Developing Game-Themed Applications with XNA Game Studio

Section I: Overview and Introduction
e1. Defining and Controlling a circle

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• You can start with this begin template source (a completely empty project), and here is the end project source code we will generate at the end of this tutorial.
• Here is the keyboard mapping for the game controller.

Goals:

• To experience with defining objects and interacting with users via the XNSCS1Lib library.
• We will create this program where the program draws and allows the user to move a circle by manipulating the left thumbstick (or i,j,m,k keys).

Notice:  To work with the XNACS1Lib Library, a bare minimum project must include:

• Fonts: the Arial.spritefont must be part of the project
• 2 functions:
• InitializeWorld(): allocate memory and initialize instance variables.
• UpdateWorld(): poll user input and update application state.
• Note: drawing happens by default!

• SourceCode folder contains an template SimpleXNA project.
• UsefulFiles folder contains:
• Arial.spritefont - this is the font we need in the project. We must create a proper folder and add this file into the project.
• XCS1Lib_PC.dll and XNACS1Lib_XBOX.dll - these are the library files for Windows/PC projects and for XBOX 360 console projects respectively. We must include the reference to the appropriate file in our project.

1. Fix the compile error by including XNACS1Lib_PC.dll as a library reference for the project.
2. Include code to define and control the circle.
3. Show how to include the font file in the Content folder.

• Create a folder for the library file:
• Go to explorer
• navigate to SimpleXNA
• Create a new folder: name it SupportFiles
• Copy UsefulFiles/XNACS1Lib_PC.dll into SupportFiles folder
• Include the library file as part of the project:
• Go back to XNA GS
• Right-Mouse-Button click over the project Reference folder:
• Add Reference
• Click on Browse tab
• navigate and select: SupportFiles/XNACS1Lib_PC.dll

2. Define and control a circle: 

• Instance variable: Define a circle

XNACS1Circle circle; // The circle



• InitializeWorld(): during initialization, we allocate memory and initialize the center position:

  protected override void  InitializeWorld() {   World.SetWorldCoordinate(new Vector2(0f, 0f), 15f); // Define world coordinate   circle = new XNACS1Circle(new Vector2(5f, 5f),      // center                                  1.0f);               // radius }

  
  
• UpdateWorld(): update the center of the circle by the left thumbstick (or the arrow keys):

protected override void  UpdateWorld() {    if (GamePad.ButtonBackClicked())         this.Exit();    center.Center += GamePad.ThumbSticks.Left;    EchoToBottomStatus("Circle drawn at: " + circle.Center);    EchoToTopStatus("i-up m-down j-left k-right"); }

• Create the proper resource folder, in the GS:
  • Right-Mouse-Button over the Content folder
    • Add -> New Folder:  name the new folder: Resources
  • Right-Mouse-Button over the newly created Resources folder
    • Add -> New Folder:  name the new folder: Fonts
  • Copy UsefulFiles/Arial.spritefont into SupportFiles folder
• Include the font file as part of the project:
• Right-Mouse-Button click over the newly created Fonts folder:
  • Add -> Existing Item ...
  • Navigate to UsefulFiles/Arial.spritefont

Now finally we can compile and run the application and observe the output messages.