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Planck.js

Planck.js is JavaScript rewrite of Box2D physics engine for cross-platform HTML5 game development.

Motivations

  • Taking advantage of Box2D's efforts and achievements
  • Developing readable and maintainable JavaScript code
  • Optimizing the library for web and mobile platforms
  • Providing a JavaScript-friendly API

Projects

Games

Game Development

Other Projects

Articles and Tutorials

Integration

Testbed Examples

See here for testbed examples.

Community

Updates and news: Twitter @Piqnt
Source code and issues: GitHub
Community discussions: Discord

Try it

To try Planck.js, simply add planck-with-testbed.js script to your HTML code and call planck.testbed(callback) with your code in callback. For example:

<html><body>
  <script src="//cdn.jsdelivr.net/npm/planck-js@latest/dist/planck-with-testbed.js"></script>
  <script>
    planck.testbed(function(testbed) {
      var world = planck.World();
      // rest of your code
      return world; // make sure you return the world
    });
  </script>
</body></html>

Check out Car example on JS Bin to try it in practice. Also see example directory for more testbed usage examples.

Install

CDN

Planck.js is available on jsDelivr.

NPM

npm install planck-js --save

API and Architecture

Planck.js includes Box2D algorithms without modification and its architecture is very similar to Box2D. However some internal changes and refactoring are made during rewrite to address differences between C++ and JavaScript.

Planck.js public API (see API Doc) closely follows Box2D API (see Resources), with the following differences:

  • b2 prefix is dropped from class names, for example b2World is now available as planck.World.
  • Method names are converted from UpperCamelCase to lowerCamelCase.
  • Definition classes/objects (BodyDef, FixtureDef, etc.) are replaced by inline JavaScript objects ({}).
  • Shapes are considered immutable and are not cloned when used to create fixtures.
  • Listener classes are replaced with simple functions.
  • World#on(eventName, listenerFn) and World#off(eventName, listenerFn) are added to add and remove event listeners. Currently supported events are:
    • 'begin-contact'
    • 'end-contact'
    • 'pre-solve'
    • 'post-solve'
    • 'remove-joint'
    • 'remove-fixture'
    • 'remove-body'

Resources and References

Following resources are recommended if you are interested in learning about Box2D/Planck.js's internal details.

Rendering and Integration

Planck.js core library does not include any graphics by default, which means you have several options:

  • Use Testbed, see Try it section to run release files in a web browser (or Development to debug testbed locally).
  • Use an existing renderer, see Integration examples.
  • Develop a renderer or integrate with a rendering library.

To create a renderer or integrate with a rendering library all you need to do is call world.step(timeStep) in each frame, and then iterate over world entities to draw or update them. You may also want to listen to world events to remove objects which are removed from the world. For example:

<script src="./path/to/planck.min.js"></script>
<script>
  var world = planck.World();

  // rendering loop
  (function loop() {
    // in each frame call world.step(timeStep) with fixed timeStep
    world.step(1 / 60);
    // iterate over bodies and fixtures
    for (var body = world.getBodyList(); body; body = body.getNext()) {
      for (var fixture = body.getFixtureList(); fixture; fixture = fixture.getNext()) {
        // draw or update fixture
      }
    }
    // request a new frame
    window.requestAnimationFrame(loop);
  })();

  world.on('remove-fixture', function(fixture) {
    // remove fixture from ui
  });
</script>

Development

For development, you can run testbed locally with a live build and try examples in example directory.

  1. Install git and npm

  2. Clone or download this repository

  3. Install npm dependencies:

     npm install
    
  4. Run testbed and open it in your web browser (see command-line output for URL to open):

     npm run testbed
    

Credits

Box2D is a popular C++ 2D rigid-body physics engine created by Erin Catto. Box2D is used in several popular games, such as Angry Birds, Limbo and Crayon Physics, as well as game development tools and libraries such as Apple's SpriteKit.

Planck.js is developed and maintained by Ali Shakiba.

TypeScript definitions for planck.js are developed by Oliver Zell.

License

Planck.js is available under the zlib license.

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2D JavaScript Physics Engine

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