ch2.htm

对于程序员来说可以利用JAVA来开发网络游戏！

is such an integral part of the Java runtime system. Unlike other
popular game programming languages such as C and C++, Java was
designed from the ground up to support networking over the Internet.
For this reason, the networking support in Java is much easier
to use and a lot more secure than add-on networking libraries
for C/C++.
<P>
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<TR><TD><B>Note</B></TD></TR>
<TR><TD>
<BLOCKQUOTE>
Network programming has long been a very complex and highly specialized area of software development. Prior to Java, most programmers had to focus all their efforts on network programming alone just to develop enough skills to do anything useful. Java has 
changed all that and made network programming a realistic pursuit for the rest of us.</BLOCKQUOTE>

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<P>
<P>
Combine Java's extensive network support with its platform independence
and you have a gaming platform that crosses all boundaries for
availability to users. With a networked Java game, you could be
sitting in front of a Windows 95 machine playing a game of Poker
with players in other parts of the world using completely different
machines, such as Sun workstations or Macintoshes. That's about
as good as it gets when it comes to distributed game play! You
learn all about network programming in Java on <A HREF="ch18.htm" >Day 18</A>,
&quot;Networking with Java.&quot;
<P>
Using the Space Invaders example again, there isn't a very clear
way to add network support because the original game was basically
a single player game. However, nothing is stopping you from adding
a mode in which two players join forces and battle the aliens.
Using this approach, you have to define a means of sending data
back and forth between the players so that each player's game
is up to date with the other player's actions. This technique
is known as synchronization and is a key topic on <A HREF="ch17.htm" >Day 17</A>,
&quot;The Basics of Multiplayer Gaming.&quot;
<H3><A NAME="MediaManagement"><B>Media Management</B></A></H3>
<P>
The last issue in regard to Java's support for games is <I>media</I>
<I>management</I>. Media management refers to the tracking of
media objects (graphics, sounds, and so on) as they are being
transferred across the Internet. If you didn't guess, the whole
issue of media management is unique to Web games because traditional
games reside on a single machine and get all their data from a
CD-ROM or hard drive.
<P>
To understand why media management is an issue, think about where
the data comes from when a game is playing. In a traditional game,
the data comes straight from the hard drive or CD-ROM. When you
consider distributed Java games, it becomes difficult to nail
down exactly where the game's content is coming from. Of course,
a Java game executes locally on the end user's machine, but it
is initially transferred from whatever Web server it is installed
on. Java games could certainly still be shipped on a CD-ROM like
traditional games, but doing so would bypass the whole point of
incorporating Java games into online Web content. For this reason,
most Java games transfer their data (media objects) over an Internet
connection.
<P>
Because transferring data over the Internet takes a finite amount
of time (often too finite!), it becomes necessary for Java games
to keep up with the time at which certain data is available for
use. In other words, you don't have the luxury of speedy hard
drive access, so you have to take into account the amount of time
it takes to transfer data over an Internet connection. For example,
it would be a bad thing to display a game screen when you have
the graphics for only half of the objects being displayed. Java
provides a feature for keeping up with which media objects have
been transferred, and therefore which ones are available for use.
Unfortunately, the current release of Java only supports the tracking
of images, and not sounds. You learn the details about tracking
images later this week on <A HREF="ch5.htm" >Day 5</A>, &quot;Java
Graphics Techniques.&quot; Media tracking support for sounds and
other types of media has been promised in a future release of
Java.
<P>
Returning to the trusted Space Invaders example, it's not too
difficult to determine what media objects the game is composed
of. Basically, each graphic element in the game is stored as an
image, which has to be transferred for the game to run correctly.
In addition to the images, you also have to deal with the individual
sound effects and the looped music sound. These elements are equally
important media content that have to be transferred along with
the images.
<H2><A NAME="GameDesign"><B><FONT SIZE=5 COLOR=#FF0000>Game Design</FONT></B></A>
</H2>
<P>
Now that you understand some of the reasons that Java is cool
for writing games, let's take a conceptual look at game design.
The rest of today's lesson focuses on the flow of thought necessary
to come up with a game plan. This thought should take place before
you begin to write any Java code. I know you're probably itching
to get into the technical side of things, but please be patient.
You'll get a good dose of Java code in due time!
<P>
Do you have some ideas of games you would like to write? If so,
you probably already realize that coming up with a good game idea
is often the easy part. Taking a game concept and making it reality
is where most of us fall short. That's okay; you just have to
take it a step at a time and think through the development process.
<P>
The first step in taking a game from concept to reality is to
get a solid idea of what you want the game to be. This doesn't
need to be an itemized list of every scene and every little creature
and interaction. It simply needs to state some minimal ground
rules about what your goal is for the final game.
<P>
Here are the key items you should address when beginning the game
development process:
<UL>
<LI>Basic idea
<LI>Storyline
<LI>Play modes
</UL>
<H3><A NAME="BasicIdea"><B>Basic Idea</B></A></H3>
<P>
The first thing you should do is determine the basic idea behind
your game. Is it a shoot-em-up, a maze game, a role-playing adventure
game, or some mixed combination? Or do you have an idea of a game
that doesn't really fit in an existing category? Is the object
to rescue good guys, kill bad guys, or just explore a strange
environment? What time frame is your game set in, or does it even
have a time frame? Write all this stuff down. Whatever comes to
mind, write it down, because brainstorms come and go and you don't
want to forget anything. Forcing yourself to formalize your ideas
causes you to think more about the game and clears up a lot of
things.
<P>
If you are having trouble coming up with a basic game idea, think
about the influences of a lot of the popular computer games. Many
games are based on movies, some on historical events, and others
on sports. Ultimately, computer games are models of the world
around us, whether fantasy or real, so look no farther when dreaming
up your game. Movies in particular can provide a lot of good creative
settings and storylines for games.
<P>
<CENTER><TABLE BORDERCOLOR=#000000 BORDER=1 WIDTH=80%>
<TR><TD><B>Note</B></TD></TR>
<TR><TD>
<BLOCKQUOTE>
Currently, there are even a few cases in which a game idea has served as the basis for a movie, which is pretty surprising. The really strange thing is that some of the movies are based on games with a very limited plot. For example, the immensely popular 
Mortal Kombat game, which is basically a straight-up fighting game with no plot, was made into a movie.</BLOCKQUOTE>

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<P>
<P>
Regardless of your inspiration, just remember that your game has
to be fun. Actually, that's why I think computer games are so
alluring to programmers. The overriding design goal is always
to maximize fun! Who wouldn't want to spend all day trying to
figure out the best way to have fun? If your game isn't fun to
play, the most dazzling graphics and sound won't be able to save
it. The point I'm trying to make is that you must make fun the
priority when designing your game. After you have a basic idea
of what your game will be and you've decided that you're going
to make it fun at all costs, you can develop a storyline.
<H3><A NAME="Storyline"><B>Storyline</B></A></H3>
<P>
Even if your game is a simple action game, developing a storyline
helps you to establish the landscape and think up creatures to
populate your game world. Putting your game in <BR>
the context of a story also brings the game player closer to your
world. For games in which the story is a more integral part, it
is often useful to develop a storyboard along with the storyline.
A <I>storyboard</I> tells the story scene by scene by using rough
sketches of each scene. A storyboard basically enables you to
create a visual layout of the entire game, based on the story.
Having a storyboard to reference helps ensure that you don't lose
sight of the story when you get into heavy development.
<H3><A NAME="PlayModes"><B>Play Modes</B></A></H3>
<P>
The final thing to consider when laying out your initial game
design is what play modes you will support. Will it be single
player, two player, networked, or some combination? This might
sound like a fairly simple decision, but it can have huge repercussions
on the game logic later. Even though Java provides a lot of support
for networking, network games typically incur a significantly
more complex design.
<P>
On the other hand, many single-player games will require some
degree of artificial intelligence to make the computer opponent
challenging to play against. Artificial intelligence can easily
get complicated and difficult to implement, so you need to weigh
your resources heavily into your game design when deciding on
play modes. Speaking of artificial intelligence, you learn all
about it on <A HREF="ch15.htm" >Day 15</A>, &quot;Teaching Games
to Think.&quot;
<H2><A NAME="Summary"><B><FONT SIZE=5 COLOR=#FF0000>Summary</FONT></B></A>
</H2>
<P>
Today you learned what Java has to offer games on the Web. Some
of the requirements of Web games were discussed, along with how
Java addresses many of the problems inherent in moving games to
the Web. You learned about the primary features of Java that directly
impact game development, along with their benefits and limitations.
In short, you learned today that Java, although not perfect (yet),
is positioned to be an extremely viable development tool for games
on the Web.
<P>
You finished up today's lesson with a discussion of general game
design ideas. Although not etched in stone, these ideas and suggestions
serve as good guidelines when you start working out your masterpiece.
This discussion also serves as a good ending to today's lesson,
because you will continue with more theory on <A HREF="ch3.htm" >Day 3</A>.
Tomorrow's lesson focuses on object-oriented programming in Java,
a topic you won't want to miss!
<H2><A NAME="QA"><B><FONT SIZE=5 COLOR=#FF0000>Q&amp;A</FONT></B></A>
<BR>
</H2>

<TABLE>
<TR VALIGN=TOP><TD WIDTH=50><B>Q</B></TD><TD><B>Does Java provide support for 3D graphics?</B>
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=50><B>A</B></TD><TD>No, not yet. The standard Java 1.0 API has no support for 3D graphics, but a future release of Java could well fix this. Also, there are some third-party Java graphics libraries in the works that might make 
viable alternatives to writing your own 3D graphics code.
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=50><B>Q</B></TD><TD><B>How do you play music in Java?</B>
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=50><B>A</B></TD><TD>Currently, the only way to play music is to loop a sampled sound clip stored in the ULAW sound format. There is talk of MIDI extensions for Java, but nothing real has surfaced yet. Keep your eyes open, though!
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=50><B>Q</B></TD><TD><B>Are there any limitations to how Java games can be networked?</B>
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=50><B>A</B></TD><TD>Not really. As long as you stay within the network security bounds imposed by Java, which you are forced to do anyway, the options available for network games are wide open. You can theoretically have as many 
players as you want, interacting however you choose to allow them.
</TD></TR>
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<P>
<H2><A NAME="Workshop"><B><FONT SIZE=5 COLOR=#FF0000>Workshop</FONT></B></A>
</H2>
<P>
The Workshop section provides questions and exercises to help
solidify the material you learned today. Try to answer the questions
and at least go over the exercises before moving on to tomorrow's
lesson. You'll find the answers to the questions in appendix A,
&quot;Quiz Answers.&quot;
<H3><A NAME="Quiz"><B>Quiz</B></A></H3>
<OL>
<LI>What user input devices does Java currently support?
<LI>What are some limitations of the sound support in Java 1.0?
<LI>What is a media object?
<LI>What is a storyboard used for?
</OL>
<H3><A NAME="Exercises"><B>Exercises</B></A></H3>
<OL>
<LI>Get on the Web and check out some Java games. Hint: A good
place to start is the Gamelan Web site, which is located at <TT><A HREF="http://www.gamelan.com<">http://www.gamelan.com<</A></TT>.
Gamelan has an entire section devoted to Java games.
<LI>Perform the preliminary design for a game of your own, addressing
each of the issues mentioned at the end of today's lesson.
<LI>Check out Javasoft's Web site at <TT><A HREF="http://www.javasoft.com<">http://www.javasoft.com<</A></TT>
for the latest news on Java; who knows, by the time you read this
there could be new enhancements to Java such as more advanced
sound support.
</OL>
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