Adobe After Effects CS4 - Manual (Page 670)

664 USING AFTER EFFECTS CS4
Expressions
Last updated 12/21/2009
The offset value, but not the timeless value, is also used to control the initial value of the wiggle function.
For example, this expression on the Opacity property sets the Opacity value to a random value that does not vary with time:
seedRandom(123456, true);
random()*100
The multiplication by 100 in this example converts the value in the range 0–1 returned by the random method into a
number in the range 0–100; this range is more typically useful for the Opacity property, which has values from 0% to 100%.
random() Return type: Number.
Returns a random number in the range 0–1.
random(maxValOrArray) Return type: Number or Array.
Argument type: maxValOrArray is a Number or Array.
If maxValOrArray is a Number, this method returns a number in the range from 0 to maxValOrArray. If
maxValOrArray is an Array, this method returns an Array with the same dimension as maxValOrArray, with each
component ranging from 0 to the corresponding component of maxValOrArray.
random(minValOrArray, maxValOrArray) Return type: Number or Array.
Argument type: minValOrArray and maxValOrArray are Numbers or Arrays.
If minValOrArray and maxValOrArray are Numbers, this method returns a number in the range from
minValOrArray to maxValOrArray. If the arguments are Arrays, this method returns an Array with the same
dimension as the argument with the greater dimension, with each component in the range from the corresponding
component of minValOrArray to the corresponding component of maxValOrArray. For example, the expression
random([100, 200], [300, 400]) returns an Array whose first value is in the range 100–300 and whose second
value is in the range 200–400. If the dimensions of the two input Arrays don’t match, higher-dimension values of the
shorter Array are filled out with zeros.
gaussRandom() Return type: Number.
Returns a random number. The results have a Gaussian (bell-shaped) distribution. Approximately 90% of the results
are in the range 0–1, and the remaining 10% are outside this range.
gaussRandom(maxValOrArray) Return type: Number or Array.
Argument type: maxValOrArray is a Number or Array.
When maxValOrArray is a Number, this method returns a random number. Approximately 90% of the results are in
the 0 to maxValOrArray range, and the remaining 10% are outside this range. When maxValOrArray is an Array, this
method returns an Array of random values, with the same dimension as maxValOrArray. 90% of the values are in the
range from 0 to maxValOrArray, and the remaining 10% are outside this range. The results have a Gaussian (bell-
shaped) distribution.
gaussRandom(minValOrArray, maxValOrArray) Return type: Number or Array.
Argument type: minValOrArray and maxValOrArray are Numbers or Arrays.
If minValOrArray and maxValOrArray are Numbers, this method returns a random number. Approximately 90% of
the results are in the range from minValOrArray to maxValOrArray, and the remaining 10% are outside this range. If
the arguments are Arrays, this method returns an Array of random numbers with the same dimension as the argument
with the greater dimension. For each component, approximately 90% of the results are in the range from the
corresponding component of minValOrArray to the corresponding component of maxValOrArray, and the
remaining 10% are outside this range. The results have a Gaussian (bell-shaped) distribution.
noise(valOrArray) Return type: Number.