kotsoft

Thanks! With 3D the main challenge might be visualizing the layers separately. Ideally each of the phases would have some kind of metaball effect and also be transparent and even refract. Will be pretty tough to do and will have to fight with uncanny valley effect.

Sometimes for sandbox I feel like 2D can be more fun because people can target particles they interact with better.

Maybe WebXR will be good for the 3D version.

Yeah agree. The objective was more to make a physics toy that would run on single core on a phone than something for actual scientific or industrial use. I could add additional iterations or do pressure projection but then there would be complaints about it being slow & choppy.

There are also some large density ratios between the materials which further increased the difficulty, and would also increase the number of pressure projection iterations on a grid. I tried to simulate buoyancy without cheating (e.g. giving different materials different acceleration to gravity)

Yeah, pretty much this, I've experimented with putting on the GPU a bit but I would say particle based is 3x faster than a multithreaded & SIMD CPU implementation. Not 100x like you will see in Nvidia marketing materials, and on mobile, which this demo does run on, GPU often becomes weaker than CPU. Wasm SIMD only has 4 wide but the standard is 8 or 16 wide on most CPUs today.

But yeah, once you need to do graphics on top, that 3x pretty much goes away and is just additional frametime. I think they should work together. On my desktop stuff, I also have things like adaptive resolution and sparse grids to more fully take advantage of things that the CPU can do that are harder on GPU.

The Wasm demo is still in its early stages. The particles are just simple points. I could definitely use the GPU a bit more to do lighting and shading a smooth liquid surface.

You actually can adjust the settings for this. In settings>simulation, instead of sameRestDensity being 8 make it 0 and make it higher for diffRestDensity. I recommend doing it with low gravity as well (you can get zero g by clicking enable accelerometer on computers without accel)

Thanks! I am definitely working on bringing more to the WASM world. I'd begun experimenting with 3D and multithreading and then last week decided to circle back to the 2d demo and polish it up a bit more.

With keyboard there are also the shortcuts: 1-4 to emit the different materials a/r to attract repel from mouse x/c to rotate a bit

This is still the same kind of simulation, based on the Particle-based Viscoelastic Fluid Simulation paper. I updated it to use Wasm SIMD more fully with the help of Clang Vector Extensions, Compiler Explorer and Wasm Analyzer. Compiler explorer to play around with patterns and Wasm Analyzer to double check the final compilation.

Thanks. It's a WebAssembly simulation so mostly CPU and very light on the GPU because it's just drawing points. It will actually run on mobile too with multitouch.

I'm not sure if the between layers thing might be a similar thing to when bubbles show up on the sides and bottom of a glass of water. Some of the bubbles are also staying because once it's settled down, there isn't enough action to cause them to pop. The constant associated with the surface tension in the sim can also be turned down.