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Dynamics

Set attributes on a per particle basis

When you select a particle object, the Per Particle (Array) Attributes section of the Attribute Editor displays attributes you can set on an individual particle basis. By default, the following attributes are displayed:

The attributes provide different ways to control position or motion.

The position, velocity, and acceleration attributes offer a direct approach to controlling particle motion. The attributes rampPosition, rampVelocity, or rampAcceleration let you use a ramp texture to control the position, velocity, or acceleration. The mass attribute affects motion calculations resulting from another object’s dynamic influences on the particles, for instance, fields or collisions. The following pages introduce techniques for setting these and other per particle attributes.

If you add other per particle attributes to a particle object, for example, rgbPP or opacityPP, the attributes appear at the bottom of the Per Particle (Array) Attributes section.

Note Per particle attributes are unavailable in the Channel Box and Attribute Spreadsheet.

Techniques for setting per particle attributes

There are various techniques to set per particle attributes:

• Use the Component Editor to select individual particles in the particle object and assign values (see Set particle attributes with the Component Editor).
• Use a ramp texture to vary values (see Set particle attributes with a ramp texture).
• Create a creation or runtime expression to assign a unique value to each particle (see Expressions).

Note the following:

• You cannot key per particle attributes.
• The techniques above are listed in order of increasing complexity and versatility.
• Not all techniques are available for each attribute. To see which techniques are available, right click the box to the right of the attribute name in the Per Particle (Array) Attributes section of the Attribute Editor.
• If you set the position, velocity, or acceleration and use a ramp to set its counterpart ramp attribute, only the ramp value is used.
• To avoid unexpected results, do not set a combination of values for position, velocity, and acceleration.