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

Linetest Axis Aligned Bounding Box

We can use the existing Raycast against the AABB function to check if a line intersects an AABB. Given a line segment with end points A and B, we can create a ray out of the line:

ray.origin = A
ray.direcion = Normalized(B - A);

With this ray, we can perform a Raycast. If the ray intersects the AABB, we check to make sure that the value of t is less than the length of the line. If it is, the segment intersects the Bounding Box:

Getting ready

We are going to implement a function to check if a Line and an AABB intersect. This function will return a Boolean result. We can avoid checking the length of the line segment by squaring it, and also squaring the value of t. That way, the actual comparison is done in a squared space.

How to do it…

Follow these steps to implement line testing against an AABB:

  1. Declare the Linetest function in Geometry3D.h:

    bool Linetest(const AABB& aabb, const Line& line);
  2. Implement the Linetest function in Geometry3D.cpp:

    bool Linetest...