As you learn about each of these different areas of game programming, I want to help put them into perspective by explaining how they would impact the development of a Java Space Invaders game. This will help you to see how each of these areas impacts a real game, and it might also help you get ideas about designing a real game.

Graphics and Animation

What good is a game without graphics? In most cases, not much! Fortunately, Java delivers the goods when it comes to graphics. The standard Java API includes wide support for all kinds of neat graphics features such as images, color models, and 2D graphics primitives. Although Java as a whole is still largely limited by its relatively slow performance, the support is in place for very powerful graphics. As future releases of Java address the speed concerns, game programmers will be able to more fully exploit the graphics capabilities Java provides. You get the whole scoop on graphics later this week on Chapter 5, "Java Graphics Techniques."

What about animation? Most games would be pretty boring without it! Although the standard Java API doesn't provide any specific animation support, it is riddled with features that make implementing animation very easy. One of the most important aspects of Java is its multithreaded design, which provides a powerful framework for establishing the all-important timing necessary for animations. You learn all about implementing animation in Java later this week on Chapter 6, "Sprite Animation."

In the context of a real game, the graphics and animation form the majority of the look of the game. In a Space Invaders game, for example, the graphics and animation account for the aliens, the player's ship, any barriers that the player can hide behind, the missiles being fired back and forth, and any explosions that take place when a missile collides with something. Furthermore, the display of the title screen and score would also fall under the area of graphics programming.

User Input

User input is a very critical area of game development because it dictates how a game "feels" to the game player. User input is also important because it establishes the primary interface between the player and the game. Java provides support for the two major input devices in use on most computer systems these Chapters-the keyboard and mouse. When programming in Java, you monitor these input devices by responding to user input events generated when the user manipulates one of the devices.

Although it would certainly be nice if Java supported other input devices such as joysticks and flight yokes, the reality is that these devices aren't available on a wide variety of platforms. Hopefully a future version of Java will provide some degree of support for these gaming devices, because they are typically used in addition to the keyboard and mouse.

Even without the support for game-specific input devices, the support for the keyboard and mouse is enough to provide an effective user interface to most games. If you're skeptical, you can judge for yourself next week on Chapter 9, "Handling User Input with Java."

Using the Space Invaders example again, the user input requirements of the game consist of the inputs necessary to control the player's ship and fire missiles. For a game like this in which the ship simply moves from side to side, the best approach is probably to just use the left and right arrow keys to handle the ship's movement. You could also detect side to side mouse movement and use it to control the ship. You would designate another key, such as the spacebar, as the fire button. Likewise, a mouse click could also serve as the fire button for the mouse interface.

Sound

Rounding out the "big three" areas of game development is sound. Sound is currently the weakest area of Java's support for gaming. Release 1.0 of Java supports playing sound waves only in the ULAW format, which is popular on Sun workstations. Although the current Java sound support provides built-in sound mixing and the capability to play looped sounds, it is pretty limited because all sounds must be in the ULAW format (which is a low-quality sound format). Furthermore, there is no support for manipulating sounds at a lower level, which is often useful in games. A future release of Java will no doubt remedy many of the current limitations in regard to sound.

Even with its limitations, the current Java sound support is enough to add simple sound effects and music to Java games. Actually, the fact that Java provides a built-in sound mixer in the first release is a big deal. Contrast this situation with that of Windows 3.1, which didn't have any sound mixing support until very late in the product cycle.

You learn all about sound programming in Java, as well as the ULAW sound format, next week on Chapter 12, "Playing Sound with Java."

Going back to the Space Invaders example, the sound programming aspect of the game consists of writing code to handle all the sound effects in the game, as well as the background music. You might wonder how to add music considering the fact that Java doesn't yet support the popular MIDI music standard. The truth is that the original Space Invaders arcade game was developed well before the MIDI standard, so someone improvised back then! Similarly, you have to improvise music in Java by playing looped wave sounds repeatedly. Admittedly, this isn't the ideal approach, but it's the only approach you have-for now.

Networking

Now that the concept of a "computer in every home" is inching closer to reality, game developers can no longer ignore the potential of multiplayer network games. The desire of game players to connect and play games with other real people is just too strong to ignore. This is evident in the recent surge of commercial games that support network play. CivNet comes to mind as an example of a popular single player game (Civilization) that has been revamped for network play.

Networking is the one area where Java really shines because it 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++.

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 Chapter 18, "Networking with Java."

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 Chapter 17, "The Basics of Multiplayer Gaming."

Media Management

The last issue in regard to Java's support for games is media management. 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.

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.

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 Chapter 5, "Java Graphics Techniques." Media tracking support for sounds and other types of media has been promised in a future release of Java.

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.

Game Design

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 toChapter'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!

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.

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.

Here are the key items you should address when beginning the game development process:

• Basic idea
• Storyline
• Play modes