QuickB2 is a complete abstraction of Box2D, providing grouped hierarchies, extensible classes, and event-driven callbacks. The high-level interface enables developers to create physics simulations that are impractical to write using Box2D’s API alone. It takes care of things that you don’t want to, so that you can concentrate on your game.

Here are some examples of what it can do: http://quickb2.dougkoellmer.com/bin/qb2DemoReel.swf

Here is a place where you can ask questions: http://quickb2.dougkoellmer.com/forum

I’ve just gone and looked through the demo reel, and I have to say this is quite impressive. Obviously having a nicer to use, ActionScript 3 style syntax rather than the C++ syntax is a bonus, but what really makes this cool is the features that this library has, over and above the basics of Box2D.  Things like shape cutting, soft bodies; breakable joints etcetera.

You can find out more information, and download the source code from Google Code, at: http://code.google.com/p/quickb2/

Just a little demo I’ve been working on, following my previous post: http://www.psyked.co.uk/actionscript/starrequests-simple-box2d-flickr-mashup-sample.htm. I’ve basically updated the code a little and swapped out the rectangular Box2D objects for star-shaped Box2D objects, and the code is available on GitHub: http://github.com/psyked/StarRequests-Examples/tree/master/Box2d-Flickr-Shapes/

^ This time, that’s an image – saves on the page rendering time!

Another update on the Box2D classes I’m working on.  No new features, but some pretty cool expansions and improvements to the library object creation.

If you check out the previous post, you’ll see that the the dynamically drawn shapes weren’t exactly perfect; nor were they very efficient.  Oh they worked fine, and traced the detail of the shape very well – but it took a decent chunk of system resources to animate and ended up with some overlaid shapes; which all made the Box2D a bit sluggish and the behaviours buggy.

So, stealing incorporating ideas from other projects has been the name of the game – namely the ear clipping optimisation code from Splashdust.net, combined with some of my own cobbled-together more optimised code for tracing curved edges.

Live demo:

Mouse interaction is enabled in the below example – click and drag the objects to check out how it works.

Download the source code for this demo.

* The source code isn’t exactly cleaned up – sometime, eventually, it will be.

(The image above this text is actually the Flash movie, if you hadn’t guessed.  Try using your mouse to interact.  If it’s blank, then something’s gone wrong!)

I’ve been busy working on my Box2D classes again. (As before here and here.)  I’m not quite ready to go through the code with some tutorials yet, but you can download the source for this demo here.  This version has had a bit more of a proper code cleanup – I’ve un-hacked some hacks I did earlier in development, and added a few more utility functions, but most importantly this version supports SWF library asset importing of multiple shapes, and shapes with curved edges (which it couldn’t do previously).

I feel like I should put that in bold or something, because it’s probably my most-clever bit of code to date.  I’m going to settle for saying it twice though: You can import library objects with multiple shapes, and shapes with curved and straight edges.  Have a look at the screenshot below and compare it with the Box2D display;

In Flash IDE:

In Box2D:

You can download the source for this demo here.

I’m going to get this as a project on some publicly-available source repository soon.  I’d love to hear feedback on it now though!

Awesome thing: Creating Custom Polygons

Or rather the methods for creating them.  Shapes in Box2D come in three basic flavours – circle, rectangle and custom polygon.  Moreover, everything must be convex (no inny bits), have no more than 8 sides, and can’t have holes.  On the plus side you can still make larger, more complex objects out of smaller ones – but it all involves a lot of thinking.

So, here’s the solution – or rather, the options.

Polygon creation option #1 – Creating a polygon from an array of points.

Using some clever triangulation code from Splashdust.net, there’s a simple method for creating any custom shape from an array of Point objects.  With this method you can create a shape with any number of sides, and not worry about whether the shape is concave or convex.  It’ll still break if the edges of your shape interest each other, and doesn’t support holes in the objects you’re creating, but it’s a start.

var array:Array = [ new Point( 0, 0 ), new Point( 10, 0 ), new Point( 10, 10 ), new Point( 20, 10 ), new Point( 20, 0 ), new Point( 30, 0 ), new Point( 30, 30 ), new Point( 0, 30 ) ];

world.createComplexPolygon( 50, 50, array );

Polygon creation option #2 – Creating a polygon from a shape in a library.

This is where things get cool.  Creating a shape from a series of points is all well and good, but it’s a laborious process to set up and modify.  You can create a shape in the Flash IDE, add your symbol to your library and import it to Box2D.  Currently this method only supports single shapes on a single layer, and only straight edges – but multiple shapes, layers and curved edges are definitely on the list for the future.

world.createPolyFromLibraryShape( 300, 100, "sampleShape", "vectorassets.swf" );

Minor thing #1: Mouse interaction

What fun is a simulation if you can’t interact with it? So we now have an easy way to add mouse joints to move things about.  In the next version it’s my plan to add a method for filtering out objects, presumably based on each bodies userData.

world.mouseInteraction = true;

Minor thing #2: Framerate-independent animation.

I stole this idea wholeheartedly from QuickBox2D.  Too good an idea to pass up I’m afraid, this just means that the simulation of the Box2D world is based on a timer, not a framerate.  In theory then, the simulation doesn’t slow down or speed up depending on the framerate – which is useful for many things, like graphic-intensive applications and/or memory optimisation.

world.framerateIndependantAnimation = true;

And here’s some code for a quick example with framerate independent animation and mouse interaction enabled;

var options:Box2DWorldOptions = new Box2DWorldOptions( 500, 280, 30, 9.8 );
options.setWorldEdges( true, true, true, true );
var world:Box2DWorld = Box2DUtils.createBoxedWorld( options );
world.debugDraw = true;
world.mouseInteractExclusions = new Array();
world.mouseInteraction = true;
world.framerateIndependantAnimation = true;
addChild( world );

I’ve compiled all of my source files into a handy project file if you want to take a look.  Documentation and comments are a bit sparse, but hopefully it’ll prove useful!

Download the project files [Zip, 48kb]

Simples!