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- Herausgeber: Packt Publishing
- Kategorie: Fachliteratur
- Sprache: Englisch
If you are really passionate about games and have always wanted to write your own, this book is perfect for you. It will help you get started with programming in C++ and explore the immense functionalities of UE4.
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Seitenzahl: 309
Veröffentlichungsjahr: 2015
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Learning C++ by Creating Games with UE4
Learning C++ by Creating Games with UE4
Copyright © 2015 Packt Publishing
All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.
Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.
Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.
First published: February 2015
Production reference: 1180215
Published by Packt Publishing Ltd.
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ISBN 978-1-78439-657-2
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Credits
Author
William Sherif
Reviewers
Brandon Mann
Matt Sutherlin
Alan Wolfe
Commissioning Editor
Edward Bowkett
Acquisition Editor
Subho Gupta
Content Development Editor
Anand Singh
Technical Editor
Saurabh Malhotra
Copy Editors
Dipti Kapadia
Deepa Nambiar
Project Coordinator
Rashi Khivansara
Proofreaders
Martin Diver
Lawrence A. Herman
Paul Hindle
Indexer
Hemangini Bari
Graphics
Sheetal Aute
Production Coordinator
Melwyn D'sa
Cover Work
Melwyn D'sa
About the Author
William Sherif is a C++ programmer with more than 8 years' programming experience. He has a wide range of experience in the programming world, from game programming to web programming. He has also worked as a university course instructor (sessional) for 7 years.
He has released several apps on to the iTunes store, including strum and MARSHALL OF THE ELITE SQUADRON.
In the past, he has won acclaim for delivering course material in an easy-to-understand manner.
I'd like to thank my family, for their support when I was writing this book; Mostafa and Fatima, for their hospitality; as well as Ryan and Reda, for letting me write.
About the Reviewers
Brandon Mann is a well-rounded game developer with over 7 years of professional game-development experience. He has worked on a wide range of titles, from Indie Games to AAA titles, and at companies such as Warner Bros., Midway, and 343 Industries. He has worked on several titles, including Blacklight, Tango Down, Gotham CityImpostors, and Battle Nations.
Matt Sutherlin has been working in the games industry for over a decade now, where he's held job titles ranging from QA and scripter to engine programmer, and technical artist. Most recently, he has been heavily focusing on graphics technology, working on engine renderers, art pipelines, and shaders for AAA titles, such as Heroes of the Storm and Halo 5: Guardians.
I would like to thank my beautiful wife, Megan, for years of support and understanding and Matthew Phillips for giving me my debut in the industry.
Alan Wolfe is a self-taught game and engine programmer who has worked at companies such as inXile Entertainment, Midway, Warner Bros., and Blizzard Entertainment. He has worked on titles including Line Rider 2, Unbound, Gotham City Impostors, Battle Nations, Insanely Twisted Shadow Planet, and StarCraft II: Heart of the Swarm. Alan is currently a senior engine programmer at Blizzard Entertainment, where he works on StarCraft II and Heroes of the Storm.
I'd like to thank Packt Publishing and the author for allowing me to contribute to this book and to help budding game programmers learn the same way I did. If you want to succeed as a game programmer, practice implementing everything you learn, hang out with like-minded individuals, who want to achieve the same things you do, and never stop learning new things.
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Preface
So, you want to program your own games using Unreal Engine 4 (UE4). You have a great number of reasons to do so:
So, you can use UE4 to write the main parts of your game once, and after that, deploy to iOS and Android Marketplaces without a hitch. (Of course, there will be a few hitches: iOS and Android in app purchases will have to be programmed separately.)
What is a game engine anyway?
A game engine is analogous to a car engine: the game engine is what drives the game. You will tell the engine what you want, and (using C++ code and the UE4 editor) the engine will be responsible for actually making that happen.
You will build your game around the UE4 game engine, similar to how the body and wheels are built around an actual car engine. When you ship a game with UE4, you are basically customizing the UE4 engine and retrofitting it with your own game's graphics, sounds, and code.
What will using UE4 cost me?
The answer, in short, is $19 and 5 percent of sales.
"What?" you say. $19?
That's right. For only $19, you get full access to a world class AAA Engine, complete with a source. This is a great bargain, considering the fact that other engines can cost anywhere from $500 to $1,000 for just a single license.
Why don't I just program my own engine and save the 5 percent?
Take it from me, if you want to create games within a reasonable time frame and you don't have a large team of dedicated engine programmers to help you, you'll want to focus your efforts on what you sell (your game).
Not having to focus on programming a game engine gives you the freedom to think only about how to make the actual game. Not having to maintain and bug-fix your own engine is a load off your mind too.
A game's overview – the Play-Reward-Growth loop
I want to show you this diagram now because it contains a core concept that many novice developers might miss when writing their first games. A game can be complete with sound effects, graphics, realistic physics, and yet, still not feel like a game. Why is that?
Starting at the top of the loop, Play actions committed during the game (such as defeating a monster) result in rewards for the player (such as gold or experience). These rewards, in turn, can be used for in-game Growth (such as stats increases or new worlds to explore). This Growth then drives the gameplay in new and interesting ways. For example, a new weapon can change the basic mechanics of fighting, new spells let you take on groups of monsters with a completely different approach, or new modes of transportation can let you reach areas that were previously inaccessible.
This is the basic core loop that creates interesting gameplay. The key is that Play must result in some kind of Reward—think of glittering gold pieces popping out of nasty baddies. For rewards to have a point, it must result in some kind of Growth in the gameplay. Think about how many new locations were unlocked with the hook shot in The Legend of Zelda.
A game that is only Play (without Rewards or Growth) won't feel like a game: it will feel only like a really basic prototype of a game. For example, imagine a flight simulator with just an open world and no goals or objectives as well as without the ability to upgrade your plane or weapons. It wouldn't be much of a game.
A game with only Play and Rewards (but no Growth) will feel primitive and simple. The rewards will not satisfy the player if they cannot be used for anything.
A game with only Play and Growth (without Rewards) will just be seen as a mindless increasing challenge, without giving the player a sense of gratification for his achievements.
A game with all three elements will keep the player engaged with an entertaining Play. The Play has a rewarding result (loot drops and story progression), which results in the Growth of the game world. Keeping this loop in mind while you are devising your game will really help you to design a complete game.
Tip
A prototype is the proof of concept of a game. Say, you want to create your own unique version of Blackjack. The first thing you might do is program a prototype to show how the game will be played.
Monetization
Something you need to think about early in your game's development is your monetization strategy. How will your game make money? If you are trying to start a company, you have to think of what will be your sources of revenue from early on.
Are you going to try to make money from the purchase price, such as Jamestown, The Banner Saga, Castle Crashers, or Crypt of the Necrodancer? Or, will you focus on distributing a free game with in-app purchases, such as Clash of Clans, Candy Crush Saga, or Subway Surfers?
A class of games for mobile devices (for example, builder games on iOS) make lots of money by allowing the user to pay in order to skip Play and jump straight to the rewards and Growth parts of the loop. The pull to do this can be very powerful; many people spend hundreds of dollars on a single game.
Why C++
UE4 is programmed in C++. To write code for UE4, you must know C++.
C++ is a common choice for game programmers because it offers very good performance combined with object-oriented programming features. It's a very powerful and flexible language.
What this book covers
Chapter 1, Coding with C++, talks about getting up and running with your first C++ program.
Chapter 2, Variables and Memory, talks about how to create, read, and write variables from computer memory.
Chapter 3, If, Else, and Switch, talks about branching the code: that is, allowing different sections of the code to execute, depending on program conditions.
Chapter 4, Looping, discusses how we repeat a specific section of code as many times as needed.
Chapter 5, Functions and Macros, talks about functions, which are bundles of code that can get called any number of times, as often you wish.
Chapter 6, Objects, Classes, and Inheritance, talks about class definitions and instantiating some objects based on a class definition.
Chapter 7, Dynamic Memory Allocation, discusses heap-allocated objects as well as low-level C and C++ style arrays.
Chapter 8, Actors and Pawns, is the first chapter where we actually delve into UE4 code. We begin by creating a game world to put actors in, and derive an Avatar class from a customized actor.
Chapter 9, Templates and Commonly Used Containers, explores UE4 and the C++ STL family of collections of data, called containers. Often, a programming problem can be simplified many times by selecting the right type of container.
Chapter 10, Inventory System and Pickup Items, discusses the creation of an inventory system with the ability to pick up new items.
Chapter 11, Monsters, teaches how to create monsters that give chase to the player and attack it with weapons.
Chapter 12, Spell Book, teaches how to create and cast spells in our game.
What you need for this book
To work with this text, you will need two programs. The first is your integrated development environment, or IDE. The second piece of software is, of course, the Unreal Engine itself.
If you are using Microsoft Windows, then you will need Microsoft Visual Studio 2013 Express Edition for Windows Desktop. If you are using a Mac, then you will need Xcode. Unreal Engine can be downloaded from https://www.unrealengine.com/.
Who this book is for
This book is for anyone who wants to write an Unreal Engine application. The text begins by telling you how to compile and run your first C++ application, followed by chapters that describe the rules of the C++ programming language. After the introductory C++ chapters, you can start to build your own game application in C++.
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, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "The variableType is going to tell you what type of data we are going to store in our variable. The variableName is the symbol we'll use to read or write that piece of memory".
A block of code is set as follows:
New terms and important words are shown in bold. Text that appears on the screen appears like this: From the File menu, select New Project...
Note
Extra information that is relevant, but kind of a side note, appears in boxes like this.
Tip
Tips and tricks appear like this.
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Questions
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Chapter 1. Coding with C++
You're a first-time programmer. You have a lot to learn!
Academics often describe programming concepts in theory but like to leave implementation to someone else, preferably someone from the industry. We don't do that in this book—in this book, we will describe the theory behind C++ concepts and implement our own game as well.
The first thing I will recommend is that you do the exercises. You cannot learn to program simply by reading. You must work with the theory with the exercises.
We are going to get started by programming very simple programs in C++. I know that you want to start playing your finished game right now. However, you have to start at the beginning to get to that end (if you really want to, skip over to Chapter 12, Spell Book, or open some of the samples to get a feel for where we are going).
In this chapter, we will cover the following topics:
Setting up our project
Our first C++ program will be written outside of UE4. To start with, I will provide steps for both Xcode and Visual Studio 2013, but after this chapter, I will try to talk about just the C++ code without reference to whether you're using Microsoft Windows or Mac OS.
Using Microsoft Visual C++ on Windows
In this section, we will install a code editor for Windows, Microsoft's Visual Studio. Please skip to the next section if you are using a Mac.
Note
The Express edition of Visual Studio is the free version of Visual Studio that Microsoft provides on their website. Go to http://www.visualstudio.com/en-us/products/visual-studio-express-vs.aspx to start the installation process.
To start, you have to download and install Microsoft Visual Studio Express 2013 for Windows Desktop. This is how the icon for the software looks:
Tip
Do not install Express 2013 for Windows. This is a different package and it is used for different things than what we are doing here.
Once you have Visual Studio 2013 Express installed, open it. Work through the following steps to get to a point where you can actually type in the code:
Tip
Note that there is a small box at the bottom with the text Solution name. In general, Visual Studio Solutions might contain many projects. However, this book only works with a single project, but at times, you might find it useful to integrate many projects into the same solution.
Now you are in the Visual Studio 2013 environment. This is the place where you will do all your work and code.
However, we need a file to write our code into. So, we will add a C++ code file to our project, as shown in the following screenshot:
Add your new source code file as shown in the following screenshot:
You will now edit Source.cpp. Skip to the Your First C++ Program section and type in your code.
Using XCode on a Mac
In this section, we will talk about how to install Xcode on a Mac. Please skip to the next section if you are using Windows.
Xcode is available on all Mac machines. You can get Xcode using the Apple App Store (it's free), as shown here:
Note
You might be tempted to click on the SpriteKit Game icon, but don't click on it.
Tip
Git is a Version control system. This basically means that Git keeps the snapshots of all the code in your project every so often (every time you commit to the repository). Other popular source control management tools (scm) are Mercurial, Perforce, and Subversion. When multiple people are collaborating on the same project, the scm tool has the ability to automatically merge and copy other people's changes from the repository to your local code base.
Okay! You are all set up. Click on the main.cpp file in the left-hand side panel of Xcode. If the file doesn't appear, ensure that the folder icon at the top of the left-hand side panel is selected first, as shown in the following screenshot:
Creating your first C++ program
We are now going to write some C++ source code. There is a very good reason why we are calling it the source code: it is the source from which we will build our binary executable code. The same C++ source code can be built on different platforms such as Mac, Windows, and iOS, and in theory, an executable code doing the exact same things on each respective platform should result.
In the not-so-distant past, before the introduction of C and C++, programmers wrote code for each specific machine they were targeting individually. They wrote code in a language called assembly language. But now, with C and C++ available, a programmer only has to write code once, and it can be deployed to a number of different machines simply by sending the same code through different compilers.
Tip
In practice, there are some differences between Visual Studio's flavor of C++ and Xcode's flavor of C++, but these differences mostly come up when working with advanced C++ concepts, such as templates.
One of the main reasons why using UE4 is so helpful is that UE4 will erase a lot of the differences between Windows and Mac. The UE4 team did a lot of magic in order to get the same code to work on both Windows and Mac.
Note
A real-world tip
It is important for the code to run in the same way on all machines, especially for networked games or games that allow things such as shareable replays. This can be achieved using standards. For example, the IEEE floating-point standard is used to implement decimal math on all C++ compilers. This means that the result of computations such as 200 * 3.14159 should be the same on all the machines.
Write the following code in Microsoft Visual Studio or in Xcode:
Press Ctrl + F5 to run the preceding code in Visual Studio, or press + R to run in Xcode.
The first time you press Ctrl + F5 in Visual Studio, you will see this dialog:
Select Yes and Do not show this dialog again—trust me, this will avoid future problems.
The first thing that might come to your mind is, "My! A whole lot of gibberish!"
Indeed, you rarely see the use of the hash (#) symbol (unless you use Twitter) and curly brace pairs {} in normal English texts. However, in C++ code, these strange symbols abound. You just have to get used to them.
So, let's interpret this program, starting from the first line.
This is the first line of the program:
This line has two important points to be noted:
This is the next line of code:
The comments beside this line explain what the using statement does: it just lets you use a shorthand (for example, cout) instead of the fully qualified name (which, in this case, would be std::cout) for a lot of our C++ code commands. Some people don't like a using namespace std; statement; they prefer to write the std::cout longhand every time they want to use cout. You can get into long arguments over things like this. In this section of the text, we prefer the brevity that we get with the using namespacestd; statement.
This is the next line:
This is the application's starting point. You can think of main as the start line in a race. The int main() statement is how your C++ program knows where to start; take a look at the following figure:
If you don't have an int main() program marker or if main is spelled incorrectly, then your program just won't work because the program won't know where to start.
The next line is a character you don't see often:
This { character is not a sideways mustache. It is called a curly brace, and it denotes the starting point of your program.
The next two lines print text to the screen:
The cout statement stands for console output. Text between double quotes will get an output to the console exactly as it appears between the quotes. You can write anything you want between double quotes except a double quote and it will still be valid code.
Tip
To enter a double quote between double quotes, you need to stick a backslash (\) in front of the double quote character that you want inside the string, as shown here:
The \ symbol is an example of an escape sequence. There are other escape sequences that you can use; the most common escape sequence you will find is \n, which is used to jump the text output to the next line.
The last line of the program is the return statement:
This line of code indicates that the C++ program is quitting. You can think of the return statement as returning to the operating system.
Finally, the end of your program is denoted by the closing curly brace, which is an opposite-facing sideways mustache:
Semicolons
Semicolons (;) are important in C++ programming. Notice in the preceding code example that most lines of code end in a semicolon. If you don't end each line with a semicolon, your code will not compile, and if that happens, you can be fired from your job.
Handling errors
If you make a mistake while entering code, then you will have a syntax error. In the face of syntax errors, C++ will scream murder and your program will not even compile; also, it will not run.
Let's try to insert a couple of errors into our C++ code from earlier:
Warning! This code listing contains errors. It is a good exercise to find all the errors and fix them!
As an exercise, try to find and fix all the errors in this program.
Note
Note that if you are extremely new to C++, this might be a hard exercise. However, this will show you how careful you need to be when writing C++ code.
