BOX英文版——Part1.doc

HOME ABOUT Box2D 2.1a Tutorial – Part 1 Posted by?Allan Bishop?on Wednesday, July 14, 2010 ·?View Comments? Physics engines are arguably one of the most engaging elements in interactive media. Not only do they add visual realism but they also allow a greater interactive experience.The Flash platform has a multitude of physics engine libraries available but the one I will be focusing on is?Box2D 2.1a?- arguably the most powerful and feature rich physics engine of them all. A little background info: Box2D is the brainchild of Erin Catto,?Blizzard’s Principle Software Engineer. Box2D is in fact written in C++, but such is its popularity it spawned many ports with ActionScript 3 being no exception. In charge of the manual porting to ActionScript 3 has been?BorisTheBrave?who has kept up with Erin’s updates. With the release of 2.1 emerged a new port, created by?Jesse Sternberg,?who leveraged Alchemy to generate AS3 code from the C++ version. He has also made a framework?WCK?to allow developers to create Box2D objects by using the Flash IDE to layout the various elements. However, for now, I will be focusing on BorisTheBrave’s port which you can download from?here. Box2D can be fairly intimidating to begin developing with due to its sheer scale so we are going to ease into it. I have based my following tutorial heavily on Box2D manual’s Hello World?tutorial, the major changes being all the code examples are written in AS3 and a few minor creative liberties that I have taken. Make sure you are familiar with the following definitions from the Box2D manual: shape: A 2D geometrical object, such as a circle or polygon. rigid body: A chunk of matter that is so strong that the distance between any two bits of matter on the chunk is completely constant. They are hard like a diamond. In the following discussion we use body interchangeably with rigid body. fixture: A fixture binds a shape to a body and adds material properties such as density, friction, and restitution. world: A