Game Development Patterns with Unreal Engine 5: Build maintainable and scalable systems with C++ and Blueprint

Game Development Patterns with Unreal Engine 5

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To my wife, Becky, for her unrivaled love, support, and understanding as I pursue my career goals, and for always being by my side throughout all of the challenges. To my boys, Jack, Zach, and Lincoln, for their support and excitement at the prospect of me writing an actual book.

– Stuart Butler

To my wife, Rosie – her unconditional love and support for my efforts to reach my goals continue to keep me sane and true. To my parents, Martin and Sheila, for giving me the foundation I needed to succeed. To my sister, Amy, and her husband, Phil, for inspiring me to drive for better.

– Tom Oliver

Foreword

Stuart Butler and Tom Oliver are two of the most talented game developers and educators that I have had the pleasure of working with. Both are experts in the technologies that underpin modern video games and have a wealth of experience in turning imagination into reality through the creative sorcery of design and code.

Like most coders, my first programming project was getting the terminal to print out Hello World. From here, I started to tinker, making increasingly more complex and challenging projects in a very solution-focused manner. My code was often a sprawling mess of comments and redundancy; it wasn’t very efficient, but it worked (usually). It wasn’t until I had to revisit (and decipher) old code or if I had to collaborate with fellow developers that my cluttered code became a problem. Fortunately, my teacher introduced me to the world of design patterns.

Design patterns are one of the most valuable assets in the game developer’s arsenal. They keep your workflow manageable and efficient, and common patterns make collaboration easier. In the fast-paced, multi-disciplinary world of game development, design patterns are an essential ally.

Through this book, you will learn the essential principles of programming and build a strong understanding of the value and application of design patterns. You will benefit from an appreciation of how these approaches work in practice through working with one of the most powerful tools in game development, the Unreal Engine 5 games engine. You will learn the essential grounding to allow you to seamlessly blend between the Unreal Blueprint visual scripting system and C++, allowing you to develop complex and scalable video game projects.

Butler and Oliver are exceptional developers, designers, and world-leading experts in the Unreal Engine. The knowledge they share through this book will be invaluable to anyone working with this tool. Their step-by-step approach and the strong focus on practical examples and learning through doing will help you get the most out of your game’s development projects.

Unlock the full potential of the Unreal Engine with Games Development Patterns.

Prof. Christopher J. Headleand

National Teaching Fellow, Head of Games Development,

Staffordshire University

Contributors

About the authors

Stuart Butler is an Unreal Engine expert with over 13 years of experience in teaching game development in higher education. Stuart has published projects in a multitude of disciplines, including technical design, art, and animation. Stuart is the course director for games technology at Staffordshire University, responsible for the programming team within the UK’s largest games education department. Stuart is also an Unreal Authorized Instructor and has published work as an educational content creator with Epic Games, developing learning materials for Unreal Engine 5. Stuart holds a BSc (hons) in computer games design and a PgC in higher and professional education.

I would like to thank my family for their unwavering support and my colleagues at Staffs Uni for inspiring me to pursue my ambitions. I’d also like to thank Greg Penninck, Bobbie Fletcher, and Justin Mohlman especially, for believing in me throughout my career so far and providing some amazing opportunities. Lastly, I’d like to thank Tom for joining me on this adventure to becoming published authors.

Tom Oliver is a game programmer with over 10 years of experience in working with game engines, both commercially and in an educational capacity. He has used Unreal Engine for contract work both in and out of the games industry, from creating systems for games to mixed reality training simulations. Tom is a senior lecturer and course leader at Staffordshire University, responsible for maintaining the award-winning structure and teaching of the course in the UK’s largest games education department. Tom holds a BSc (hons) in computer games design and programming and a PgC in higher and professional education. Tom specializes in researching gameplay systems driven by mathematical phenomena.

I would like to thank my family for always being my tribe and my colleagues at Staffs Uni for being my squadron. Special thanks to Yvan Cartwright and Paul Roberts for starting the programming fire in me – I hope that this book shows that I paid attention, and Davin Ward, for sticking with me for the last decade. Lastly, thank you to Stu for navigating these word-filled waters with me – we did the thing.

About the reviewer

Ahmed Farrag, a proficient game developer with an MSc in computer science, excels in Unreal Engine development and problem-solving. He is currently the Unreal Engine lead developer at TransformologyXR, building on a rich background that includes contributions to Rumbling Games Studios, Astra Nova, Epoch, and Camouflage Studios.

Ahmed’s portfolio boasts a range of titles, including the successfully published titles Vulcan Runner and Knights of Lights: The Prologue, and the upcoming releases Atlantis Heroes and Kingdom Sports. His unwavering commitment to innovation in delivering exceptional interactive experiences makes him a standout in the industry.

Table of Contents

Preface

Part 1: Learning from Unreal Engine

1

Understanding Unreal Engine 5 and its Layers

Technical requirements

Introducing Unreal Engine 5

Installing Unreal Engine 5 and preparing your development environment

The Fuzzy layer – bridging the gap from C++ to Blueprint

Property Specifiers

Function Specifiers

Useful inheritance

Translating back from Blueprint to C++

Worked example

Summary

Questions

Answers

2

Hello Patterns

Technical requirements

S.O.L.I.D. principles

Single responsibility

Open-closed

Liskov substitution

Interface segregation

Dependency inversion

Exploring solutions to common problems

The moving box problem

The rotating box problem

The cascading cast chain problem

The trade-off

Summary

3

UE5 Patterns in Action – Double Buffer, Flyweight, and Spatial Partitioning

Technical requirements

Double buffer

Flyweight

Spatial partitioning

Introducing World Partition

Understanding when objects are loaded

Ensuring actors are loaded when required

Enabling World Partition on an existing level

Summary

4

Premade Patterns in UE5 – Component, Update Method, and Behavior Tree

Technical requirements

Understanding and creating components

Applying the update method for prototyping gameplay

Working with behavior trees

Creating the AI controller

Creating the Blackboard asset

Building the behavior tree

Summary

Part 2: Anonymous Modular Design

5

Forgetting Tick

Technical requirements

Before we begin

A world that ticks

A clock that stops

Event driven systems

Summary

6

Clean Communication – Interface and Event Observer Patterns

Technical requirements

Interfacing communication across classes in UE5

Blueprint interfaces

Interface events versus functions

Interfaces in C++

Building an example interface communication

Implementing event delegate communication across UE5

Event delegates in Blueprint

Event delegates in C++

Building a useful delegate tool

Summary

7

A Perfectly Decoupled System

Technical requirements

Using UML to plan a sample hierarchy

What are the types of class relations?

What is a sequence diagram?

Decoupling the reference train

Modularity and decoupling

Establishing infrastructure

Implementing decoupled design in an example

Benefits of decoupling

Summary

Part 3: Building on Top of Unreal

8

Building Design Patterns – Singleton, Command, and State

Technical requirements

Implementing a Singleton pattern – understanding why it’s a Pandora’s box

Implementing the Command pattern for different use cases

Command pattern for undo functionality in Blueprint Utilities

Command pattern for gameplay in C++

Creating the many levels of a state machine

Exploring animation state machines

Enum/switch implementation

Static versus instanced states

Concurrent state machines

Hierarchical state machines

Pushdown automata

Summary

9

Structuring Code with Behavioral Patterns – Template, Subclass Sandbox, and Type Object

Technical requirements

Exploring the template pattern

Building the template (parent class)

Creating child classes

Template pistol

Template shotgun

Understanding subclass sandbox

Building the sandbox (parent class)

Creating child classes

Sandbox pistol

Sandbox shotgun

Type object pattern

Variants

Data Tables

Data Assets

Summary

10

Optimization through Patterns

Technical requirements

Using dirty flags to reduce unnecessary processing

Application of dirty flags

How data locality affects code efficiency

Hot/cold splitting

Contiguous arrays

Object pooling our resources to save time later

Implementing object pooling

Making an object pool

Summary

Index

Other Books You May Enjoy

Preface

Welcome to Game Development Patterns with Unreal Engine 5. In this book, we will be exploring design patterns, a series of tools and practices through which we can learn to write faster and easier to work with code. We will also be exploring a range of different patterns and learn to apply them to project development in Unreal Engine 5.

By the end of this book, you will be able to design systems with the perfect C++/Blueprint blend for maintainable and scalable systems.

Who this book is for

This book is targeted at beginner and intermediate game developers who are working with Unreal Engine and would like to improve their C++ coding practices. This book will help you produce clean, reusable code using design patterns. We will be covering some introductory tasks to show the key fundamentals of using Unreal Engine 5 and some of its tools; however, we will not be teaching you Unreal Engine from scratch.

You would benefit from having some experience with Unreal Engine 4 or 5, but you do not need a deep working understanding of the toolset.

What this book covers

Chapter 1

, Understanding Unreal Engine 5 and Its Layers, explores Unreal Engine 5 and offers a brief history. We will look at the fuzzy layer that bridges the gap between C++ and Blueprint and learn how to translate Blueprint back to C++.

Chapter 2

, Hello Patterns, focuses on the principles that underpin all good code. We will explore design patterns as well as some common Blueprint mistakes, looking at how we can fix them.

Chapter 3

, UE5 Patterns in Action – Double Buffer, Flyweight, and Spatial Partitioning, discovers how Unreal Engine 5 employs these three design patterns as we explore a range of tools within the engine.

Chapter 4

, Premade Patterns in UE5 – Component, Behavior Tree, and Update Method, utilizes the pre-built implementations of these three design patterns and explores the tools within the engine to expand simple systems.

Chapter 5

, Forgetting Tick, develops your understanding of Tick, looks at why its usage can cause issues, and explores two approaches to building systems without it.

Chapter 6

, Clean Communication – Interface and Event Observer Patterns, explores design patterns that allow us to improve how different actors communicate with each other, producing more efficient solutions to communication.

Chapter 7

, A Perfectly Decoupled System, discovers how we can use UML as a methodology for planning class hierarchies, to decouple the reference train.

Chapter 8

, Building Design Patterns – Singleton, Command, and State, examines these three design patterns to understand their usage, limitations, and suitability across a range of game genres.

Chapter 9

, Structuring Code with Behavioral Patterns – Template, Subclass Sandbox, and Type Object, explores the three most common structural patterns while building weapons classes in C++, which we will expand with Blueprint, exploring how the two languages can be used together.

Chapter 10

, Optimization through Patterns, dives into the key elements of optimization before releasing games by exploring the Dirty Flag, Data Locality, and Object Pooling design patterns.

To get the most out of this book

You will need a version of Unreal Engine 5 installed on your computer. All code examples have been tested on Unreal Engine 5.0.3, and they should work with later versions of the Engine. However, this may not be the case if Epic Games makes any major changes to the core engine.

If you are using the digital version of this book, we advise you to type the code yourself or access the code from the book’s GitHub repository (a link is available in the next section). Doing so will help you avoid any potential errors related to the copying and pasting of code.

We’ve included commented versions of the code found within the book as part of the GitHub repository, as opposed to including comments in the code samples, making the code easier to read and follow within the book.

Download the example code files

You can download the example code files for this book from GitHub at https://github.com/PacktPublishing/Game-Development-Patterns-with-Unreal-Engine-5

. If there’s an update to the code, it will be updated in the GitHub repository.

We also have other code bundles from our rich catalog of books and videos available at https://github.com/PacktPublishing/

. Check them out!

Conventions used

There are a number of text conventions used throughout this book.

Code in text: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: This also applies to the ScoreWidget class we will use to display the player’s score, which has been provided as part of the Chapter Resources folder.

A block of code is set as follows:

class APlayerController_CH7 : public APlayerController

{

public:

    void Init();

protected:

    UPROPERTY(EditAnywhere)

    TSubclassOf _PlayerPawn;

    UPROPERTY(VisibleAnywhere, BlueprintReadOnly)

    TObjectPtr _Character;

}

Bold: Indicates a new term, an important word, or words that you see on screen. For instance, words in menus or dialog boxes appear in bold. Here is an example: Enable the checkbox next to Editor symbols for debugging and click Apply.

Tips or important notes

Appear like this.

Get in touch

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and mention the book title in the subject of your message.

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Part 1:Learning from Unreal Engine 5

In this part, we will be exploring Unreal Engine and the design patterns that are already included in the engine, or available to use as part of the many tools within the engine.

We will start by exploring Unreal Engine 5 and how it works with layers of code, before exploring a series of common mistakes that developers make when using Blueprint and seeing how to fix them. We will then discover a range of different patterns, exploring these with examples built from a mix of Blueprints and C++ and using a variety of tools, including World Partition and AI Behavior Trees.

This part has the following chapters:

Chapter 1

, Understanding Unreal Engine 5 and Its Layers

Chapter 2

, Hello Patterns

Chapter 3

, UE5 Patterns in Action – Double Buffer, Flyweight, and Spatial Partitioning

Chapter 4

, Premade Patterns in UE5 – Component, Behavior Tree, and Update Method

1

Understanding Unreal Engine 5 and its Layers

Design patterns are a series of tools and practices by which we can learn to write faster and easier-to-work-with code.

Applying design patterns to projects developed in Unreal Engine 5 (UE5) will allow you to make your projects more performant, easier to read, and build upon, as well as develop an improved understanding of how the engine works.

We’re going to begin by developing an understanding of the history of Unreal Engine and ensuring that we are all set up to work with the engine, covering some basic ideas of how C++ and Unreal Engine’s visual scripting language, Blueprint, are linked.

In this chapter, we’re going to cover the following main topics:

Introducing Unreal Engine 5

Installing Unreal Engine 5 and preparing your development environment

The Fuzzy layer – bridging the gap from