Adobe 12040118 - After Effects Standard, Tutorial

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posterizeTime(framesPerSecond) Return type: Number.
Argument type: framesPerSecond is a Number.
The framesPerSecond value becomes the frame rate from which the rest of the expression operates. This expression allows you to set the frame
rate for a property to be lower than the frame rate of the composition. For example, the following expression updates the property value with a
random value once per second:
posterizeTime(1);
random()
value Return type: Number, Array, or String.
Represents the value at the current time for the property containing the expression.
Time conversion methods (expression reference)
timeToFrames(t = time + thisComp.displayStartTime, fps = 1.0 / thisComp.frameDuration, isDuration = false) Return type: Number.
Argument type: t and fps are Numbers; isDuration is a Boolean.
Converts the value of t, which defaults to the current composition time, to an integer number of frames. The number of frames per second is
specified in the fps argument, which defaults to the frame rate of the current composition (1.0 / thisComp.frameDuration). The isDuration
argument, which defaults to false, should be true if the t value represents a difference between two times instead of an absolute time. Absolute
times are rounded down toward negative infinity; durations are rounded away from zero (up for positive values).
framesToTime(frames, fps = 1.0 / thisComp.frameDuration) Return type: Number.
Argument type: frames and fps are Numbers.
The inverse of timeToFrames. Returns the time corresponding to the frames argument, which is required. It doesn’t have to be an integer. See
timeToFrames for explanation of the fps argument.
timeToTimecode(t = time + thisComp.displayStartTime, timecodeBase = 30, isDuration = false) Return type: String.
Argument type: t and timecodeBase are Numbers; isDuration is a Boolean.
Converts the value of t to a String representing timecode. See timeToFrames for an explanation of the t and isDuration arguments. The
timecodeBase value, which defaults to 30, specifies the number of frames in one second.
timeToNTSCTimecode(t = time + thisComp.displayStartTime, ntscDropFrame = false, isDuration = false) Return type: String.
Argument type: t is a Number, ntscDropFrame and isDuration are Booleans.
Converts t to a String representing NTSC timecode. See timeToFrames for an explanation of the t and isDuration arguments. If ntscDropFrame is
false (the default), the result String is NTSC non-drop-frame timecode. If ntscDropFrame is true, the result String is NTSC drop-frame timecode.
timeToFeetAndFrames(t = time + thisComp.displayStartTime, fps = 1.0 / thisComp.frameDuration, framesPerFoot = 16, isDuration =
false)
Return type: String.
Argument type: t, fps, and framesPerFoot are Numbers; isDuration is a Boolean.
Converts the value of t to a String representing feet of film and frames. See timeToFrames for an explanation of the t, fps, and isDuration
arguments. The framesPerFoot argument specifies the number of frames in one foot of film. It defaults to 16, which is the most common rate for
35mm footage.
timeToCurrentFormat(t = time + thisComp.displayStartTime, fps = 1.0 / thisComp.frameDuration, isDuration = false) Return type: String.
Argument type: t and fps are Numbers; isDuration is a Boolean.
Converts the value of t to a String representing time in the current Project Settings display format. See timeToFrames for a definition of all of the
arguments.
An optional ntscDropFrame argument was added to the timeToCurrentFormat() function in After Effects CS5.5 and later. Default: ntscDropFrame =
thisComp.ntscDropFrame.
If you want more control over the look of timecode in your footage, use the timeToCurrentFormat method or other timeTo methods to generate
the timecode instead of using the Timecode or Numbers effect. Create a text layer, add an expression to the Source Text property, and enter
timeToCurrentFormat() in the expression field. With this method, you can format and animate the timecode text. In addition, the timecode uses
the same display style defined by the current project settings.
Vector Math methods (expression reference)
Vector Math functions are global methods that perform operations on arrays, treating them as mathematical vectors. Unlike built-in JavaScript
methods, such as Math.sin, these methods are not used with the Math prefix. Unless otherwise specified, Vector Math methods are lenient about
dimensions and return a value that is the dimension of the largest input Array object, filling in missing elements with zeros. For example, the
expression add([10, 20], [1, 2, 3]) returns [11, 22, 3].
JJ Gifford’s website provides explanations and examples that show how to use simple geometry and trigonometry with expressions.