I don’t see the NearestParticle mentioned anywhere.
The correct approach would be:
*Create a NearestParticle operator.
*Drag from Particles input to create InputParticles and pick the PRT Hair.
*Drag from Position input to create a Position inputChannel.
*Click the button Add Particle Query in the NearestParticle to add a ParticleQuery connected to the same input nodes.
*Pick the Tangent channel, output to Velocity, multiplied by some factor.
Without the Nearest Particle, you cannot tell the ParticleQuery the index of the particle to query.
Alternatively, you can
- Create a Stoke>PVelocitySplat operator
- Drag from input sockets to create InputParticles and Position inputs.
- Enter manually “Tangent” in place of the “Velocity” property to expose the Tangent channel.
- Uncheck the >Remove Divergence option to get the field verbatim as defined by the particles. If you leave it on, you will get an “uncompressible fluid” field
- Connect the Tangent output multiplied by some factor to the Velocity output.
Both do about the same, but the PVelocitySplat produces a cleaner field that gives you more options. However, it might be a bit slower.
To get that data into FumeFX, you can then create a Field Force spacewarp (which has its own multiplier, but it creates an acceleration field and not a velocity field, so it will behave differently). Or you can export the field as FXD files.