Book Image

Box2D for Flash Games

Book Image

Box2D for Flash Games

Overview of this book

Physics games are getting more and more popular, and Box2D is the best choice if you are looking for a free, stable and robust library to handle physics. With Box2D you can create every kind of 2D physics game, only coding is not the fun part, but the game itself. "Box2D for Flash Games" will guide you through the process of making a Flash physics game starting from the bare bones and taking you by hand through complex features such as forces, joints and motors. As you are learning, your game will have more and more features, like the physics games you are used to playing. The book analyzes two of the most played physics games, and breaks them down to allow readers to build them from scratch in a step-by-step approach. By the end of the book, you will learn how to create basic primitive bodies as well as complex, compound bodies. Motors will give life to cars, catapults and siege machines firing bullets, while a complete collision management will make your game look even more realistic. If you want to make full Flash games with physics, then Box2D for Flash Games will guide you through the entire process of making a Flash physics game.
Table of Contents (15 chapters)
Box2D for Flash Games
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Making bodies rotate around a point – revolute joints


Revolute joints force two bodies to be pinned in a common anchor point, leaving only a single degree of freedom: the rotation around the anchor point. One of the most common uses of revolute joints is the creation of wheels and cogs.

We will create wheels later when we build the siege machine. At the moment, I just want to add another box to our script and pin it to the ground body to make you see how to interact with revolute joints. We need to make only some changes in the Main function:

public function Main() {
  world=new b2World(new b2Vec2(0,9.81),true);
  debugDraw();
  var bodyDef:b2BodyDef=new b2BodyDef();
  bodyDef.position.Set(320/worldScale,470/worldScale);
  var polygonShape:b2PolygonShape=new b2PolygonShape();
  polygonShape.SetAsBox(320/worldScale,10/worldScale);
  var fixtureDef:b2FixtureDef=new b2FixtureDef();
  fixtureDef.shape=polygonShape;
  var groundBody:b2Body=world.CreateBody(bodyDef);
  groundBody.CreateFixture(fixtureDef...