Adobe After Effects - Manual (Page 699)

maskOpacity
maskFeather
maskExpansion
invert
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value
valueAtTime(t)
Note:
velocity
velocityAtTime(t)
speed
speedAtTime(t)
wiggle(freq, amp, octaves=1, amp_mult=.5, t=time)
for direct numerical manipulation through expressions.
Return type: Property.
Returns the opacity value of a mask as a percentage.
Return type: Property.
Returns the feather value of a mask, in pixels.
Return type: Property.
Returns the expansion value of a mask, in pixels.
Return type: Boolean.
Returns true if the mask is inverted or false if it is not.
Property attributes and methods (expression reference)
Return type: Number, Array, or String.
Returns the value of a property at the current time.
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))
Dan Ebberts provides more examples and techniques for using the valueAtTime and velocityAtTime methods on his MotionScript website .
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.
Return type: Number or Array.
Argument type: t is a Number.
Returns the temporal velocity value at the specified time.
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.
Return type: Number.
Argument type: t is a Number.
Returns the spatial speed value at the specified 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.
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