This tab contains settings that affect the physics of the particles emitted by the tool. These settings do not directly affect the appearance of the particles. They modify behavior like velocity, spin, quantity and lifespan instead.

The Random Seed slider is used to seed all of the variance and random number generators used by the tool when creating the particle system. Two pEmitter tools with exactly the same settings for all controls and the same random seed will generate exactly the same particle system. Changing the random seed will cause variation between the tools. Click on the Randomize button to automatically set a randomly-chosen value for the Random Seed.

This control is used to set the amount of new particles generated on each frame. A value of 1 would cause one new particle to be generated each frame. By frame 10, there would be a total of 10 particles in existence (unless Particle Lifespan was set to less than 10).

Animate this parameter to specify the number of particles generated in total. For example, if only 25 particles in total are desired, animate the control to produce five particles on frame 0-4, then set a key on frame five to generate zero particles for the remainder of the project.

This modifies the amount of particles generated for each frame, as specified by the Number control. For example, if Number is set to 10.0 and Number Variance is set to 2.0, the emitter will produce anywhere from 9-11 particles per frame. If the value of Number Variance is more than twice as large as the value of Number, it is possible that no particles will be generated for a given frame.

This control determines how long a particle will exist before it disappears or `dies'. The default value of this control is 100 frames, although this can be set to any value. The timing of many other particle controls is relative to the Lifespan of the particle. For example, the size of a particle can be set to increase over the last 80% of its life, using the Size Over Life graph in the Style tab of the pEmitter.

Like Number Variance, the Lifespan Variance control allows the Lifespan of particles produced to be modified. If Particle Lifespan were set to 100 frames and the Lifespan Variance to 20 frames, particles generated by the emitter would have a lifespan of 90-110 frames.

This provides the ability to specify from where the color of each particle is derived. The default setting is Use Style Color, which will provide the color from each particle according to the settings in the Style tab of the pEmitter tool.

The alternate setting is Use Color From Region, which overrides the color settings from the Style tab and uses the color of the underlying bitmap region.

The 'Use Color From Region' option only makes sense when the pEmitter region is set to use a bitmap produced by another tool in the composition. Particles generated in a region other than a bitmap region will be rendered as white when the 'Use Color From Region' option is selected.

This control determines whether or not particles can be `born' outside of the boundaries of the pEmitter region. By default, the value is set to zero, which will restrict the creation area for new particles to the exact boundaries of the defined region. Increasing this control's value above 0.0 will allow the particle to be born slightly outside of the boundaries of that region. The higher the value, the `softer' the region's edge will become.

These determine the initial speed or velocity of new particles. By default, the particle has no velocity and will not move from its point of origin unless acted upon by outside forces. A velocity setting of 10.0 would cause the particle to cross the entire width of the image in one step so a velocity of 1.0 would cause the particle to cross the width of the image over 10 frames.

Velocity Variance modifies the velocity of each particle at birth, in the same manner described in Lifespan Variance and Number Variance above.

This determines the angle at which particles with velocity applied will be heading at its birth.

This is as above, except this control determines the angle of the particles along the Z space axis (toward or away from the camera).

This menu control provides two options to help determine the orientation of the particles emitted. When the particles are spherical, the effect of this control will be unnoticeable.

The particles will be oriented as specified by the Rotation controls, regardless of velocity and heading.

The particles will be oriented in the same direction as the particle is moving. The Rotation controls can now be used to rotate the particle's orientation away from its heading.

These controls allow for Rotation of the individual particles. This can be particularly useful when dealing with a bitmap particle type, as the incoming bitmap may not be oriented in the desired direction.

Rotation XYZ Variance can be used to randomly vary the rotation by a specified amount around the center of the Rotation XYZ value to avoid having every particle oriented in the exact same direction.

These provide a spin to be applied to each particle at birth. The particles will rotate 'x' degrees each frame, as determined by the value of Spin XYZ.

The Spin XYZ variances will vary the amount of rotation applied to each frame in the manner described by Number Variance and Lifespan Variance documented above.

This tab of controls consists of 32 checkboxes that can be used to assign the particles generated by this pEmitter to a specific set.

These controls are useful when a pMerge tool is used to combine multiple pEmitter streams into one. Assigning sets allows individual groups of particles to be addressed by modifier tools like pDirectionalForce and pTurbulence. Sets can also be used to differentiate the particles created with a pSpawn or a pChangeStyle tool from their source particles.

To assign the particles created by a pEmitter to a given set, simply select the checkbox of the set number you want to assign. A single particle stream can be assigned to one or multiple sets.

The Style tab provides controls that affect the appearance of the particles, allowing the look and feel of the particles to be determined and animated over time. Please see 'Particle Styles' in the Particles chapter to learn more about styles.

The controls found under the Region tab are used to determine what portion of the image will actually generate particles. This has no affect on where a particle can go, only on where it is actually created or born. Only one region can be applied to any given particle emitter.

2D-type regions will produce particles along a flat plane in Z Space, usually positioned at Z = 0.0. 3D emitters possess depth and can produce particles inside a user-defined, three-dimensional region.

There are seven types of regions available, each with its own set of controls as described in the Particle Common Controls.