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- Herausgeber: Packt Publishing
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
XNA Game Studio enables hobbyists and independent game developers to easily create video games. It gives you the power to bring your creations to life on Windows, the Xbox 360, the Zune, and the Windows Phone platforms. But before you give life to your creativity with XNA, you need to gain a solid understanding of some game development concepts.This book covers both the concepts and the implementations necessary to get you started on bringing your own creations to life with XNA. It details the creation of four games, all in different styles, from start to finish using the Microsoft XNA Framework, including a puzzler, space shooter, multi-axis shoot-'em-up, and a jump-and-run platform game. Each game introduces new concepts and techniques to build a solid foundation for your own ideas and creativity. Beginning with the basics of drawing images to the screen, the book then incrementally introduces sprite animation, particles, sound effects, tile-based maps, and path finding. It then explores combining XNA with Windows Forms to build an interactive map editor, and builds a platform-style game using the editor-generated maps. Finally, the book covers the considerations necessary for deploying your games to the Xbox 360 platform.By the end of the book, you will have a solid foundation of game development concepts and techniques as well as working sample games to extend and innovate upon. You will have the knowledge necessary to create games that you can complete without an army of fellow game developers at your back.
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Table of Contents
XNA 4.0 Game Development by Example Beginner's Guide
XNA 4.0 Game Development by Example Beginner's Guide
Copyright © 2010 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: September 2010
Production Reference: 1180910
Published by Packt Publishing Ltd.
32 Lincoln Road
Olton
Birmingham, B27 6PA, UK.
ISBN 978-1-84969-066-9
www.packtpub.com
Cover Image by Vinayak Chittar (<[email protected]>)
Credits
Author
Kurt Jaegers
Reviewers
Rodolfo Rigo Calabrezi
Dustin Heffron
Alexandre Ribeiro de Sá
Acquisition Editor
David Barnes
Development Editor
Wilson D'souza
Technical Editor
Dayan Hyames
Copy Editor
Laxmi Subramanian
Indexers
Hemangini Bari
Monica Ajmera Mehta
Editorial Team Leader
Aditya Belpathak
Project Team Leader
Ashwin Shetty
Proofreaders
Jacqueline McGhee
Chris Smith
Graphics
Nilesh R. Mohite
Production Coordinator
Arvindkumar Gupta
Cover Work
Arvindkumar Gupta
About the Author
Kurt Jaegers is a database administrator by day, and a long-time hobbyist game developer, having built games for everything from the Commodore 64 to the Xbox 360. He is the owner of xnaresources.com, one of the earliest XNA-focused tutorial websites.
I would like to thank my wife Linda for proofreading the earliest versions of this book, as well as my brother Jason for providing the graphics for Flood Control, Asteroid Belt Assault, and the map tiles for Gemstone Hunter, along with the title screens for all of the games.
I would also like to thank the team at Packt Publishing for guiding me through my first book-authoring experience.
About the Reviewers
Rodolfo Rigo Calabrezi has worked in desktop publishing and web advertising campaigns, PC and mobile applications, critical systems and web 2.0 frontend. In the 90s, he made games for the MSX and TRS-Color platforms. In 2004, he worked as the CTO at Eleven Cells, a game development studio. He built an impressive professional network. He was a member of IGDA, working directly on programming, game design, art production, and QA. He teaches and gives lectures in schools about game development. He is in charge of Quantix Games, a Brazilian game development studio. He knows PHP, HTML, CSS, JavaScript, C/C++, C#, HLSL, engine architecture, graphics pipeline, ODE, Ageia, Direct3D, OpenGL, Jupiter, Cipher, PopCap, HGE, XNA, and Flash and is learning UDK and Unity. For DCC, he works with Photoshop, Flash, modo, Reason, and Nuendo, and is learning XSI and Maya. He is familiar with the following platforms—PC, PocketPC, Amiga, Xbox 360, and PS2, and is new to iPhone and iPad.
He is interested in development for other console platforms like PS3, Nintendo Wii, and DS.
Dustin Heffron is an avid gamer and programmer. He graduated in 2010 from Penn State University with a Bachelor's of Science degree in Computer Science. He has had 7+ years of experience programming in various languages and environments, including all C-based languages and most .NET languages. He has worked with XNA since 2007 and applied it in a variety of military and video game related projects.
Currently, Dustin works for the Applied Research Lab at Penn State as a Graphical User Interface programmer and Acid Lab Studios as Lead Programmer. He is planning on releasing his first episodic commercial game, "The Scarab Gauntlet" in late 2010, with additional episodes to follow.
I would like to thank my boss Mitch Lebold for giving me the opportunity to research and apply XNA to a variety of real-world projects. Without this experience, I wouldn't be the developer I am today. I would also like to thank Andy Strauch, producer and founder of Acid Lab Studios for giving me the opportunity to program such a great game and being patient with me during the busier times of life. Lastly, I would like to thank Packt Publishing for letting me review this insightful book, which I've greatly enjoyed reading.
Alexandre Ribeiro de Sá is a Producer, Director, Programmer and self-proclaimed frustrated artist. Alexandre was present in many game development community websites in Brazil giving support in translation and writing articles about software development and CG. Today as a producer, programmer, and sometimes as a game designer in his own game studio, the Vortex Game Studios in São Paulo, Brazil, he works with outsourcing and in his own games titles for computer and video game consoles.
Preface
The Microsoft XNA Framework provides a powerful set of tools to allow development teams of any size, from the individual developer to larger independent teams, to rapidly develop high performance quality games for multiple Microsoft-related platforms.
This book will present a series of video games, utilizing XNA Game Studio and the XNA Framework to delve into the world of 2D game development targeting the Microsoft Windows environment. We will utilize XNA's 2D graphics capabilities to present our games to the player, and look at the fundamental systems behind several game design challenges, such as path-finding, collision detection, special effects, and more.
Each of the four games in this book cover a new gaming style, and introduce progressively more advanced techniques and systems to provide a foundation for bringing your own creations to life.
What this book covers
Chapter 1, Introducing XNA Game Studio begins by looking at the history of the XNA Framework and its predecessors, and installing the Windows Phone Development Tools package that includes the version 4.0 release of the XNA tools. We wrap up this chapter by looking at the building blocks of an XNA game and putting together an XNA mini-game called SquareChase.
Chapter 2, Flood Control – Underwater Puzzling introduces a board-based puzzle game called Flood Control. We introduce the XNA Content Pipeline, and build a recursive function to determine the state of the game board while playing.
Chapter 3, Flood Control – Smoothing out the Rough Edges refines and completes the Flood Control game, adding animated rotation, movement, and fading of game pieces. We will implement a scoring system and cover displaying text to the screen.
Chapter 4, Asteroid Belt Assault – Lost in Space begins developing our second game. This time we put together a space-based shooter. We will create a basic moving star field using a simple particle system, and introduce frame-based sprite animation. We will add moving asteroids to our star field and examine how to detect collisions between asteroids and make them respond realistically. We add a player-controlled spaceship, and enemies that can fly across the screen following pre-defined waypoints.
Chapter 5, Asteroid Belt Assault – Special Effects wraps up Asteroid Belt Assault. We implement collision detection between the player, enemies, asteroids, and bullets and create particle-based explosions. Finally, we will look at loading and playing sound effects to bring life to our in-game events.
Chapter 6, Robot Rampage – Multi-Axis Mayhem begins the construction of a tank-based game in which the player can move and fire independently using either an Xbox 360 controller or the keyboard. We build a tile-map based game world and a camera class to view a screen-sized area of the larger world, and implement player collision with the walls of the tile map.
Chapter 7, Robot Rampage – Lots and Lots of Bullets completes Robot Rampage by expanding on our particle-based explosion system, and adding enemies, player goals, and weapon upgrades to our tile map. We allow the player to fire at the enemies with several different weapons. Finally, we create an implementation of the A* path-finding algorithm to allow the enemy tanks to track down the player.
Chapter 8, Gemstone Hunter – Put on your Platform Shoes introduces a side-scrolling, jump-and-run platform game. We start by evolving our tile-based mapping system to allow multiple layers of tiles, and look at combining XNA and Windows Forms to produce a map editor for Gemstone Hunter. As part of this process, we will look at building more complex solutions that contain multiple projects, and separate our game's tile engine into a Game Library project.
Chapter 9, Gemstone Hunter – Standing on Your Own Two Pixels concludes the Gemstone Hunter project by examining an alternative method for frame-based sprite animation using player and enemy graphics from the XNA Platform Starter Kit. We implement platform physics and bring the game together by loading levels and reacting to their embedded code values.
What you need for this book
In order to install and use the Microsoft XNA 4.0 tools, you will need a Windows PC with either Microsoft Windows Vista or Microsoft Windows 7, and a video card supporting DirectX 9 or later. Shader Model 1.1 is required for XNA, but it is highly recommended that your video card support Shader Model 2.0 or later, as many of the XNA samples available online require 2.0 support.
Who this book is for
If you are an aspiring game developer who wants to take a shot at creating games for the Microsoft Windows platform with the XNA Framework, then this book is for you. Using this book, you can get started with creating games without any game development experience. A basic knowledge of C# would be helpful to kick start your game development, but it's not essential.
Conventions
In this book, you will find several headings appearing frequently.
To give clear instructions of how to complete a procedure or task, we use:
Time for action – heading
Instructions often need some extra explanation so that they make sense, so they are followed with:
What just happened?
This heading explains the working of tasks or instructions that you have just completed.
You will also find some other learning aids in the book, including:
Have a go hero – heading
These set practical challenges and give you ideas for experimenting with what you have learned.
You will also 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 are shown as follows: "If the mouse reports that the left button is pressed, the code checks with the currentSquare object by calling its Contains() method to determine if the mouse's coordinates fall within its area."
A block of code is set as follows:
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: "Run your game by clicking on Start Debugging from the Debug menu".
Tip
Tips and tricks appear like this.
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Tip
Downloading the example code for this book
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Errata
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Questions
You can contact us at <[email protected]> if you are having a problem with any aspect of the book, and we will do our best to address it.
Chapter 1. Introducing XNA Game Studio
With the release of Windows 95, Microsoft also introduced the DirectX Application Programming Interface (API), which allowed Windows-based applications to integrate closely, in a standard way, with the graphics hardware available on the system. Prior to DirectX, most PC game development targeted MS-DOS, as Windows-based graphics were too slow for most gaming needs.
Although faster, working with the DirectX API could be challenging. The DirectX Software Development Kit (SDK) is targeted at C++, with no official support for other languages. The developer is also faced with large volumes of background work to get a DirectX project to the point where he can display images on the screen before ever considering the logic of the game itself.
In 2002, Microsoft released Managed DirectX as an interface to the API from its new .NET development environment. The .NET Framework consists of a set of code libraries to perform common programming tasks, and the Common Language Runtime (CLR) which allows code written in the various .NET languages (including Visual Basic .NET and C#) to be compiled into common runtime code. In order to support devices such as Windows Mobile phones, a subset of the .NET Framework was released, called the .NET Compact Framework. The .NET CF, as it is often abbreviated, removed non-essential components of the full Framework in the interest of saving storage space on handheld devices.
While Managed DirectX 2.0 was still in the beta phase, the project was cancelled, and Microsoft XNA was introduced in its place. XNA consists of the XNA Framework, a set of code libraries to perform common graphics, sound, and other game related tasks, and XNA Game Studio, an extension of the Visual Studio C# interface that includes a number of project templates to make use of the XNA Framework.
The XNA project templates include an integrated game loop, easy to use (and fast) methods to display graphics, full support for 3D models, and simple access to multiple types of input devices.
In addition to Windows games, XNA allows deployment to both the Xbox 360, the Zune handheld media player (with XNA 3.1) and Windows Phone 7 Series phones (with XNA 4.0). For the first time, a game console manufacturer has released a supported method for individual game developers to create (and sell!) content for their game console. Microsoft has even established the Xbox Indie Games system on Xbox Live to allow you to sell your creations to the world.
Tip
What does XNA stand for, anyway?
According to the developers, XNA is an acronym for "XNA's Not Acronymed".
In this introductory chapter you will:
Overview of the games
Many beginning developers make the mistake of attempting to tackle far too large a project early on. Modern blockbuster video games are the result of the efforts of hundreds of programmers, designers, graphic artists, sound effects technicians, producers, directors, actors, and many other vocations, often working for years to create the game.
That does not mean that the efforts of a solo developer or small team need to be dull, boring, and unplayable. This book is designed to help you develop a solid understanding of 2D game development with XNA Game Studio. By the time you have completed the projects in this book, you will have the knowledge necessary to create games that you can complete without an army of fellow game developers at your back.
In this chapter, you will build your first XNA mini game, chasing squares around the screen with your mouse cursor. In subsequent chapters the following four more detailed games are presented:
Flood Control: An explosion in one of the research laboratories has cracked the pressure dome protecting your underwater habitat. Work quickly to construct a series of pipes to pump water out of the habitat before it floods. Flood Control is a board-based puzzle game with simple game mechanics and slowly increasing difficulty.
Asteroid Belt Assault: After being separated from your attack fleet in Hyper Space, you find yourself lost in an asteroid field without communications or navigation systems. Work your way through the chaos of the asteroid belt while combating alien pilots intent upon your destruction. A vertically scrolling space shooter, Asteroid Belt Assault introduces scrolling backgrounds, along with player and computer controlled characters.
Robot Rampage: In the secret depths of a government defence facility, a rogue computer has taken control of robotic factories across the world, constructing an army of mechanical soldiers. Your mission—infiltrate these factories and shut down their network links to break the computer's control. A multi-axis shooter utilizing both of the analog control sticks on the Xbox 360 gamepad controller, Robot Rampage generates and manages dozens of on-screen sprites and introduces world map construction.
Gemstone Hunter: Explore the Australian wilderness, abandoned mines and ancient caves in a search for fabulous treasures. In Gemstone Hunter you will construct a classic platform-style game, including a Windows Forms-based level editor and a multi-map "world" to challenge the player.
The games are each presented over two chapters. In the first chapter, the basics are implemented to the point where the game is playable. In the second chapter, features and polish are added to the game.
Each game introduces new concepts and expands on topics covered in the previous games. At the end of each game chapter, you will find a list of exercises challenging you to use your newly gained knowledge to enhance previous games in the book.
We will focus on Windows as our platform for the games presented in this book. That said, the code presented in this book requires very little in the way of changes for other XNA platforms, generally only requiring implementation of platform-specific controls (gamepads, touch screen, and so on) and consideration of the differences in display sizes and orientation on non-Windows devices.
System requirements
In order to develop games using XNA Game Studio, you will need a computer capable of running both Visual C# 2010 Express and the XNA Framework extensions. The general requirements are:
Component
Minimum requirement
Notes
Operating System
Windows Vista SP2
or
Windows 7 (All editions except Starter)
As of XNA 4.0, Windows XP is no longer officially supported.
Graphics card
Shader Model 1.1 support
DirectX 9.0 support
Microsoft recommends Shader Model 2.0 support as it is required for many of the XNA Starter Kits and code samples. The projects in this book similarly require Shader Model 2.0 support.
Optional requirements
Windows Phone
DirectX 10 or later, Compatible Video Card
Development tools include a Windows Phone emulator to test applications without deployment to a physical device.
Zune platform
Zune Software 3.0 or higher, Visual C# 2008, XNA Game Studio 3.1
Only required if you plan to deploy games to a Zune handheld device. Zune development is supported under XNA 3.1.
Xbox Live
Xbox Live Silver membership, XNA Creator's Club Premium membership
Xbox Live Silver is free. The XNA Creator's Club Premium membership costs $49 for 4 months or $99 for 1 year.
Tip
HiDef vs. Reach
As of version 4.0, XNA now supports two different rendering profiles. The HiDef profile is available on the Xbox 360 and Windows PCs with DirectX 10 or better video cards, and uses Shader Model 3.0. The Reach profile is available on all XNA platforms, and uses Shader Model 2.0. If you have a DirectX 9 video card, or wish to distribute your games to computers with DirectX 9 support, you will need to right-click on your project in Solution Explorer and select Properties. On the XNA Game Studio tab, select the Reach profile.
Installing XNA Game Studio
To get started developing games in XNA, you will need to download and install the software. You will need both Visual C# and XNA Game Studio. With the release of XNA 4.0, the install packages have been consolidated, and both required components are included in the Windows Phone Developer Tools package.
Time for action – installing XNA Game Studio
Tip
Other versions of Visual Studio and XNA
Different versions of Visual Studio and XNA can be installed on the same PC without interfering with each other. If you wish to target the Zune platform, you will need to install Visual C# 2008 Express and XNA 3.1. Additionally, Visual Studio Express and Visual Studio Professional can coexist on the same PC, and XNA will integrate with both of them if it is installed after Visual Studio.
What just happened?
You have now successfully installed the Windows Phone Developers Tools, including XNA Game Studio 4.0 and the Redistributable Font Pack provided by Microsoft for XNA developers.
Tip
The redistributable fonts package
To use its integrated text drawing methods, XNA games need to convert normal Windows fonts into an internal format called a SpriteFont. These SpriteFonts get distributed with your game, which means you will not be able to use most of the fonts on your computer due to licensing restrictions. For this reason, Microsoft has provided a selection of fonts that XNA developers can freely distribute without purchasing an individual license to do so.
Building your first game
XNA attempts to simplify many of the basic elements of game development by handling things like the game update loop and simplifying the display of graphical objects. To illustrate just how much of the background work is integrated into the XNA project templates, let's jump in straight away and create your first game within a few minutes of finishing the installation.
In SquareChase, we will generate randomly positioned squares of different colors while the user attempts to catch them with their mouse pointer before they disappear. While building the project, we will discuss each of the major code sections pre-defined by the XNA templates.
Time for action – creating a new Windows game project
What just happened?
Each of the XNA project templates is a series of files and settings that get copied to your new project folder. Included in this set of files is the Game1.cs file, which is the heart of your XNA game.
Tip
Backup your projects
When you create your project, the Location field specifies where it will be saved. By default, Visual Studio creates a folder in your user documents area called Visual Studio 2010 to store both programs and configuration information. Under this folder is a Projects folder that contains subfolders for each new project you create. Make backups of your projects on a regular basis. You do not want to lose your hard work to a disk failure!
Anatomy of an XNA game
The most basic XNA game will have all of its code contained in the file called Game1.cs. This file is generated when you create a new project, and contains override declarations for the methods used to manage your game. In addition to the Game1 class' declarations area, there are five primary methods you will customize for any XNA project.
The declarations area
Right below the class declaration for Game1 is the class level declarations area. By default, this area contains two variables:
The graphics object provides access to, not surprisingly, the system's video card. It can be used to alter the video mode, the size of the current viewport (the area that all drawing work will be clipped to if specified), and retrieve information about Shader Models the video card supports.
XNA provides the SpriteBatch class to allow you to (very quickly) draw 2D images (called "sprites") to the screen.
The declarations area is the spot for any variables that need to be maintained outside of any of the individual methods listed below. In practice, any data you need to keep track of throughout your game will be referenced, in some way, in your declarations section.
Time for action – draw SquareChase!
What just happened?
Any time you use a SpriteBatch object to draw to the display, you need to wrap the calls inside a Begin() and End() pair. Any number of calls to spriteBatch.Draw() can be included in a single batch and it is common practice to simply start a Begin() at the top of your Draw() code, use it for all of your drawing, and then End() it right before the Draw() method exits. While not benefiting our SquareChase game, batching sprite drawing calls greatly speeds up the process of drawing a large number of images by submitting them to the rendering system all at once instead of processing each image individually.
The SpriteBatch.Draw() method is used to draw a Texture2D object to the screen. There are a number of different options for how to specify what will be drawn. In this case, the simplest call requires a Texture2D object (squareTexture), a destination Rectangle (currentSquare), and a tint color to apply to the sprite. The expression playerScore % 3 takes the player's score, divides it by 3, and returns the remainder. The result will always be 0, 1, or 2. This fits perfectly as an index to the elements in the colors array, allowing us to easily change the color of the square each time the player catches one.
Finally, the spriteBatch.End() tells XNA that we have finished queuing up sprites to draw and it should actually push them all out to the graphics card.
Time for action – play SquareChase!
What just happened?
You just finished your first XNA game, that's what!
Granted it is not exactly the next blockbuster, but at only 33 lines of code, it implements a simple game mechanic, user input, score tracking and display, and clock-based timing. Not bad for a few minutes work.
Have a go hero
As simple as it is, here are a couple of enhancements you could make to SquareChase:
Summary
You now have a development environment set up for working on your XNA game projects, including Visual Studio Express and XNA Game Studio 4.0.
We also saw how the XNA game loop initializes and executes, and constructs an elementary game by expanding on the default methods provided by the Windows Game template.
It is time to dive head first into game creation with XNA. In the next chapter, we will begin building the puzzle game Flood Control in which the player is challenged to pump water out of their flooding underwater research station before the entire place really is underwater!
Chapter 2. Flood Control – Underwater Puzzling
It was just another day at the bottom of the ocean until an explosion in one of the storage bays cracked the protective dome around Deep Sea Research Lab Alpha. Now the entire place is flooding, and the emergency pump system is a chaotic jumble of loose parts.
This chapter focuses on the following concepts:
Designing a puzzle game
The Puzzler has always been a popular game genre. From old standbys like Tetris to modern crazes like Bejeweled, puzzle games are attractive to players because they do not require a long-term time investment or a steep learning curve.
The game mechanic is the heart of any good puzzle game. This mechanic is usually very simple, with perhaps a few twists to keep the players on their toes.
