In this group of tutorials, we will study a Motion particle system starting with a simple circle shape and, as we progress, we will take a look at the ways we can customize our particle system.

But first we need to introduce a few new words: particle system, cell, cell source, particles and emitter. A particle system is a special and very customizable type of animation. One popular example of a particle system is a snowfall. If you have seen a holiday cartoon with falling snow, that falling snow is created with a particle system.

There are two main parts to a Particle System. One is the Cell, which is the layer in the Layers panel that will be duplicated. In our snowfall scene, the circle on the Cell layer is the prototype for our particles and the Cell Source is the small circle that we will draw on the screen. The particle system will make many snowflakes. Each snowflake is called a Particle and is "born" or placed on the screen. Once these particles are born, they begin to move down the screen simulating a natural snowfall animation.

The creation and animation of these particles are controlled by the Emitter, which has many parameters that we can customize. For example, we can tell the Emitter how many duplicates to create, how fast to create them and how long the duplicates "live" or remain on the screen. We can also control the prototype as to the color, opacity and many other parameters.

The best way to understand the parts of a particle system is to take a look at one. Our first step will be to draw a small circle on an empty layer in an empty Motion^R project.

1. Start a new Motion project, which will have one empty Group layer by default.
   
   
2. Rename the Group layer to 'Snow'.
   
   
3. With the Snow layer selected, draw a small circle with the Circle tool about 10 pixels and at the center of the Canvas. You will get a new sublayer in the Snow group named Circle in both the Layers pane and the Timeline. The layers in the Timeline extend to the end, so the circle will be on the screen for the entire duration.
   
   At this point, we have one circle shape on the Canvas. Let’s tell Motion that we want this shape to be the Cell Source for the Cell in our particle system.
   
   
4. With the Circle shape sublayer (below the Snow group layer) selected, click Object - Make Particles. You will see that the original Circle shape layer, the Cell Source, is moved to the bottom of the Layers pane and the visibility of this layer is turned off.
   
   

Why did Motion turn off the original circle? The Emitter will be creating numerous copies of the original circle and moving them around the Canvas. If the original circle (cell source) were visible, it would not move as part of the particle animation. In fact, it would not move at all. So we really don’t need the original shape to be visible.

You will also notice that we have two new sublayers added to the Snow group, which are the Emitter and another Circle layer. The Emitter layer is the control for our particle system and the new Circle layer is the Cell and the item that will be duplicated as particles in our particle system. These new layers are also added to the Timeline.

If you play the animation, you should see many circles, or snowflakes, appearing and moving over the screen. But they are not falling like snow. So we would need to change some of the parameters.

Note: In this tutorial, we used a circle shape as the Cell Source for our particle system. However, you can also use text, clips, images and image sequences.

Tutorial Example:


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