Using Particle Systems

Despite their sophistication, particle systems are easy to set up and simple to use. This section describes how to use pre-made particle systems from the Particle Emitters category of the Library. Afterward, this section explains how to create a simple particle system of your own.

Particle Systems and Layer Sizes

Particle systems often create particles that grow or move off the Canvas before they die. This can make the size of a layer or group much larger than that of the Canvas. Although the particles are not visible once they move off the Canvas (unless Show Full View Area is turned on in the View menu), they are still present in the project and are processed. If you apply a filter to a layer containing growing particles, or use that layer as a source object, it is recommended that you select the Fixed Resolution checkbox in the Group tab of the Inspector (available only when a group is the selected object). The Fixed Resolution parameter allows you to set the specific width and height of a group, cropping anything beyond those values. For more information, see Fixing the Size of a Group.

Using the Particle Library

The easiest way to add a particle system to your project is to use one of the presets in the Particle Emitters category of the Library. There are many types of particle effects to choose from. If you find one that is close to what you need, you can easily customize its parameters after you add it to your project. Particle systems are added to a project exactly like any other object.

Figure. Library showing Particle Emitters categories.
To add a particle system from the Library
  1. In the Library, click the Particle Emitters category.

  2. Click one of the particle subcategories, such as Nature, Pyro, SciFi, and so on.

  3. Select a particle preset in the Library stack.

    An animated preview of the selected particle emitter plays in the Preview area. While it is playing, you can drag the pointer around in the Preview area to see how the particle looks while in motion.

    Figure. Library Preview area showing particle emitter preview.

    Note: If the preview does not automatically start playing, click the Play button in the Preview area. To automatically play items selected in the File Browser or Library, choose Motion > Preferences (or press Command-Comma), then select “Play items automatically on a single click” in the File Browser & Library section of the General pane.

  4. When you find a particle preset you want to use, do one of the following:

    • Click Apply to add the selected particle system to your project at the center of the Canvas.

      Note: If Create Layers At is set to “Start of project” in the Project pane of Motion Preferences, the particle system is added at the first frame.

    • Drag the particle system into the Canvas to the position where you want it to appear.

    • Drag the particle system into a group in the Layers tab or Timeline layers list. The particle system appears at the center of the Canvas.

    • Drag the particle system to the track area of the Timeline. When you reach the frame where you want the new particles to start, release the mouse button.

    The new particle system layer appears in your project, composited against any other layers that you’ve already added.

Motion Blur and Particles

To achieve the optimal look for the following particle emitters, it is recommended that you enable motion blur in your project:

  • Jelly Bands

  • Light Transit 1

  • Light Transit 2

  • Light Transit 3

  • Light Transit 4

  • Rain Streaks

  • Silly String 1

  • Silly String 2

Note: To enable motion blur, choose Motion Blur from the Render pop-up menu (in the Status Bar), or choose View > Render Options > Motion Blur (or press Option-M).

Once you have added a particle system from the Library, the system acts exactly as it did in the Preview area. If necessary, you can edit a particle system’s Emitter parameters in the HUD to tailor them to your own use.

Note: You can only modify a particle system after it has been added to a project.

The HUD displays a selected particle system’s most essential parameters, including the size and number of particles that are created, how long they remain onscreen, how fast they move, and the direction and area in which they travel. Select an individual cell in the Layers tab or Timeline to edit its parameters in the HUD.

For more detailed information on using the particle HUD, see Customizing a Particle System Emitter. For more comprehensive information on customizing all of a particle system’s parameters, see Emitter and Cell Parameters.

Creating a Simple Custom Particle System

While Motion comes with a wide variety of particle system presets, many times you’ll want to create something completely new. Creating a particle system begins with selecting a layer in your project to use as the source for a cell within a new particle emitter.

You can use any layer in your project as a source for a cell in an emitter, including still graphics, animation or video clips, or shapes created in Motion. The layer you select when you create an emitter becomes the first cell in that particle system. In the Layers tab, cells appear as a sublayer under the emitter layer. The cell specifies the look of the actual particles generated in the Canvas.

Note: You can also use a group as the source for an emitter cell, but keep in mind that your project’s interactivity may slow drastically.

Figure. Canvas window showing a particle system, identifying the emitter and the particles.
To create an emitter
  1. Place a layer that you want to use to generate particles into your project.

    This example uses an image of a simple white circular gradient, such as the “basic blur” image located in the Library (in the Particle Images subcategory of the Content category).

    Figure. Canvas window showing a simple white circle object.
  2. Move the object in the Canvas to the location where you want the center of your particle system to be.

  3. Select the object, then do one of the following:

    • In the Toolbar, click the Make Particles icon.

      Figure. Make Particles icon in the Toolbar.
    • Press E.

Once an emitter is added to the project, the following occurs:

  • An emitter appears in the Layers tab and is selected.

  • A cell containing the image to be “particle-ized” appears underneath the emitter.

  • The original source layer (the cell source) is disabled.

    Note: Changes made to the original source layer, such as opacity or shearing, are respected in the particles even after the emitter is created.

  • In the Canvas, the emitter bounding box appears, which can be transformed using the onscreen controls.

  • The first particle appears in the Canvas in the same location as the original layer. Although it appears as if the particle is selected, the bounding box represents the emitter.

  • The Emitter HUD is displayed. If you have hidden the HUD, press F7.

    Note: For projects with a frame rate greater than 30 frames per second (fps), at times only the bounding box (not the first particle) may appear at the first frame of your project. Because Motion generates particles at a default rate of 30 per second, there is no guarantee that a particle will appear on every frame.

    Figure. Canvas window showing a particle system at frame 1.

    By default, the first frame of a new particle system (with a single cell) has one particle. If you play your project, additional particles are generated and emerge from the center of the emitter.

    By default, new cells emit one particle per frame in all directions (for 30 fps projects), and each particle moves 100 pixels per second away from the emitter over a lifetime of 5 seconds (150 frames in a 30-frames-per-second project).

    Figure. Canvas window showing particle system at frame 30.

    Note: The Initial Number parameter in the Emitter or Particle Cell tab of the Inspector allows you to change the default behavior so that a particle system begins with a burst of particles at the first frame. For more information, see Emitter and Cell Parameters.

The Predictability of Particle Systems

When you create a particle system or modify one of the parameters of an existing particle system, the path of each particle in that system is immediately calculated and predetermined. While the number and motion of particles may seem random, they are actually completely predictable based on that system’s parameters. Playing the same particle system twice with the same parameters results in exactly the same particle motion. This means that once you create a particle system that looks right, it is always the same.

Using Multiple Cells Within a Single Emitter

When you create a particle system from scratch, you don’t have to restrict yourself to using just one cell. You can create a particle system that emits many different kinds of overlapping particles by placing multiple cells inside of a single emitter in the Layers tab.

You can add as many cells as you want within a single emitter. Each cell has its own particle cell parameters that govern how particles from that cell are created. When selected in the Layers tab, each cell displays its own Particle Cell tab in the Inspector. Particle systems with multiple cells generate particles from each cell simultaneously, according to each cell’s parameters.

For an example of using multiple cells within a single emitter, see Example 2: Creating Animated Pixie Dust.

Additional cells can be created by either selecting multiple sources when initially creating the emitter, or by dragging additional source layers onto the emitter in the Layers tab.

Note: When multiple sources are used to create a particle system, the resulting emitter is positioned at the average of the sources’ position.

Customizing a Particle System Emitter

When you create an emitter, the particle system starts working according to the default parameters in its Emitter and Particle Cell tabs, located in the Inspector. You can use the Emitter HUD to easily change the most important of these parameters to suit your needs.

To display the HUD for a particle emitter
  • Select the emitter for which you want to display the HUD.

    The HUD appears when you select the emitter. If the HUD does not appear, press F7.

Using the HUD to Create a Simple Smoke Effect

In this example, use the Emitter HUD to create a smoke effect. Use the emitter created in Creating a Simple Custom Particle System A Blur image from the Content category in the Library will serve as the cell source.

Before making adjustments to the selected particle system, it may be helpful to move the playhead forward in the Timeline to a frame where you can see the particle system in full effect. That way, any adjustments you make are readily apparent.

Figure. Canvas window showing a particle system at frame 30.

The first thing you may notice in this example is that the size of each particle is so big that it’s hard to make out any texture in the particle system.

To modify the particles’ appearance using the Emitter HUD
  1. In the Emitter HUD, drag the Scale slider to the left to reduce every particle’s size so that the individual particles are more identifiable.

    Figure. HUD and Canvas window showing Emitter controls and the effect of reducing the scale.
  2. In the HUD, click anywhere along the outer edge of the emission control and drag to define a narrow segment that limits the range of the angle at which particles are created (the emission range).

    Both points defining the emission range rotate around the center of the emission control symmetrically, so your initial wedge points to the right. As you adjust the emission range, the particles rearrange themselves in the Canvas, enabling you to see the resulting effect.

    Figure. HUD and Canvas window showing the effect of limiting the emission range and direction.
  3. To make the particles drift upward, drag in the middle of the Emission Range segment, rotating the arrow counterclockwise until it points up and slightly to the right of the center control.

    Figure. HUD and Canvas window showing effect of changing emission direction.

    The emission angle of the particles updates in the Canvas to reflect the new setting in the HUD.

  4. Drag to lengthen the arrow so that it is approximately halfway between the center and the edge of the emission control to create a slowly drifting column of particles.

    Figure. HUD and Canvas window showing effect of changing emission speed.

    Remember: While the angle of the arrow controls the emission angle of the particles, the length of the arrow controls the speed of the particles. The longer the arrow, the faster the particles, and vice versa.

    At this point, the particles are all moving in the correct direction, but there aren’t very many of them (there isn’t much of a fire yet).

  5. Move the Birth Rate slider to the right to increase the number of particles created by the emitter.

    As you increase the birth rate, more particles are created, forming a nearly unified column of “smoke.” The particles move farther apart as they drift away from the emitter.

    Figure. HUD and Canvas window showing effect of changing the birth rate.

    As you can see, a single object can be used to create a credible column of smoke rising gently into the sky.

    While the HUD controls are quite powerful, the Emitter and Particle Cell tabs in the Inspector have many more parameters you can customize. For more information, see Emitter and Cell Parameters.

Emitter HUD Parameters

The HUD contains the most frequently used emitter controls that are necessary to modify a particle system’s size and shape. These parameters are a subset of those found in the Emitter tab of the Inspector. In 2D projects, the Emitter HUD contains a group of sliders and the emission control, which provides a visual way to manipulate three different particle system parameters: Emission Range, Emission Angle, and Speed.

Figure. HUD showing 2D emitter controls.

When 3D is enabled in the Emitter tab of the Inspector, the Emitter HUD offers additional 3D controls. In 3D, the emission control modifies the Emission Latitude and Emission Longitude parameters.

Figure. HUD showing 3D emitter controls.

When an emitter and the Adjust 3D Transform tool (in the Toolbar) are selected, the 3D Emitter HUD expands to display additional controls that allow you to transform the emitter in X, Y, and Z space, regardless of whether the group containing the emitter is 2D or 3D.

Figure. HUD showing emitter controls when Adjust 3D Transform tool is selected.

For more information on using the 3D transform controls in the HUD, see 3D Transform Tools.

For particle systems containing multiple cells, the Emitter HUD parameters simultaneously modify the effect of each cell’s parameters relative to one another. This means that for a particle system consisting of two cells with different scale values, changing the scale in the HUD resizes both cells simultaneously. For example, increasing the scale in the HUD by 200% does not change the scale of both cells to 200%, but resizes the cells relative to their original scale values.

Figure. Canvas window showing a particle system with two cells, each scaled relative to its original size.

For this reason, in emitters with multiple cells, the HUD parameters are displayed as percentages. When you modify the parameters of a single cell, the cell parameters are adjusted directly.

Figure. HUD showing emitter controls.
  • Birth Rate: A slider that defines how many particles are created every second.
  • Life: A slider that defines how long each particle remains onscreen (in seconds) before disappearing from existence.
  • Scale: A slider that defines the size of each particle, relative to the original size of the cell.
  • Emission Control: A graphical control that lets you modify several parameters.
    • Emission Range (2D only): Drag the two points on the outer ring of the graphical emission control to define the range of degrees at which particles are generated. In other words, the Emission Range parameter defines the size of the “slice” of the pie graph that the particles fill when generated.
    • Emission Angle: Drag inside the emission control to change the direction in which particles are emitted, inside the area defined by the Emission Range.
    • Speed (2D only): Drag inside the emission control to shorten or lengthen the arrows to define how quickly particles move away from the emitter.

      Use the following modifier keys to more precisely manipulate the graphical emission control in the HUD:

      • Shift (while adjusting Angle): Restricts angles to 45 degree increments.
      • Shift (while adjusting Range): When working with a 2D emitter, restricts to 22.5-degree increments.
      • Command: When working with a 2D emitter, adjusts Angle only.
      • Option: When working with a 2D emitter, adjusts Speed only.
  • Emission Latitude/Emission Longitude Control (3D only): When using a 3D particle emitter (when the 3D checkbox is selected in the Emitter tab of the Inspector), the emission control of the HUD lets you modify the Emission Latitude and Emission Longitude parameters.
    Figure. HUD showing 3D emitter controls.

    Drag the sphere in the center of the circle to modify the emission direction (in degrees latitude and longitude) of the particles. You can also enter specific values in the Emitter tab of the Inspector.

    Figure. HUD showing 3D emission control sphere rotated and offset.

    Drag the Emission Range slider (above the sphere) to define the range of degrees at which particles are generated. In other words, this control defines the size of the cone that the particles fill when generated in 3D space.

    Figure. HUD showing 3D emission control with reduced Emission Range.

Particle Emitters and the Properties Tab

Emitter parameters can be modified in the Properties tab of the Inspector like any other object in Motion. The following sections briefly discuss using some of the parameters in the Properties tab with a particle system (not all parameters in the Properties tab are discussed). For more information on the Properties tab parameters, see Parameters in the Properties Tab.

Note: When a particle cell is selected, only the Timing parameter appears in the Properties tab of the Inspector. This allows you to control the In and Out points of the particle cell.

Important: Some operations that can be performed in the Properties tab, as well the application of certain filters or a mask, cause a group to be rasterized. For more information, see About Rasterization.

Transform Parameters

As a particle system plays, the cells in the system are duplicated, according to the parameters for that system, to create each individual particle in the Canvas. Because all particles emerge relative to the position of the emitter (because the emitter can be a point, a circle, geometry, a sphere, and so on), changing the emitter’s position in the Canvas also changes the position of every particle in that system.

Figure. Canvas window showing a particle system moved as a contained system.

The exception to this is if the emitter’s position is animated using a behavior or keyframes. In this case, particles emerging from the emitter’s position at each frame continue to move relative to that position, regardless of changes to the emitter’s position in subsequent frames. This results in a trail of particles following the path of the emitter.

Figure. Canvas window showing an animated particle system.

The Attach to Emitter parameter in the Particle Cell tab of the Inspector modifies this behavior. When set to 0%, the particles are completely independent of the emitter. When set to 100%, the particles try to keep up with the position of the animated emitter. Depending on any applied behaviors, such as Drag, the particles may not be able to keep up with the emitter.

Modifying an emitter’s other transformation parameters (Rotation, Scale, Shear, and Anchor Point) changes the distribution of particles from that emitter and transforms each particle. For example, if you create an emitter, then modify its Shear parameter, the distribution of the emitted particles changes to reflect the new plane of the emitter, and the particles are sheared along the same plane.

Figure. Particle system with Shear effect applied.

Blending

Any changes you make to the opacity or blend mode parameters for an emitter are applied to the particle system as a whole—the result of the emitter is blended into the scene. For more information about blend modes, see Using Blend Modes. For more information about the Preserve Opacity setting, see Preserve Opacity Option.

Note: Within the emitter, the particles can be blended additively or normally (using the Additive Blend checkbox).

Lighting

A 2D or 3D emitter can interact with lights in a 3D project. As with all layers, the Shading pop-up menu (in the Lighting controls in the Properties tab of the Inspector) must be set to On or Inherited for the lights to affect the particles. For more information on using lights, see Lighting.

Shadows

A 2D or 3D emitter can cast and receive shadows in a 3D project. If the 3D checkbox is selected in the Emitter tab of the Inspector, Render Particles must be set to In Global 3D (Better) for particles to cast shadows. For more information on using shadows, see Shadows.

Reflections

A 2D or 3D emitter can cast reflections in a 3D project, but only a 2D emitter can receive reflections. For more information on using reflections, see Reflections.

Note: When the 3D checkbox in the Emitter tab of the Inspector is selected, the Reflections parameter does not appear in the Properties tab.

Drop Shadow

Drop shadows can be applied to a 2D particle system. When the Drop Shadow parameter is enabled for the source object (in the Properties tab in the Inspector), each generated particle appears with a drop shadow. For more information on working with drop shadows, see Drop Shadows.

Note: This parameter is not available with the Box or Sphere emitter shapes, or when the 3D checkbox is selected in the Emitter tab of the Inspector.

Timing

Once you create a particle system, its duration can be as long or short as necessary, regardless of the duration of the original layers used to create the particle system. The duration of a particle system is defined by the duration of the emitter object. Changing the In or Out point of an emitter in the Properties tab, Timeline, or mini-Timeline changes the duration of the entire particle system.

By default, particles are generated by every cell in a system over the entire duration of the emitter. The duration of each individually generated particle is defined by the Life parameter of the cell that generated it, and not by the duration of the cell itself.

The duration of the cell actually controls the duration over which new particles are generated. You can change a cell’s duration by dragging either its position or its In and Out points in the Timeline. In this way, you can adjust the timing that defines when each cell’s particles emerge.

Figure. Timeline tab showing emitter with varied cell durations.

For example, you can create a particle system that simulates an explosion by offsetting the appearance of three different types of particles. First, dense white particles emerge from the center. Half a second later, more diffuse orange particles appear around a larger area. One second after that, small sparks emerge from underneath both of these layers as they fade away.

Figure. Canvas window showing three-stage explosion.

You can offset a cell in the Timeline or mini-Timeline to start before the emitter. This creates a “preroll” in which the particle simulation starts before the particles are drawn.

For more information on adjusting the timing of layers in the Timeline, see Using the Timeline.