Adobe 12040118 - After Effects Standard, Руководство

Страница: 564 / 614

To the top
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. Using true for the timeless argument 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 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.
In After Effects CS6, the behavior of random() is changed to be more random when layer ids are close together. The wiggle() expression is not
affected.
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.
Argument type: valOrArray is a Number or an Array [2 or 3].
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 will also 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. Example: ro 360*noise(time)
Interpolation methods (expression reference)
For all of the Interpolation methods, the argument t is often time or value, though it can have other values, instead. If t is time, the interpolation
between values happens over a duration. If t is value, then the expression maps one range of values to a new range of values.
For additional explanations and examples of the Interpolation methods, see JJ Gifford’s website .
Chris and Trish Meyer provide additional information and examples for these methods in an article on the ProVideo Coalition website .