I just found out about Voronoi particle tracking so i'm definitively not an expert. I just want to share what I have found to help others on there journey.
The author of the posted Shadertoy examples has a blog where he talks about it: https://michaelmoroz.github.io/Reintegration-Tracking/
Some papers that are talking about it are not behind a paywall (anymore) https://core.ac.uk/download/pdf/11143248.pdf and https://www.cs.rochester.edu/u/kautz/papers/voronoi-tracking.pdf
This was shared on the sharetoy facebook group:
"For those who would like to understand the magic principle behind Voronoï particle tracking, I commented & refactored 2 different great shaders:
These shaders implement to very different ideas:
- 1: explicit: introduce an intermediate Voronoï structure to track particles closest to the pixel (RGBA = 4 ids).
- 2: implicit: try to store particle of pos(x,y) as close as possible to location (x,y) in the buffer, by smart slow resorting along simulation.
( Of course you might loose a particle from time to time since collisions are not managed - even if not supposed to occurs in incompressible fluids some do happen, thus some "repopulate void" slow particle creation. + some redundancy in neighborhood thanks to the Voronoï areas, and/or storing 4 partics in RGBA )."