Adobe 12040118 - After Effects Standard, Tutorial

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Values of propertyGroup relative to Position property of a brush stroke
A. propertyGroup(4) B. propertyGroup(3) C. propertyGroup(2) D. propertyGroup(1) E. Position propertyIndex value is 2; Rotation
propertyIndex value is 4.
In this example, the propertyGroup method for each brush stroke targets the Brush property group because that group is two property groups up
from the Rotation property. The propertyIndex attribute in each Brush stroke then returns a unique value for each Brush stroke. The resulting value
is then multiplied by the time and 200 and applied to each rotation value, rotating each brush stroke differently, creating swirling paint strokes:
propertyGroup(2).propertyIndex * time * 200
Animating a brush stroke with an expression
Key attributes and methods (expression reference)
When you access a Key object, you can get time, index, and value properties from it. For example, the following expression gives you the value of
the third Position keyframe: position.key(3).value.
The following expression, when written on an Opacity property with keyframes, ignores the keyframe values and uses only the placement of the
keyframes in time to determine where a flash should occur:
d = Math.abs(time - nearestKey(time).time);
easeOut(d, 0, .1, 100, 0)
value Return type: Number or Array.
Returns the value of the keyframe.
time Return type: Number.
Returns the time of the keyframe.
index Return type: Number.
Returns the index of the keyframe.
MarkerKey attributes (expression reference)
You can access values for composition markers and layer markers using the same methods. Access layer markers through the thisLayer.marker
object; access composition markers through the thisComp.marker object.
For the purpose of expressions, markers are a special type of Key object, so you can use methods such as nearestKey(time) to access markers,