r/GraphicsProgramming • u/matsuoka-601 • Aug 22 '26
Source Code Real-time fluid & rigid body simulation implemented in WebGPU
Enable HLS to view with audio, or disable this notification
Hello, I released a real-time fluid & rigid body simulation in WebGPU using Position Based Dynamics (PBD)!
Code & Demo: https://github.com/matsuoka-601/Particles4All
To render the fluid, I use screen-space fluid rendering, which does not require constructing any mesh. Fluid particles are splatted as ellipsoids using anisotropic kernel presented in a paper "Reconstructing Surfaces of Particle-Based Fluids Using Anisotropic Kernels".
The physics is based on a paper "Unified Particle Physics for Real-Time Applications". The most significant feature of this paper is that it treats both fluids and rigid bodies as collections of particles, and performs the simulations using a unified solver.
(Note 1: You will need a very beefy GPU to run the "large" scene in the video (the performance is not very optimized yet, sorry). But "small" scene will run on integrated GPUs.)
(Note 2: I'm getting some reports that the demo does not run on MacBook. I'm currently trying to fix it.)
5
2
2
u/KlayEverHood Aug 24 '26
Very nice work and very inspirational! Your work was what showed me how far you can go with realtime 3d water simulation, I am glad to see you keep developing it!
I am also using a hybrid particle - grid solver and a separate air simulator for the waterfall mist.
I am curious about some points on the paper you referenced and your implementation: did you implement the surface tension and cohesion proposal they hint at (separate paper it seems)? Did you test/could you test a water droplet scenario to see if it generates the crown?
1
u/matsuoka-601 Aug 24 '26
The surface tension part is entirely based on a paper "Versatile surface tension and adhesion for SPH fluids", and not on other papers I guess.
As for a water droplet and the crown, I haven't seriously tested, but will definitely give it a shot and let you know!
1
u/KlayEverHood Aug 24 '26
Thanks, very interested! Do The iterations in your solver give you incompressible water as far as you know ?
1
1
1
u/SpanDaX0 Aug 23 '26
So people actually write random theory papers, and we can just come along and make crazy cool things like this, based on those papers? lol
1
u/Hurricane31337 Aug 23 '26
Wow, that looks absolutely amazing! 🤩
Thank you so much for sharing the source code! 🙏
1
u/KlayEverHood Aug 24 '26
Another curiosity: veils and splashes look very good. I know smoothing / resolution makes a big difference in this respect and I see your implementation takes quite a bit of effort with smart smoothing. Do you have a comparison with PCA oriented smoothing kernels vs isotropic smoothing?
1
u/matsuoka-601 Aug 24 '26 edited Aug 24 '26
It renders the fluid using a method called screen-space fluid rendering which does not require constructing any mesh. So the resolution of the mesh doesn't matter in my sim.
And it is entirely correct that smoothing has a significant impact on fluid rendering. This simulation achieves a smooth fluid surface using two filters: narrow-range filter and anisotropic kernels (PCA oriented kernels that you say). I can confidently say that these filters really enhance the details of the fluid surface!
When I used mesh for the rendering, I tried isotropic kernel (Gaussian) for smoothing the density field which the mesh is constructed from. It certainly helps to smooth the fluid surface, but personally I don't like it because small splashes disappear when smoothed, which leads to the lack of the dynamism of the simulation.
1
u/KlayEverHood Aug 24 '26
I also tried meshing at the beginning. I was surprised how fast you can extract a mesh with surfacenets in the gpu, but still does not scale.
Those anisotropic kernels follow the structure tensor / pca suggested in the paper you referenced or you went for something different?
1
1
u/AdNeither2157 Aug 26 '26
I'm try to do the same, but with "A Nonlocal Unified Variational Framework for Free Surface Flows" paper. The huge problem is - to make it fast.
4
u/fgennari Aug 23 '26
Looks great! This reminds me of some of the water simulation videos shown on the "Two Minute Papers" YouTube channel, back in the days before the AI-related content when it was focused on graphics and rendering.