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.

Please ensure you’ve enabled both spin and velocity caching in any referenced tyFlow objects! Otherwise those values won’t be read properly by the operator and you will get incorrect results.


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.