1).position
Note: If you use a specific time in an expression, After Effects ignores the remapped time.

After Effects expression elements reference

Using the expression elements reference
Use the After Effects expression elements along with standard JavaScript elements to write your expressions. You can
use the Expression Language menu at any time to insert methods and attributes into an expression, and you can use
the pick whip at any time to insert properties.
If an argument description contains an equal sign (
uses the included default value if you don't specify a different value.
Some argument descriptions include a number in square brackets—this number indicates the dimension of the
expected property or Array.
Some return-value descriptions include a number in square brackets—this number specifies the dimension of the
returned property or Array. If a specific dimension is not included, the dimension of the returned Array depends on
the dimension of the input.
• "Global objects" on page 556
• "Time conversion methods" on page 557
• "Vector Math methods" on page 558
• "Random Numbers methods" on page 559
• "Interpolation methods" on page 561
• "Color Conversion methods" on page 562
argument. For example, to get the Position value 5
time
function to retrieve a property, the remapped time is used.
source
function, the position values use the remapped time:
source
) and a value (such as
=
or ), then the argument
t=time width=.2
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