SFML Game Development: If you've got a firm grasp of C++ with a secret hankering to create a great game, this book is for you. Every practical aspect of programming an interactive game world is here – the only real limit is your imagination.

Table of Contents

SFML Game Development

Credits

Foreword

About the Authors

About the Reviewers

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Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Errata

Piracy

Questions

1. Making a Game Tick

Introducing SFML

Downloading and installation

A minimal example

A few notes on C++

Developing the first game

The Game class

Game loops and frames

Input over several frames

Vector algebra

Frame-independent movement

Fixed time steps

Other techniques related to frame rates

Displaying sprites on the screen

File paths and working directories

Real-time rendering

Adapting the code

Summary

2. Keeping Track of Your Textures – Resource Management

Defining resources

Resources in SFML

Textures

Images

Fonts

Shaders

Sound buffers

Music

A typical use case

Graphics

Audio

Acquiring, releasing, and accessing resources

An automated approach

Finding an appropriate container

Loading from files

Accessing the textures

Error handling

Boolean return values

Throwing exceptions

Assertions

Generalizing the approach

Compatibility with sf::Music

A special case – sf::Shader

Summary

3. Forge of the Gods – Shaping Our World

Entities

Aircraft

Alternative entity designs

Rendering the scene

Relative coordinates

SFML and transforms

Scene graphs

Scene nodes

Node insertion and removal

Making scene nodes drawable

Drawing entities

Connecting entities with resources

Aligning the origin

Scene layers

Updating the scene

One step back – absolute transforms

The view

Viewport

View optimizations

Resolution and aspect ratio

View scrolling

Zoom and rotation

Landscape rendering

SpriteNode

Landscape texture

Texture repeating

Composing our world

World initialization

Loading the textures

Building the scene

Update and draw

Integrating the Game class

The run() method

Summary

4. Command and Control – Input Handling

Polling events

Window events

Joystick events

Keyboard events

Mouse events

Getting the input state in real time

Events and real-time input – when to use which

Delta movement from the mouse

Playing nice with your application neighborhood

A command-based communication system

Introducing commands

Receiver categories

Command execution

Command queues

Handling player input

Commands in a nutshell

Implementing the game logic

A general-purpose communication mechanism

Customizing key bindings

Why a player is not an entity

Summary

5. Diverting the Game Flow – State Stack

Defining a state

The state stack

Adding states to StateStack

Handling updates, input, and drawing

Input

Update

Draw

Delayed pop/push operations

The state context

Integrating the stack in the Application class

Navigating between states

Creating the game state

The title screen

Main menu

Pausing the game

The loading screen – sample

Progress bar

ParallelTask

Thread

Concurrency

Task implementation

Summary

6. Waiting and Maintenance Area – Menus

The GUI hierarchy, the Java way

Updating the menu

The promised key bindings

Summary

7. Warfare Unleashed – Implementing Gameplay

Equipping the entities

Introducing hitpoints

Storing entity attributes in data tables

Displaying text

Creating enemies

Movement patterns

Spawning enemies

Adding projectiles

Firing bullets and missiles

Homing missiles

Picking up some goodies

Collision detection and response

Finding the collision pairs

Reacting to collisions

An outlook on optimizations

An interacting world

Cleaning everything up

Out of view, out of the world

The final update

Victory and defeat

Summary

8. Every Pixel Counts – Adding Visual Effects

Defining texture atlases

Adapting the game code

Low-level rendering

OpenGL and graphics cards

Understanding render targets

Texture mapping

Vertex arrays

Particle systems

Particles and particle types

Particle nodes

Emitter nodes

Affectors

Embedding particles in the world

Animated sprites

The Eagle has rolled!

Post effects and shaders

Fullscreen post effects

Shaders

The bloom effect

Summary

9. Cranking Up the Bass – Music and Sound Effects

Music themes

Loading and playing

Use case – In-game themes

Sound effects

Loading, inserting, and playing

Removing sounds

Use case – GUI sounds

Sounds in 3D space

The listener

Attenuation factor and minimum distance

Positioning the listener

Playing spatial sounds

Use case – In-game sound effects

Summary

10. Company Atop the Clouds – Co-op Multiplayer

Playing multiplayer games

Interacting with sockets

TCP

UDP

Socket selectors

Custom protocols

Data transport

Network architectures

Peer-to-peer

Client-server architecture

Authoritative servers

Creating the structure for multiplayer

Working with the Server

Server thread

Server loop

Peers and aircraft

Hot Seat

Accepting new clients

Handling disconnections

Incoming packets

Studying our protocol

Understanding the ticks and updates

Synchronization issues

Taking a peek in the other end – the client

Client packets

Transmitting game actions via network nodes

The new pause state

Settings

The new Player class

Latency

Latency versus bandwidth

View scrolling compensation

Aircraft interpolation

Cheating prevention

Summary

Index

SFML Game Development

SFML Game Development

Copyright © 2013 Packt Publishing

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First published: June 2013

Production Reference: 1170613

Published by Packt Publishing Ltd.

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ISBN 978-1-84969-684-5

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Cover Image by Vivek Sinha (<[email protected]>)

Credits

Authors

Artur Moreira

Henrik Vogelius Hansson

Jan Haller

Reviewers

Brandon DeRosier

Karol Gasiński

Eyal Kalderon

Acquisition Editor

Edward Gordon

Lead Technical Editor

Mayur Hule

Technical Editors

Sanhita Sawant

Priya Singh

Nitee Shetty

Dennis John

Project Coordinator

Amey Sawant

Proofreaders

Dan McMahon

Stephen Swaney

Indexer

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Graphics

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Production Coordinator

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Cover Work

Pooja Chiplunkar

Foreword

I'm really honored to write the first words of this book, the very first one about SFML. When I started to write this library, in 2006, I couldn't imagine that it would become so much popular. Around 100,000 visitors per month, 100 new forum posts everyday... this is huge! And this is just the beginning; with the release of SFML 2.0, the library makes an important step forward. While SFML 1 is a constantly evolving (understand unstable) API, SFML 2.0 is meant to be a robust, stable, and mature foundation for the future. And hopefully a solid base for more and more great games.

Increasing popularity also means more effort from the authors to provide complete and quality documentation. Sadly, this is often overlooked by developers.

Although I do my best to provide detailed tutorials for SFML, they are nothing more than an improved API documentation. Users often ask me where they can find a more complete guide to start programming games with SFML. And until today, I had nowhere to direct them to. But Artur, Henrik, and Jan did a great job to fill this hole. They have gathered their wisdom and experience into a unique book that covers the basics of game programming, as well as everything that SFML has to offer—from audio to network, through advanced graphics. What I really appreciate about this book is that it is written with the same philosophy that is behind SFML: good design, simplicity, and modern code.

I hope you will enjoy reading this book as much as I did and find what you're looking for; whether you're a beginner who wants to learn game programming with SFML, or a more experienced programmer who wants to improve his design and technical skills. And don't hesitate to come to the SFML forum if you have questions or comments. I, the authors of this book, and all the community will be glad to answer you.

Laurent Gomila

Author of SFML

Software Engineer, Tegesoft, France

About the Authors

Artur Moreira is a game development enthusiast who ultimately aims to start a new game development company in his home country. He has been programming games and game-related software for over 4 years. Most of the effort in that time was put in creating an open source game-making library with lots of flexibility and portability. The library is called Nephilim and is known for supporting all major desktop and mobile operating systems, making game development fully cross-platform and fast. Alongside this big project, he keeps making his own prototypes and games for educational and commercial purposes.

Aside from the programming, he also puts some focus in creative areas such as 3D modeling, digital painting, and music composing.

I would like to thank, first of all, my girlfriend for her patience and unconditional support every single time the writing was taking all of my time and energy. Also, I can't be thankful enough for the support of my parents and sisters, along with all the closest relatives, whose support is ever-present and always helpful. On the technical side, I would like to directly thank Jan Haller and Henrik Vogelius Hansson, the co-authors of the book, for their remarkable collaboration, skill, and teamwork. It's been always a pleasure to work with them.

Henrik Vogelius Hansson has always been in love with both games and programming. He started his education fairly early and continued on into the indie scene with Defrost Games and their game Project Temporality. The next company that hired him was Paradox Development Studio where he got to work on titles such as Crusader Kings 2.

Beside the game companies, Henrik has also been very active in the SFML community and has even provided a binding for Ruby called rbSFML.

I would like to thank my co-authors, Jan and Artur, for the amazing cooperation and great times. I am also very happy and would like to thank my family that encouraged me to pursue this line of work. Also special thanks to my grandmother.

Jan Haller is a Master's degree student of Electrical Engineering and Information Technology. In his free time, he occasionally develops games in C++. He is also interested in the creation of graphics and 3D models.

In 2008, Jan stumbled upon SFML. Since then, he has used the library for many of his works. One of his bigger projects was a 2D Jump'n'Run game, where the character has to find its way through different levels, defeating enemies and collecting various items. During the years, Jan has actively participated in the SFML community, getting a lot of insights into the development of SFML 2. He has also written a C++ library called Thor, which extends SFML by ready-to-use features such as particle systems or animations.

I would like to thank Laurent Gomila for the passion and huge efforts he invested into the Simple and Fast Multimedia Library. It has always been interesting to discuss with him about the library and its development process. I would also like to thank my co-authors, Artur Moreira and Henrik Vogelius Hansson, who have been a very nice team to work with.

About the Reviewers

Brandon DeRosier is a free software supporter, software engineer, and a hobbyist game developer living in the Greater Boston area. Driven by an early interest in programming, he took to the reverse engineering of his favorite games of his childhood; he would later write several small augmentation tools to run alongside these games. Over time, he developed his skills as a programmer—as well as an interest in music composition, animation, and interactive media. Currently, he is directing these skills and interests towards game design.

As a member of the Free Software Foundation, he understands that the concealing of source code is unethical and regressive; dedicated to the digital rights of users everywhere, he has actively participated in the development and distribution of free software.

Brandon is currently pursuing a Bachelor of Science degree in Computer Science at Wentworth Institute of Technology in Boston and takes pride in helping others learn. Occasionally, he gives lectures in classes and clubs, with hopes of encouraging interest in interactive media development with frameworks such as SFML and LWJGL.

I'd like to thank my partner, Yamilah Atallah, for brainstorming game ideas with me, coming up with meaningful concepts and wonderful designs, and changing my life in so many positive ways; with this support, my interest in game development has grown.

Karol Gasiński is a programmer, entrepreneur, and traveler living in Poland, Europe. He works as a Graphic Software Engineer at an Intel Research & Development facility, and has worked on 6 generations of Intel graphic cards. As a member of KHRONOS group, Karol contributes to the development of OpenGL and OpenGL ES Specifications—the industry standard for high-performance graphics.

Outside of his work, Karol's biggest passion is game development and low-level programming. He has been associated with the games industry for over 6 years. In the past, he has worked on mobile versions of games such as Medieval Total War, Pro Evolution Soccer, and Silent Hill. Currently he is the founder and chairman of the Polish Conference on Computer Games Development—the biggest and fastest growing industry event in the country.

Karol gives lectures on most Polish conferences and events for game developers including WGK, GameDay, SWPC, the DigitalFrontier course, IGK, and others. You can also meet him on GDC Europe and GDC San Francisco, where each year he gathers inspiration for his new games.

Eyal Kalderon is a self-taught computer programmer and high school student. Having been introduced to the programming scene at a fairly young age, Eyal developed his early skills in Visual Basic and made a switch to C# early on. Eyal has made himself at home for several years now programming with C and C++ and using shell scripts to automate every task he finds boring. After trying SDL, Eyal switched to SFML in 2010, enjoyed it, and has been following its progress closely ever since.

Understanding the power of print, having gained much from the Internet and professional publications, Eyal chose to erect 'nullpwd' (nullpwd.wordpress.com) in March of 2010, a casual software-centered blog that acts as an unintimidating front for various software topics, such as programming, penetration systems, and the current happenings of the open source community.

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Preface

Welcome to the pages of SFML Game Development!

Whether you are just grabbing our book in a store, previewing it in your e-book reader, or you have already bought it—you have taken your first step in becoming a game developer by picking up this book.

Game development is a very interesting topic, as it combines many different fields such as software development, graphical design, music composition, and storytelling. Nowadays, there is an enormous variety of games available, yet developers never cease to be creative and to come up with innovations. This book conveys the process of game development in a way that covers state-of-the-art techniques, leaving you ready to implement your own ideas.

It does not matter if you are already an experienced developer or an ambitious newcomer to the field of making games. Although the book requires no previous knowledge on game development, we also teach valuable concepts and techniques that will help you grow as a game developer.

Throughout the book, we develop a 2D game with SFML. We focus on a top-scrolling aircraft shooter, where the player acts as a pilot and is confronted with various challenges. We begin with the bare bones of each element and continuously add functionality as we progress in the book. In every chapter, new features are introduced, and the code is updated accordingly. Therefore, you will not only see the concepts in theory, but also will have a direct implementation at hand, which you can investigate and extend the way you like.

That said, we would like to wish you a great journey through the chapters of this book. May it be a good experience in all its extent! Please enjoy!

What this book covers

Chapter 1, Making a Game Tick, introduces the SFML library and shows you basic concepts such as the game loop and rendering.

Chapter 2, Keeping Track of Your Textures – Resource Management, covers the loading and management of external resources such as images, fonts, and sounds.

Chapter 3, Forge of the Gods – Shaping Our World, builds up the framework of the game world and addresses the concept of scene graphs and game entities.

Chapter 4, Command and Control – Input Handling, shows how to react to user input from the keyboard, mouse, and joystick.

Chapter 5, Diverting the Game Flow – State Stack, covers switching between application states such as different menus, or between menus and the game itself.

Chapter 6, Waiting and Maintenance Area – Menus, introduces a simple graphical user interface in the menus.

Chapter 7, Warfare Unleashed – Implementing Gameplay, approaches actual gameplay mechanisms. Enemies, bullets, missiles, power-ups and collision detection are implemented.

Chapter 8, Every Pixel Counts – Adding Visual Effects, enhances the graphical appearance of the game by adding animations, particle systems, and shaders.

Chapter 9, Cranking Up the Bass – Music and Sound Effects, explains a way to integrate audio into the game.

Chapter 10, Company Atop The Clouds – Co-op Multiplayer, covers networking basics and a multiplayer implementation over the network.

What you need for this book

Since this book is built around the SFML library, you need to download and install it. You can get SFML at www.sfml-dev.org; the first chapter gives a brief installation guide.

In case you decide to recompile SFML yourself, you will also require the cross-platform build tool CMake, which can be downloaded from www.cmake.org.

Who this book is for

SFML Game Development is aimed at audiences of all ages who already know how to program in C++, at least to an intermediate level. It is optimal if the reader already has some experience in programming and knows the language well.

The ideal reader for such a book would be a person who is experienced in C++ and would now like to enter the world of game development in a simple yet serious way. However, if the reader already knows a good deal of it and still wants to read through the pages to see different approaches, or if he simply wants to learn more about SFML in a bigger practical example, we strongly encourage to read on!

Conventions

In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.

Code words in text are shown as follows: To manage all these screens and transitions, we create the StateStack class.

A block of code is set as follows:

namespace GUI

{

    class Component : public sf::Drawable,public sf::Transformable

  {

        public:

          typedef std::shared_ptr Ptr;

                          Component();

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

: mChildren()

, mSelectedChild(-1)

{

}

void Container::pack(std::shared_ptr component)

{

New terms and important words are shown in bold. Words that you see on the screen, in menus or dialog boxes for example, appear in the text like this: It shows a background with a little information about the game, besides its title and then blinks a big old Press any key to continue message.

Note

Warnings or important notes appear in a box like this.

Tip

Tips and tricks appear like this.

Reader feedback

Feedback from our readers is always welcome. Let us know what you think about this book—what you liked or may have disliked. Reader feedback is important for us to develop titles that you really get the most out of.

To send us general feedback, simply send an e-mail to <[email protected]>, and mention the book title via the subject of your message.

If there is a topic that you have expertise in and you are interested in either writing or contributing to a book, see our author guide on www.packtpub.com/authors.

Customer support

Now that you are the proud owner of a Packt book, we have a number of things to help you to get the most from your purchase.

Downloading the example code

You can download the example code files for all Packt books you have purchased from your account at http://www.packtpub.com. If you purchased this book elsewhere, you can visit http://www.packtpub.com/support and register to have the files e-mailed directly to you.

Errata

Although we have taken every care to ensure the accuracy of our content, mistakes do happen. If you find a mistake in one of our books—maybe a mistake in the text or the code—we would be grateful if you would report this to us. By doing so, you can save other readers from frustration and help us improve subsequent versions of this book. If you find any errata, please report them by visiting http://www.packtpub.com/submit-errata, selecting your book, clicking on the errata submission form link, and entering the details of your errata. Once your errata are verified, your submission will be accepted and the errata will be uploaded on our website, or added to any list of existing errata, under the Errata section of that title. Any existing errata can be viewed by selecting your title from http://www.packtpub.com/support.

Piracy

Piracy of copyright material on the Internet is an ongoing problem across all media. At Packt, we take the protection of our copyright and licenses very seriously. If you come across any illegal copies of our works, in any form, on the Internet, please provide us with the location address or website name immediately so that we can pursue a remedy.

Please contact us at <[email protected]> with a link to the suspected pirated material.

We appreciate your help in protecting our authors, and our ability to bring you valuable content.

Questions

You can contact us at <[email protected]> if you are having a problem with any aspect of the book, and we will do our best to address it.

Chapter 1. Making a Game Tick

Through the words in this book, we will attempt to convey the best knowledge we possibly can. We aim to teach techniques that we learned along the years, techniques that we would like to have been told about in our early days of game development. We now write this book to save your time, by showing you directly the solution to common problems, and why things work the way they do.

Alongside our attempt to teach the basics and a little beyond game development, we will especially focus on the Simple and Fast Multimedia Library (SFML). Every part of this book will be about developing a game and leveraging the advantages that SFML is able to provide us.