GraphicsDeviceManager graphics;
Texture2D texRedPanda;//镜头信息参数
Vector3 pos, lookat, up;
//World,View,Project矩阵
Matrix world,view, project;
BasicEffect basicEffect;
//顶点结构
VertexPositionTexture[] vpt;
VertexDeclaration vertexDec;public GameMain()
{graphics = new GraphicsDeviceManager(this);Content.RootDirectory = "Content";
}protected override void Initialize()
{//初始化镜头信息pos = new Vector3(0, 0,200);lookat = Vector3.Zero;up = Vector3.Up;//初始化变换矩阵world = Matrix.Identity;bbWorld = Matrix.Identity;view = Matrix.CreateLookAt(pos, lookat, up);project = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, 800f/600f, 1, 1000);vpt = new VertexPositionTexture[6];GraphicsDevice.RenderState.CullMode = CullMode.None;base.Initialize();
}protected override void LoadContent()
{texRedPanda = Content.Load<Texture2D>("RedPanda");basicEffect = new BasicEffect(GraphicsDevice, null);vertexDec = new VertexDeclaration(GraphicsDevice, VertexPositionTexture.VertexElements);//定义三角形的各顶点坐标和纹理坐标vpt[0] = new VertexPositionTexture(new Vector3(-25,-25, 0), new Vector2(0, 1));vpt[1] = new VertexPositionTexture(new Vector3(-25, 25, 0), new Vector2(0, 0));vpt[2] = new VertexPositionTexture(new Vector3(25,-25, 0), new Vector2(1, 1));vpt[3] = new VertexPositionTexture(new Vector3(-25, 25, 0), new Vector2(0, 0));vpt[4] = new VertexPositionTexture(new Vector3(25, 25, 0), new Vector2(1, 0));vpt[5] = new VertexPositionTexture(new Vector3(25,-25, 0), new Vector2(1, 1));
}protected override void Update(GameTime gameTime)
{// Allows the game to exitif (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)this.Exit();base.Update(gameTime);
}protected override void Draw(GameTime gameTime)
{GraphicsDevice.Clear(Color.Black);//设置变换矩阵参数basicEffect.World = world;basicEffect.View = view;basicEffect.Projection = project;//设置绘制纹理basicEffect.TextureEnabled = true;basicEffect.Texture = texRedPanda;basicEffect.Begin();foreach (var pass in basicEffect.CurrentTechnique.Passes){pass.Begin();GraphicsDevice.VertexDeclaration = vertexDec;GraphicsDevice.DrawUserPrimitives<VertexPositionTexture>(PrimitiveType.TriangleList, vpt,0, 2);pass.End();}basicEffect.End();base.Draw(gameTime);
}

float x0, z0;
x0=pos.X;
z0=pos.Z;
if (Keyboard.GetState().IsKeyDown(Keys.Left))
{pos.X = x0 * (float)Math.Cos(0.1d) + z0 * (float)Math.Sin(0.1d);pos.Z = (-x0) * (float)Math.Sin(0.1d) + z0 * (float)Math.Cos(0.1d);
}
if (Keyboard.GetState().IsKeyDown(Keys.Right))
{pos.X = x0 * (float)Math.Cos(-0.1d) + z0 * (float)Math.Sin(-0.1d);pos.Z = (-x0) * (float)Math.Sin(-0.1d) + z0 * (float)Math.Cos(-0.1d);
}
view = Matrix.CreateLookAt(pos, Vector3.Zero, Vector3.Up);//将视点 位置显示在标题栏
Window.Title = pos.ToString();

float4x4 World;
float4x4 View;
float4x4 Projection;
texture Texture;sampler textureSampler=sampler_state
{texture=<Texture>;magfilter = LINEAR; minfilter = LINEAR;mipfilter=LINEAR; AddressU = CLAMP; AddressV = CLAMP;
};struct VertexShaderInput
{float3 Pos:POSITION0;float2 TexCoord:TEXCOORD0;
};struct VertexShaderOutput
{float4 Position : POSITION0;float2 TexCoord:TEXCOORD0;
};VertexShaderOutput VertexShaderFunction(VertexShaderInput input)
{VertexShaderOutput output;float4x4 worldViewMatrix = mul(World, View);   float3 positionVS = input.Pos + float3(worldViewMatrix._41, worldViewMatrix._42, worldViewMatrix._43);output.Position = mul(float4(positionVS, 1.0f), Projection);output.TexCoord=input.TexCoord;return output;
}float4 PixelShaderFunction(VertexShaderOutput input) : COLOR0
{return tex2D(textureSampler,input.TexCoord);
}technique BillBoard
{pass BillBoard{VertexShader = compile vs_1_0 VertexShaderFunction();PixelShader = compile ps_1_0 PixelShaderFunction();}
}