Hi all,

I finally took a couple of days and put together a light Processing-specific wrapper around the JBox2d physics library.  It's called BoxWrap2d, and you can check it out at http://www.jbox2d.org/processing.  It should make doing rigid body physics in Processing about as simple as possible.

At the moment, though, this is basically one very rough and jagged edge, certainly not a release quality library yet!  There's a lot of functionality available (in fact, all the functionality of JBox2d if you have the guts to dig in and learn that), but there are some things missing, some things broken (probably, at least, though I don't know what yet!), and some things that could be a lot easier to do.  Plus, right now there's only Javadoc documentation.

But it's got boxes, circles, convex polygons, and a bunch of joints, which should be a start.  If you're interested, give it a d/l and try it out.  Let me know if you have any suggestions.

Oh, and this will probably only work with newer versions of Processing, because JBox2d uses Java 1.5.  Also, please ignore the extraneous import statements that show up when you import the library, I'm aware of the problem and will try to clean those up at some point soon.

No problem at all, I just hope it is useful to someone! :>

Honestly, the Java port of Box2d was mainly done to scratch my own itch, as I've been stuck in particles + springs territory for a while myself, never quite having the energy to make a full rigid body engine.  Turns out that I both learned more and ended up with a better engine by porting Box2d than I would have by fighting through it all myself!

Don't knock particles and springs, though - if those are all you need, they will usually be a lot faster than a full rigid body engine.

im trying to apply some forces to rigid bodies, but i cant seem to get it to work. reading the box2d manual doesnt seem to be the best thing to do.. processing says most of the Body functions are not available?
where can i get a list of functions for this processing version ?

i want to create a basic attraction/repulsive program.

@crmx: You should be able to call physics.applyForce(body, forceX, forceY) - however, it appears that the version of the library that's online is older than the one I've got on my machine, which I didn't realize until just now!  In particular, it lacks the applyForce function in the wrapper.

As a temporary workaround until I upload a new version (I want to make sure the local one I've got actually works right...), you can do the following:
Code:

Vec2 force = new Vec2(forceX, forceY);
Vec2 applicationPoint = body.getWorldCenter();//gets body center of mass
body.applyForce(physics.screenToWorldVector(force), physics.screenToWorld(applicationPoint));
 

Which is not too difficult, the only tricky bit is that the physics coordinates differ from the screen coordinates so you need to manually transform them first...this is one of the annoying things that this wrapper intends to hide from you most of the time.

In any case, I'll upload a new version soon.

hey!

the library looks really good and it's fun to code with!

is there a way to change the size of an object? (or even better... changing the complete shape).


best, hansi.

Ah, funnily I was starting to take a look again at that library, wondering if there is an update on boxwrap2d to follow the latest version of JBox2D.

You are right, I see neither circles nor joints, if I change the formers to rects I can visualize them.
I see the same issue with Processing 0154, not with 0135. Looks like some change in the underlying libraries has broken the wrapper.

Many thanks for this update (and the coming one!).
I downloaded the new version, and I got an error: org.jbox2d.util package is missing.
Looks like a little packaging error.

I could checkout the project from SVN, and build it. I had to replace the ~1MB core.jar at the root by the 224KB one found in processing-1.0.1/lib. The exported jar is a bit big (379KB) compared to your, but the SwingingDemo works fine once I removed the sizeSet = true; line from the end.

Note: I added .svn/ to the exclude path of data, and **/.svn/* to the exclude path of src.
The export to jar feature of Eclipse is annoying because I have to re-specify what to export each time.

Okay, a new .zip is up, let's see if this one does it!  (Works on my computer, then again, so did the last one!)