JavaScript physics

Posted on 2009-01-16 by David

I made a very basic physics demo in JavaScript to practice using the MooTools library. It uses Verlet integration as outlined in Thomas Jakobsen’s paper.

Chain of particles attached by joints

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nniico says:

2009-08-29 at 2:02 pm

Great demo, but what about collisions, frictions, etc. ? Do you have a more complete engine?
David says:

2009-08-29 at 3:46 pm

No, but check out Box2DJS – http://box2d-js.sourceforge.net/. It’s a full physics engine rather than just a demo.
Ben says:

2010-06-10 at 8:39 pm

Great work. Its missing self-collision though. I’m just mentioning this because it looks a bit weird without it.
David says:

2010-06-10 at 10:14 pm

Collisions would actually be quite easy to implement for this, since it uses Verlet integration. Apply a basic circle-circle collision test, then just modify the particles’ positions so they’re no longer overlapping.

Keep in mind conservation of momentum when modifying the positions. Verlet integration works by implicitly keeping track of the velocity by holding on to the previous position (i.e. $v = x - x*$ , where $x*$ is the previous position), so momentum would be conserved like $\Delta (m_1 (x_1 - x_1*)) + \Delta (m_2 (x_2 - x_2*)) = 0$ .