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

Triangle to Oriented Bounding Box


Like triangle to AABB, testing a triangle and an Oriented Bounding Box (OBB) is done using the SAT. In fact, the only difference in the actual test is the rotation frame of the bounding box.

Getting ready

We already have the GetInterval support function written for both the OBB and the Triangle. We just need to write the OverlapOnAxis support function and the actual SAT test.

How to do it…

Follow these steps to check if a triangle and an OBB intersect:

  1. Declare OverlapOnAxis and TriangleOBB in Geometry3D.h:

    bool OverlapOnAxis(const OBB& obb, 
       const Triangle& triangle, const vec3& axis);
    bool TriangleOBB(const Triangle& t, const OBB& o);
  2. Add a convenience macro to Geometry3D.h:

    #define OBBTriangle(o, t) \
        TriangleOBB(t, o)
  3. Implement OverlapOnAxis in Geometry3D.cpp:

    bool OverlapOnAxis(const OBB& obb, 
    const Triangle& triangle, const vec3& axis) {
        Interval a = GetInterval(obb, axis);
        Interval b = GetInterval(triangle, axis...