Behavior Controls

The Behavior controls are linked to the particle type selected in the Workspace panel. You need to add an emitter to access particle types.

For information on adding emitters, see Adding Particles to Clips.

Note: The Behavior controls (and the Particles controls) are not available when a particle type is not selected in the Workspace panel.

As explained for some of the emitter properties, the particle types have many properties in common with emitters. The reason for this is that an emitter has scaling factors that globally scale the corresponding properties for all its particle types.

About Property Units

The properties of particle types do not use "real world" units. For example, a size of 100 does not indicate 100 pixels, and a life of 50 does not indicate 50 frames.

One exception is Visibility, which uses percentage. Another is the over-life properties; they are scaling factors, so they use percentage also.

Instead, the properties of particle types simply use a range of values. For most of them, the range starts at 0. Negative values can be used for Weight, Spin, Weight Over Life, and Spin Over Life.

When a particle type property is set to the top of the range, the resulting value for the particles can still be very small or even 0 depending on the emitter scaling factor. For example, if the particle type Size property is set to 200 and the emitter Size property (which is a scaling factor) is set to 10%, the resulting particle size is very small.

Suppose you want particles that move very fast. If you have already set the Velocity property to 200, and it is not fast enough, you can increase the emitter Velocity property to effectively increase the velocity of the particles.

Note: Instead of entering a very large value, you can use the corresponding emitter scaling factor.

Basic Behavior Properties

The values of each basic property are applied when the particle is created; they have no effect on how the particle behaves over time.

Note: The only properties that determine how the particles behave over time are the over-life properties described in Over-Life Behavior Properties.

Life

Life is the length of time that a particle is "alive." A higher value means the particles live longer. (You cannot control exactly how many frames each particle lives.)

Note: A particle can be alive but not visible. Visibility, Life Opacity, and Size are three settings that can cause a live particle to be invisible.

Number

Controls how many particles are created. Higher values mean more particles are created.

There is a tendency to want to use a large number of particles when creating an emitter. Often, the effect is better with fewer particles. For example, the Simple Explosion library emitter needs fewer than 100 particles.

In most cases, it is not the number of particles that creates the effect you want, but the correct choice of particle shape and size. For example, if you want billowing smoke, use a particle shape that looks like a puff of smoke, make it big enough to see, and then use as few of them as possible.

In addition to Number, several variables influence the number of particles created per frame: the shape of the emitter (for example, point or line), the Number Variation value, the Single Particle property, emitter Number, and the frame rate of the footage that is input into the Particles operator.

Size

Determines how big the particles appear.

Note: Remember that since the Size property is a relative value, you are not setting the size as a number of pixels.

Velocity

Controls how fast the particles move away from the emitter.

Weight

Weight values can be negative or positive. A particle with zero weight is weightless. A particle with a positive weight falls (moves toward the bottom of the image) and a particle with a negative weight rises (moves toward the top of the image).

Spin

Spin values can be negative or positive. A positive spin means that the particles rotate clockwise. A negative spin means a counter-clockwise rotation. A value of 0 means no spin.

Motion Randomness

Determines how randomly a particle moves. Note that this property seems to "override" the Velocity and Weight settings; the random motion may cause particles to reverse direction.

Bounce

Applies only when a particle hits a deflector. Higher values mean more bounce. Note that when a particle has a zero bounce value, it may be able to pass through a deflector. For example, if a particle has a positive weight (so it falls) and a zero bounce, and it comes to rest on a deflector, it may eventually sink through the deflector. A very small Bounce value prevents this problem.

Visibility

Determines the transparency of the particles. A value of 0 means invisible and 100 means completely opaque. Some particle types look best completely visible (thick smoke, for example), but others look best with some transparency.

There is an additional opacity control for the particle type named Life Opacity. See Life Opacity for more information. The opacity of the shape image is also important. See Working with Particle Shapes for more information.

Note: Other than visibility and opacity, the size of a particle can make it invisible. That is, a particle with a very small size may not be visible.

Variation Behavior Properties

The basic properties are applied to every particle of the particle type that is created. If you want variety in a property, use the variation properties. Variation creates more realistic effects.

There are variation properties for eight of the basic properties. See Basic Behavior Properties for descriptions of the basic properties.

When a variation property is set to 0, there is no variation; every particle created has exactly the same value for the given property. Higher values of variation result in particles that have a wider variety of values for the given property.

For example, if the Size Variation property is set to 0, all new particles of this type have the same size (which is determined by the Size property). If Size Variation is set to a higher value, some particles are created larger than others. The basic size of the particles is still determined by the Size property.

Weight Variation and Spin Variation

The two basic properties that have both negative and positive values (Weight and Spin) have variation properties (Weight Variation and Spin Variation). However, these properties may not produce the results you expect if you use them with the basic properties.

Suppose you want the particles to spin in both directions (clockwise and counter-clockwise). You could set the Spin property so the particles have some spin, and then set Spin Variation to 10, for example.

However, this would make most (if not all) of the particles spin in one direction, depending on the values you set for each property. To make an approximately equal number of particles spin in each direction, leave the Spin value at 0, and only set a Spin Variation value.

Over-Life Behavior Properties

There are six over-life properties that change their corresponding basic properties over the life of a particle. The basic and variation properties only determine the values for the particle at the time the particle is created.

If you make the Size Over Life curve increase, for example, particles become larger as they get older.

Note: To use the over-life properties, you should use the Timeline in Graph mode because the best way to see and adjust these properties is with a curve and not at a single moment in time.

The over-life properties are scaling factors (in percentage), so they need to scale something. If the Size value is 0, for example, the Size Over Life values do nothing—the particles will not be visible.

Note: There is no Visibility Over Life property; you set this using the Life Opacity gradient. (Also, there are no Life Over Life and Number Over Life properties.)

Timeline Graphs

For the six over-life properties, the X-axis represents the particle's life in percentage. It does not matter how long the life is; 0% represents the birth (start of the particle's life), and 100% represents the death (end of its life).

This range of percentages is shown in the Timeline and has no correlation to the frames in the project. Keyframes can be added as usual, but you cannot add keyframes before 0% or after 100%.

Size Over Life, Velocity Over Life, Motion Randomness Over Life, and Bounce Over Life

These four properties all work the same way. The values along the Y-axis are scaling factors that are applied to the basic property.

For example, if the Size Over Life graph in the Timeline is a horizontal line at 200, the particle is the same size its whole life. If the horizontal line is at 80, the particle is still the same size its entire life, but it is smaller. However, if the Size Over Life graph is set to 80 at birth (0%) and 200 at death (100%), the size increases over the particle's lifetime.

Use the over-life properties together for complex effects. For example, to make particles appear to fly at the camera, increase the Velocity Over Life and Size Over Life toward the end of the life (usually more rapidly toward the end). Or increase Velocity Over Life and Motion Randomness to make the particles scatter as they get older.

Weight Over Life and Spin Over Life

Unlike the other four over-life properties, weight and spin have both negative and positive values. For both, the possible values range from –100 to 100.

If you set the birth value in the Weight Over Life graph to a negative number, and set the death value to a positive number, the particles are "light" at first (so they float), and they get heavier as they get older.

Note that a negative value in the Weight Over Life graph "reverses" the basic Weight value. For example, if the basic Weight value is positive (so the particle falls), setting the birth value in the Weight Over Life graph to a negative number makes the particle rise initially. Conversely, if the basic Weight value is negative (so the particle rises instead), then a negative initial keyframe in the Weight Over Life graph makes the particle fall.

Although the Timeline graphs for the six over-life properties are special, you can still use the regular Timeline features such as math operations to modify the graphs.

For example, you can reverse a complex Size Over Life graph horizontally to convert it from a growing effect to a shrinking effect. To do this, select the Size Over Life channel (to select all its keyframes), and click Math Operations. In the Math Operations dialog, select Reverse and click OK.

The Weight Over Life and Spin Over Life graphs can have negative values, so for these two graphs, you can also use the Negate math operation to flip the graph vertically along the 0 line of the Y-axis.

Over Life Properties on Behavior Panel

It is easier to use the Timeline to set the over-life properties; the fields are used more often to look at a snapshot of the over-life properties. However, you can shift an entire Timeline curve by adjusting the corresponding over-life field in the Behavior panel. The over-life controls ignore the Animate button; they always shift the curve. Also, the value that appears in each over-life field equals the value at the start of life (0%).