Adobe AFTER EFFECTS 5.5 Help Manual page 399

Adobe After Effects Help
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Setting values for keyframes and duration
Define segments by setting values for the keyframe and duration parameters according to
the following descriptions of their function:
Keyframes Sets the number of keyframe segments to loop. For the loop_in expression,
the specified range is measured from the first keyframe. For example, loop_in("cycle" , 1)
loops the segment bounded by the first and second keyframes. For the loop_out
expression, the specified range is measured backward from the last keyframe. For
example, loop_out("cycle" , 1) loops the segment bounded by the last keyframe and
second-to-last keyframe. The default value of 0 means that all keyframes will loop.
Duration Sets the number of composition seconds in a segment to loop. For the
loop_in_duration expression, the specified range is measured from the first keyframe. For
example, loop_in_duration("cycle" , 1) loops the first second of the entire animation. For the
loop_out expression, the specified range is measured backward from the last keyframe.
For example, loop_out_duration("cycle" , 1) loops the last second of the entire animation.
The default of 0 means that, for the loop_in_duration expression, the segment to loop
begins at the layer Out point; for the loop_out_duration expression, the segment to loop
begins at the layer In point.
Note: Keyframes or duration values that are too large are clipped to the maximum legal
value. Values that are too small result in a constant loop.
Viewing function arguments and default values
The expressions function menu now lists arguments and default values. This makes it
easier to remember what elements you can control when you write an expression. For
example, in the function menu, the Property function for wiggle lists "wiggle(freq, amp,
octaves = 1, amp_mult =.5, t = time)." The parenthetical listings indicate that the wiggle
function accepts five arguments. The "=" in the last three arguments indicates that using
those parameters is optional. If you specify no values for them, they default, respectively,
to 1, .5, and the current time.
Using the "has_parent()" function
You can now indicate in your expression that you want to retrieve a parent layer's property
by using the "has_parent()" function. You can also allow for the possibility that there may
not be a parent layer at present. For example, the following expression indicates that the
layer to which you apply it would wiggle based on the position of the layer's parent. If the
layer has no parent, then it would wiggle based on its own position. If the layer is parented
later, then its behavior will change at that point:
idx = index;
if (has_parent) {
idx = parent.index;
}
this_comp.layer(idx).position.wiggle(5, 20)
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(5.5) Expressions
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