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

Circle to rectangle

We can simplify the problem of determining if a circle and rectangle intersect down to testing if a point is contained within a circle. We can do this by finding the Closest Point to the circle on the rectangle.

To find the closest point on the rectangle to the circle, if the position of the circle is outside the range of the rectangle on any axis, we clamp that point to the edge of the rectangle. The resulting point is guaranteed to be on the rectangle. If this point is inside the circle, we know a collision has happened.

If the center point of the circle was inside of the rectangle, it is treated as the closest point. In this case, the distance between the position of the circle and the closest point will be zero:

Getting ready

In order to determine if a circle and rectangle are intersecting, we must find the Closest Point on the rectangle to the center of the circle. To do this we just have to clamp the center of the circle to the min and max values of the rectangle.