Introduction to XNA Graphics Programming

Asst. Prof. Rujchai Ung-arunyawee

COE, KKU

Processes in XNA

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

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);

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);

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 optionsSetting 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

Initialize() method (cont.) Initializing vertex shaders to convert your

primitive objects to pixel output Initializing audio objectsSetting up other game objects

LoadGraphicsContent() method

For loading binary image and model content through the graphics pipeline.

UnloadGraphicsContent() method

For loading binary image and model content loaded in LoadGraphicsContent method the program exit.

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.

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 updatesadvancing animations, detecting collisions,

and tracking and modifying game scores

XNA Vertex types A vertex stores information, which could include

X, Y, and Z positions, image coordinates, a normal vector, and color.

XNA Primitive Objects

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

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

Using BasicEffect class Declared as member variable of the Game

classBasicEffect effect;

Created in Initialize() method effect = new BasicEffect(graphics.GraphicDevice,null);

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);

Using BasicEffect class (cont.) Used in Draw() method

effect.Begin();

foreach (EffectPass CurrentPass in effect.CurrentTechnique.Passes)

{

CurrentPass.Begin();

// draw here

device.DrawPrimitives(PrimitiveType.LineList, 0, 3);

CurrentPass.End();

}

effect.End();

Model construction1. Creates an array of vertex and assigns

value to them

2. Represents a list of 3D vertices to be streamed (VertexBuffer object)

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);

}

VertexBuffer object Declared as member variable of the Game

classVertexBuffer vertexBuffer;

Created and filled with the vertex array vertexBuffer = new VertexBuffer(graphics.GraphicsDevice,

vertexCount * VertexPositionColor.SizeInBytes,

ResourceUsage.WriteOnly);

vertexBuffer.SetData<VertexPositionColor>(vertices);

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 verticesdevice.VertexDeclaration = new VertexDeclaration(device, VertexPositionColor.VertexElements);// Set the vertex sourcedevice.Vertices[0].SetSource(vertexBuffer, 0, VertexPositionColor.SizeInBytes);