Rotation operator

The Rotation operator allows you to control particle orientations.


Orientation

  • Orientation type: the starting orientation value, prior to any further modifications.

Inherit previous: uses the current value of a particle’s orientation as the start value.

Random 3D: uses a random orientation as the start value.

Random horizontal: uses a random orientation around the world’s Z-Axis as the start value.

World space: uses a world-aligned orientation as the start value.

Travel direction: uses an orientation aligned to the particle’s velocity as the start value.

Custom vector direction: uses an orientation aligned to a custom data channel as the start value.

Surface align: uses an orientation aligned to the closest point on a scene object’s surface mesh as the start value.

Sibling align: uses an orientation aligned to the adjacent sibling of each particle, if such a sibling exists.

Facing average: uses an orientation directed towards the average position of selected input objects as the start value.

Facing closest: uses an orientation directed towards the closest input object as the start value.

Align to neighbors: uses an orientation directed towards the particle’s neighbors as the start value.

Closest edge on shape: the orientation will be derived from the vector defined by the closest edge on the particle shape to the particle location.

  • Affect particle shape orientation: controls whether a particle’s shape mesh orientation will be affected by the particle’s orientation change.

Disabling “affect particle shape orientation” can have a big impact on memory usage and performance, because each particle’s mesh will have to be manually adjusted in order to compensate for the particle’s orientation change.

  • X/Y/Z: controls the amount of offset applied to starting orientations, along each axis.

  • Divergence: controls the degrees of random divergence to apply to starting orientations.

  • Restrict diverg. to axis: restricts the amount of divergence applied to each axis.

Divergence Axis:
  • X/Y/Z: the amount of divergence to apply to each axis.

Vector/Target

  • Channel: the channel to derive the custom vector direction from.

Banking

  • Multiplier: the amount of banking to apply to starting orientations, around the particle’s travel direction.

  • Smooth: the amount of temporal smoothing to apply to banking values, based on changes to the particle’s travel direction over time.

Neighbors:

  • Radius: The particle neighbor search radius. Nearby particles within this radius will be considered neighbors.

Forward Vector:

  • Auto: the forward vector of the surface alignment transforms will be automatically computed based on the orientation of the up vector.

  • From surface: the forward vector of surface alignment transforms will be derived from the surface itself.

  • From velocity: the forward vector of surface alignment transforms will be derived from each particle’s velocity direction.

  • From particle: the forward vector of surface alignment transforms will be derived from each particle’s transform forward vector.

  • From world: the forward vector of surface alignment transforms will be defined in world space.

  • X/Y/Z: allows users to define world-space forward vectors, when “from world” is enabled.

  • Orthogonal: controls whether surface alignment orientations will be made orthogonal to the up vector.

Up Vector:

  • Vertex normal: controls whether the up vector of surface alignment transforms will be derived from the nearest vertex normal.

  • Face normal: controls whether the up vector of surface alignment transforms will be derived from the nearest face normal.

Simulation Groups

  • Simulation groups: controls which particle simulation groups nearby particles must match in order to be considered neighbors.

Objects

  • Object list: the list of input objects used for surface alignment or facing mode.

Sample

  • Sample: controls which sampler will be used for surface alignment.

Proximity influence

The proximity influence extends outwards from nearby objects

  • Distance: particles within this distance will be fully affected.

  • Falloff: the effect on particles beyond the base distance, but within this falloff distance, will diminish according to the inverse-square law.

Interpolation

  • Value: the amount to interpolate particle orientations from their previous value to the new value.

  • Variation %: the per-particle percentage of variation to apply.

In order to animate particles rotating towards a particular target orientation, set the operator’s timing to “continuous” and set the interpolation value to something less than 1. Smaller interpolation values will result in slower interpolation speeds.

Uniqueness

  • Seed: the seed value for all varied parameters.