- value
- Return type: Number, Array,
or String.
Returns the value of a property at the current
time.
- valueAtTime(t)
- Return
type: Number or Array.
Argument type: t is
a Number.
Returns the value of a property at the specified
time, in seconds.
For example, to have a property value for
each frame chosen randomly from a set of four values, set your four
values as keyframes at 0, 1, 2, and 3 seconds, and then apply the
following expression to the property:
valueAtTime(random(4))
- velocity
- Return
type: Number or Array.
Returns the temporal velocity value
at the current time. For spatial properties, such as Position, it
returns the tangent vector value. The result is the same dimension
as the property.
- velocityAtTime(t)
- Return
type: Number or Array.
Argument type: t is
a Number.
Returns the temporal velocity value at the specified
time.
- speed
- Return
type: Number.
Returns a 1D, positive speed value equal to
the speed at which the property is changing at the default time.
This element can be used only for spatial properties.
- speedAtTime(t)
- Return
type: Number.
Argument type: t is a Number.
Returns
the spatial speed value at the specified time.
- wiggle(freq, amp, octaves=1, amp_mult=.5, t=time)
- Return
type: Number or Array.
Argument type: freq, amp, octaves, amp_mult,
and t are Numbers.
Randomly shakes (wiggles)
the value of the property.
freq value is
the frequency in wiggles per second.
amp value
is the amplitude in units of the property to which it is applied.
octaves is
the number of octaves of noise to add together. This value controls how
much detail is in the wiggle. Make this value higher than the default
of 1 to include higher frequencies or lower to include amplitude
harmonics in the wiggle.
amp_mult is the
amount that amp is multiplied by for each octave.
This value controls how fast the harmonics drop off. The default
is 0.5; make it closer to 1 to have the harmonics added at the same
amplitude as the base frequency, or closer to 0 to add in less detail.
t is
the base start time. This value defaults to the current time. Use
this parameter if you want the output to be a wiggle of the property
value sampled at a different time.
Example: position.wiggle(5, 20, 3, .5) produces
about 5 wiggles per second with an average size of about 20 pixels.
In addition to the main wiggle, two more levels of detailed wiggles
occur with a frequency of 10 and 20 wiggles per second, and sizes
of 10 and 5 pixels, respectively.
This example, on a two-dimensional
property such as Scale, wiggles both dimensions by the same amount:
v = wiggle(5, 10);
[v[0], v[0]]
This example, on
a two-dimensional property, wiggles only along the y axis:
freq = 3;
amp = 50;
w = wiggle(freq,amp);
[value[0],w[1]];
Paul Tuersley
provides a script on the AE Enhancers forum that automatically adds wiggle, smooth,
and loop expressions to selected properties.
Dan
Ebberts provides an example expression and a detailed explanation
on his MotionScript website that shows how
to use the time parameter of the wiggle method
to create a looping animation.
- temporalWiggle(freq, amp, octaves=1, amp_mult=.5, t=time)
- Return
type: Number or Array.
Argument type: freq, amp, octaves, amp_mult,
and t are Numbers.
Samples the property
at a wiggled time. The freq value is the frequency
in wiggles per second, amp is the amplitude in
units of the property to which it is applied, octaves is
the number of octaves of noise to add together, amp_mult is the
amount that amp is multiplied by for each octave,
and t is the base start time. For this function
to be meaningful, the property it samples must be animated, because
the function alters only the time of sampling, not the value. Example: scale.temporalWiggle(5, .2)
- smooth(width=.2, samples=5, t=time)
- Return
type: Number or Array.
Argument type: width, samples,
and t are Numbers.
Smooths the property
values over time, converting large, brief deviations in the value
to smaller, more evenly distributed deviations. This smoothing is
accomplished by applying a box filter to the value of the property
at the specified time. The width value is the
range of time (in seconds) over which the filter is averaged. The samples value
is the number of discrete samples evenly spaced over time; use a
larger value for greater smoothness (but decreased performance).
Generally, you’ll want samples to be an odd number
so that the value at the current time is included in the average.
Example: position.smooth(.1, 5)
- loopIn(type="cycle", numKeyframes=0)
- Return
type: Number or Array.
Loops a segment of time that is measured
from the first keyframe on the layer forward toward the Out point
of the layer. The loop plays from the In point of the layer. The numKeyframes value
determines what segment is looped: The segment looped is the portion
of the layer from the first keyframe to the numKeyframes+1 keyframe.
For example, loopIn("cycle", 3) loops the segment
bounded by the first and fourth keyframes. The default value of
0 means that all keyframes will loop.
You can use keyframe-looping methods to
repeat a series of keyframes. You can use these methods on most
properties. Exceptions include properties that can’t be expressed
by simple numeric values in the Timeline panel, such as the Source Text
property, path shape properties, and the Histogram property for
the Levels effect. Keyframes or duration values that are too large
are clipped to the maximum allowable value. Values that are too
small result in a constant loop.
loop type
|
result
|
|---|
cycle
|
(default) Repeats the specified segment.
|
pingpong
|
Repeats the specified segment, alternating
between forward and backward.
|
offset
|
Repeats the specified segment, but offsets
each cycle by the difference in the value of the property at the
start and end of the segment, multiplied by the number of times
the segment has looped.
|
continue
|
Does not repeat the specified segment, but
continues to animate a property based on the velocity at the first
or last keyframe. For example, if the last keyframe of a Scale property
of a layer is 100%, the layer continues to scale from 100% to the
Out point, instead of looping directly back to the Out point. This
type does not accept a keyframes or duration argument.
|
Todd Kopriva provides an example project
on his blog that demonstrates the use of
the loopIn and loopOut methods,
and all of the loop types.
Paul Tuersley provides a script
on the AE Enhancers forum that automatically adds wiggle, smooth,
and loop expressions to selected properties.
- loopOut(type="cycle", numKeyframes=0)
- Return
type: Number or Array.
Loops a segment of time that is measured
from the last keyframe on the layer back toward the In point of
the layer. The loop plays until the Out point of the layer. The
segment to loop is determined by the specified number of keyframes. The numKeyframes value
sets the number of keyframe segments to loop; the specified range
is measured backward from the last keyframe. For example, loopOut("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. See the
entry for loopIn for more information.
David
Van Brink provides an instructional article and sample project on
his omino pixel blog that show how to
use the Echo effect, the Particle Playground effect, and the loopOut method
to animate a swarm of stylized swimming bacteria.
- loopInDuration(type="cycle", duration=0)
- Return
type: Number or Array.
Loops a segment of time that is measured
from the first keyframe on the layer forward toward the Out point
of the layer. The loop plays from the In point of the layer. The
segment to loop is determined by the specified duration. The duration value
sets the number of composition seconds in a segment to loop; the specified
range is measured from the first keyframe. For example, loopInDuration("cycle",1) loops
the first second of the entire animation. The default of 0 means
that the segment to loop begins at the layer Out point. See the
entry for loopIn for more information.
- loopOutDuration(type="cycle", duration=0)
- Return
type: Number or Array.
Loops a segment of time that is measured
from the last keyframe on the layer back toward the In point of
the layer. The loop plays until the Out point of the layer. The
segment to loop is determined by the specified duration. The duration value
sets the number of composition seconds in a segment to loop; the specified
range is measured backward from the last keyframe. For example, loopOutDuration("cycle", 1) loops
the last second of the entire animation. The default of 0 means
that the segment to loop begins at the layer In point. See the entry
for loopIn for more information.
- key(index)
- Return
type: Key or MarkerKey.
Argument type: index is
a Number.
Returns the Key or MarkerKey object by number.
For example, key(1) returns the first keyframe.
- key(markerName)
- Return type: MarkerKey.
Argument type: markerName is
a String.
Returns the MarkerKey object with this name. Use
only on marker properties.
- nearestKey(t)
- Return
type: Key or MarkerKey.
Returns the Key or MarkerKey object
nearest to a designated time.
- numKeys
- Return
type: Number.
Returns the number of keyframes on a property.
Returns the number of markers on a marker property.
Note: If
you use the Separate Dimensions command to separate the dimensions
of the Position property into individual components, the number
of keyframes changes, so the value returned by this method changes.
- propertyGroup(countUp = 1)
- Return
type: Group.
Returns a group of properties relative to the
property on which the expression is written. For example, if you
add the propertyGroup(1) expression to the Rotation
property of a brush stroke, the expression targets the Transform property
group, which contains the Rotation property. If you add propertyGroup(2) instead,
the expression targets the Brush property group. This method lets
you establish name-independent relationships in the property hierarchy.
This method is especially useful when duplicating properties that contain
expressions.
The numProperties method for propertyGroup returns
the number of properties in the property group.
This example
returns the number of properties in the group that contains the property
on which the expression is written:
thisProperty.propertyGroup(1).numProperties
- propertyIndex
- Return
type: Number.
Returns the index of a property relative to
other properties in its property group, including property groups
within masks, effects, text animators, selectors, shapes, trackers,
and track points.
- name
- Return
type: String.
Returns the name of the property or property
group.
