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Chipmunk 2d physics engine, in Javascript

Chipmunk for Javascript!

This is a port of the Chipmunk Physics library to Javascript!

Check out the sexy demos! (Surprisingly, works best in Safari)


  • It is slower than the C version (duh, its in javascript). Specifically, physics simulations using chipmunk-js runs about 3 times slower than the C equivalent.
  • I haven't implemented chipmunk's spatial hash, and I have no intention to do so.
  • The feature set is lagged a little from the real Chipmunk library. Chipmunk-js currently corresponds to Chipmunk 6.1.1 published in August 2012.


The API for Chipmunk-js is almost identical to chipmunk-physics. Except:

  • The cp prefix has gone

  • Most functions are wrapped by their containing objects

  • Some functions took an array-and-length. Arrays are now all simply javascript arrays, and the length argument has been removed. Eg:

cpMomentForPoly(mass, numVerts, *verts, offset); ```



cp.momentForPoly(mass, verts, offset); ```

  • Lots of trivial getters and setters have been removed.
  • Lists of verticies are described using a flattened JS array of [x1,y1,x2,y2,...] instead of an array of objects. Ie, [0,0, 0,1, 1,1, 1,0] instead of [cp.v(0,0), cp.v(0,1), cp.v(1,1), cp.v(1,0)].

On a website

<script src="cp.min.js"></script>
var space = new cp.Space();
space.addBody(new cp.Body(...))
// ...

If any exceptions are thrown or anything, use cp.js instead of cp.min.js and post the stack trace you get to the issue page.

From nodejs

npm install chipmunk

cp = require('chipmunk');
var space = new cp.Space();
space.addBody(new cp.Body(...))
// ... 


This code creates a new space, sets 10 physics iterations per update (these increase simulation stability). Then it adds a bunch of line segments to the space.

In C, this code looked like:

  cpSpace *space = cpSpaceNew();
  space->iterations = 10;
  cpVect offset = cpv(-320, -240);
  for(int i=0; i<(bouncy_terrain_count - 1); i++){
    cpVect a = bouncy_terrain_verts[i], b = bouncy_terrain_verts[i+1];
    cpShape *shape = cpSpaceAddShape(space, cpSegmentShapeNew(cpSpaceGetStaticBody(space), cpvadd(a, offset), cpvadd(b, offset), 0.0f));
    cpShapeSetElasticity(shape, 1.0f);

In javascript, the equivalent code is:

  var space = new cp.Space();
  space.iterations = 10;
  var offset = cp.v(-320, -240);
  for(var i=0; i<(bouncy_terrain_verts.length - 1); i++){
    var a = bouncy_terrain_verts[i], b = bouncy_terrain_verts[i+1];
    var shape = space.addShape(new cp.SegmentShape(space.staticBody, cp.vadd(a, offset), cp.vadd(b, offset), 0));


Like Chipmunk, chipmunk-js is MIT licensed.

Copyright (c) 2007 Scott Lembcke and Joseph Gentle
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.