Book Image

Game Physics Cookbook

By : Gabor Szauer
Book Image

Game Physics Cookbook

By: Gabor Szauer

Overview of this book

Physics is really important for game programmers who want to add realism and functionality to their games. Collision detection in particular is a problem that affects all game developers, regardless of the platform, engine, or toolkit they use. This book will teach you the concepts and formulas behind collision detection. You will also be taught how to build a simple physics engine, where Rigid Body physics is the main focus, and learn about intersection algorithms for primitive shapes. You’ll begin by building a strong foundation in mathematics that will be used throughout the book. We’ll guide you through implementing 2D and 3D primitives and show you how to perform effective collision tests for them. We then pivot to one of the harder areas of game development—collision detection and resolution. Further on, you will learn what a Physics engine is, how to set up a game window, and how to implement rendering. We’ll explore advanced physics topics such as constraint solving. You’ll also find out how to implement a rudimentary physics engine, which you can use to build an Angry Birds type of game or a more advanced game. By the end of the book, you will have implemented all primitive and some advanced collision tests, and you will be able to read on geometry and linear Algebra formulas to take forward to your own games!
Table of Contents (27 chapters)
Game Physics Cookbook
Credits
About the Author
Acknowledgements
About the Reviewer
Acknowledgements
www.PacktPub.com
Customer Feedback
Preface
Index

Circle


A circle is defined by a point in space and a Radius. The circle is an extremely simple shape as shown in the following diagram:

Getting ready

Intersection algorithms for the circle are as simple as its definition. For this reason, a circle is often the first choice to approximate the bounding volume of objects. Arguably, the circle is the most commonly used 2D primitive.

How to do it…

Follow these steps to implement a two-dimensional circle:

  1. Start the declaration of the Circle structure in Geometry2D.h by creating the variables that make up a circle:

    typedef struct Circle {
       Point2D position;
       float radius;
  2. Next, declare an inline constructor that will create a circle at origin with a radius of 1:

       inline Circle() : radius(1.0f) {}
  3. Finish the declaration of the Circle structure by creating an inline constructor that lets us specify the position and radius of the circle being created:

       inline Circle(const Point2D& p, float r):
          position(p), radius(r) {}
    } Circle;

How it works...