FluidSim

FluidSim is a real-time fluid simulator built in C++ around Smoothed Particle Hydrodynamics (SPH), with the entire physics step — density, pressure, viscosity, and gravity — executing on the GPU as GLSL compute shaders backed by OpenGL Shader Storage Buffer Objects. Spatial hashing keeps neighbor queries at O(n), and particles render as instanced quads, color-coded by velocity: tight pressurized splashes read differently than slow, gas-like expansion at a glance.

The project was built collaboratively with Owen Poole, as much a GPGPU learning exercise as a fluid simulator. We took Sebastian Lague's fluid-simulation video as the starting point, read the same papers he referenced — Müller et al. (2003) and Monaghan (1992) — and derived the SPH math ourselves. His implementation is HLSL; we deliberately chose GLSL to learn a different shader pipeline rather than transliterate.

The sim is interactive: mouse forces push or pull particles with configurable strength and radius, and gravity, target density, and mouse force are all adjustable at runtime through an ImGui panel. Frame-stepping controls allow pausing and advancing one frame at a time for inspecting behavior.

The full control set, from the README:

Known limits, honestly stated: the simulation becomes unstable and can crash above roughly 300,000 particles (root cause never identified), it's 2D only, and further GPU-side optimizations like prefix-sum compaction were scoped out. The project isn't in active development — it stands as finished work, not abandoned work.