Adobe AFTER EFFECTS 5.5 Help Manual page 262

Adobe After Effects Help
Using Help | Contents
Effect attributes and methods
Boolean active Returns a true value if the effect is turned on, or a false value if it is off.
Property param(name) {name is a string} Returns a property within an effect. For example,
"effect("Bulge").param("Bulge Height")" . Effect point controls are always in layer space.
Property param(index) {index is a number} Returns a property within an effect. After
Effects finds the effect by its index in the Effect Controls window, starting at 1 and
counting down from the top. This form is not recommended because indexes are not
always in contiguous order in the Effect Controls window. If an effect parameter doesn't
have a name, use the pick whip to select it.
Mask attributes and methods
You cannot access the mask shape when using expressions.
Property opacity Returns the mask's Opacity value as a percentage.
Property feather Returns the mask's Feather value in pixels.
Property expansion Returns the mask's Expansion value in pixels.
Boolean invert Returns a true value if the mask is inverted, or a false if it is not.
Property attributes and methods
Number or Array value Returns the property's value at the current time.
Number or Array value_at_time(t) {t is a number} Returns the property's value at the
specified time in seconds.
Number or Array velocity 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.
Number or Array velocity_at_time(t) {t is a number} Returns the temporal velocity value at
the specified time.
Number speed 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.
Number speed_at_time(t) {t is a number} Returns the spatial speed value at the specified
time.
Number or Array smooth(width=.2, samples=5, t=time) {width, samples, and t are
numbers} Applies a box filter to the value of the property at the specified time, and
smooths the result over time. Width (in seconds) is the range of time over which the filter is
averaged. Samples equals the number of discrete samples evenly spaced over time.
Generally, you'll want samples to be an odd number so that the value at the current time is
included in the average. For example, "position.smooth(.1, 5)" .
Number or Array temporal_wiggle(freq, amp, octaves=1, amp_mult=.5, t=time) {freq,
amp, octaves, amp_mult, and t are numbers} Samples the property at a wiggled time. Freq
is calculated in wiggles per second, amp is calculated 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. For example,
"scale.temporal_wiggle(5, .2)" .
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