Adobe After Effects CS4 - Manual (Page 667)

661 USING AFTER EFFECTS CS4
Expressions
Last updated 12/21/2009
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.