Random Numbers¶
These items deal with randomness in expressions.
Note
The wiggle() method—which is used to randomly vary a property value—is in the Property attributes and methods category.
Methods¶
gaussRandom()¶
gaussRandom([maxValOrArray=1])
Description¶
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.
Parameters¶
| Parameter | Type | Description |
|---|---|---|
maxValOrArray |
Number or Array | Optional. The max value (or array) to generate a random number to, from 0. Defaults to 1. |
Returns¶
Number or Array
gaussRandom(minValOrArray, maxValOrArray)¶
gaussRandom(minValOrArray, maxValOrArray)
Description¶
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.
Parameters¶
| Parameter | Type | Description |
|---|---|---|
minValOrArray |
Number or Array | The min value (or array) to generate a random number from. |
maxValOrArray |
Number or Array | The max value (or array) to generate a random number to. |
Returns¶
Number or Array
noise(valOrArray)¶
noise(valOrArray)
Description¶
Returns a number in the range from -1 to 1.
The noise is not actually random; it is based on Perlin noise, which means that the return values for two input values that are near one another tend to be near one another.
This type of noise is useful when you want a sequence of seemingly random numbers that don't vary wildly from one to the other—as is usually the case when animating any apparently random natural motion.
Parameters¶
| Parameter | Type | Description |
|---|---|---|
valOrArray |
Number or an Array (2- or 3-dimensional) | The input value (or array) to use to generate the random number. |
Returns¶
Number
Example¶
rotation + 360*noise(time)
random()¶
random([maxValOrArray=1])
Description¶
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.
Note
In After Effects CC and CS6, the behavior of random() is changed to be more random when layer IDs are close together. The wiggle() expression is not affected.
Parameters¶
| Parameter | Type | Description |
|---|---|---|
maxValOrArray |
Number or Array | Optional. The max value (or array) to generate a random number to, from 0. Defaults to 1. |
Returns¶
Number or Array
random(minValOrArray, maxValOrArray)¶
random(minValOrArray, maxValOrArray)
Description¶
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.
Parameters¶
| Parameter | Type | Description |
|---|---|---|
minValOrArray |
Number or Array | The min value (or array) to generate a random number from. |
maxValOrArray |
Number or Array | The max value (or array) to generate a random number to. |
Returns¶
Number or Array
seedRandom()¶
seedRandom(offset[, timeless=false])
Description¶
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.
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%.
Parameters¶
| Parameter | Type | Description |
|---|---|---|
offset |
Number | The value with which to offset the seed. This is also used to control the initial value of the wiggle() function. |
timeless |
Boolean | Optional. 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. Defaults to false. |
Returns¶
None
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