![]() This example will wrap many of the more verbose pieces of Box2D in wrapper classes to simplify the API you need to expose to your game. This article is going to build up a small example that shows you how to use Box2D and how it might integrate into your game engine. So that you don’t go insane with all the namespacing, it’s recommended that you pull out some of the most-used classes into easy-to-access variables, as shown below: This pulls in the Box2DWeb library and example.js file that will contain all the example code.Īll of Box2DWeb comes namespaced inside of the Box2D object, sometimes pretty deeply nested under sub-objects. The examples below are going to use the following basic HTML wrapper: To get a Box2D world up and running, you’ll need to pull in the library, which is packed up nicely in a single JavaScript file Box2dWeb-2.1.a.3.js If you’re interested in really diving into Box2D, the official Box2D C++ manual also makes for a worthwhile read, although it contains some newer features not found in Box2DWeb. Some work has also been done to convert directly from C++ to JavaScript using emscripten (See box2d.js) but this has a different API than box2dweb and doesn’t appear to be kept up.īox2DWeb doesn’t have it’s own documentation per se, but it shares the same API as the Flash library it was converted from, so the Box2DFlash Documention can be used to figure out the Box2DWeb API. There are a few ports floating about, but the most popular one is Box2DWeb: To get a JavaScript version, some ambitious folks have taken advantage of the similarities between ActionScript and JavaScript and created a converter that converted the ActionScript to JavaScript. Box2D is the 2D physics engine of choice for many games, and thus was ported wholesale over to Flash and ActionScript a while back. One reason for this is that it was used as the simulation engine behind mega-hit Angry birds, whose physics-based gameplay required a bullet-proof physics implementation. Of the myriad of open-source 2D engines that are available, one stands out: Box2D. For an overview of a number of different engines, take a look at Chandler Prall’s JavaScript Physics Engine Comparison. To this end a number of different Physics engines, both 2D and 3D have made their way to JavaScript, many of them ports from other languages, but some written from scratch. The idea behind using a physics engine in your game is that instead of hacking together a very-loose approximation of how real objects might interact for your game, dropping in an engine whose sole purpose is to run the physics simulation allows you to leave it to the engine to handle object dynamics and interactions and concentrate on the game itself. If all you need is to calculate when a couple of rectangles overlap, it’s not a big deal, but for games that involve lots of irregularly shaped sprites moving and reacting to each other realistically, you’ll want to use an industrial strength tool to get the job done. One of the most complicated and math-intensive components of game development is collision detection and response.
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