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

Raycast Oriented Bounding Box

We can extend the same slab method used for raycasting against an AABB to also work with an OBB. The key difference is how we find the values of and .

Getting ready

We are going to implement a function that finds the entry and exit points of a Raycast against an OBB. This function will only return the entry point. The function returns a scalar value t. This scalar value is the time along the ray at which the intersection happened. If the intersection is invalid, a negative number is returned.

How to do it…

Follow these steps to implement raycasting against an OBB:

  1. Declare the Raycast function in Geometry3D.h:

    float Raycast(const OBB& obb, const Ray& ray);
  2. Start implementing the Raycast function in Geometry3D.cpp by declaring a few local variables to keep the code readable. We want to store the half extents of the box as a linear array, and each axis of the OBBs rotation frame as a vector:

    float Raycast(const OBB& obb, const Ray& ray) {
       const float...