Table Of ContentFocus On
3D Terrain
Programming
Trent Polack
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To my Mom, my step-dad, my sister Gabby,
and all of my friends.
And also to an imaginary tiger-sized cat.
Foreword
H
ow many times have you visited your favorite programming
forum or mailing list and been amazed at the sheer number
of posts on terrain rendering algorithms that seem to fly at you from
every angle? Terrain rendering seems to be a favorite subject among
today’s hobbyist programmers; it serves as an excellent portal to more
demanding problems and their solutions. However, terrain rendering
is by no means a simple problem, and a particular solution can get
rather complex. People from all walks of “programming” life have
tried their hand at coming up with the next best solution for rendering
their idea of a perfect world. Some even dare say that there are as
many terrain rendering algorithms as there are people who write
terrain engines. Most of these solutions are variations of more widely
accepted solutions. These solutions are generally accepted by people
as solutions that give good performance. Some of them have been
around for quite a while and have been modified over the years to
adapt to the ever-changing hardware they are meant to run on.
This book takes three of these generally accepted solutions and puts
them through their paces. I am very pleased to say that one of these
solutions came from my very own puddle of programming ideas
I have popping up every now and again in a flash of enlightenment.
As this book compares three terrain rendering solutions without any
prejudice or bias, I am not one to talk about them, obviously. I will
leave that to the author.
—Willem H. de Boer
Acknowledgements
Wow, so many people need to be thanked. Let’s start with the trademark peo-
ple: my family and friends. First of all, I want to thank my mom, my step-dad,
my sister, and my dog. They rock, and without them, I wouldn’t be writing
this right now. I’d also like to thank my friends. Thanks to Kyle Way (you
owe me) for dealing with me at late times in the night and always distracting
me with things. Thanks to Nate, Renae, and Randy for always being there.
Also thanks to Luke, Claudia, Amanda, Laurelin, Marissa, Ella, Rebecca,
Lacee, Laura, and everyone else. You know who you are!
Next it’s time to thank the people I’m not so close to. (In fact, these are the
people who are as good of friends as any, but I’ve never actually seen them
before.) First of all, thanks to Evan for being a good programming partner
and a good friend. Also thanks to Ron for helping me out a ton and for just
being a good guy. Also, a huge thanks to Dave Astle, Kevin Hawkins, and
Jeff Molofee for getting me where I am today and being great mentors. Also
thanks to Mike, Sean, and Warren for being three really cool guys. I’d also
like to give a huge thanks to all the guys in #gamedev who put up with my
late-night rants about green bunnies and cats running around my monitor
waging war over Christmas lights.
Now, I’d like to thank all the people who made this book possible. A huge
thanks goes to Emi Smith, André LaMothe, and Karen Gill for helping to
make this book the best it could be, for actually giving me the opportunity
to write it, and just generally being a great bunch of people. I’d also like to
give another huge thanks to Willem de Boer, Stefan Rottger, and Mark
Duchaineau for giving me ideas and reviewing respective chapters to make
them the best they could be. In addition, thanks to the people at Longbow
Digital Arts for letting me use a demo of TreadMarksfor this book’s CD, the
guys at Digital Awe for letting me put Tropical Stormon the CD, and the rest
of the guys who let me use their demos on the book’s CD: Thatcher Ulrich,
Leonardo Boselli, and Serba Andrey.
Finally, I’d like to thank the people and things that had no idea they were
even involved with this book at all. A huge thanks goes to Fender for making
my incredible guitar. Also, Pepsi Corporation deserves a thanks or two for
making the legendary Mountain Dew. Another really big thank you goes to
the guys at New Found Glory for being a great band and also to Tool, the
Offspring, Blink 182, and Nirvana. And finally, thanks to the people at Pacific
Sun for providing my “coding clothing.”
About the Author
Trent Polack is a high school student currently attending Kalkaska
High School. He has been programming in various languages since he
was nine years old, when his cousin showed him the joys of QBASIC.
Trent is an active contributor to the programming community, con-
tributing several tutorials to GameDev.net and its affiliates. He has a
passion for game programming, namely graphics, databases, and,
most of all, engine coding. When Trent is not programming, he takes
a large interest in reading (especially books by the late Douglas
Adams), basketball, playing guitar, and listening to music.
Contents at a Glance
Letter from the Series Editor . . . . . xii-xiii
Introduction . . . . . . . . . . . . . . . . . . . xiv
Part One
Introduction to Terrain Programming. . 1
CHAPTER 1 The Journey into the Great Outdoors. . 3
CHAPTER 2 Terrain 101 . . . . . . . . . . . . . . . . . . 15
CHAPTER 3 Texturing Terrain. . . . . . . . . . . . . . 39
CHAPTER 4 Lighting Terrain. . . . . . . . . . . . . . . 57
Part Two
Advanced Terrain Programming . . . . 73
CHAPTER 5 Geomipmapping for
the CLOD Impaired . . . . . . . . . . . . . 75
CHAPTER 6 Climbing the Quadtree. . . . . . . . . . 105
CHAPTER 7 Wherever You May ROAM. . . . . . . . 127
CHAPTER 8 Wrapping It Up:
Special Effects and More . . . . . . . 165
APPENDIX What’s on the CD. . . . . . . . . . . . . . 205
Index . . . . . . . . . . . . . . . . . . . . . 209
Contents
Introduction . . . . . . . . . . . . . . . . . . . xiv
Part One
Introduction to Terrain Programming. . 1
The Journey into
CHAPTER 1
the Great Outdoors . . . 3
“Terrain? No Thanks,I Already Ate.” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
General Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Terrain and Game Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Demo Building Made Easy!. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
The Main Demos. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
The Book at an Itty-Bitty Glance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Part One:Introduction to Terrain Programming. . . . . . . . . . . . . . . . . . . . . . 11
Part Two:Advanced Terrain Programming. . . . . . . . . . . . . . . . . . . . . . . . . . . 12
The Demos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Terrain 101 . . . . . . . . 15
CHAPTER 2
Heightmaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
The Creation of a Base Terrain Class. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Loading and Unloading a Heightmap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
The Brute Force of the Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Fractal Terrain Generation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Fault Formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Midpoint Displacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Contents ix
Texturing Terrain . . . . 39
CHAPTER 3
Simple Texture Mapping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Procedural Texture Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
The Region System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
The Tile System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Creating the Texture Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Improving the Texture Generator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Using Detail Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Lighting Terrain . . . . . 57
CHAPTER 4
Height-Based Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Coloring the Light Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Hardware Lighting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Lightmapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Slope Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Okay,Slope Lighting Is Cool,But How Is It Performed?. . . . . . . . . . . . . . . . 66
Creating a Slope-Lighting System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Dynamically Creating Lightmaps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Part Two
Advanced Terrain Programming . . . . 73
Geomip-mapping for
CHAPTER 5
the CLOD Impaired . . . 75
CLOD Terrain 101. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Why Bother with CLOD Terrain? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Not Everything Is Happy in the Land of CLOD Terrain . . . . . . . . . . . . . . . . 78
Wrapping Up Your Introduction to CLOD Terrain. . . . . . . . . . . . . . . . . . . . 78
Geomipmapping Theory for the Semi-CLOD Impaired . . . . . . . . . . . . . . . . . . . . 79
Simply the Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Triangle Arrangement Made Easy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
