Developer Builds Unbounded Hash-Grid Fluid Simulation in VRChat, Up to One Million Particles
Developer Michael Moroz implemented a real-time hash-grid fluid particle simulation in VRChat. Because of the hash structure, the simulation is naturally unbounded—fluid can theoretically fill the entire virtual world—with a current cap of one million particles. The simulation runs locally; according to a repost, the author is ZibraAI's chief research engineer Mykhailo Moroz, and a 100k-particle version runs on any PC.
Confirmed
- The simulation is based on a hash grid, making it nearly unbounded in space and free from traditional fixed-grid limits
- Particle cap is set at one million, enough to fill a large area
- The project supports "manipulator" objects such as attractor spheres that gather fluid into a ball
- Gravity is adjustable: low gravity sends fluid flying, and reversed gravity behaves distinctively in unbounded mode
- Runs locally on the user's machine
- Rendering so far is only a "Mentos-style" particle effect; the author plans to keep improving isosurface rendering
- The author explained the technical choice: hash particle simulation beats sparse-tree grids—sparse trees need indirect addressing to find neighbors, while hash grids' only downside is hash collisions, and the bottleneck is latency, making them faster overall
Why it matters
- Million-particle unbounded real-time fluid simulation inside a social VR platform shows the upper bound of consumer-grade real-time graphics in open virtual worlds
- The author's first-hand hash-grid vs. sparse-tree analysis offers valuable practical guidance for unbounded particle simulation design
2026-09-10 ~ 2026-09-11 · 7 related posts
Primary sources
- Dev Implements Boundless Hash Grid Fluid Simulation in VRChat — Michael_Moroz_ ·
- Hash grid fluid sim in VRChat is boundless, dev runs 1M particles across the world — Michael_Moroz_ ·
- Why Hash Grids Beat Sparse Trees for Particle Simulation, From the Author — Michael_Moroz_ ·
- [source] Dev Implements Boundless Hash Grid Fluid Simulation in VRChat — Michael_Moroz_ · 2026-09-10
- Dev's real-time fluid sim handles 1M particles, gravity inversion and attractor objects — Michael_Moroz_ · 2026-09-10
- [source] Why Hash Grids Beat Sparse Trees for Particle Simulation, From the Author — Michael_Moroz_ · 2026-09-10
4 near-duplicate retellings: Michael_Moroz_ · Iri_146 · ZeroStateReflex · Michael_Moroz_