Introduction to XNA Graphics Programming

1. Introduction to XNA Graphics Programming Asst. Prof. Rujchai Ung-arunyawee COE, KKU

2. Processes in XNA

3. XNA Project Template • Program Class • Main() method • Game1 Class • Game1() method(constructor) • Initialize() method • LoadGraphicsContent() method • UnloadGraphicsContent() method • Update() method • Draw() method • GraphicsDeviceManager object • ContentManager object

4. GraphicsDeviceManager object • Required by every XNA application. • Handles the configuration and management of the graphics device. • GraphicsDevice class is used for drawing primitive-based objects. • Declared as a member of the game class. • GraphicsDeviceManager graphics; • Created in the game class constructor. • graphics = new GraphicsDeviceManager(this);

5. ContentManager Object • Used to load, manage, and dispose of binary media content through the content pipeline. • Graphics and media content can be loaded with this object when it is referenced in the game project. • Declared as a member of the game class. • ContentManager content; • Created in the game class constructor. • content = new ContentManager(Services);

6. Initialize() method • Traps the one-time game startup event. • Natural place to trigger basic setup activities such as the following: • Setting window properties such as the title or full screen options • Setting the perspective and view to define how a user sees the 3D game • Initializing image objects for displaying textures • Initializing vertices for storing color, and image coordinates to be used throughout the program

7. Initialize() method (cont.) • Initializing vertex shaders to convert your primitive objects to pixel output • Initializing audio objects • Setting up other game objects

8. LoadGraphicsContent() method • For loading binary image and model content through the graphics pipeline.

9. UnloadGraphicsContent() method • For loading binary image and model content loaded in LoadGraphicsContent method the program exit.

10. Draw() method • Handles the drawing (also known as rendering) for the game program. • Starts by clearing the screen background, setting the screen color, and then drawing the graphics onto the screen.

11. Update() method • Checks and handles game-time events. • mouse clicks, keyboard presses, game-pad control events, and timers • Also a place for many other activities that require continuous checks or updates • advancing animations, detecting collisions, and tracking and modifying game scores

12. XNA Vertex types • A vertex stores information, which could include X, Y, and Z positions, image coordinates, a normal vector, and color.

13. XNA Primitive Objects

14. XNA Primitive Objects (cont.) • Total triangle list vertices = Ntriangles * 3 vertices • Total triangle strip vertices = Ntriangles + 2 vertices • Total line list vertices = Nlines * 2 vertices • Total line strip vertices = Nlines + 1 vertex

15. Drawing 3D in XNA • uses shader-based rendering to convert vertex data into pixel output • must use a shader to draw 3D graphics • Shaders can be used to manipulate all vertex properties (e.g.,color, position, and texture) • Built-in shader class name BasicEffect • you will need to write your own shader to implement the effect

16. Using BasicEffect class • Declared as member variable of the Game class • BasicEffect effect; • Created in Initialize() method • effect = new BasicEffect(graphics.GraphicDevice,null);

17. Using BasicEffect class (cont.) • Initialized in Initialize() method // Calculate the effect aspect ratio, world, projection, and view matrix GraphicsDevice device = graphics.GraphicsDevice; float aspectRatio = (float)device.Viewport.Width / device.Viewport.Height; // Set the World Matrix effect.World = Matrix.Identity; // Set the Viewing Matrix effect.View = Matrix.CreateLookAt(new Vector3(0.0f, 0.0f, 2.0f), Vector3.Zero, Vector3.Up); // Set the Projection Matrix effect.Projection = Matrix.CreatePerspectiveFieldOfView( MathHelper.ToRadians(60.0f), aspectRatio, 1.0f, 10.0f);

18. Using BasicEffect class (cont.) • Used in Draw() method effect.Begin(); foreach (EffectPass CurrentPass ineffect.CurrentTechnique.Passes) { CurrentPass.Begin(); // draw here device.DrawPrimitives(PrimitiveType.LineList, 0, 3); CurrentPass.End(); } effect.End();

19. Model construction • Creates an array of vertex and assigns value to them • Represents a list of 3D vertices to be streamed (VertexBuffer object)

20. Create and assign value to Vertex • private void CreateModel() { • // size of 3D Axis • float axisLength = 1f; • // Number of vertices we´ll use • int vertexCount = 6; • VertexPositionColor[] vertices = new VertexPositionColor[vertexCount]; • // X axis • vertices[0] = new VertexPositionColor(new Vector3(-axisLength, 0.0f, 0.0f), Color.White); • vertices[1] = new VertexPositionColor(new Vector3(axisLength, 0.0f, 0.0f), Color.White); • // Y axis • vertices[2] = new VertexPositionColor(new Vector3(0.0f, -axisLength, 0.0f), Color.White); • vertices[3] = new VertexPositionColor(new Vector3(0.0f, axisLength, 0.0f), Color.White); • // Z axis • vertices[4] = new VertexPositionColor(new Vector3(0.0f, 0.0f, -axisLength), Color.White); • vertices[5] = new VertexPositionColor(new Vector3(0.0f, 0.0f, axisLength), Color.White); • // fill the vertex buffer with the vertices • vertexBuffer = new VertexBuffer(graphics.GraphicsDevice, • vertexCount * VertexPositionColor.SizeInBytes, • ResourceUsage.WriteOnly); • vertexBuffer.SetData<VertexPositionColor>(vertices); • }

21. VertexBuffer object • Declared as member variable of the Game class VertexBuffer vertexBuffer; • Created and filled with the vertex array vertexBuffer = newVertexBuffer(graphics.GraphicsDevice, vertexCount * VertexPositionColor.SizeInBytes, ResourceUsage.WriteOnly); vertexBuffer.SetData<VertexPositionColor>(vertices);

22. GraphicDevice Preparation for Drawing • Declare a correct vertex type to the graphic device • Set the vertex source of the graphic device to the game vertex buffer GraphicsDevice device = graphics.GraphicsDevice; // Create a vertex declaration to be used when drawing the vertices device.VertexDeclaration = new VertexDeclaration(device, VertexPositionColor.VertexElements); // Set the vertex source device.Vertices[0].SetSource(vertexBuffer, 0, VertexPositionColor.SizeInBytes);