nikolausrauch / 2d-fluids

Proof of concept implementations of different fluid dynamic solvers in C++

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This repository contains proof-of-concept C++ implementations of different fluid dynamics solvers in 2D.
The goal is to provide minimalistic and straightforward implementations, emphasizing ease of understanding.
I decided to keep simulation code mostly independent (single file), which means that routines are at times duplicated (e.g. SPH density estimation, eos, boundary particles, ...).

Features

• Methods
  • WCSPH: Weakly Compressible SPH
  • PCISPH: Predictive-Corrective Incompressible SPH [Solenthaler 2009]
  • PBF: Position Based Fluid [Macklin 2013]
  • PF: Projective Fluids
  • IISPH: Implicit Incompressible SPH [Ihmsen 2013]
  • DFSPH: Divergence-Free SPH
  • FLIP: Fluid Particle in Cell
  • Stable-Fluid: Eulerian based Fluid
• Utility
  • 2D-Viewer with OpenGL2 and ImGui/ImPlot (standalone repo)
  • Minimal Performance Monitoring
  • Hash-Grid Nearest Neighbor Search
  • Uniform-Grid Nearest Neighbor Search
  • Minimalistic Generic Scene Description

Minimal Example

Scene setup is independent of the used simulator. An instance of Scene provides an interface to construct geometry (Box, Circle) that can either be a boundary or fluid body (currently no dynamic boundaries).
The simulator (WCSPH, PCISPH, PBF, IISPH) initializes its data (e.g. fluid and ghost particles) from the description via void Simulation::create(const Scene&).

/* scene description */
Scene desc;

/*left, right, bottom boundary*/
desc.add(Scene::Box{ {-5.00f, -3.50f}, { 5.00f, -3.25f}, Scene::eType::BOUNDARY });
desc.add(Scene::Box{ {-5.00f, -3.25f}, {-4.75f,  8.00f}, Scene::eType::BOUNDARY });
desc.add(Scene::Box{ { 4.75f, -3.25f}, { 5.00f,  8.00f}, Scene::eType::BOUNDARY });

/* fluid */
desc.add(Scene::Box{ {-4.72f, -3.23f}, { 4.73f,  0.00f}, Scene::eType::FLUID_BODY });
desc.add(Scene::Circle{ {0.0f, 3.5f}, 0.75f, Scene::eType::FLUID_BODY});

/* simulation handler (Implicit Incompressible SPH) */
IISPH simulation;
simulation.timeStep = 1.0 / 240.0f;
simulation.stepPerFrame = 1;

/* load scene (initialize fluid and boundary particles) */
simulation.create(scene);

/* solve dynamics -> time += stepPerFrame*timeStep */
simulation.update();

iisph_waterdrop.mp4

📚 Useful Resources

Eurographics Tutorial - Koschier et al. 2019
SPH Fluids in Computer Graphics - Ihmsen et al. 2014
Fluid Engine Development - Doyub Kim
SPlisHSPlasH - Jan Bender