Learning XNA 3.0 phần 3 pdf

80 | Chapter 5: Sound Effects and Audio As with the XACT tool, when using Windows Vista, you should start the XACT Auditioning Utility with administrator privileges (right-click and select “Run as Administrator”). Because XACT uses networking protocols to communicate with the Auditioning Utility, you will need to unblock the ports for both XACT and the Auditioning Util- ity. If you followed the steps in Chapter 1, these ports should have been unblocked when you installed XNA Game Studio 3.0. If you have anything running on port 80, the auditioning tool will not work, as it uses that port to communicate with XACT. Also, if you have Internet Information Services (IIS) installed on your PC, be aware that when IIS is running it will block the communication between XACT and the XACT Auditioning Utility. You’ll need to stop the ser- vice before you’re able to play audio files through the XACT Audition- ing Utility. Once you’ve started the XACT Auditioning Utility, it will sit in a “Waiting for the XACT authoring tool to connect” state (see Figure 5-4) until you play sounds from within XACT itself. Figure 5-2. Wave files added to your wave bank Using XACT | 81 With the Auditioning Utility running, you can right-click on any sound, cue, or wave within XACT and select Play in order to hear the sound. In addition to playing sounds within XACT, you can modify some properties of the sounds themselves. When you select a sound name in the sound bank, XACT will display properties for that sound in the bottom-left pane of the XACT project win- dow. You’ll notice some options here that allow you to modify the volume, pitch, priority, and looping for that sound. In regard to this current project, the start.wav file may be a bit quiet for some people’s tastes, so feel free to modify the volume and play the sound until you find a volume that sounds good to you. Figure 5-3. Your XACT project now has a cue! Figure 5-4. The XNA Auditioning Utility waiting for XACT to connect 82 | Chapter 5: Sound Effects and Audio You want your track.wav file to loop indefinitely in your application, and you can change a setting within XACT to accomplish that without any need for extra coding in XNA. To set the looping property of the track sound, select the item named track in the Sound Name section of the Sound Bank window. In the properties pane located in the bottom-left corner of the project window, click the Infinite checkbox under the Looping section (see Figure 5-5). This setting will cause the sound to loop indefinitely when you start the associated cue from your XNA code. Finally, if you click on a cue name rather than a sound name in the Sound Bank win- dow, you’ll see some different options in the bottom-left pane of the XACT window. This pane allows you to modify how the cue will play different sounds associated with that cue. Currently, you only have one sound associated with this cue, but you can add as many as you like. If you have multiple sounds for a cue, XACT will select a different one of those sounds to play each time you call that particular cue from your XNA code. This is helpful for sounds like explosions or crashes that are similar yet slightly different from each other. For example, in real life, all explosions sound slightly different, and this gives you a way to simulate that. In the properties pane, you can also specify different weights or likelihoods that a particular sound will play when the selected cue is called. Figure 5-5. Set infinite looping on the track sound Implementing XACT Audio Files in Code | 83 Once you’re satisfied with your sounds, save your project, close XACT and the Audi- tioning Utility, and head back to your game project in Visual Studio. Implementing XACT Audio Files in Code The first step in implementing the XACT audio project in your XNA project is to include the file you saved from XACT in your XNA project. Remember that previ- ously you copied the .wav files to the Content\Audio directory within your project, but you didn’t include those files in your XNA project through Visual Studio. As I mentioned previously, the only file that you actually need to include in the XNA game project is the project file you created in XACT. Hopefully, you named the XACT project file GameAudio.xap and saved it in the project’s Content\Audio direc- tory. If so, add it to your project now by right-clicking the Content\Audio folder in Solu- tion Explorer, selecting Add ➝ Existing Item, and browsing to your GameAudio.xap file. To load the data from your XACT project file into objects that you can use to play the sounds in XNA, you need to add the following class-level variables at the top of your Game1 class: AudioEngine audioEngine; WaveBank waveBank; SoundBank soundBank; Cue trackCue; The first variable represents something called a sound engine. This object will be used in the creation of your WaveBank and SoundBank objects and is the core object used for XNA sound. As you’ve probably already guessed, the WaveBank and SoundBank objects will correspond to the sound and wave bank sections of your XACT file. The Cue object is used to pull out individual cues from the sound bank to play those cues. You can play a cue without holding onto a variable for that particular cue, but with- out holding onto the cue itself you cannot pause/stop/start/resume or interact with that sound once it has begun playing. Once you’ve added those variables, you need to initialize them. To do so, add these lines of code in your Game1’s LoadContent method: audioEngine = new AudioEngine(@"Content\Audio\GameAudio.xgs"); waveBank = new WaveBank(audioEngine, @"Content\Audio\Wave Bank.xwb"); soundBank = new SoundBank(audioEngine, @"Content\Audio\Sound Bank.xsb"); This is one area where the content pipeline treats sound files differently than most other resources. To load sound into memory, you don’t use the Content.Load method you used for the resources you’ve dealt with thus far; instead, you use a more tradi- tional constructor call to instantiate each object. However, the content pipeline is still involved in the parsing of this audio data. At compile time, the content pipeline takes the file created by XACT, parses it, and 84 | Chapter 5: Sound Effects and Audio splits it into different files for use in your code at runtime. After compiling your game, take a look at your project’s bin\x86\Debug\Content\Audio folder in Windows Explorer, and you’ll see the actual files that are referenced in your constructors. For each .xap file (XACT project file), the content pipeline generates an .xgs file. For each wave bank within those project files, it generates an .xwb file, and for each sound bank it generates an .xsb file. These files are then loaded in your code via the constructors of their respective objects. Notice that the sound and wave banks also require that the audio engine object be passed into their constructors. Finally, note that the parameters passed to these objects in your code are actual filenames and paths, rather than the asset names that are used for most resources in XNA. Once the objects have been instantiated, you’re ready to use them to play audio. Audio is played by identifying and playing cues that you created in your XACT file. When you dropped the start.wav entry from the wave bank into the cue section of the sound bank, XACT created a cue called start and associated that cue with the sound that plays that particular .wav file. To play that cue, you get the Cue object from the SoundBank object using the SoundBank.GetCue method. You then call the Cue object’s Play method. For example, the following code will play the start cue: trackCue = soundBank.GetCue("track"); trackCue.Play( ); If you play the cue and hold onto an instance of that cue with a Cue object, as is done in this example, you have access to the Cue’s Stop, Pause, and other methods, which allow you to modify the sound as it plays. If you don’t need that kind of functional- ity, you can instead play the sound directly from the SoundBank object without using a Cue object: soundBank.PlayCue("track"); In this case, you’re going to want to hold onto the Cue object for the soundtrack so that you can pause it if needed, but you don’t need to do that for the start sound (once the start sound plays, you won’t ever need to stop it or pause it). You’ll want both of these sounds to play as soon as the game begins. You can accom- plish this by playing both sounds immediately after you initialize the objects in the LoadContent method of your Game1 class. Add the following lines of code at the end of your LoadContent method: // Start the soundtrack audio trackCue = soundBank.GetCue("track"); trackCue.Play( ); // Play the start sound soundBank.PlayCue("start"); Note that if you hold onto the Cue object when you play a sound, you need to make sure that your Cue object stays in scope for as long as you need it. Otherwise, the gar- bage collector will pick it up and the sound will no longer be usable. Using the Simplified API for Sound and Audio | 85 The final change that you need to make is to call the Update method of the AudioEngine object once per frame to keep the AudioEngine in sync with the game. You can do this in the Update method of your Game1 class. Omitting the call to AudioEngine.Update can result in sounds becoming out of sync and eventually cause issues. Add the following line of code immediately before the call to base.Update in the Update method of your Game1 class: audioEngine.Update( ); Compile and run the game, and you should hear both the starting intro noise and the background soundtrack. Also, the background track should loop until the game is over because you set it to infinitely loop in your XACT project. As you can see, XACT is a pretty powerful tool that allows you to modify different aspects of a sound file at design time. It’s a great way to speed up development, as well as to fine-tune your sounds and sound effects. Using the Simplified API for Sound and Audio When developing for the Xbox 360 and the PC, it’s a good idea to take advantage of the benefits that XACT offers. However, XACT isn’t supported on the Zune, so the XNA Framework 3.0 provides a simplified sound API that’s been added to allow developers to play audio on the Zune. You can also use the simplified API in projects for the Xbox 360 and the PC, if you find that you don’t require the additional fea- tures provided by XACT. Close your current XNA game project and create a new XNA Windows Game project in Visual Studio called SimpleSounds. To play a sound using the simplified sound API, the first step is to add a sound file to your project. Remember that when dealing with XACT, the actual sound files them- selves are not added to the project in Visual Studio. That is not the case, however, when dealing with the simplified sound API. In this case, audio files are treated like other resources in the content pipeline and have to be added to the Visual Studio project just as you’ve done with your 2D images thus far in this book. The sound API in XNA 3.0 supports the .wav, .wma, and .mp3 file types. In this example, you’ll be using the start.wav file used in the previous example in this chap- ter. You should already have this file on your hard drive, but if not, you’ll find it with the Chapter 5 source code in the SimpleSounds\Content\Audio folder. Add a new content folder to your project by right-clicking the Content node in Solu- tion Explorer and selecting Add ➝ New Folder. Name the folder Audio. Then, add the start.wav file to the project by right-clicking the new Content\Audio folder in Solution Explorer, selecting Add ➝ Existing Item , navigating to the start.wav file, and selecting it. 86 | Chapter 5: Sound Effects and Audio As with the other resources, when you’ve added the file to the project, you should be able to view its properties in Visual Studio and see that the content pipeline has assigned it an asset name and other properties. Once you’ve loaded the sound into your project, you need to create a variable of type SoundEffect into which you’ll load the sound file through the content pipeline. Add the following class level variable to your Game1 class: SoundEffect soundEffect; Once you’ve created the SoundEffect variable, load the file into the variable by add- ing the following code to your LoadContent method: soundEffect = Content.Load<SoundEffect>(@"Audio\start"); To play the sound, you call the Play method of the SoundEffect object. SoundEffect. Play returns an object of type SoundEffectInstance, which you can use to pause, stop, and start the sound as well as to adjust the volume and other aspects of the sound. To play the sound when the game begins, add the following code to the end of your LoadContent method, immediately after loading the sound from the content pipeline: SoundEffectInstance soundEffectInstance = soundEffect.Play( ); While it lacks any of the design-time sound development options available when using XACT, the sound API in XNA 3.0 gets the job done. As mentioned previously, the majority of the examples throughout the rest of this book use XACT for audio mainly to familiarize the reader with the tool. However, feel free to use the simpli- fied audio API instead if you prefer. Adding More Sound to Your Game Let’s take a minute now and add another sound feature to your XNA game. Close the SimpleSounds project and open the AnimatedSprites project you used at the begin- ning of this chapter. In the game that you’re building, a user-controlled sprite will be moving around the screen, with the objective of avoiding the automated sprites that are flying in from all directions. (That’s right; plunk your money down now, this is going to be one amaz- ing game.) You’re moving along in that direction, and you’ll get there soon enough. Even though the automated sprites in the game currently don’t move, you can still add some code to play a sound effect whenever your user-controlled sprite collides with an automated sprite. You’ll be passing the name of a cue to be played in the event of a collision into each Sprite object, so you’ll first need to open your Sprite.cs file and add to the Sprite class a class-level variable that will hold the name of the cue to be used. In addition, you’ll need to use the auto-implemented properties feature of C# 3.0 to create a public get accessor and a protected set accessor for this variable: public string collisionCueName { get; private set; } Adding More Sound to Your Game | 87 If you’re new to C# 3.0 and are unfamiliar with this feature, auto-implemented properties allow developers to create accessors for a given variable at the point in code where the variable is declared. This streamlines the code, making it easier to implement and read. (Feel free to read up on auto-implemented properties further on the Internet if you’d like to find out more about this or other features added in C# 3.0.) Finally, add a parameter of type string to the end of the parameter list in both con- structors. In the first constructor, pass the new parameter on to the call to the sec- ond constructor. In the body of the second constructor, assign the new parameter’s value to the collisionCueName variable. Your new Sprite class constructors should look like this: public Sprite(Texture2D textureImage, Vector2 position, Point frameSize, int collisionOffset, Point currentFrame, Point sheetSize, Vector2 speed, string collisionCueName) : this(textureImage, position, frameSize, collisionOffset, currentFrame, sheetSize, speed, defaultMillisecondsPerFrame, collisionCueName) { } public Sprite(Texture2D textureImage, Vector2 position, Point frameSize, int collisionOffset, Point currentFrame, Point sheetSize, Vector2 speed, int millisecondsPerFrame, string collisionCueName) { this.textureImage = textureImage; this.position = position; this.frameSize = frameSize; this.collisionOffset = collisionOffset; this.currentFrame = currentFrame; this.sheetSize = sheetSize; this.speed = speed; this.collisionCueName = collisionCueName; this.millisecondsPerFrame = millisecondsPerFrame; } Next, open your AutomatedSprite.cs file. You’ll need to add a string parameter rep- resenting the collision cue name to both of the constructors in the AutomatedSprite class. Each of these constructors will accept the cue name parameter and pass that value on to the base class’s constructors. Your AutomatedSprite constructors should look like this: public AutomatedSprite(Texture2D textureImage, Vector2 position, Point frameSize, int collisionOffset, Point currentFrame, Point sheetSize, Vector2 speed, string collisionCueName) : base(textureImage, position, frameSize, collisionOffset, currentFrame, sheetSize, speed, collisionCueName) { } public AutomatedSprite(Texture2D textureImage, Vector2 position, Point frameSize, int collisionOffset, Point currentFrame, Point sheetSize, Vector2 speed, int millisecondsPerFrame, string collisionCueName) 88 | Chapter 5: Sound Effects and Audio : base(textureImage, position, frameSize, collisionOffset, currentFrame, sheetSize, speed, millisecondsPerFrame, collisionCueName) { } Your UserControlledSprite class won’t be using the collision sounds because when the player collides with a sprite, you’ll be playing the sound of the object she runs into, not a sound for the player object itself. Therefore, you don’t need to add a parameter to the constructors for the UserControlledSprite class, but you do need to pass the value null on to the base class constructors for that parameter. The UserControlledSprite class constructors should now look like this: public UserControlledSprite(Texture2D textureImage, Vector2 position, Point frameSize, int collisionOffset, Point currentFrame, Point sheetSize, Vector2 speed) : base(textureImage, position, frameSize, collisionOffset, currentFrame, sheetSize, speed, null) { } public UserControlledSprite(Texture2D textureImage, Vector2 position, Point frameSize, int collisionOffset, Point currentFrame, Point sheetSize, Vector2 speed, int millisecondsPerFrame) : base(textureImage, position, frameSize, collisionOffset, currentFrame, sheetSize, speed, millisecondsPerFrame, null) { } You’ll be accessing the Game1 class from the SpriteManager to play the Cue. In the Game1 class, add the following public method, which you’ll be calling from within the SpriteManager class: public void PlayCue(string cueName) { soundBank.PlayCue(cueName); } You currently don’t have a cue to play for collisions with the skull ball sprite. The only files that you added to your XACT project previously were the start and soundtrack sounds. There is a file called skullcollision.wav located with the source code for Chapter 5, in the AnimatedSprites\Content\Audio folder. Copy this file to your game project’s Content\Audio folder using Windows Explorer. Again, because you’ll be using XACT to play this sound file, don’t add the file to your project in Visual Studio. Start XACT and open up the game’s audio file (GameAudio.xap), which you created earlier in this chapter. The file should be located in your game project’s Content\ Audio folder. Once the project is loaded, open the Wave Bank and Sound Bank win- dows by double-clicking on the Wave Bank and Sound Bank nodes in the tree menu on the left side of the XACT project window. Adding More Sound to Your Game | 89 Add the skullcollision.wav sound file to the Wave Bank window by right-clicking somewhere in the blank portion of that window and selecting Insert Wave File(s) Then, drag the newly created skullcollision item from the Wave Bank window and drop it in the Cue Name section of the Sound Bank window to generate a cue name for the sound. Your Sound Bank window in XACT should now look something like Figure 5-6. You may want to adjust the volume of the skullcollision sound, as it is somewhat quiet by default. Do this by selecting the item in the Sound Name section of the Sound Bank window and editing the volume property in the bottom-left pane. Save the XACT file and return to the code in Visual Studio. The final code changes take place in the SpriteManager class. First, you’ll need to pass the name of the cue used for collisions to the constructor of each instance of AutomatedSprite that you’re creating. Each of the AutomatedSprite objects is created in the LoadContent method of the SpriteManager class. Add the name of the cue as the final parameter of each of those constructors, as shown here: spriteList.Add(new AutomatedSprite( Game.Content.Load<Texture2D>(@"Images/skullball"), new Vector2(150, 150), new Point(75, 75), 10, new Point(0, 0), new Point(6, 8), Vector2.Zero, "skullcollision")); spriteList.Add(new AutomatedSprite( Game.Content.Load<Texture2D>(@"Images/skullball"), new Vector2(300, 150), new Point(75, 75), 10, new Point(0, 0), new Point(6, 8), Vector2.Zero, "skullcollision")); spriteList.Add(new AutomatedSprite( Game.Content.Load<Texture2D>(@"Images/skullball"), new Vector2(150, 300), new Point(75, 75), 10, new Point(0, 0), new Point(6, 8), Vector2.Zero, "skullcollision")); Figure 5-6. Skull collision cue and sound created [...]... for use in XNA games • XACT allows developers to modify sound properties such as volume, pitch, looping, and more at design time • To support development on the Zune, the XNA Framework 3. 0 includes a simple sound API that allows developers to implement sound without using XACT, which is not supported on the Zune • My ally is XNA, and a powerful ally it is Life creates XNA, makes it grow XNA s energy... grow XNA s energy surrounds us and binds us You must feel the XNA around you, between you, me, the tree, the rock, everywhere Test Your Knowledge: Quiz 1 What do you use to reference a sound that has been included in an XACT audio file? 2 What are the pros and cons of using the simple sound API available in XNA 3. 0 instead of using XACT? 3 Fact or fiction: the only way to get a soundtrack to loop during... volume of your sounds using XACT 5 How do you pause and restart a sound in XNA when using XACT audio files? 6 What, according to Michael Scott, did Abraham Lincoln once say which is a principle that Michael carries with him in the workplace? Test Your Knowledge: Exercise 1 Try experimenting with different sounds and sound settings in XNA using XACT Find a few wav files and plug them into the game Experiment... progresses through your game, you’ll make the enemies spawn more rapidly and have them move at faster speeds And now, one more question: “This is great, Aaron! Why is this so much fun?” That’s just XNA, my friend XNA rocks! At this point, you’ll want to make the game window a bit larger so you have more room to work with Add this code at the end of the constructor in your Game1 class: graphics.PreferredBackBufferHeight... (right-click on the project in the Solution Explorer and select Add ➝ Class ) Name it ChasingSprite.cs, and replace the code that’s generated with the following: using System; using Microsoft .Xna. Framework; using Microsoft .Xna. Framework.Graphics; namespace AnimatedSprites { class ChasingSprite : Sprite { // Save a reference to the sprite manager to // use to get the player position 102 | Chapter 6: Basic... the name of the class from ChasingSprite to EvadingSprite and also change the names of the constructors Your EvadingSprite.cs file should now look like this: using System; using Microsoft .Xna. Framework; using Microsoft .Xna. Framework.Graphics; namespace AnimatedSprites { class EvadingSprite : Sprite { // Save a reference to the sprite manager to // use to get the player position SpriteManager spriteManager;... Game.GraphicsDevice.PresentationParameters.BackBufferWidth - frameSize.X), Game.GraphicsDevice.PresentationParameters.BackBufferHeight); speed = new Vector2(0, -((Game1)Game).rnd.Next(enemyMinSpeed, enemyMaxSpeed)); break; case 3: // TOP to BOTTOM position = new Vector2(((Game1)Game).rnd.Next(0, Game.GraphicsDevice.PresentationParameters.BackBufferWidth - frameSize.X), -frameSize.Y); speed = new Vector2(0, ((Game1)Game).rnd.Next(enemyMinSpeed,... serves to keep the player guessing The first thing you need to do is create some variables that will help you define how often to create your automated sprites Creating Sprites at Random Intervals | 93 First, to handle the random factor in your game, create the following variable at the class level in your Game1 class: public Random rnd { get; private set;} Then, initialize the Random object in the... position.X += speedVal; if (player.Y < position.Y) position.Y -= speedVal; else if (player.Y > position.Y) position.Y += speedVal; base.Update(gameTime, clientBounds); } } } Creating a Chasing Sprite | 1 03 There are a couple of things to note about this code First, the namespace that you’re using is AnimatedSprites This was what you should have named your project way back in the first couple of chapters... “intelligent.” While it seems simplistic, programming something that would be able to fool somebody regardless of the line of questioning is extremely difficult How does that apply to what we’re talking about with XNA? Well, even though the Turing Test wasn’t a video game, the same principle is behind the essence of nearly all artificial intelligence as related to video games When programming a computercontrolled . new Vector2(1 50, 30 0), new Point(75, 75), 10, new Point (0, 0) , new Point(6, 8), Vector2.Zero, "skullcollision")); Figure 5-6. Skull collision cue and sound created 90 | Chapter 5:. Game.Content.Load<Texture2D>(@"Images/skullball"), new Vector2 ( 30 0, 1 50) , new Point(75, 75), 10, new Point (0, 0) , new Point(6, 8), Vector2.Zero, "skullcollision")); spriteList.Add(new. Game.Content.Load<Texture2D>(@"Images/skullball"), new Vector2( 600 , 400 ), new Point(75, 75), 10, new Point (0, 0) , new Point(6, 8), Vector2.Zero, "skullcollision")); Finally,