Particle Force operator

The Particle Force operator allows you to influence particle motion using particles from another flow.

A common application of this effect is to upsample simulations, by driving a high resolution flow with the motion computed in a lower resolution flow.


Source Particles

  • Include this flow’s particles: the current flow’s particles will contribute forces.

  • Particle list: the input particle objects which will be used to derive particle forces.

  • Offset: the frame offset that the input flow object will be evaluated at.

  • Simulation groups: controls which particle simulation groups will be read from the input flow objects.

Particle Influence

  • Accelerator: the nearest-neighbor search algorithm used to find particles in the input flow that are closes to particles in the current event.

  • Absolute radius: the radius of each particle force will be set to a specific value.

  • Radius: the specific radius value.

  • Shape radius: the radius of each particle force will be set to each particle’s shape mesh radius.

  • Scale radius: the radius of each particle force will be set to each particle’s maximum scale dimension.

  • Multiplier: the multiplier to apply to shape/scale radius values.

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

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

When upsampling a simulation using the Particle Force operator, a good rule of thumb is to set “radius” to roughly 75-100% of the radius of the input particles, and to set “falloff” to roughly 50% of the radius of the input particles.

Force

  • Add/Blend/Replace: controls how forces computed by the operator will affect existing particle velocities.

  • Vel strength %: the percentage of the computed force to apply to particle velocity channels.

  • Spin strength %: the percentage of the computed force to apply to particle spin channels.

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

Test TRUE If

  • Max influence: particles will satisfy the TRUE condition if the combined max influence of input particles (based on the radius and falloff values) is less than this value.

Uniqueness

  • Seed: the seed value for all varied parameters.