LIBRARY: Tutorials Reviews Interviews Editorials Features Business Authors RSS Feed

noise()

noise() After Effects hidden gem of the week

CreativeCOW.net Adobe After Effects Tutorial


noise() – After Effects hidden gem of the week
Dan Ebberts Dan Ebberts
Sacramento, California, USA

©2004 by Dan Ebberts and CreativeCow.net. All rights are reserved.

Article Focus:
The After Effects expression language has a seldom-used random number generator that is really quite a gem. Dan Ebberts says “seldom-used” because he doesn't believe he's ever seen it used in a single expression he's seen posted on the internet. It’s not the easiest command to understand and the documentation is pretty sparse but once you get past that it’s very cool.

Download Movie

the objective


Before we get into how to use it, let’s set up a scenario where we might want to use it (if we only knew that it existed). Suppose you had a grid of dots and you wanted to generate an undualting 3D motion like the dots were attached to a flag waving in the wind or were floating on water. One way to do this would be to set up a grid of dots and then have a comp-sized layer of Fractal Noise below and have each dot’s z position related to the luminace of the Fractal Noise patten directly below the dot. Let’s say we want brighter areas of the noise to move the dots closer to the camera and the darker areas to move the corresponding dots away from the camera. As we animate the “Evolution” parameter of the Fractal Noise we would expect the dots to undulate as the underlying luminance vlaues change. Note that what we’re looking for is not independent random motion for each dot. We want it to appear as if the dots are connected to an undulating surface. That means that the position of each dot is related to that of its neighbor.


best laid plans


OK this sounds like a cool project – let’s get started. There’s just one problem. As you may have discovered, there’s no way (without the help of a plugin) to access pixel luminance values from an expression. There are some nifty plugins that will let you do this “Anarchy Toolbox” from Digital Anarchy has “Color Sampler”, “Expression Effects” from Bresnev Shu has “Color Analysis Node”, and Useful Things from Profound Effects also gives you access to the pixel color and luminance values. Each of these wonderful plugins provides you a way to solve our design problem (and much, much more). But in this very specialized, particular case (where we want to use fractal noise to generate an undulating motion) we’re going to be able to pull this off with the tools provided within AE’s expression language.


noise() to the rescue


The trick to all this is the “noise()” function. What this lets us do is create our own Perlin noise space (if you’re interested in the math, use Google to look up “Perlin noise” which is the basis of many fractal noise patterns). It gives us access to a 3D noise structure that extends in all directions. We can simulate moving through it in any direction. We won’t be able to see it like you can with Fractal Noise, but we’ll be able to see the affect it has on our dots. Picture it as a gigantic wispy fog bank that you can wander around in and take sample fog density readings wherever you are.

The noise() function accepts a single parameter that can have one, two, or three dimensions. It’s useful to visualize these as offsets in x, y, and z directions. If you supply a one-dimensional parameter the results of varying that parameter would be like moving along a straight line in our fractal noise environment. A two-dimensional parameter would be like moving around in a single plane of the noise space, and a three-dimensional parameter gives you access to the whole 3D space. The output is a number between 0 and 1 that is somewhat random, but has correlation to nearby points.

OK – so here’s the plan. We’ll set our dots up in a grid (actually, we’ll apply an expression that will allow our dots to position themselves in a grid - much less work). We’ll use each dot’s x and y position as the first two inputs to the noise() function. We’ll use the result of the noise() functin to calculate each dot’s z displacement based on the value of the noise field at that x/y location. We’ll use time as the third dimension of the input to noise() that will effectively move our plane throught the 3D fractal noise space. The result should be undulating dots.

So our position expression for each dot will be a combination of grid-positioning for x and y and a noise() component for z. Let’s tackle the grid part first. We’re going to set up a 10 x 10 grid of dots.


creating the grid




Start by creating a 640 x 480 comp several seconds in length. Then add a 30x30 solid layer. Make it 3D and set the quality to best. Make it a circle/dot by double clicking on the circular mask tool. Add this expression to the Position Property:

numRows = 10;
numCols = 10;

row = Math.floor((index - 1)/numCols);
col = (index - 1)%numCols;
x = col*width + width/2;
y = row*height + height/2;
xOffset = (this_comp.width - numCols*width)/2;
yOffset = (this_comp.height - numRows*height)/2;

[x,y,position[2]] + [xOffset,yOffset,0]

Now duplicate the “dot” layer 99 times. I do this by selecting the layer, hitting Ctrl+d 9 times, select all the dots and hit Ctrl+d nine more times. The dots should spread themselves out to fill in a 10x10 grid. Note that you can create any grid size you want by changing the “numRows” and “numCols” parameters and making the appropriate number of duplicates. If you want smaller dots, just start with a smaller solid – the expression will adjust.

At this point you might want to create a camera and position it so that you can see the grid on an angle so you’ll be able to clearly see motion in the z direction. I added a light for dramatic effect. Note – put the camera and light on the bottom of the layer stack, otherwise it will mess up the grid calculation, which relies on the layer index and expects layer 1 to be the first dot.


adding the undulations




Now that we’ve demonstrated that we can, in fact, generate a self-populating 10x10 grid of dots without too much trouble, we’re ready to add in the undulating part of the expression. Delete 99 of the dot layers so we’ll only have to modify one expression – then we’ll recreate the duplicates.

Here’ the modified expression:

numRows = 10;
numCols = 10;
xyCompress = 200;
speedCompress = 1;
amplitude = 100;

row = Math.floor((index - 1)/numCols);
col = (index - 1)%numCols;
x = col*width + width/2;
y = row*height + height/2;
xOffset = (this_comp.width - numCols*width)/2;
yOffset = (this_comp.height - numRows*height)/2;

z = amplitude*noise([x/xyCompress,y/xyCompress,time/speedCompress]);

[x,y,z] + [xOffset,yOffset,0]

Let’s take a look at what’s different. You’ll notice that we’ve added three new parameters at the top of the expression. The first one, “xyCompress” that will define how closely correlated the z position of adjacent dots will be. The larger this number is, the more related adjacent positons will be. In other words, larger values of “xyCompress” will give you a smoother undulation, smaller values will give you more chaotic undulation. The next new parameter is “speedCompress”. This will determine how fast we move through our fractal noise field. In practical terms, the larger the value of “speedCompress” the slower the undulation. The last new parameter is “amplitude”. This simply scales the output of the noise() function (which is normally between 0 and 1) to the range of z movement (in pixels) that we want in our undulation. In this case, we’ll get values between 0 and 100 pixels.

Finally, the lst new line of code – where all the action takes place – is the call to noise(). We feed it the x and y position of our dot (scaled by “xyCompress”) and the current comp time (scaled by “speedCompress”) and get a z offset that we multiply by “amplitude”. Then all we have to do is replace “position[2]” from our first expression with “z” and we’re done.

Create the 99 duplicates again and preview. If you did everything correctly, you should be rewarded with a nice 10x10 grid of undulating dots.


wrapping up


Once you get your brain wrapped around noise(), you start to see where it can come in handy to have access to a 3D noise field within the environment of After Effects expressions. Think about it. Natural effects like wind flowing through a field of grass or lilypads on a pond. The possibilities are endless. That’s my hidden gem of the week. 8^>

##Dan Ebberts

Feel Free to discuss this technique in the After Effects forum here at CreativeCOW.





Please visit our forums and view other articles at CreativeCOW.net if you found this page from a direct link.




Comments

Re: noise()
by Michael Sigmon
AMC Theaters uses an undulating wave as a background, if you've been to one of their theaters you'll see this before the trailers start. Then the undulating wave is disrupted like the wake left behind by a boat zipping through a body of water. I understand the concept, you'd modify the amplitude by the result of some other formula. I can kind of picture what the formula needs to do, but I'm sort of stuck trying to express that in script. Anybody have a hint?
Re: noise()
by Michael Sigmon
put the expression in an external file, have your solid's position read the external file and you can tweak the variables without deleting 99 layers, tweaking, and copying again.
-2


Related Articles / Tutorials:
Adobe After Effects
Imagineer mocha Pro 5 Plug-In for Adobe: An In Depth Review

Imagineer mocha Pro 5 Plug-In for Adobe: An In Depth Review

Imagineer mocha Pro 5 Plug-in for Adobe brings all the amazing features of the professional version of the mocha Planar Tracker directly into After Effects and Premiere Pro in the form of a plugin. In this in-depth review, After Effects tutorial guru Tobias Gleissenberger of Surfaced Studio will show you what you can do with this new plug-in, and discuss what he likes and doesn't like about the new update.

Tutorial
Tobias Gleissenberger
Adobe After Effects
After Effects 2015.3 - My Favorite Features

After Effects 2015.3 - My Favorite Features

Learn why you should upgrade to After Effects CC 2015.3 - 13.8.1 - a close and detailed look at the latest release of After Effects (August 2016). Roei Tzoref will be focusing on his favorite features that set this release apart from previous versions: Performance, Queue in AME, Lumetri Color new features, and more.

Tutorial
Roei Tzoref
Adobe After Effects
Advanced Masking in Adobe After Effects

Advanced Masking in Adobe After Effects

Some of the coolest stuff you can do inside of Adobe After Effects is only possible once you unlock the power of masks. Join After Effects whiz Tobias Gleissenberger of Surfaced Studio to learn about mask animation and interpolation, using the variable width feathering tool, managing mask modes and ordering, and more.

Tutorial
Tobias Gleissenberger
Adobe After Effects
Fixing Common After Effects Problems and Mistakes

Fixing Common After Effects Problems and Mistakes

Got problems using Adobe After Effects? Exported files too large, Expressions not working, mixing shapes and makes, modes/switches, selecting previews for layers vs. comps - Surfaced Studio's Tobias Gleissenberger shows you fast fixes for these and more!

Tutorial
Tobias Gleissenberger
Adobe After Effects
mocha AE Planar Tracker for Absolute Beginners

mocha AE Planar Tracker for Absolute Beginners

Want to learn how to create advanced visual effects? Learn how to use mocha AE to track your shot and add advanced visual effects to live action footage inside Adobe After Effects. mocha can help you track shots that would be hard to track using traditional 2D point or feature trackers because it is a PLANAR TRACKER. A planar tracker uses planes and textures to track as opposed to points or groups of pixels. This allows the tracker to stay on track even if your shot contains motion blur or a very shallow depth of field. mocha AE comes included with Adobe After Effects and is available since CS3 and there is no reason for you not to use this awesome tool to make it easier for you to track your shot, replace screens or rotoscope!

Tutorial
Tobias Gleissenberger
Adobe After Effects
How to Make After Effects Faster with Proxies

How to Make After Effects Faster with Proxies

Learn how to make Adobe After Effects faster by using PROXIES! A proxy is a placeholder that stands in place for a very large video file or image sequence in your project. You can easily create proxies for the large source files that you are using and After Effects will automatically link them to the item in your project panel.

Tutorial
Tobias Gleissenberger
Adobe After Effects
Stabilize & Smooth: mocha 5 Plug-in for Adobe & Avid

Stabilize & Smooth: mocha 5 Plug-in for Adobe & Avid

Imagineer Systems and Boris FX product specialist Mary Poplin shows you how to stabilize with the new mocha Pro 5 plug-in inside of Avid Media Composer, Adobe Premiere Pro and After Effects. This tutorial covers artistic stabilization, such as smoothing out camera movements or stabilizing around moving objects, completely locking down shots, and automatically replacing edge fill on planar backgrounds.

Tutorial
Mary Poplin
Adobe After Effects
Adobe After Effects Puppet Tool

Adobe After Effects Puppet Tool

Become a puppet master by learning how to use the Puppet Tool in Adobe After Effects! This intermediate-level tutorial from After Effects guru Tobias will show you how the Puppet Tool allows you to add joints and animations to bring life to any static image!

Tutorial
Tobias Gleissenberger
Adobe After Effects
How to Spawn A Clone in Adobe After Effects

How to Spawn A Clone in Adobe After Effects

Want to learn how to create a cool clone spawn effect in Adobe After Effects? Follow along with After Effects whiz Tobias from Surfaced Studio in this exciting new visual effects tutorial that combines green screen using Keylight, CC Vector Blur, the Liquefy Effect, CC Particle World, and much more, delivered in Tobias' inimitable style!

Tutorial
Tobias Gleissenberger
Adobe After Effects
Creating A Flame on Your Finger with After Effects

Creating A Flame on Your Finger with After Effects

It is easy to do some motion tracking and attach a basic stock footage element of fire onto your hands, but there is a little bit of work involved if you actually want to make it look good. In this intermediate tutorial by After Effects expert Tobias, you'll see how to use a fire stock footage element to set your thumb on fire! There are lots of useful tricks for null objects, expressions, and more in this tutorial that will help you create all sorts of other cool visual effects -- or set even more things on fire!

Tutorial
Tobias Gleissenberger
MORE
© 2016 CreativeCOW.net All Rights Reserved
[TOP]