Newton's Poleless Magnet


    1.2.0 • Public • Published


    Install for Cocos Creator 3D

    Install module via npm for cocos creator 3d: usage : npm install github:cocos-creator/ammo.js#cocos-master --save

    Compile pipeline

    1. ./
    2. replace code of builds/node/ammo.js.fix
    3. npm run uglifyjs



    Example code to give you an idea of the API:

    ammo.js is a direct port of the Bullet physics engine to JavaScript, using Emscripten. The source code is translated directly to JavaScript, without human rewriting, so functionality should be identical to the original Bullet.

    Note: ammo.js has just been updated to a new porting approach. If you find some part of the Bullet API that is not supported that you need, please see

    'ammo' stands for "Avoided Making My Own js physics engine by compiling bullet from C++" ;)

    ammo.js is zlib licensed, just like Bullet.

    Discussion takes place on IRC at #emscripten on Mozilla's server (


    builds/ammo.js contains a prebuilt version of ammo.js. This is probably what you want.

    You can also build ammo.js yourself, as follows:


    The most straightforward thing is if you want to write your code in C++, and run that on the web. If so, then you can build your C++ code with emscripten normally and either build and link Bullet using

    or you can use Bullet directly from emscripten-ports, with -s USE_BULLET=1. In both cases, you don't need ammo.js, just plain Bullet.

    If, on the other hand, you want to write code in JavaScript, you can use the autogenerated binding code in ammo.js. A complete example appears in


    That is HelloWorld.cpp from Bullet, translated to JavaScript. Other examples in that directory might be useful as well. In particular see the WebGL demo code in


    Bindings API

    ammo.js autogenerates its API from the Bullet source code, so it should be basically identical. There are however some differences and things to be aware of:

    • See for a description of the bindings tool we use here, which includes instructions for how to use the wrapped objects.

    • All ammo.js elements should be accessed through Ammo.*. For example, Ammo.btVector3, etc., as you can see in the example code.

    • Member variables of structs and classes can be accessed through setter and getter functions, that are prefixed with |get_| or |set_|. For example,


      will get m_rayToWorld from say a ClosestRayResultCallback. Native JavaScript getters and setters could give a slightly nicer API here, however their performance is potentially problematic.

    • Functions returning or getting float& or btScalar& are converted to float. The reason is that float& is basically float* with nicer syntax in C++, but from JavaScript you would need to write to the heap every time you call such a function, making usage very ugly. With this change, you can do |new btVector3(5, 6, 7)| and it will work as expected. If you find a case where you need the float& method, please file an issue.

    • Not all classes are exposed, as only what is described in ammo.idl is wrapped. Please submit pull requests with extra stuff that you need and add.

    • There is experimental support for binding operator functions. The following might work:

      Operator Name in JS
      = op_set
      + op_add
      - op_sub
      * op_mul
      / op_div
      [] op_get
      == op_eq

    Reducing Build Size

    The size of the ammo.js builds can be reduced in several ways:

    • Removing uneeded interfaces from ammo.idl. Some good examples of this are btIDebugDraw and DebugDrawer, which are both only needed if visual debug rendering is desired.

    • Removing methods from the -s EXPORTED_RUNTIME_METHODS=[] argument in For example, UTF8ToString is only needed if printable error messages are desired from DebugDrawer.


    • It's easy to forget to write |new| when creating an object, for example

      var vec = Ammo.btVector3(1,2,3); // This is wrong! Need 'new'!

      This can lead to error messages like the following:

      Cannot read property 'a' of undefined Cannot read property 'ptr' of undefined

      This is an annoying aspect of JavaScript, sadly.

    Reporting Issues

    If you find a bug in ammo.js and file an issue, please include a script that reproduces the problem. That way it is easier to debug, and we can then include that script in our automatic tests.

    Release Process

    Pushing a new build in builds/ammo.js should be done only after the following steps:

    • Build using python closure which generates the asm.js build, and python closure wasm which generates the wasm build.

    • Make sure it passes all automatic tests using python (build-name) Note that it uses SpiderMonkey by default, and SPIDERMONKEY_ENGINE is defined in ~/.emscripten, see the script contents for details.

    • Run the WebGL demo in examples/webgl_demo and make sure it looks ok, using something like firefox examples/webgl_demo/ammo.html (chrome will need a webserver as it doesn't like file:// urls)

    Upstream Version

    Bullet 2.82 patched with raycast fix from 2.83




    npm i @cocos/ammo

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    9.57 MB

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