Random Motion. The Basics. Randomness is one of the most asked about uses of expressions and After effects gives us a pretty good arsenal of tools with which to implement it. The basic random method has several different flavors. Some examples would probably be helpful in understanding the different ways you can call random Random Expression. Result. random number between 0 and 1. So you can see that the random method is pretty flexible. Well illustrate how you might use this with a few examples. Lets say you wanted to randomly position a layer within the comp. Any of these expressions for Position will do the trick. Comp. width,this. Comp. height. random0,0,this. Read Data On Serial Port. Comp. width,this. Comp. height. x randomthis. Object-Wiggle.gif' alt='After Effects Mac' title='After Effects Mac' />Comp. Comp. height. x randomthis. Comp. width. y randomhis. Comp. height. While the expressions above do indeed position the layer randomly, if you try any them youll discover what seems to be a serious limitation of the random method. After Effects ltAE2 AE. Adobe After Effects CS4 Mac,software PC site, free software download soft for pcCreate compelling motion graphics and blockbuster visual effects with flexible tools. The ideal combination for the cyclist who cares about their skin and the after effects from cycling. The Soft Chamois cream offers great protection when in the saddle, whilst. You get a different result on each frame. This is great if you want to have a layer frenetically hop all over the place. Most of the time though, you want a more controlled randomness. The best plugins and scripts for 3D, VFX and motion graphics software including Adobe After Effects, Cinema 4D and Premiere Pro. Lots of video tutorials showing how. This is where seed. Random comes in. Seed Random to the Rescueseed. After Effects Cc2017Random is a clever method that Adobe came up with to let us control the rate of randomness. Actually it has more than one use. You can also use it just to change the sequence of random numbers generated by random. Random has two parameters. After Effects CcThe first one is the random seed, and the second is a truefalse flag that tells After Effects whether or not the random numbers generated by random will be timeless. Well get back to that timeless business in a minute, but first lets look at the other parameter. In its simplest form, seed. Random just seeds the random number generator to produce a particular sequence of random numbers that will change on every frame. As an example, these two expressions will generate completely different sequences of random numbers which will change on each frame. Random9. 99. OK here comes the cool part. By setting the second parameter of seed. Random to true, the numbers generated by random will be the same on every frame. Heres an example expression for Position that will move a layer to a random position and hold it at that location. Random3,true. randomthis. Comp. width,this. Comp. height. Remember that without the seed. Random call, the layer would bounce around to a different Position on each frame. How does that help usHaving a layer move to a random Position and stay there is pretty boring, right Yes it is. But all we need to do to get a new position is change the seed. So to get the layer to move around randomly in an orderly fashion, all we have to do is update the seed periodically and get a new random Position from random. Lets construct an example. Say we want our layer to move to a new random Position every half second. All we need is some new code in our expression that will change the seed every half second. This After Effects Script allows you to easy add premade after. After Effects. After Effects. Final Effects Complete 7 AE brings over 120 designer effects and transitions to Macintosh and Windows versions of Adobe After Effects and. How would we do that Remember that the Math. Java. Script function rounds down to the nearest integer. We can use that to generate a seed that changes every half second by dividing the current time by. Heres an example you would change the value of hold. Time to change the length of time each Position is held. Time. 5 time to hold each position seconds. Math. floortimehold. Time. seed. Randomseed,true. Comp. width, this. Comp. height. Now the layer still moves around randomly, but it does it a half second intervals. Lets make a modification so that our motion stays in the title safe area of the comp. Well do this by restricting the results of the calls to random to the values between 1. Heres the modified code random position every. Time. 5 time to hold each position seconds. Val 0. 1his. Comp. Comp. height. max. Val 0. 9his. Comp. Comp. height. seed Math. Time. seed. Randomseed,true. Val,max. Val. Note that theres a slightly simpler way to do this by using the posterize. Time method in conjunction with seed. Random, but well look at that when we delve into using expressions to manipulate time. OK, thats better, but what if we wanted the layer to move smoothly from one Position to the otherThis brings us to one of the most important concepts for generating random motion, which is that whenever you set the seed to a particular number, the random sequence generated by random will always be the same. For example if we set the seed to 1, random might give us. If we change the seed to 2, we might get. But if we change the seed back to 1, we will get. So how does this help us generate smooth random motion Lets look again at our example above. For the first half second, the seed calculates out to be 0. So for every frame in the first half second, the call to random generates the same random Position based on a seed of 0. After the first half second, the seed changes to 1 and the random Position changes. So what if we were to peek ahead by changing the seed to the value that well be using in the next half second to see what the next Position will be, and start heading there The sequence would be to calculate the seed for this half second, use that to get the random Position for this half second which will be our starting Position, bump the seed by one and use that to see what the random starting Position for the next half second will be which well use as the ending Position for the current half second segment. OK, heres the code random motion synchronized. Dur. 5 duration of each segment of random motion. Val 0. 1his. Comp. Comp. height. max. Val 0. 9his. Comp. Comp. height. seed Math. Dur. seg. Start seedeg. Dur. seed. Randomseed,true. Val randommin. Val,max. Val. seed. Randomseed1,true. Val randommin. Val,max. Val. easetime,seg. Start,seg. Start seg. Dur, start. Val, end. Val. Youll notice in the demo movie weve now got multiple stars, all at different random positions. They all have identical copies of the random position expression, so you might be wondering why they have different positions. It turns out that for any given random seed, the random values generated will be unique to each layer. Internally After Effects somehow modifies the seed so that it is unique for each layer, comp, property, effect, etc. Most of the time this is a very handy feature, but there are some occasions where it would be nice to be able to force two different layers to generate the same random numbers. Anyway, to recap, the seed is derived from the time and the segment duration and becomes our segment number where segment 0 starts at time 0, segment 1 starts at time. Once we have the seed, we seed the random number generator with it and call random to get the starting Position for this segment. Then we bump the seed, seed the random number generator with the new seed and call random again to get the starting Position of the next segment which is, of course, the ending Position for the current segment. Then we just use ease to interpolate between the two Positions so that the layer eases from one Position to the next. You can change the interpolation from ease to linear for a different effect. So thats all you need to generate basic random motion in After Effects. Ah, if only life were so simple.