How To Create A Randomizer In Animate With A Range Of Numbers To Randomize

Accept control of randomly animated movements. Hither'southward how to apply the random expression in Subsequently Furnishings.

The random expression in After Effects is both a versatile and essential. There are many applications were the random expression tin assist ease the brunt of small deadening animation tasks that slowly eat at your time animative. However, the random expression can be kinda confusing if yous're new to expressions in after effects.

Today I'one thousand going to break downwardly the ins-and-outs of the random expression so you can start incorporating this powerful tool into your motion design workflow. Let's get going and learn how to control the random expression....

What is the Random Expression in After Furnishings?

The random expression is used in Afterward Effects to generate random values for the belongings it'due south applied to. That seems adequately straight forward, simply did you lot know there are a few different random expressions available in After Effects?

Here'south a list of random expressions in that we will cover :

random(maxValOrArray);
random(minValOrArray, maxValOrArray);
gaussRandom(minValOrArray, maxValOrArray);
seedRandom(seed, timeless = imitation);

And then, you may be asking yourself, "why are in that location and then many options to generate a random number?" Well, As an creative person you're going to demand a little fleck of control, and these various random expressions offer unique ways of controlling randomness in After Furnishings.

New to Expressions in After Furnishings?

If y'all are new to expressions and are wanting to follow along, hither is how you add together an expression to a property in After Effects:

Select a layer and discover a property you want to affect (similar opacity).
Option (alt on PC) + click on the stopwatch icon next to your desired belongings.
Copy and paste, or type the expressions from this commodity in the expression editor.

Now, let's take a wait at the many random expression options...

Random Expression Breakdown

We're going to go ane expression at a time, from easiest to hardest, and breakdown what's happening.

The Basic Random Expression

The most bones course of the random expression in After Effects is simply random();.

random(50);

In the example above, Afterwards Effects will return random values between 0 and fifty every frame. The number typed in the parentheses is the maximum value we set for this property.

If you were to apply this expression to the opacity layer information technology would randomly choose a value between 0 and fifty every frame. If you were to blazon 100 instead of fifty, then the opacity value would randomly animate between 0 and 100. Random isn't only for opacity either. Yous can also randomize only about whatsoever belongings in After Effects, including scale (encounter below).

Before We Go on...

Something confusing you lot may run across when working with the random expression is that properties calling for two dimensions, or 2 values, need special attention. These multi-value 'buckets' are called arrays. Information technology's just a little bit more lawmaking to help Afterwards Effects interpret what information goes where. For example, some properties that call for two values are scale, position, and ballast point.

//One value
random(50);
//Two values
p = random(50);
[p,p];

All we did is identify the random expression inside of the variable p, and then typed an array using brackets using the p variable. This will call back the same value for both dimensions.

When you start writing an expression you take to end with the same number of values equally you started with. If you're placing an expression on position then you'll start with two numbers, an x and a y value. When wrapping up your expression, After Effects will nevertheless be expecting values for both the ten and the y position.

When you're working with properties like rotation or opacity you won't have to worry about using an array to wrap upwards your code. These backdrop are only using a single value.

GAINING A Fiddling MORE CONTROL

If yous're looking to add together a little chip more than control to the range of random values you can type random(minValOrArray, maxValOrArray);.

random(forty,75);

Okay, so what's happening here and how exactly is this different? In the previous example you only provided ane value, which was the maximum allowed value. In this example we are able to prepare both a minimum and maximum value, allowing united states of america define a custom range of values.

If the expression above was applied to the opacity property, nosotros would generate random numbers between 40 and 75 every frame. You tin can type any number you want for the minimum and maximum values, but the smaller number should always exist the first number.

Interestingly, note that if yous typed random(0,100); for opacity this would be the exact same as typing random(100); because 0 is already the minimum value allowed, and 100 is already the maximum value. Pay attending to the property's value limitations when typing out your expressions and this could help you keep your lawmaking clean.

Brand the Random Experience Natural

Accept you always heard of Gaussian distribution? Not many people have, and though that may sound complex it's fairly simple to wrap your caput around. Let's take a look at our next random expression gaussRandom(); using the opacity property with a range of 0-100%.

Bell Curve-V1-01.png — Gaussian Distribution Bell Curve

Neat image, but how does this apply to this random expression in After Effects? Instead of a uniform distribution of the random values, gaussian distribution will assistance achieve a more natural await by using a falloff equation. Stay with me hither...

From the example above, the values between 40-59% will be chosen approximately 38% of the time. As your values get further from the middle number it will be chosen less. Although this may be obvious, 50% has a slightly higher chance of being picked than 49% due to the falloff of the curve. If this was a raffle betwixt 100 people you would desire to be number 50. Your odds of winning would be dramatically better than poor person number i or 100!

Here is what gaussRandom looks like in code class:

gaussRandom(minValOrArray);
gaussRandom(minValOrArray, maxValOrArray);

Like nosotros explained for the random(); expression above, you can as well cull between providing a single value or a range of values for the gaussRandom(); expression.

How to Control the Random Expression

If y'all only stick with the random(); expression by itself, what plays back will be unlike every time. Thankfully the Adobe After Effects team hooked us up with an expression that can aid us out.

Random Consistency

Using the seedRandom method will allow you replay the same random movements every time. This is achieved by setting the "seed" value, which volition tell After Effects which random algorithm pattern to cull and so use during each playback.

To be clear seedRandom really won't work past itself. We demand to complete this lawmaking by using one of the expressions nosotros previously covered. Below I will add in a seed value, and then complete the code by calling the gaussRandom method.

seedRandom(20, timeless = imitation);
gaussRandom(20,100);

Using this modest snippet of code y'all now accept a lot more control over your animations. Also, you can substitution gaussRandom(); with random(); to produce a different expect.

I should warn you though, the same seed will use the same randomness regardless of the layer it's used on. For instance, if you copy and paste an expression from one layer's position to another, they volition move in the aforementioned exact pattern. To fix this simply change the seed and it volition motion differently.

True or Imitation

Something that may exist confusing about seedRandom(); is the timeless argument. What happens if you modify it to true?

It'southward quite unproblematic and i'll utilise GIFs to aid y'all wrap your head around how it works. The following GIF has been slowed downwardly with an expression posterizeTime();

If y'all leave the timeless statement equal to simulated your value will change each frame. In the case below the Timeless set to "true".

Setting information technology "true" makes the seed "timeless" which means it stays the same on each frame, simply information technology will still cull a random value.

The opacity value could randomly gear up to 50%, and then it would remain that way throughout playback. Simply change the seed value if yous want a different opacity value.

Pro Tip: Use the Layer Index with the Random Expression

Setting a specific seed value every fourth dimension you implement this code tin be tedious. Here'southward a elementary solution that will lift some of that burden and help salvage y'all time.

Instead of typing in a numerical value, you can accept Afterwards Furnishings use the layers number.

If y'all utilize index in your expression for layer 20, then the seed number volition be 20. Doing this volition make sure that changes in value won't follow the same patterns of other layers in your composition. To achieve this simply type the word index where the seed value goes, like and so:

seedRandom(index, false);
gaussRandom(20,100);

This is extremely helpful if yous are copying and pasting expressions across several layers, and will salve y'all time from going into each layer and irresolute the seed.

A Absurd Example For the Random Expression

Let's take some of that knowledge we but learned and prove you something cool! Hither'south a rig that randomly showtime when a layer should animate on.

We used the random expression in this example to permit Later Effects starting time and cull when our animation should outset! What'southward smashing is that it is random for every layer. Could you imagine having more than circles than that? Without the random expression yous'd have to animate each one of them differently or fifty-fifty offset each layer. That would take a really long time!

The example higher up utilizes a little more than expression noesis than nosotros explained here, so nosotros're going to give abroad the project file for free! And, since there is a petty bit more expression magic happening in this file I sprinkled in a few notes to help you reverse engineer the project.

Learn Expressions in After Effects

Wow! We covered a lot of footing in this commodity. Expressions in general tin be a flake scary, but when you break them downwards ane at a time it really helps to get a concur on them.

Think about expressions as a language. Start with commonly used words, implement them as much as you can, and slowly start to build your vocabulary. When you know more words you tin can start creating bigger sentences, and in this case y'all'll start edifice more complex lawmaking.

If you want to learn more well-nigh using expressions in After Effects we take a ton of other great expression content here on School of Motility. Here are a few of our favorite tutorials: