WP7 HUB_XNA overview

Uploaded on

Fase 3.5

Fase 3.5

More in: Education
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
No Downloads


Total Views
On Slideshare
From Embeds
Number of Embeds



Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

    No notes for slide
  • Start Visual StudioSelect File>New>Project to open the New Project dialogSelect XNA Game Studio 4 from the list of available templates on the leftSelect Windows Phone Game (4.0) from the template selection.Change the name to PongGame.Click OK.The project will now be created.Click Run to run the project. The emulator will start and display the blue screen.Click Stop to stop the program.Close Visual Studio and return to the presentation.
  • Open the PongGame project in Demo 2 Dot Sizes.Run the program.Rotate the emulator display so that it is landscape with the controls on the right. Explain that this is the default orientation for Windows Phone games.Open the file Game1.cs and navigate to the Draw method.Change the draw position and size of the dot in response to suggestions from the class.Try to draw the dot off the screen. Ask what will happen.Answer: XNA will just clip the display. This will work fineTry to draw a really big dot. Ask what will happen.Answer: The dot will be clipped again.Put the
  • Open the PongGame project in Demo 2 Moving Dot.Run the program.Show that the dot moves slowly down the screen.Ask what controls the speed of movement:Answer It is the rate at which Update is called and the size of the change applied to the position of the dot.Open the file Game1.cs and navigate to the Update method.Change the code to:ballRectangle.X++;ballRectangle.X++;Ask what this would do to the game.Answer: It would cause the ball to move across the screen and not down. The ball will also move twice as fast.Make the point that the game is presently being
  • Start Visual StudioOpen the project Demo 1 Bouncing Ball in the demo folder.Run the project. Show that the ball bounces from each edge.Close Visual Studio and return to the presentation.
  • Start Visual StudioOpen the project Demo 2 Paddle Control in the demo folder.Run the project. Ensure that the emulator is in landscape mode as per the above display.Click on the top of the screen to make the left paddle move up. Click on the top to make the paddle move down.Close Visual Studio and return to the presentation.
  • Start Visual StudioOpen the project Demo 3 Complete Game in the demo folder.Run the project. Ensure that the emulator is in landscape mode as per the above display.Show that the left paddle is controlled by the user and the right hand one has “unbeatable” AI.Ask how this was done.Answer: The Y position of the right hand paddle is set by the Y position of the ball.Ask how we can make the computer beatable. Answer: We could instead make the computer paddle move towards the ball at a speed slightly less than that of the ball. This would just require the use of a conditional statement to update the Y position accordingly.Make the point that they will be working on this game on the practical session to improve gameplay and make it multi-player.
  • Use a vector in case the way that the accelerometer works changes at some future time 
  • It is only possible to demonstrate this using an actual phone, as the emulator does not provide accelerometer simulation.Start Visual StudioOpen the project Demo 1 Tipping Pong in the demo folder.Set the deployment to Windows Phone 7 DeviceRun the project. Show that by tipping the phone the left paddle can be made to move up and down.
  • Use a vector in case the way that the accelerometer works changes at some future time 
  • I’ve written a content extension for a wordlist importer, you can write others.
  • Make the point that for sound effects you need wav files
  • Make the point that content can be organised into folders
  • Note that this is an improvement over the SoundEffect class, where the Play method is “fire and forget
  • Note that I use the length of the acceleration vector to set the pitch of the sound.
  • Note that I use the length of the acceleration vector to set the pitch of the sound.
  • This is a primitive form of looping, but we have a much better one.
  • This is how to really make sounds loop
  • Start Visual StudioOpen the project Demo 2 Game with Sounds in the demo folder.Run the project. Ensure that your machine has sound enabled.The program will make sounds when the ball hits objects.
  • Make the point that you can tailor the resolution and frequency to suit the application and keep the file small.
  • If the action isn’t content, the sound won’t work.
  • If people have used XNA before this will be obvious stuff. But for Silverlight folks this will be new.
  • If people have used XNA before this will be obvious stuff. But for Silverlight folks this will be new.
  • If people have used XNA before this will be obvious stuff. But for Silverlight folks this will be new.We will cover SoundEffectInstance in the XNA part of the course.
  • If people have used XNA before this will be obvious stuff. But for Silverlight folks this will be new.
  • If people have used XNA before this will be obvious stuff. But for Silverlight folks this will be new.
  • Start Visual StudioOpen the project Demo 3 Silverlight with Sound in the demo folder.Run the project. Ensure that your machine has sound enabled.The program will make sounds when you click on the equals button.
  • http://blogs.msdn.com/b/shawnhar/archive/2010/07/12/orientation-and-rotation-on-windows-phone.aspx
  • The scaler is magic. If you find that your game is running a bit slow, decrease the resolution and let the scaler take the strain.Fast moving games can run with much lower resolutions. The scaler will interpolate to make the pictures look good.http://blogs.msdn.com/b/shawnhar/archive/2010/07/12/resolution-and-scaling-on-windows-phone.aspx
  • http://blogs.msdn.com/b/shawnhar/archive/2010/07/12/orientation-and-rotation-on-windows-phone.aspx


  • 1. Windows Phone 7 XNA
    A different kind of phone, designed for a life in motion
  • 2. Gettingstartedwithxna
    A frameworktocreategameapplications
  • 3. Topics
    Overview of XNA
    How games run
    The XNA Game class
    Adding and managing game assets
    Creating and drawing game sprites
  • 4. XNA
    XNA is a framework for writing games
    It includes a set of professional tools for game production and resource management
    Windows Phone uses version 4.0 of the framework
    This is included as part of the Windows Phone SDK
  • 5. 2D and 3D games
    XNA provides full support for 3D games
    It allows a game program to make full use of the underlying hardware acceleration provided by the graphics hardware
    For the purpose of this course we are going to focus on 2D gaming
    Windows Phone games be either 2D or 3D
  • 6. XNA and Silverlight
    XNA is completely different from Silverlight
    The way that programs are constructed and execute in XNA is quite different
    XNA has been optimised for game creation
    It does not have any elements for user interface or data binding
    Instead it has support for 3D rendering and game content management
  • 7. XNA and Programs
    XNA provides a set of classes which allow you to create gameplay
    The classes represent game information and XNA resources
    XNA is also a very good example of how you construct and deploy a set of software resources in a Framework
  • 8. Creating a Game
    The Windows Phone SDK provides a Windows Phone game project type
  • 9. The Game Project
    The solution explorer shows the items that make up our game project
    The solution will also contain any content that we add to the game project
  • 10. Empty Game Display
    At the moment all our game does is display a blue screen
    This is because the behaviour of the Draw method in a brand new project is to clear the screen to blue
  • 11. Demo 1: New Game
  • 12. What a Game Does When it Runs
    Initialise all the resources at the start
    fetch all textures, models, scripts etc
    Repeatedly run the game:
    Update the game world
    read the user input, update the state and position of game elements
    Draw the game world
    render the game elements on the viewing device
  • 13. XNA Game Class Methods
    partialclassPongGame : Microsoft.Xna.Framework.Game
    protectedoverridevoid Update(GameTimegameTime)
    protectedoverridevoid Draw(GameTimegameTime)
  • 14. XNA Methods and games
    Note that our program never calls the LoadContent, Draw and Update methods
    They are called by the XNA Framework
    LoadContent is called when the game starts
    Draw is called as often as possible
    Update is called 30 times a second
    Note that this is not the same as an XNA game on Windows PC or Xbox, where Update is called 60 times a second
  • 15. Loading Game Content
    // Create a new SpriteBatch, which can be used to
    // draw textures.
    spriteBatch = newSpriteBatch(GraphicsDevice);
    LoadContent is called when our game starts
    It is where we put the code that loads the content into our game
    Content includes images, sounds, models etc.
  • 16. Game Content
    Games are not just programs, they also contain other content:
    Images for textures and backgrounds
    Sound Effects
    3D Object Meshes
    We need to add this content to our project
    The XNA framework provides a content management system which is integrated into Visual Studio
  • 17. Image Resources
    This is a Ball image
    I have saved it as a PNG file
    This allows the image to use transparency
    You can use any image resource you like
    The resources are added to the Visual Studio project
    They are held in the Content directory as part of your project
  • 18. Using the Content Pipeline
    Each resource is given an asset name
    The Load method of Content Manager provides access to the resource using the Asset Name that we gave it
    ballTexture = Content.Load<Texture2D>("WhiteDot");
  • 19. Storing the Ball Texture in the game
    // Game World
    Texture2D ballTexture;
    XNA provides a Texture2Dtype which holds a 2D (flat) texture to be drawn on the display
    The game class needs to contain a member variable to hold the ball texture that is to be drawn when the game runs
    This variable will be shared by all the methods in the game
  • 20. Loading Content into the Ball Texture
    // Create a new SpriteBatch, which can be used to // draw textures.
    spriteBatch = newSpriteBatch(GraphicsDevice);
    ballTexture = Content.Load<Texture2D>("WhiteDot");
    LoadContentis called when a game starts
    It loads an image into the ball texture
    The content manager fetches the images which are automatically sent to the target device
  • 21. Making a “sprite”
    A sprite is an object on the screen of a game
    It has both a texture and a position on the screen
    We are creating a sprite object for the ball in our game
    We now have the texture for the object
    The next thing to do is position it on the screen
  • 22. Coordinates and Pixels
    When drawing in XNA the position of an object on the screen is given using coordinates based on pixels
    A standard Windows Phone screen is 800 pixels wide and 480 pixels high
    This gives the range of possible values for display coordinates
    If you draw things off the screen this does not cause XNA problems, but nothing is drawn
  • 23. X and Y in XNA
    The coordinate system used by XNA sprite drawing puts the origin (0,0) in the top left hand corner of the screen
    Increasing X moves an object across the screen towards the right
    Increasing Y moves an object down the screen towards the bottom
    It is important that you remember this
  • 24. Positioning the Ball using a Rectangle
    // Game World
    We can add a rectangle value to the game to manage the position of the ball on the screen
    We will initialise it in the LoadContent method
  • 25. The Rectangle structure
    Rectangle ballRectangle = newRectangle(
    0, 0,
    ballTexture.Width, ballTexture.Height),
    Rectangle is a struct type which contains a position and a size
    The code above creates a rectangle positioned at 0,0 (top left hand corner) the same size as ballTexture
    We could move our ball by changing the content of the rectangle
  • 26. Drawing a Sprite
    In game programming terms a “sprite” is a texture that can be positioned on the screen
    We now have a ball sprite
    We have the texture that contains an image of the ball
    We have a rectangle that gives the position and size of the sprite itself
  • 27. XNA Game Draw Method
    protectedoverridevoid Draw(GameTimegameTime)
    The Draw method is called repeatedly when an XNA game is running
    It has the job of drawing the display on the screen
    A brand new XNA game project contains a Draw method that clears the screen to CornflowerBlue
    We must add our own code to the method to draw the ball
  • 28. Sprite Batching
    2D Graphics drawing is handled by a set of “sprite” drawing methods provided by XNA
    These create commands that are passed to the graphics device
    The graphics device will not want to draw everything on a piecemeal basis
    Ideally all the drawing information, textures and transformations should be provided as a single item
    The SpriteBatch class looks after this for us
  • 29. SpriteBatch Begin and End
    protectedoverridevoid Draw(GameTimegameTime)
    // Code that uses spriteBatch to draw the display
    The call to the Begin method tells SpriteBatch to begin a assembling a new set of drawing operations
    The call to the End method tells SpriteBatch that the there are no more operations and causes the rendering to take place
  • 30. Using SpriteBatch.Draw
    spriteBatch.Draw(ballTexture, ballRectangle, Color.White);
    The SpriteBatch class provides a Draw method to do the sprite drawing
    It is given parameters to tell it what to do:
    Texture to draw
    Position (expressed as a Rectangle)
    Draw color
  • 31. Rectangle Fun
    new Rectangle(
    0, 0,
    new Rectangle(
    0, 0, // position
    200,100) // size
    new Rectangle(
    50, 50, // position
    60, 60) // size
  • 32. Demo 2: Dot Sizes
  • 33. Screen Size and Scaling
    We need to make our game images fit the size of the screen
    We can find out the size of the screen from the GraphicsDevice used to draw it
    We can use this information to scale the images on the screen
  • 34. Creating the ballRectangle variable
    ballRectangle = newRectangle(
    0, 0,
    GraphicsDevice.Viewport.Width / 20,
    GraphicsDevice.Viewport.Width/ 20);
    If we use this rectangle to draw our ball texture it will be drawn as a square which is a twentieth of the width of the screen
    We can then set the position parts of the rectangle to move the ball around the screen
  • 35. Moving the ball around the screen
    At the moment the ball is drawn in the same position each time Draw runs
    To move the ball around we need to make this position change over time
    We need to give the game an update behaviour
    We must add code to the Update method in the game
    The Update method is where we manage the state of the “game world”
  • 36. The Update Method
    protectedoverridevoid Update(GameTimegameTime)
    // TODO: Add your update logic here
    The Update method is automatically called 30 times a second when a game is running
    It is in charge of managing the “game world”
    In a pong game this means updating the bat and the ball positions and checking for collisions
  • 37. Simple Update Method
    protectedoverridevoid Update(GameTimegameTime)
    Each time the game updates the X and Y position of the ball rectangle is increased
    This will cause it to move across and down the screen
    Note that I call the base method to allow my parent object to update too
  • 38. GameTime
    At the moment the Update method is called sixty time a second or once every 16.66 milliseconds
    We can also let the update "free run", in which case we need to know the time since the last call so we can move objects the right distance
    This is what the GameTime parameter is for, it gives the time at which the method was called
  • 39. Demo 2: Moving Dot
  • 40. Summary
    XNA is a Framework of methods that are used to write games
    You create the games using Visual Studio
    Games have initialise, update and draw behaviours
    Game objects are held as textures objects and their position and dimensions as rectangle structures
  • 41. Creatinggameplaywithxna
  • 42. Topics
    Controlling the movement of a sprite
    Creating multiple sprites
    Using touch input to control sprite movement
    Detecting sprite collisions
    Displaying text
  • 43. XNA and Pong
    Last time we got a ball to move down the screen
    Now we need to make the ball bounce around the screen
    Now we need to discover how we can create paddles and control them using a gamepad or keyboard
    Then we can start building a game
  • 44. Accurate ball positioning
    float ballX = 0;
    float ballY = 0;
    The Rectangle provides integer properties that can be used to position the drawing operation
    To get more precise control over the movement of an object we need to use floating point position variables
  • 45. Accurate ball positioning
    ballRectangle.X = (int)(ballX + 0.5f);
    ballRectangle.Y = (int)(ballY+ 0.5f);
    The floating point position values are converted to integers to set the position of the draw rectangle
    This is performed during the Update method
  • 46. Controlling Ball Movement
    float ballXSpeed = 3;
    float ballYSpeed = 3;
    To manage the speed of the ball we can use a pair of member variables in our game class
    One for the X speed and one for the Y speed
    Each time Update is called these are used to update the values of the X and Y position of the draw rectangle
  • 47. Moving the Ball
    ballX = ballX + ballXSpeed;
    ballY= ballY + ballYSpeed;
    The Update method is where the speed values are used to update the rectangle position for the ball
    The next call of Draw will draw the ball in the new position
  • 48. Going off the Edge
  • 49. Making the Ball Bounce
    if (ballX < 0 ||
    ballX+ ballRectangle.Width > GraphicsDevice.Viewport.Width)
    ballXSpeed = -ballXSpeed;
    When the ball reaches the edge of the screen it must change direction
    We can do this by reversing the sign of the speed value to reverse the effect of the update
  • 50. Demo 1: Bouncing Ball
  • 51. Making a Paddle
    The paddle is made from a texture, just like the ball
    This time I’ve made a slightly more interesting one which uses transparency
    The paddle is loaded as a texture resource, just as the ball is
  • 52. Game Variables
    // Game World
    floatballXSpeed = 3;
    floatballYSpeed = 3;
    floatlPaddleSpeed = 4;
    floatlPaddleY; // Repeat these for the right paddle
    // Distance of paddles from screen edge
    int margin;
  • 53. Loading GameTextures
    protectedoverridevoid LoadContent()
    ballTexture = Content.Load<Texture2D>("ball");
    lPaddleTexture = Content.Load<Texture2D>("lpaddle");
    rPaddleTexture = Content.Load<Texture2D>("rpaddle");
    // scale the texture draw rectangles here
    When the game starts the LoadContent method is called to load textures and other game assets
    We now have three textures in the game
  • 54. Setting up the paddles
    margin = GraphicsDevice.Viewport.Width / 20;
    lPaddleRectangle =newRectangle(
    margin, 0,
    GraphicsDevice.Viewport.Width / 20,
    GraphicsDevice.Viewport.Height / 5);
    rPaddleRectangle = newRectangle(
    GraphicsDevice.Viewport.Width– lPaddleRectangle.Width- margin, 0,
    GraphicsDevice.Viewport.Width / 20,
    GraphicsDevice.Viewport.Height / 5);
    This code positions the paddles on the screen and sets up their sizes
  • 55. Initial game positions
    The LoadContent method puts the paddles and balls at their starting positions as shown above
  • 56. Paddle control
    We can use the Windows Phone touch screen to control a paddle
    The touch screen can track up to four inputs and can detect when touch events start and end
    We are just going to test for touches to move the paddle up or down
  • 57. Getting the Touch Panel status
    TouchCollection touches = TouchPanel.GetState();
    The TouchPanel class provides a GetState method that will return the touch panel status
    This returns a collection of TouchLocation values that describe the present state of the touch panel
    This can contain up to four values
  • 58. Using the Touch information
    if (touches.Count > 0)
    if (touches[0].Position.Y > GraphicsDevice.Viewport.Height/ 2)
    lPaddleY = lPaddleY + lPaddleSpeed;
    lPaddleY = lPaddleY - lPaddleSpeed;
    If we have a touch location we use the position of the touch to move the paddle up or down
  • 59. Using the Touch information
    if (touches.Count > 0)
    if (touches[0].Position.Y > GraphicsDevice.Viewport.Height/ 2)
    lPaddleY = lPaddleY + lPaddleSpeed;
    lPaddleY = lPaddleY - lPaddleSpeed;
    If the collection contains some TouchLocationwe update the paddle position
  • 60. Using the Touch information
    if (touches.Count > 0)
    if (touches[0].Position.Y > GraphicsDevice.Viewport.Height/ 2)
    lPaddleY = lPaddleY + lPaddleSpeed;
    lPaddleY = lPaddleY - lPaddleSpeed;
    Get the touch location at the start of the collection
  • 61. Using the Touch information
    if (touches.Count > 0)
    if (touches[0].Position.Y > GraphicsDevice.Viewport.Height/ 2)
    lPaddleY = lPaddleY + lPaddleSpeed;
    lPaddleY = lPaddleY - lPaddleSpeed;
    Test the Y component of the position of touch against half the height of the screen
  • 62. Using the Touch information
    if (touches.Count > 0)
    if (touches[0].Position.Y > GraphicsDevice.Viewport.Height/ 2)
    lPaddleY = lPaddleY + lPaddleSpeed;
    lPaddleY = lPaddleY - lPaddleSpeed;
    Move the paddle down if the player touches the bottom half of the screen
  • 63. Using the Touch information
    if (touches.Count > 0)
    if (touches[0].Position.Y > GraphicsDevice.Viewport.Height/ 2)
    lPaddleY = lPaddleY + lPaddleSpeed;
    lPaddleY = lPaddleY - lPaddleSpeed;
    Move the paddle up if the player touches the top half of the screen
  • 64. Using the Touch information
    if (touches.Count > 0)
    if (touches[0].Position.Y > GraphicsDevice.Viewport.Height/ 2)
    lPaddleY = lPaddleY + lPaddleSpeed;
    lPaddleY = lPaddleY - lPaddleSpeed;
    Remember that increasing Y moves things down the screen (origin at top left)
  • 65. Demo 2: Paddle Control
  • 66. Detecting Collisions
    We need to make the ball bounce off the paddles when the two collide
    In the console version of the game we tested to see if ball and paddle occupied the same part of the screen
    In the case of XNA we need to see if the rectangles which control the position of the ball and paddle intersect
  • 67. Rectangle Intersection
    if (ballRectangle.Intersects(lPaddleRectangle))
    ballXSpeed = -ballXSpeed;
    The Rectangle structure provides a method called Intersects which can be used to detect if two rectangles intersect
    If the paddle and ball rectangles intersect we must reverse the X direction of movement of the ball to have it bounce off the paddle
  • 68. Completing the Game
    A finished game must also detect when the ball reaches the edges of the screen
    This is when a point has been scored
    I will leave you to create this code
    However, you will also need to draw text on the screen to display messages to the players
    This turns out to be very easy
  • 69. Adding a SpriteFont
    A SpriteFont is a content item that lets you draw text on the screen
    It provides a set of character designs of a particular size
  • 70. SpriteFont XML
    The font used and the size are set in an XML file
    You can edit this to get different sizes and styles
  • 71. Loading a Font
    SpriteFont font;
    // Rest of LoadContent here
    font = Content.Load<SpriteFont>("MessageFont");}
    The Content Manager will fetch the font
    The font can be stored in a variable which a member of the game class
    You can use multiple fonts if you want different text styles
  • 72. Drawing text
    protectedoverridevoid Draw(GameTimegameTime)
    "Hello world",
    newVector2(100, 100),
    // Rest of Draw here
    The DrawString method renders a string using the font that has been loaded
  • 73. Demo 3: Completed Pong Game
  • 74. Summary
    Objects in games can be made to move by updating their position information
    It is best if the game manages position in floating point values
    The TouchPanel provides a collection of TouchLocation values that describe touch actions
    XNA games can draw text using SpriteFonts
  • 75. Gamesonwindowsphone
  • 76. Topics
    Using the Accelerometer to control gameplay
    Playing sounds in XNA games
    Playing sounds in Silverlight programs
    Using media in XNA games
    Windows Phone games and orientation
  • 77. The Accelerometer
    The Accelerometer can measure acceleration in X, Y and Z
    You can use just the X and Y values to control sprites in 2D games
    The values that are returned are in the range -1 to +1 in each axis
    When the value is 0 this means the device is flat on that axis
  • 78. XNA 4.0 Accelerometer
    The accelerometer in XNA 4.0 is event driven
    The accelerometer generates events when new readings are available
    You must bind a method to the event
    The method can store the settings for later use
  • 79. XNA and Silverlight
    The reason why the accelerometer is event driven is that XNA actually uses the same sensor interface as Silverlight
    This means that we need to include the appropriate sensor library into our programs to obtain accelerometer readings
  • 80. Adding the Sensors library
    We need to add Microsoft.Devices.Sensors to the solution references to bring in the library
  • 81. Adding the Namespace
    Once you have added the library you can use the Sensors objects
    Adding the namespace to your program makes the code a bit cleaner
    Note that you only have to do this for the accelerometer
  • 82. Creating an Accelerometer
    Accelerometeracc = newAccelerometer();
    acc.ReadingChanged += newEventHandler<AccelerometerReadingEventArgs> (acc_ReadingChanged);
    The above code runs in the Initialise method to set up the accelerometer
    Initialise is called by XNA when a game starts
    It creates a new Accelerometer, binds an event handler to it and then starts it running
  • 83. Accelerometer Events
    Vector3accelState = Vector3.Zero;
    (object sender, AccelerometerReadingEventArgs e)
    accelState.X = (float)e.X;
    accelState.Y = (float)e.Y;
    accelState.Z = (float)e.Z;
    This method runs when a new reading is available from the accelerometer
    It copies the readings into a vector
  • 84. Using the reading
    lPaddleY = lPaddleY - (accelState.X * lPaddleSpeed);
    The Pong game only needs to use a single axis
    This is the X axis, that runs along the long length of the phone
    We have to reverse the sense of the position update as the value of Y increases down the screen
  • 85. The accelerometer and orientation
    The accelerometer provides the same readings irrespective of the orientation of the device
    In other words the direction of the axes does not change when the orientation changes
    For this reason I would advise you to fix the orientation of a tipping game
  • 86. “Tipping” games
    The accelerometer makes it very easy to create “tipping” games, which simulate gravity moving items around the screen
    The further you tip the device the greater the force acting on the object
    This leads to a very simple physics model, which is actually very effective
  • 87. Demo 1: Tipping Pong game
  • 88. Threads and Contention
    It turns out that there is a potential problem with the way we are using the accelerometer
    It is prone to errors caused by the way that we are using two separate threads of execution to work with the accelerometer values
    One thread stores the values in the vector
    The other thread reads the values back
    At the moment these threads are not synchronised, and this can cause problems
  • 89. What might happen…
    Update runs and reads the X value of the acceleration
    The Accelerometer event fires and starts running. It generates and stores new values of X, Y and Z
    Update reads the Y and Z values from the updated values
    Update now has “scrambled” data
  • 90. Processes and processors
    The problem is caused by the way that the operating system runs multiple processes
    Each process is given control for a small time interval and then another is allowed to run
    If one process is allowed to interrupt another we can get them “fighting” over data
  • 91. Adding a Lock
    We solve the problem by using a “lock” object
    A process can “grab” the lock object and hold onto it while it does something that must not be interrupted
    At the end of the action it releases the lock object
    If another process needs to use the lock it will be paused until the lock becomes available
  • 92. Accelerometer Events and Lock
    objectaccelLock = newobject();
    (object sender, AccelerometerReadingEventArgs e)
    lock (accelLock)
    accelState.X = (float)e.X;
    accelState.Y = (float)e.Y;
    accelState.Z = (float)e.Z;
    The lock object is just a token which is grabbed and released by the lock keyword
  • 93. Accelerometer Events and Lock
    lock (accelLock)
    lPaddleY = lPaddleY - (accelState.X * lPaddleSpeed);
    In the Update method the statement that uses the accelerometer reading is protected by a lock
    This means that it is not possible for the reading process to be interrupted
  • 94. Locks and Programs
    The locking behaviour is provided by the operating system
    A process that cannot run because it is waiting for a lock will be held until it can
    It is important that code that uses a lock does not take a long time to complete
    This might cause other processes to get stuck waiting for the lock to become available
  • 95. “Deadly Embrace”
    It is also important that two processes don’t each end up waiting for a lock the other has
    This causes both processes to be stuck
    You can do this by making a process either “produce” or “consume” data
    You only tend to get deadly embraces when a process is both a producer and a consumer
  • 96. Sounds as Content
    XNA uses a Content Manager to look after the resources used by a game
    Each content type has a “pipeline” of processors that bring it into the project and then package it for inclusion in the game distributable
    You don’t need to worry how this works
    You can write your own content library if you wish
  • 97. XNA Sound Types
    Sound effects
    wav files held in memory for quick playback
    Background music
    wma and mp3 files loaded and played
    Managed as media (more on this later)
  • 98. Preparing Sounds
    A good tool for preparing sound files is Audacity
    It will also convert between mp3 and wav format
    You can download it for free from
  • 99. Adding Content
    The simplest way to add content is to drag and drop it into the solution
    You can place it alongside images, or in separate folders
  • 100. Content Properties
    The content Properties pane identifies the asset name and the importer to use
  • 101. SoundEffect variables
    // Sound effects
    These game member variables hold the sound effects for the “Pong” game
    They will be initialised with content when the game starts running
    We do this in LoadContent method does this
  • 102. The LoadContent method
    // rest of LoadContent here
    dingSound= Content.Load<SoundEffect>("ding");
    explodeSound = Content.Load<SoundEffect>("explode");
    LoadContent is called when the game starts
    The game contains a Content Manager which manages game content (surprisingly)
    The Load method uses Generics to determine the required loader
  • 103. Simple Sound Playback
    if (ballY < 0 || ballY+ ballRectangle.Height > GraphicsDevice.Viewport.Height)
    ballYSpeed = -ballYSpeed;
    An instance of the SoundEffect class provides a Play method that plays the sound instantly
    The Pong game will play the ding sound when the ball hits the top or bottom of the screen
  • 104. Complex Sound Playback
    Sometimes the sound playback is more complex
    We might want to play an engine sound continuously when the “engine” is running
    We might also want to vary the pitch of the sound as it plays
    To do this we use a SoundEffectInstance
    This is an object that serves as a handle to a playing sound
  • 105. The SoundEffectInstance
    engineInstance = engineSound.CreateInstance();
    When we call the Play method on a sound effect this is a “fire and forget” kind of sound playback
    To get more control over a sound we need to create an object that represents it
    A SoundEffect can be asked to create an object representing an instance of a sound being played by using the CreateInstance method
  • 106. Playing Sounds
    The Play method on a SoundEffectInstance will start sound playback
    We can also call Pause and Stop to control the sound
  • 107. Controlling Volume
    engineInstance.Volume= accelVector.Length() / volFactor;
    The Volume property lets you adjust the volume of a playing sound
    The range is from 0 to 1:
    0 no sound
    +1 maximum volume
  • 108. Controlling Pitch
    engineInstance.Pitch = accelVector.Length() / soundFactor;
    The Pitch property lets you adjust the pitch of a playing sound
    The range is from -1 to 1:
    -1 octave low
    0 normal pitch
    +1 octave high
  • 109. Controlling Position
    engineInstance.Pan = cheesePan;
    The Pan property lets you adjust the pan position of a playing sound
    The range is from -1 to 1:
    -1 hard left
    0 center
    +1 right
  • 110. Sound Status
    if (engineInstance.State == SoundState.Stopped)
    The SoundEffectInstance exposes a property that gives the playing status
    This is updated when the sound stops playing
    The code above will play the sound again if it is stopped
    This is a primitive kind of looping
  • 111. Looping Sounds
    engineInstance.IsLooped = true;
    I can get the looping effect by simply restarting playback from the SoundEffectInstance each time the game detects that it has stopped
    However, there is a much easier way of getting this effect
    I simply set the IsLooped property to true
  • 112. Demo 2: Games with Sounds
  • 113. Silverlight and XNA
    If you want to play sound effects in a Silverlight program you use the XNA SoundEffect class
    The process is as follows:
    Add XNA to a Silverlight game
    Load the sound effect from a resource
    Play the sound effect as with XNA
    Keep the XNA system updated
  • 114. Adding XNA to a Silverlight Game
    The first thing to do is add the reference to the XNA Framework to the solution
    You might get a warning when you do this, but it is OK
  • 115. Adding XNA to a Silverlight Game
    Next you add the namespaces so you can easily use the objects
  • 116. Adding Sound Resources
    Now you can add the sound itself
    These are stored as items of content in the solution
    wav files work well
    Create a folder in your solution to keep things tidy
  • 117. Adding Sound Resources
    Now you need to set the properties of the sound item
    Make sure the build action is set to Content
  • 118. Loading a SoundEffect
    Beep = SoundEffect.FromStream(TitleContainer.OpenStream("Sounds/beep.wav"));
    This code runs at the start of the game
    It creates a SoundEffect value from the sound resources
    This mechanism is used in Silverlight because there is no Content Manager for a Silverlight application
  • 119. Playing a SoundEffect
    The Play method works in exactly the same was as in XNA
    If you want more control of the sound playback you can create and use SoundEffectInstance values to control a sound during playback
  • 120. Keeping XNA Awake
    The XNA framework is driven by repeated calls of Draw and Update methods
    In Silverlight these do not happen
    We need to update XNA to allow sound playback
    The FrameworkDispatcher.Update() method must be called at regular intervals to keep XNA sound working
    The best way to do this is to create a timer
  • 121. Creating a Timer
    DispatcherTimer timer = newDispatcherTimer();
    timer.Tick += newEventHandler(timer_Tick);
    timer.Interval = TimeSpan.FromTicks(333333);
    A DispatcherTimer is a timer that runs in the same thread as the Silverlight page
    We can create one that fires at the same rate as XNA, 30 times a second
    We can also bind a method to the tick event
  • 122. The Timer Tick event handler
    voidtimer_Tick(object sender, EventArgs e)
    When the timer ticks it just updates the XNA framework to keep sound playback working correctly
    You can also use this technique to animate Silverlight displays
  • 123. Demo 3: Silverlight with Sound
  • 124. Orientation
    Windows Phone games can be played in many orientations
    By default the game is configured for landscape orientation
  • 125. Forcing Game Orientation
    You can force a particular orientation by setting the size of the back buffer
    This works by using the scaling hardware in the Windows Phone display
  • 126. The Magical Scaler
    The scaler uses hardware, so your game is not slowed down by it
    It interpolates to make the scaling look good
    It scales from 240x240 to 800x480 (or 480x800)
    It will add a letterbox (black bars) if the chosen aspect ratio doesn’t match the hardware
    Viewport properties and touch input positions in your program always match the scaled screen
  • 127. Selecting Orientations
    Your game can indicate which orientations it can support
    The game above can support anything!
  • 128. Detecting Changes
    There is an event you can bind to if you need to detect orientation changes
  • 129. Using the full screen
    The Windows Phone uses the top of the screen for status information
    This is not always displayed, but when an XNA game runs this space is always reserved for the status information
    You can see this if you change the theme background to Light
  • 130. Using the Full Screen
    If you ask to use the full screen this will hide the status bar
    You can do this in the Initialize method for your game
  • 131. XNA games and the Lock Screen
    The user of the phone can configure a Screen time-out value in the lock & wallpaper screen
    This will time the screen out after a given interval if no user input is detected
    The system checks for user input from the touch screen and the hardware buttons
    It does not test the accelerometer
    This means that games that are accelerometer controlled are liable to be timed out
  • 132. Disabling the screen timeout
    Guide.IsScreenSaverEnabled = false;
    This statement disables the screen timeout
    Your game will now run uninterrupted
    You should use this with care however
    The game is now in a position to run until the phone battery goes flat
    You can re-enable the timeout by setting the property to true
  • 133. Summary
    The Windows Phone supports gameplay in multiple orientations which you can set in your game code
    The accelerometer allows games to be controlled by tipping the phone
    XNA and Silverlight can play back sound
    XNA programs can access the media library in the phone
  • 134. Exercise 1: Use Multi-Touch in a windowsphonegame
  • 135. Exercise 2: use theaccelerometer in anxnaprogram