WebGL shader for mixed Eulerian and Lagrangian fluid simulation

Live demo at <ahref="http://git.amandaghassaei.com/FluidSimulation/"target="_blank">git.amandaghassaei.com/FluidSimulation/</a>

<imgstyle="width:100%"src="img.png"/>

This simulation solves the <ahref="https://en.wikipedia.org/wiki/Navier%E2%80%93Stokes_equations"target="_blank">Navier-Stokes equations</a> for incompressible fluids in a GPU fragment shader.

I implemented <ahref="https://en.wikipedia.org/wiki/No-slip_condition"target="_blank">no-slip boundary conditions</a> at the borders to keep the fluid contained within the bounds of the screen.

To increase performance, I solved for the velocity vector field of the fluid at a lower resolution than I used to compute the visualization of fluid flow; I used bilinear interpolation to smooth out artifacts caused by this speedup.

I've also added 160,000 <ahref="https://en.wikipedia.org/wiki/Lagrangian_particle_tracking"target="_blank">Lagrangian particles</a> on top of the simulation -

these particles are rendered using <ahref="https://threejs.org/"target="_blank">threejs</a>, but their positions are computed on the GPU.

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<b>Instructions:</b> Click and drag to apply a force to the fluid. Over time, the colored material in the fluid will dissipate:

<imgstyle="width:100%"src="img2.png"/>

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To learn more about the math involved, check out the following sources:<br/>

<ahref="https://pdfs.semanticscholar.org/84b8/c7b7eecf90ebd9d54a51544ca0f8ff93c137.pdf"target="_blank">Real-time ink simulation using a grid-particle method</a> - mixing Eulerian and Lagrangian techniques for fluids<br/>

<ahref="http://http.developer.nvidia.com/GPUGems/gpugems_ch38.html"target="_blank">Fast Fluid Dynamics Simulation on the GPU</a> - a very well written tutorial about programming the Navier-Stokes equations on a GPU.

Though not WebGL specific, it was still very useful.<br/>

<ahref="http://jamie-wong.com/2016/08/05/webgl-fluid-simulation/"target="_blank">Fluid Simulation (with WebGL demo)</a> - this article has some nice, interactive graphics that helped me debug my code.<br/>

<ahref="http://www.dgp.toronto.edu/people/stam/reality/Research/pdf/ns.pdf"target="_blank">Stable Fluids</a> - a paper about stable numerical methods for evaluating Navier-Stokes on a discrete grid.<br/>

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By <ahref="http://www.amandaghassaei.com/"target="_blank">Amanda Ghassaei</a>, code on <ahref="https://github.com/amandaghassaei/FluidSimulation"target="_blank">Github</a>.