XNA-3D-绘制三角形

一.在3D空间中绘制三角形

1.新建XNA Windows Game项目,添加成员变量:

  1: VertexPositionColor[] vertices;

  2: VertexBuffer vertexBuffer;

  3: 

  4: BasicEffect basicEffect;

  5: Matrix world;

  6: Matrix view;

  7: Matrix projection;

2.在Initialize()方法中初始化三角形顶点坐标和World,View,Projection矩阵：

  1: vertices = new VertexPositionColor[]

  2: {

  3: 	new VertexPositionColor(new Vector3(0,1,0),Color.Red),

  4: 	new VertexPositionColor(new Vector3(1,-1,0),Color.Green),

  5: 	new VertexPositionColor(new Vector3(-1,-1,0),Color.Blue)				

  6: };

  7: vertexBuffer = new VertexBuffer(GraphicsDevice,

  8: 	typeof(VertexPositionColor),

  9: 	vertices.Length,

 10: 	BufferUsage.None);

 11: vertexBuffer.SetData<VertexPositionColor>(vertices);

 12: GraphicsDevice.SetVertexBuffer(vertexBuffer);

 13: 

 14: world = Matrix.Identity;

 15: view = Matrix.CreateLookAt(new Vector3(0, 0, 5), Vector3.Zero, Vector3.Up);

 16: projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4,

 17: 	GraphicsDevice.Viewport.AspectRatio,

 18: 	1f,

 19: 	100f);

 20: 

 21: basicEffect = new BasicEffect(GraphicsDevice);

 22: basicEffect.VertexColorEnabled = true;

3.在Draw()方法中绘制三角形：

  1: basicEffect.World = world;

  2: basicEffect.View = view;

  3: basicEffect.Projection = projection;

  4: 

  5: foreach (var pass in basicEffect.CurrentTechnique.Passes)

  6: {

  7: 	pass.Apply();

  8: 	GraphicsDevice.DrawUserPrimitives<VertexPositionColor>(

  9: 		PrimitiveType.TriangleList,

 10: 		vertices,

 11: 		0,

 12: 		1);

 13: }

4.运行结果:

二.坐标变换

在Update()方法中响应键盘按键事件，进行坐标变换：

  1: KeyboardState keyboardState = Keyboard.GetState();

  2: if (keyboardState.IsKeyDown(Keys.R))

  3: {

  4: 	Matrix rototeZ = Matrix.CreateRotationZ(MathHelper.PiOver4);

  5: 	world *= rototeZ;

  6: }

  7: else if (keyboardState.IsKeyDown(Keys.Left))

  8: {

  9: 	Matrix translateLeft = Matrix.CreateTranslation(new Vector3(-0.25f, 0, 0));

 10: 	world *= translateLeft;

 11: }

 12: else if (keyboardState.IsKeyDown(Keys.Right))

 13: {

 14: 	Matrix translateRight = Matrix.CreateTranslation(new Vector3(0.25f, 0, 0));

 15: 	world *= translateRight;

 16: }

三.小技巧

如果需要设置窗口的初始大小,可以在Game类的构造器中修改属性:

  1: graphics.PreferredBackBufferWidth = 400;

  2: graphics.PreferredBackBufferHeight = 300;