Spin Operator

Click a Spin operator in an event or add a Spin operator to the particle system and then select it.

The Spin operator gives an angular velocity to particles in an event, with optional random variation. Spin is applied once per event per particle, except when using the Speed Space Follow option; however, the settings can be animated.

To simply specify particle orientation, use the Rotation operator.

Interface

The user interface appears in the parameters panel, on the right side of the Particle View dialog.

Spin Rate: The rate of revolution in degrees per second.
Variation: The maximum amount, in degrees per second, by which the spin rate can vary. The actual variation is calculated once, at random, for each particle.

Spin Axis group

Spin Axis drop-down list: The Spin Axis setting includes options that let you apply the spin on a random or specific axis, with optional random variation of the spin axis. Default=Random 3D.

Random 3DSpins each particle about an arbitrary, random 3D axis.
World SpaceThe spin axis is specified in the world coordinate space.
Use the X/Y/Z settings to specify the spin axis.
Particle SpaceThe spin axis is specified in the local coordinate space of each particle.
Use the X/Y/Z settings to specify the spin axis.
Speed SpaceThe coordinate space for particle orientation is determined by the particles' direction upon entering the event.
The X axis is aligned with the particle direction, while the Z axis is perpendicular to the X axis and is pointed upward with respect to world space as much as possible.

Use the X/Y/Z settings to specify the orientation for all particles.
Speed Space FollowThe coordinate space for particle orientation is determined by the particles' direction throughout the event. Use this option to allow particles that change direction during the event to keep the spin axis aligned with their direction.
The X axis is aligned with the particle direction, while the Z axis is perpendicular to the X axis and is pointed upward with respect to world space as much as possible.

Use the X/Y/Z settings to specify the orientation for all particles.

X/Y/Z: Use these to set the spin axis. Unavailable for the Random 3D option. Default=0,0,1. Range=–1.0 to 1.0.

To specify a single axis, set the corresponding parameter to any nonzero value, and the others to 0. A negative value flips the axis, and reverses the direction of rotation. The numeric values come into play when you give more than one axis a nonzero value, in which case their effect is relative to one another. For example, if you want the spin axis to be oriented halfway between the positive X and Y axes, you would set X and Y to the same positive amount. The actual value doesn't matter. Similarly, to set the spin axis to 30 degrees (1/3 of the angle) from the X axis to the Y axis, you'd set the Y value to twice that of the X value. For example, X=0.2 and Y=0.4, or X=0.5 and Y=1.0.
Divergence: Defines the range of variation (in degrees) for spin-axis orientation. The actual deviation is calculated at random within this range. Unavailable for the Random 3D option. Default=0. Range=0 to 180.

Uniqueness group

The Uniqueness setting affects the randomization of spin rate variation, spin axis with the Random 3D option, and Divergence with the other options.

Seed: Specifies a randomization value.
New: Calculates a new seed using a randomization formula.