Adobe After Effects Tutorial: A Flock of Particles

Click here to download the files used in this tutorial.
View the finished effect here.

Particles can do more than just add sparkle to an effect. You can use them to blow things up; make fire, smoke, rain and snow; and generally make a controlled mess of things. But you can also use particles as controllers for individual elements in crowd scenes. In this tutorial, we'll show you how to use After Effects to corral a crowd, or rather a flock, of birds that fly across your scene without the hassle of animating each one.

There are a few concepts you'll need to become familiar with if you have not used particles software or After Effects particles before. With particles, you control the forces that govern their generation and motion, rather than the precise positions of the particles themselves. This will be a big change if you are used to controlling every last detail of your scene with keyframes. But the power of particles is precisely that you don't have to control each one.

The properties you can control generally include generator type, particle size, velocity, weight or mass and other real-world forces such as wind and gravity. These properties may be termed differently by various programs and plug-ins, but they all attempt to mimic how real-world particles behave. If this vocabulary sounds familiar, don't worry, this won't turn into your college physics class.

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Let's start by creating a new 10-second composition using the NTSC DV preset that we'll call Flock of Birds.

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Import a still image you'd like to use for your background. We'll use a photograph taken from a ridge that has plenty of open sky for our flock of birds, and we'll drag it into our timeline panel.

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Create a new solid layer and name it Bird Particles. It should now be the top layer in your timeline panel. Click on this layer and go to Effect>Simulation>Particle Playground.

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The effects panel should now be open, displaying the ten main Particle Playground parameters. The first four are really separate particle systems in themselves, and they give you an incredible amount of control over how you create and generate your particles. For now, we're going to focus on just the Cannon, which is on by default. If you want to later experiment with the other particle types, you will need to manually turn the Cannon off by setting the Particles Per Second from its default value of 60 to zero.

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To see what you've got so far, scrub your current time indicator to about three

Our birds will be flying from right to left, so we'll need to do a few things to our particle generator.

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First, let's rotate it to minus 90 degrees and move it to the upper left edge. Next, let's reduce the force of gravity to just a little more than zero, so our birds gently follow the contour of the sloping ridgeline. A value of seven should do it.

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If our flock were really flying on screen, it probably would not be bunched up as if the birds were being shot from a cannon. Fortunately, this is easy to fix by changing the Barrel Radius of the Cannon from zero to a value of 75. We can adjust this later when we have turned our particles into birds and get a sense of how much space we want between them, but for now this value will be close.