AdvancED Game Design with Flash

809 Pages·2010·21.015 MB·English

by  Rex van der Spuy

REX VAN DER SPUY
AdvancED
Game Design
Flash
with
All the essential techniques that every game designer
should know.
Physics for games, pathfinding, game structure with
the MVC design pattern, tile-based games, vector
math, and advanced collision detection strategies.
AS3.0 Code compatible with Flash CS3 – CS5,
Flash Builder, and the open-source Flex SDK.
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AdvancED Game
Design with Flash

Rex van der Spuy
AdvancED Game Design with Flash
AdvancED Game Design with Flash
Copyright © 2010 by Rex van der Spuy
All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means, electronic or
mechanical, including photocopying, recording, or by any information storage or retrieval system, without the prior written
permission of the copyright owner and the publisher.
ISBN-13 (pbk): 978-1-4302-2739-7
ISBN-13 (electronic): 978-1-4302-2740-3
Printed and bound in the United States of America 9 8 7 6 5 4 3 2 1
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The source code for this book is freely available to readers at www.friendsofed.com in the Downloads section.
Credits
President and Publisher: Coordinating Editor:
Paul Manning Kelly Moritz
Lead Editor: Copy Editor:
Ben Renow-Clarke Marilyn Smith
Technical Reviewer: Compositor:
Joshua Freeney Lynn L’Heureux
Editorial Board: Indexer:
Clay Andres, Steve Anglin, Mark Beckner, Brenda Miller
Ewan Buckingham, Gary Cornell, Jonathan Gennick,
Artist:
Jonathan Hassell, Michelle Lowman, Matthew Moodie,
April Milne
Duncan Parkes, Jeffrey Pepper, Frank Pohlmann,
Douglas Pundick, Ben Renow-Clarke, Cover Designer:
Dominic Shakeshaft, Matt Wade, Tom Welsh Bruce Tang
For Mom and Jim, for all your love and support
Contents at a Glance
About the Author.....................................................................................................xiii
About the Technical Reviewer...............................................................................xiv
About the Cover Image Designer............................................................................xv
Acknowledgments....................................................................................................xi
Introduction............................................................................................................xvii
Chapter 1: Modeling Game Data...............................................................................1
Chapter 2: Vectors: Ghosts in the Machine ...........................................................67
Chapter 3: Collisions Between Circles.................................................................161
Chapter 4: Collisions Between Polygons.............................................................223
Chapter 5: Pixel-Perfect Collision and Destructible Environments....................305
Chapter 6: Explosions, Blitting, and Optimization...............................................367
Chapter 7: Make It Fun! Sound, Music, and AI.....................................................445
Chapter 8: Tile-Based Game Design.....................................................................503
Chapter 9: Pathfinding...........................................................................................623
Chapter 10: XML and External Data......................................................................691
Index.......................................................................................................................749
iv
Contents
About the Author.....................................................................................................xiii
About the Technical Reviewer...............................................................................xiv
About the Cover Image Designer............................................................................xv
Acknowledgments....................................................................................................xi
Introduction............................................................................................................xvii
Chapter 1: Modeling Game Data...............................................................................1
Verlet integration............................................................................................................................2
The problem with Euler integration...............................................................................................3
Understanding Verlet integration...............................................................................................4
Using Verlet integration..............................................................................................................5
Using the main application class.............................................................................................13
Onward to Planet X!.................................................................................................................18
Introducing the Model-View-Controller Pattern..........................................................................22
Understanding MVC.................................................................................................................23
MVC in action...........................................................................................................................25
MVC your way..........................................................................................................................30
An MVC player and map view example..................................................................................32
Verlet + MVC + physics = fun!.................................................................................................44
A crash course in the drawing API..............................................................................................49
Drawing lines............................................................................................................................50
Drawing squares......................................................................................................................50
Drawing circles.........................................................................................................................52
Adding filters.............................................................................................................................53
Gradient fills..............................................................................................................................54
Complex shapes.......................................................................................................................57
Introducing interfaces...................................................................................................................64
Summary.......................................................................................................................................66
v
CONTENTS
Chapter 2: Vectors: Ghosts in the Machine ...........................................................67
What are vectors?........................................................................................................................68
Vector characteristics...............................................................................................................69
Calculating the angle................................................................................................................73
Vector normals.........................................................................................................................75
Normalizing vectors..................................................................................................................78
Using and viewing vectors...........................................................................................................80
Creating the vector model........................................................................................................80
Creating the vector view..........................................................................................................87
Let’s see what those vectors look like!...................................................................................87
Adding and subtracting vectors...................................................................................................94
Scaling vectors.........................................................................................................................96
Gravity in action......................................................................................................................100
Real gravity.............................................................................................................................105
Projecting vectors.......................................................................................................................105
Are the vectors pointing in the same direction?...................................................................107
Projection in action.................................................................................................................110
Using vector projection for environmental boundaries........................................................113
Intersection.................................................................................................................................115
Finding the intersection point................................................................................................116
Intersection in action..............................................................................................................118
Collision and bounce..................................................................................................................121
Collision on one side of the line............................................................................................121
Resolving the collision...........................................................................................................129
Bounce....................................................................................................................................135
Momentum..............................................................................................................................138
Solid objects...........................................................................................................................139
Collision on both sides of the line..........................................................................................141
Bounce, friction, and gravity..................................................................................................146
A crash course in embedding assets........................................................................................151
Embedding fonts....................................................................................................................151
Embedding images................................................................................................................152
Important vector formulas..........................................................................................................155
Summary.....................................................................................................................................160
vi
CONTENTS
Chapter 3: Collisions Between Circles.................................................................161
Abstract classes.........................................................................................................................162
Understanding abstract and concrete classes.....................................................................162
Creating and implementing abstract classes.......................................................................166
Keyboard and mouse control.....................................................................................................176
Collision-handling basics...........................................................................................................181
Collisions between moving and stationary circles...............................................................181
Collision between a circle and a line.....................................................................................187
Collision between moving circles..........................................................................................202
Multiple-object collision..............................................................................................................211
Fast-moving circles....................................................................................................................215
Summary.....................................................................................................................................221
Chapter 4: Collisions Between Polygons.............................................................223
The separating axis theorem.....................................................................................................224
Understanding SAT................................................................................................................224
Using SAT...............................................................................................................................225
Rectangle collisions....................................................................................................................237
Rectangle collision handling in action...................................................................................238
Bounce and friction................................................................................................................242
Triangle collisions.......................................................................................................................244
SAT with triangles—the wrong way......................................................................................246
SAT with triangles—the right way.........................................................................................247
Triangle collision handling in action......................................................................................250
Triangle collision wrap-up......................................................................................................261
Oriented bounding box collisions..............................................................................................262
Polygon and circle collisions......................................................................................................267
Circle and square collisions...................................................................................................268
Circle and triangle collisions..................................................................................................276
Left-facing triangles................................................................................................................282
Case studies...............................................................................................................................283
Case study 1: Polygon environment.....................................................................................283
Case study 2: Block Game....................................................................................................286
Multilevel games.........................................................................................................................301
Summary.....................................................................................................................................303
vii
CONTENTS
Chapter 5: Pixel-Perfect Collision and Destructible Environments....................305
Vector vs. bitmap graphics........................................................................................................306
Using bitmaps.............................................................................................................................308
Bitmap collisions.........................................................................................................................309
Checking for a collision..........................................................................................................310
The problems with bitmap collision.......................................................................................314
Finding the collision boundary...............................................................................................315
Bitmap collision-detection strategies.........................................................................................320
Convex shapes.......................................................................................................................321
Surfaces..................................................................................................................................328
Concave shapes.....................................................................................................................330
Adding objects to scrolling environments.................................................................................344
Using two-dimensional arrays...............................................................................................345
Creating and adding the objects...........................................................................................349
Scrolling the objects...............................................................................................................350
Building a rotating gun turret.....................................................................................................351
Drawing and rotating the cannon..........................................................................................352
Firing bullets...........................................................................................................................355
Moving and removing bullets.................................................................................................356
Destroying things!.......................................................................................................................357
Bitmap collision using points.................................................................................................359
Erasing the bitmap.................................................................................................................360
Jagged rocks..........................................................................................................................362
Summary.....................................................................................................................................365
Chapter 6: Explosions, Blitting, and Optimization...............................................367
A simple particle explosion........................................................................................................368
Using timer events for animation...........................................................................................369
Creating the Explosion class.................................................................................................371
A more realistic explosion..........................................................................................................378
Taking a snapshot..................................................................................................................379
Slicing and dicing...................................................................................................................384
Starburst explosions...................................................................................................................396
Fast particle explosions.............................................................................................................401
Introducing bit-block transfer.................................................................................................401
Basic blitting............................................................................................................................404
viii