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UnrealScript Game
Programming
Cookbook
Discover how you can augment your game development
with the power of UnrealScript
Dave Voyles
BIRMINGHAM - MUMBAI
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UnrealScript Game Programming Cookbook
Copyright © 2013 Packt Publishing
All rights reserved. No part of this book may be reproduced, stored in a retrieval system,
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Publishing cannot guarantee the accuracy of this information.
First published: February 2013
Production Reference: 1080213
Published by Packt Publishing Ltd.
Livery Place
35 Livery Street
Birmingham B3 2PB, UK.
ISBN 978-1-84969-556-5
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Cover Image by Dave Voyles ()

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Credits
Author
Dave Voyles
Reviewers
Kolby Brooks
John P. Doran
William Gaul
Dan Weiss
Acquisition Editor
Erol Staveley
Lead Technical Editor
Arun Nadar
Technical Editors
Pooja Prakashan
Veronica Fernandes
Project Coordinator
Arshad Sopariwala
Proofreader
Maria Gould
Indexer
Tejal R. Soni
Graphics
Valentina D'silva
Aditi Gajjar
Production Coordinator
Nitesh Thakur
Cover Work
Nitesh Thakur
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About the Author
Dave Voyles has worked as a coordinator for the last two Indie Games Uprisings on Xbox
Live, an annual event organized to highlight the talented developers and their titles on Xbox
Live Indie Games. Additionally, he has released a title of his own, Piz-ong on XBLIG, as well
as projects using Unity and the Unreal Engine for game jams.
He's procient in C# and UnrealScript, and all facets of the Unreal Engine, as well as a number
of 3D modeling suites, including 3DS Max and Maya.
He has also worked as a technical reviewer on Unreal Development Kit Game Programming
with UnrealScript: Beginner's Guide, Packt Publishing and Unreal Development Kit Beginner's
Guide, Packt Publishing. Moreover, he works as managing editor at Armless Octopus, a site
dedicated to cover Indie game development with an emphasis on XNA and XBLIG. You can
nd him on Twitter under the handle
@DaveVoyles or at www.About.me/DaveVoyles.
I'd like to thank my mother and father, for always supporting my gaming
habit as a child, despite my poor taste in Sega CD era FMV games.
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About the Reviewers
Kolby Brooks took a strong interest to programming at the young age of seven, getting his
start by modifying games such as Unreal, Dirt Track Racing, and Half-Life.
He now has over 14 years of growing experience in multiple game-related elds including, but
not limited to, multiplayer anti-cheat solutions, game programming, and engine development.
As a hobby, he develops and maintains multiple third-party solutions for games such as server
tools, utilities, and modication frameworks.
You can contact Kolby by e-mail at

I would like to thank my family, especially my mother and father, for their
continued support over the years. In addition, I would like to thank Jason
Ismail and Draco Rat for being great friends and gaming buddies.
John P. Doran is a technical game designer who has been creating games for over
10 years. He has worked on an assortment of games in student, mod, and professional

projects independently as well as in teams having up to or over 70 members.
He previously worked at LucasArts on Star Wars: 1313 as a game design intern, the only
junior designer on a team of seniors. He later graduated from DigiPen Institute of Technology
in Redmond, WA, with a Bachelor of Science in Game Design.
He is currently a software engineer at DigiPen's Singapore campus while at the same time
tutoring and assisting students with difculties in Computer Science concepts, programming,
linear algebra, game design, and advanced usage of UDK, Flash, Unity, and Actionscript in a
development environment.
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He is the author of Mastering UDK Game Development Hotshot, Packt Publishing and is the
co-author of UDK iOS Game Development Beginner's Guide, Packt Publishing.
He can be found online at
and can be contacted at john@
johnpdoran.com
.
Thanks so much to the author for allowing me to give him my thoughts while
writing the book, I hope that they helped.

I'd also like to thank my brother, Chris Doran, and my girlfriend Hannah Mai
for being there for me whenever I needed them and being patient while I
was working on this.

I'd also like to thank Arun Nadar, Arshad Sopariwala, and all the lovely
people at Packt for all of their support and knowhow!
William Gaul is an aspiring game developer working primarily in the Unreal Development
Kit (UDK). Since 2008, he has learned a wide range of skills in the industry, and maintains
an active YouTube channel (
and blog
( dedicated to game development.
His programming knowledge includes Java, C/C++, UnrealScript, BASIC, HTML/CSS, and

LaTeX. He also specializes in a variety of media solutions, with experience in the Adobe
Creative Suite, Blender, and FL Studio.
Dan Weiss is currently a programmer working at Psyonix Studios in San Diego, CA. He is a
2010 graduate of DigiPen Institute of Technology, having worked on titles such as Attack of
the 50ft Robot! during his time there. He has been working in the Unreal Engine since 2004,
independently producing the mod Unreal Demolition for Unreal Tournament 2004 and Unreal
Tournament 3. At Psyonix, he has been involved with Unreal Engine work on mobile devices,
having released ARC Squadron for iOS devices.
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Table of Contents
Preface 1
Chapter 1: Development Environments 7
Introduction 7
Using UnCodeX 8
Dungeon Defenders to save the day 12
Unreal Script IDE 14
nFringe 16
Unreal X-Editor 19
Editing runtime values with Remote Control 26
Chapter 2: Archetypes and Prefabs 33
Introduction 33
Constructing a leaking pipe prefab 34
Adding particles to our prefab 37
Adding audio effects to our prefab 39
Creating a PointLight archetype 40
Creating a subarchetype from an archetype 47
Chapter 3: Scripting a Camera System 53
Introduction 53
Conguring the engine and editor for a custom camera 55
Writing the TutorialCamera class 58
Camera properties and archetypes 63
Creating a rst person camera 68
Creating a third person camera 72
Creating a side-scrolling camera 75
Creating a top-down camera 81
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ii
Table of Contents
Chapter 4: Crafting Pickups 89
Introduction 89
Creating our rst pickup 92
Creating a base for our pickup to spawn from 96
Animating our pickup 99
Altering what our pickup does 100
Allowing vehicles to use a pickup 105
Chapter 5: AI and Navigation 111
Introduction 111
Laying PathNodes on a map 114
Laying NavMeshes on a map 118
Adding a scout to create NavMesh properties 121
Adding an AI pawn via Kismet 124
Allowing a pawn to wander randomly around a map 130
Making a pawn patrol PathNodes on a map 134
Making a pawn randomly patrol PathNodes on a map 138
Allowing a pawn to randomly patrol a map with NavMeshes 139
Making a pawn follow us around the map with NavMeshes 143
Chapter 6: Weapons 149
Introduction 149
Creating a gun that res homing missiles 150
Creating a gun that heals pawns 168
Creating a weapon that can damage over time 170
Adding a ashlight to a weapon 174
Creating an explosive barrel 177
Creating a landmine 186
Chapter 7: HUD 189
Introduction 189

Displaying a bar for the player's health 190
Drawing text for a player's health 197
Displaying a bar for the player's ammo 201
Drawing text for the player's ammo 205
Drawing the player's name on screen 208
Creating a crosshair 211
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iii
Table of Contents
Chapter 8: Miscellaneous Recipes 217
Introduction 217
Creating an army of companions 217
Having enemies ash quickly as their health decreases 221
Creating a crosshair that uses our weapon's trace 224
Changing the crosshair color when aiming at a pawn 230
Drawing a debug screen 232
Drawing a bounding box around pawns 242
Index 251
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iv
Table of Contents
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Preface
The Unreal Engine was rst introduced to the gaming landscape in 1998 through Epic's
rst-person shooter, Unreal. While the core of it is written in C++, Epic managed to craft
a language of their own, called UnrealScript, which is similar to Java in a number of ways.
In November 2009, Epic released the Unreal Development Kit, an SDK utilizing the Unreal
Engine, which allows developers to write and release games of their own. Many of this
generation's leading AAA titles utilize the Unreal Engine, including the Mass Effect,
BioShock, and Gears of War franchises.

My plan with this book is to allow you to have the ability to craft worlds of your own, by
teaching you how to program for the industry's leading 3D engine for AAA development.
What this book covers
Chapter 1, Development Environments, will take us through several development
environments which can handle UnrealScript, dene some of the perks and pitfalls of each,
and highlight the benets of understanding the source code, through UncodeX and the
Dungeon Defenders Development Kit.
Chapter 2, Archetypes and Prefabs, will show you that as a programmer, one of your tasks
is to assist the level designers. This can be done in a number of ways, but one of the most
useful ways is to create what are known as prefabs and archetypes. By creating templates
for objects and actors and only exposing the variables that a designer will nd to be useful,
you can make your work, and that of a designer, far more efcient.
Chapter 3, Scripting a Camera System, tells us about cameras in UDK that are an essential
part of gameplay. They can simultaneously be one of the most frustrating yet rewarding
things to program, as once they are working correctly they can completely change a player's
experience, because you control their window to the world.
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Preface
2
Chapter 4, Crafting Pickups, tells us that articial intelligence can cover a variety of things in
UDK, so we won't delve too far down that path, at least not in this chapter. Here, we'll briey
cover it, and how the AI interacts with pickups throughout the game, specically what attracts
them to certain pickups. Furthermore, we'll dive into creating our own pickups and how they
interact with our pawn's inventory.
Chapter 5, AI and Navigation, shows us that the Unreal Engine has two ways of handling path
nding. They both have their pros and cons, despite being somewhat similar. They can simply
be broken down into waypoints and navigation meshes. Each offer their own sets of perks
and pitfalls, so we'll explore the pros and cons of both.
Chapter 6, Weapons, walks you through the weapons in UDK that are inventory items, which
can be handled by the player, and are generally used to re a projectile. On the surface, the

default weapon system found in Unreal Engine 3 may appear to be catered to creating various
types of guns as is common in most FPS games; but it's actually pretty easy to create various
sorts of weapons and usable inventory items, which may be found in other types of games
such as healing projectiles, bombs, landmines, or ashlights, as in the case with Alan Wake.
Chapter 7, HUD, shows us that heads-up display, or HUD, in addition to a user interface (UI),
offers a means for providing information to a player to allow them to interact with the game
world. UDK offers two methods for creating a HUD. The rst, and far more simple method
that we'll be covering here is the canvas. The other method, which requires knowledge of the
ash language and some fancy art skills, allows UDK to make use of a third-party tool called
ScaleForm to draw the HUD.
Chapter 8, Miscellaneous Recipes, walks you through the recipes that are going to cover
things which may not necessarily t in one particular chapter, but are still very valuable in
a number of applications. We'll go over a new scheme for aiming our weapons and drawing
a crosshair, as well as allowing our pawn to ash continuously as its health depreciates,
among other useful items.
What you need for this book
For this book you will need the following items to get started:
f The latest build of the Unreal Development Kit, which can be found at
/> f An integrated development environment
f A solid understanding of object oriented programming basics
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Preface
3
Who this book is for
This book is designed for users who have a solid understanding of object oriented
programming and want to get introduced to a powerful yet unique language using a well
established framework. Although the Unreal Development Kit offers an extensive schema
for rst-person shooters, it can be so much more if harnessed correctly. Prior experience
with 3D Math or other 3D engines will certainly be helpful as well.
Conventions

In this book, you will nd 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: "A player's view into the world is determined by the
Camera class."
A block of code is set as follows:
classTutorialGame extends UTGame;
defaultproperties
{
PlayerControllerClass=class'Tutorial.TutorialPlayerController'
DefaultPawnClass=class'Tutorial.TutorialPawn'
DefaultInventory(0)=class'UTWeap_ShockRifle'
}
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: "Scroll down to World
Properties, and left-click on that".
Warnings or important notes appear in a box like this.
Tips and tricks appear like this.
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Preface
4
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1
Development
Environments
In this chapter, we will be covering the following recipes:
f Using UnCodeX
f Dungeon Defenders to save the day
f Unreal Script IDE
f nFringe
f Unreal X-Editor
f Editing runtime values with Remote Control
Introduction
Working with UnrealScript can be a daunting task at rst glance, especially because it has
years' worth of extensive improvements and iterations, in spite of being a language only used
for this application. To make things worse, UDK does not include a development environment
out of the box, so we're forced to nd one that best suits our needs. Fortunately there are
several out there, each of which bears many pros and cons.
In this chapter, we will look at several development environments which can handle
UnrealScript, dene some of the perks and pitfalls of each, and highlight the benets
of understanding the source code, through UnCodeX and the Dungeon Defenders
Development Kit.
So with that, let's talk about integrated development environments.
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Development Environments
8
Integrated development environments
An integrated development environment (IDE) sounds far more complicated than it is,
as it simply serves as a way for a developer to talk to the machine and write code for an
application. It usually consists of three components, a source code editor, build automation

tools, and a debugger. The IDEs we'll cover in this chapter provide all three.
Using UnCodeX
Now that we know what IDEs are and how they work, how do we use the code provided
by Epic? It's there for the taking, but we need an easy way to sift through it. That's where
UnCodeX comes in. Let's take a closer look.
UnCodeX is an open source tool which provides an easy interface to browse through the
code, analyzes UnrealScript, and is capable of producing a Javadoc like documentation
of the source code.
Every good programmer knows their source material. That doesn't mean you need to know
the engine inside out, but at least take some time to understand where your most important
classes are extending from, and what's available to you. There's no sense in reinventing the
wheel if someone has done it for you already, right?
Getting ready
The rst thing we'll need to do is acquire a copy of it for ourselves. Let's head over to
and download it.
Once you have it downloaded and installed, open it up. Personally, I keep it pinned to my
taskbar as it is a constant point of reference for my work that I nd myself accessing day
in and day out, along with my other Unreal tools.
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Chapter 1
9
How to do it…
On the left-hand side of the screen, you'll see the package browser. This allows us to see all
of the packages currently contained within your UDK directory of choice.
This can be updated manually by clicking on the Tree menu in the top-left corner of the
browser, and then clicking on Rebuild and Analyse. It may take a few moments to rebuild
the package, as it is sorting through any changes you may have made since the last time you
wrote any code. You can check the current status of the operation in the bottom-left corner
of the program.
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Development Environments
10
Adjacent to the package browser is the class tree browser. Most of the IDEs we'll be working
with will include a class tree as well. The tree browser allows us to dig deeper into the code
by seeing exactly how each and every class in UDK are connected to one another.
You'll notice that all classes in UDK extend from the Object class. It's the base class for
everything in the game and allows for everything in the game to share some common
properties and functions. Actor is perhaps the class you will be most concerned with
however, as it is the base class for all gameplay objects in UDK.
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Chapter 1
11
It can be a bit overwhelming at rst, especially when you see precisely how many classes are
there. Most of what is there you will never use, but it still makes for an incredible reference.
It's not what you know, but more importantly it's about knowing where to nd what you're
looking for.
To the right of the class tree you'll see the class browser. Double-click on one of the classes
from the class tree to view its contents to the right. Other classes will be underlined and
colored blue, just like when you create a URL in a web browser or word document.
Hovering the mouse cursor over any of the underlined text in the class browser will draw
a pop up on the screen, which illustrates the location on your hard drive where you can nd
that class. This is a great way to help visualize how UDK's classes are interconnected and
assist you in understanding how to best utilize them to create your own.
There's more
UnCodeX is an essential part of any UnrealScript programmer's tool belt. It can not only help
you understand what is currently running under the hood, but also help you understand the
best practices for extending from its base classes to create your own.
As a rule of thumb, you don't need to know the base code inside out, but it's essential that
you at least have an understanding of the work Epic has laid at your ngertips. This includes
the functions such as Tick, PostBeginStart.PostBeginPlayt, and the default

properties block.
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Development Environments
12
There are a number of other great resources to nd additional content and help for UDK
and UnrealScript. These include:
f Epic's UnrealScript forum at />Programming-and-Unrealscript
f Eat 3D's UnrealScript reference at /> f Epic's UDK Gems at />DevelopmentKitGems.html
Dungeon Defenders to save the day
Epic isn't the only team to offer a plethora of knowledge at your ngertips. Trendy
Entertainment, the development studio behind Dungeon Defenders, was also kind
enough to release much of their source code and development kit, in what is known
as Dungeon Defenders Development Kit (DDDK). Similar to UnCodeX, this source code
allows you to have a far greater understanding of how an entire game is pieced together.
Getting ready
The DDDK can be found by downloading and installing the Steam client at http://store.
steampowered.com/about/
. Once installed, click on View, which is at the top of your
screen, then select Tools. The DDDK is actually a piece of DLC, and can be found here.
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