LiquidFun is an open-source 2D physics engine developed by Google, based on Box2D. It extends Box2D's capabilities by adding fluid and soft body simulation, making it particularly useful for game development and interactive applications. LiquidFun is designed to be fast, portable, and easy to use.

Pros

• Adds fluid and soft body simulation to Box2D's solid body physics
• Optimized for performance, suitable for mobile and web applications
• Cross-platform compatibility (Android, iOS, Windows, macOS, Linux)
• Well-documented with extensive examples and tutorials

Cons

• Limited to 2D physics simulations
• May require more computational resources compared to simpler physics engines
• Learning curve can be steep for developers new to physics engines
• Not actively maintained (last update in 2017)

Code Examples

1. Creating a world and adding a body:

b2World world(b2Vec2(0.0f, -10.0f));

b2BodyDef bodyDef;
bodyDef.type = b2_dynamicBody;
bodyDef.position.Set(0.0f, 4.0f);
b2Body* body = world.CreateBody(&bodyDef);

b2CircleShape circle;
circle.m_radius = 0.5f;
body->CreateFixture(&circle, 1.0f);

2. Creating a particle system for fluid simulation:

b2ParticleSystemDef particleSystemDef;
b2ParticleSystem* particleSystem = world.CreateParticleSystem(&particleSystemDef);

b2ParticleGroupDef pd;
pd.flags = b2_waterParticle;
pd.position.Set(0.0f, 10.0f);
pd.shape = &shape;
particleSystem->CreateParticleGroup(pd);

3. Stepping the simulation:

float timeStep = 1.0f / 60.0f;
int32 velocityIterations = 6;
int32 positionIterations = 2;

world.Step(timeStep, velocityIterations, positionIterations);

Getting Started

1. Clone the LiquidFun repository:

   git clone https://github.com/google/liquidfun.git
   

2. Build the library using CMake:

   cd liquidfun
   mkdir build && cd build
   cmake ..
   make
   

3. Include LiquidFun in your project:

   #include <Box2D/Box2D.h>
   #include <Box2D/Particle/b2Particle.h>
   

4. Initialize a world and start using LiquidFun features in your application.