The free Particle Illusion 2021 from Boris FX is part of the Continuum visual effects plugin suite.
The standalone version can be used with any compositing application, including After Effects, Fusion, and Nuke. An important nuance is the lack of Mocha planar tracking, but otherwise it’s a pretty full-featured product.
In the Particle Illusion 2021 update, like the commercial version that was updated last year, the main changes are the ability to emit particles in both 3D and 2D. Existing 2D particle systems can be converted to 3D with a single click.
Other changes include the ability to connect particles with lines to create animated graphics effects, turbulence controls for particle motion, and over 20 new particle presets.
Particle Illusion 2021 is available completely free for Windows 7 and above and macOS 10.13 and above. A $295 premium Continuum filter for After Effects, DaVinchi Resolve and Fusion, Media Composer, Nuke, Premiere Pro and Vegas Pro is available in the commercial version of the product.