Adobe After Effects CS3 - Manual (Page 569)

AFTER EFFECTS CS3
User Guide
564
The random and gaussRandom methods use a seed value that controls the sequence of numbers. By default, the seed
is computed as a function of a unique layer identifier, the property within the layer, the current time, and an offset
value of 0. Call
seedRandom to set the offset to something other than 0 to create a different random sequence. Use
true for the timeless argument to not use the current time as input to the random seed; this allows you to generate
a random number that doesn’t vary depending on the time of evaluation. 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 between 0 and 1 returned by the random method into
a number between 0 and 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 between 0 and 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 between 0 and maxValOrArray. If maxValOrArray is
an Array, this method returns an Array with the same dimension as maxValOrArray, with each component ranging
between 0 and 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 between minValOrArray and
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 between the corresponding components of
minValOrArray and maxValOrArray. For example, the expression
random([100, 200], [300, 400]) returns an
Array whose first value is between 100 and 300 and whose second value is between 200 and 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 between 0 and 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 of this range. When maxValOrArray is an Array,
this method returns an Array of random values, with the same dimension as maxValOrArray. Ninety percent of the
values range between 0 and the value in maxValOrArray, and the remaining 10% are outside of 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.