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