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
About the Author
About the Reviewer
Customer Feedback


Testing if an AABB and an OBB overlap can be done using the Separating Axis Theorem (SAT). This test will require a total of 15 axes to be tested. Chapter 5, 2D Collisions, provides an in-depth explanation of how the SAT works. The 15 axes of potential separation are:

  • The three axes of the AABB (world X, Y, and Z)

  • The three axes of the OBB (the OBB's orientation matrix)

  • 9 axes come from the cross-products of the three axes of the AABB and the three axes of the OBB. We take the cross product of every combination of these axes. Lists these nine combinations:

    AABB.XAxis x OBB.XAxis

    AABB.YAxis x OBB.XAxis

    AABB.ZAxis x OBB.XAxis

    AABB.XAxis x OBB.YAxis

    AABB.YAxis x OBB.YAxis

    AABB.ZAxis x OBB.YAxis

    AABB.XAxis x OBB.ZAxis

    AABB.YAxis x OBB.ZAxis

    AABB.ZAxis x OBB.ZAxis

Remember, the two shapes only overlap if all 15 axes overlap. If there is a single axis of separation, no intersection can happen.

Getting ready

Because this is our first 3D SAT test, there is some groundwork to cover...