I’m using Houdini to extract physical properties from particle data.

Specifically, I need to capture particle trajectories and velocities during the simulation.

In dynamic solvers like FLIP and Pyro, how can I extract particle trajectories that are consistently aligned by unique particle IDs?

Also, since the Pyro solver isn’t based on a particle system but rather uses a velocity field, what is the recommended method to retrieve that velocity field data?

Any advice or guidance would be greatly appreciated

You can use Trail SOP or Particle Trail SOP to generate curve from point movements over time matching by i@id attribute if desired

For smoke you can advect particles within and use Trail SOP on those

Or to get traced lines within a velocity field on any single frame you can also use Volume Trail SOP