![Box2D Logo](https://box2d.org/images/logo.svg)

# Build Status
[![Build Status](https://travis-ci.org/erincatto/box2d.svg?branch=master)](https://travis-ci.org/erincatto/box2d)

# Box2D

Box2D is a 2D physics engine for games.

## Contributing

Please do not submit pull requests with new features or core library changes. Instead, please file an issue first for discussion. For bugs, I prefer detailed bug reports over pull requests.

## Features

### Collision
- Continuous collision detection
- Contact callbacks: begin, end, pre-solve, post-solve
- Convex polygons and circles
- Multiple shapes per body
- One-shot contact manifolds
- Dynamic tree broadphase
- Efficient pair management
- Fast broadphase AABB queries
- Collision groups and categories

### Physics
- Continuous physics with time of impact solver
- Persistent body-joint-contact graph
- Island solution and sleep management
- Contact, friction, and restitution
- Stable stacking with a linear-time solver
- Revolute, prismatic, distance, pulley, gear, mouse joint, and other joint types
- Joint limits, motors, and friction
- Momentum decoupled position correction
- Fairly accurate reaction forces/impulses

### System
- Small block and stack allocators
- Centralized tuning parameters
- Highly portable C++ with no use of STL containers

### Testbed
- OpenGL with GLFW
- Graphical user interface with imgui
- Extensible test framework
- Support for loading world dumps

## Building
- Install [CMake](https://cmake.org/)
- Ensure CMake is in the user `PATH`
- Visual Studio: run `build.bat` from the command prompt
- Otherwise: run `build.sh` from a bash shell
- Results are in the build sub-folder
- On Windows you can open box2d.sln

## Building Box2D - Using vcpkg
You can download and install Box2D using the [vcpkg](https://github.com/Microsoft/vcpkg) dependency manager:

- git clone https://github.com/Microsoft/vcpkg.git
- cd vcpkg
- ./bootstrap-vcpkg.sh
- ./vcpkg integrate install
- ./vcpkg install box2d

The Box2D port in vcpkg is kept up to date by Microsoft team members and community contributors. If the version is out of date, please [create an issue or pull request](https://github.com/Microsoft/vcpkg) on the vcpkg repository.

Note: vcpkg support is not provided by the Box2D project

## Building for Xcode
- Install [CMake](https://cmake.org)
- Add Cmake to the path in .zprofile (the default Terminal shell is zsh)
    - export PATH="/Applications/CMake.app/Contents/bin:$PATH"
- mkdir build
- cd build
- cmake -G Xcode ..
- open box2d.xcodeproj
- Select the testbed scheme
- Edit the scheme to set a custom working directory, make this be in box2d/testbed
- You can now build and run the testbed

## Installing using CMake
You can use the CMake install feature to deploy the library to a central location that can
be accessed using:
```
find_package(box2d REQUIRED)
target_link_libraries(mytarget PRIVATE box2d)
```
You can build and install the library and docs using this command sequence (requires Doxygen):
```
mkdir build
cd build
cmake -DBOX2D_BUILD_DOCS=ON ..
cmake --build .
cmake --build . --target INSTALL
```
On Windows this tries to install in `Program Files` and thus requires admin privileges. Alternatively you can target another directory using something like this:
```
mkdir build
cd build
cmake -DBOX2D_BUILD_DOCS=ON -DCMAKE_INSTALL_PREFIX="C:/packages" ..
cmake --build .
cmake --build . --target INSTALL
```

## Documentation
- [Manual](https://box2d.org/documentation/)
- [reddit](https://www.reddit.com/r/box2d/)
- [Discord](https://discord.gg/NKYgCBP)

## License
Box2D is developed by Erin Catto, and uses the [MIT license](https://en.wikipedia.org/wiki/MIT_License).

## Sponsorship
Support development of Box2D through [Github Sponsors](https://github.com/sponsors/erincatto)