I have a few questions regarding the impact.js implementation of the box2d physics engine.
First, can someone explain to me what the best way is for handling particle effects where the particles are not required to have precise physical interactions? In the default box2D engine there was a collides.LITE option that seemed to work pretty well for this purpose. However in box2D, for even a modest number of particles (say 15 or so) the game can slow down substantially due to the interactions between the particles & each other as well as the environment.
A related but separate question is: what is the best way to handle collision filtering in the impact.js version of box2D? Several sources online explain that to use collision filtering for other box2D implementations, all you have to do is define the collisionBits and maskBits properties for each of your objects and box2D automatically does the rest. I tried just this in the impact.js version of box2D and was not able to manipulate the collisions at all.
Does anyone out there have any experience with this kind of thing? Many thanks.
I am actually working on some similar issues right now. I am still working on composite objects right now with collision filtering and objects with joints.
I've been using a conglomerate of this blog post http://www.emanueleferonato.com/2011/08/22/step-by-step-creation-of-a-box2d-cartruck-with-motors-and-shocks/ which isn't the box impact version of box2d so the syntax/nomiclature is off. And this one http://liza.io/box2d-i-have-conquered-you-sort-of/ which is using the impact version, but is a much simpler example.
In my more recent travels I found PiSpace which seems to have a great implementation of particles.
As I figure things out ill post again.