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

Detect when you are about to solve a collision and when you have solved it


The Pre-Solve Event is called after collision detection, but before collision resolution, so you can interact with a collision before it's solved. The Post-Solve Event occurs when a collision has been solved, and allows us to know the impulse of the collision.

  1. Add the following two functions to the customContact class:

    override public function PreSolve(contact:b2Contact, oldManifold:b2Manifold):void {
      if (contact.GetManifold().m_pointCount>0) {
        trace("a collision has been pre solved");
        var fixtureA:b2Fixture=contact.GetFixtureA();
        var fixtureB:b2Fixture=contact.GetFixtureB();
        var bodyA:b2Body=fixtureA.GetBody();
        var bodyB:b2Body=fixtureB.GetBody();
        trace("first body: "+bodyA.GetUserData());
        trace("second body: "+bodyB.GetUserData());
        trace("---------------------------");
      }
    }
  2. The PreSolve function at the moment has the same code as BeginContact and EndContact, but the code is...