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
About the Author
About the Reviewers

Picking and dragging bodies – mouse joints

Hard things first; we are going to start with one of the most difficult joints. Sad but necessary, as it will allow us to create and test other joints easily.

A mouse joint allows a player to move bodies with the mouse, and we will create it with the following features:

  • Pick a body by clicking on it

  • Move a body following the mouse as long as the button is pressed

  • Release a body once the button is released

Some quiet before the storm; the beginning of this process does not differ to other scripts you have already mastered through the book.

  1. So, we are importing the required classes:

    import flash.display.Sprite;
    import Box2D.Dynamics.*;
    import Box2D.Collision.*;
    import Box2D.Collision.Shapes.*;
    import Box2D.Common.Math.*;
  2. Then we need the class-level variables for the world itself, and the conversion from pixels to meters:

    private var world:b2World;
    private var worldScale:Number=30;

    And even the Main...