在Windows Phone中進行3D開發之十二飛行 · Windows Phone應用開發

在完成了飛船和天空的兩個元素以后，現在要作的是把二者結合起來，讓飛船在天空中自由飛翔。現在我們面對了如下兩個問題：一是空間中的位置關系，二是飛船飛行時與天空盒的碰撞或穿越。先來看第一個問題，在畫飛船的時候，是畫在了原點上，在畫天空的時候，同樣也是在原點上。飛船的坐標值很大，以至于在畫飛船的時候使用-0.02的縮放矩陣對其進行縮小處理，而天空盒的邊長僅為2個坐標單位，我們需要如何處理這個坐標關系呢？另外，渲染天空盒時攝像機是位于盒子里的，渲染飛船時攝像機是位于飛船外的，因此對于攝像機的位置選擇也是一件麻煩事。另一個問題，假設我們能夠把飛船畫在天空盒當中，并且正確的放置了攝像機，那么當飛船飛行的時候，天空會越來越近，總會達到天空盒的邊界，此時會與天空盒發生碰撞，下一刻就會穿越了，跑到天空盒外面去了，這個問題看起來也不容易解決。其實，對于這兩個問題，可以通過控制渲染器的深度緩沖區來解決。我們知道，3D和2D的最大區別就是有一個深度關系，因此渲染器會使用深度緩沖區來進行這方面的處理，利用不同的z軸坐標，在深度緩沖區中跟蹤多個物體在縱深方向的前后關系。簡單點說，就是利用一塊內存保存各頂點到攝像機的深度數據，從而決定可見的被渲染，不可見的不渲染，在視覺上產生了遮擋等深度效果。對于天空盒和飛船，目前二者都會有深度信息參與渲染，因此才會出現位置上的感覺和碰撞的可能。如果能夠對這種深度進行控制，讓天空盒不存在深度，只保留飛船和攝像機的深度信息，那么前述的兩個問題就會迎刃而解了。我們還是能過代碼體現一下。首先在MainScene中為SkyBox和Ship分別生成一個對象，并將其加入到Components中。然后在LoadContent()中確定攝像機及兩個物體的坐標信息。 ~~~ protected override void LoadContent() { // Create a new SpriteBatch, which can be used to draw textures. spriteBatch = new SpriteBatch(GraphicsDevice); camera = new Camera(this, new Vector3(100,100,100), new Vector3(0, 0, -1), Vector3.Up, MathHelper.PiOver4, GraphicsDevice.Viewport.AspectRatio, 0.1f, 500); basicEffect = new BasicEffect(GraphicsDevice); skyBox.projectionMatrix = camera.projection; skyBox.viewMatrix = Matrix.CreateWorld(new Vector3(0,0,0),new Vector3(0,0,-1),Vector3.Up); ship.projectionMatrix = camera.projection; ship.viewMatrix = camera.view * Matrix.CreateTranslation(new Vector3(4, 0, 10)); ship.worldMatrix = Matrix.CreateScale(-0.02f) * Matrix.CreateRotationZ(MathHelper.ToRadians(180))*Matrix.CreateTranslation(new Vector3(20,0,0)); } ~~~ 在上述代碼中，先創建了攝像機，將其置于(100,100,100)坐標位置，該位置可以更好的觀察飛船。天空盒的變換矩陣中，投影矩陣采用攝像機矩陣，但視圖矩陣使用了單獨的視圖矩陣，即將攝像機放置于原點位置，讓其在該視圖變換下進行渲染。這與上一節天空盒中的攝像機位置是一樣的，所以只對天空盒來說，它不受camera的影響。飛船的投影變換使用攝像機矩陣，視圖變換使用攝像機矩陣，世界矩陣使用了一個矩陣變換，即先對飛船進行縮小，然后在z軸上進行了180度的旋轉，再向x軸正向平移20個坐標單位。以期得到合適的飛船方向和比例。在Update()方法中繼續沿用之前通過響應屏幕點擊進行天空盒旋轉的處理方式。接下來，打開SkyBox類的代碼，這次我們需要修改Draw()方法了，按照剛才的解決方案，要去掉天空盒渲染時的深度信息，因此，現在的代碼變為： ~~~ public override void Draw(GameTime gameTime) { GraphicsDevice.SamplerStates[0] = SamplerState.LinearClamp; DepthStencilState depthState = new DepthStencilState(); depthState.DepthBufferWriteEnable = false; GraphicsDevice.DepthStencilState = depthState; RasterizerState rasterizerState = new RasterizerState(); rasterizerState.CullMode = CullMode.CullClockwiseFace; GraphicsDevice.RasterizerState = rasterizerState; basicEffect.TextureEnabled = true; basicEffect.Texture = texture; basicEffect.World = worldMatrix; basicEffect.View = viewMatrix; basicEffect.Projection = projectionMatrix; foreach (EffectPass pass in basicEffect.CurrentTechnique.Passes) { pass.Apply(); Game.GraphicsDevice.DrawUserPrimitives<VertexPositionNormalTexture>(PrimitiveType.TriangleList, box, 0, box.Length/3); } base.Draw(gameTime); DepthStencilState depthState2 = new DepthStencilState(); depthState2.DepthBufferWriteEnable = true; GraphicsDevice.DepthStencilState = depthState2; } ~~~ 在上述代碼中，繪制的部分是與原來相同的，但是多了DepthStencilState對象的使用，在繪制物體之前，通過設置DepthBufferWriteEnable=false可以阻止物體深度信息寫入深度緩沖區，在繪制完之后再把該屬性設置true以恢復對深度緩沖區的操作。正是因為這樣，渲染器才忽視了天空盒的深度，從而無論飛船飛行的過程中深度如何變化，都不會與天空盒發生碰撞，天空盒只是作為背景了。程序運行的效果如圖所示。 ![](https://box.kancloud.cn/2016-04-08_570727fbb451d.gif) 當然，還可以對飛船繼續施加其他變換，比如按轉彎半徑做船身傾斜的變換，以達到更逼真的視覺效果。附天空盒類的源碼： ~~~ public class SkyBox : Microsoft.Xna.Framework.DrawableGameComponent { Texture2D texture; VertexPositionNormalTexture[] box; BasicEffect basicEffect; //Game game; public Matrix worldMatrix {set;get;} public Matrix viewMatrix { set; get; } public Matrix projectionMatrix { set; get; } public SkyBox(Game game) : base(game) { worldMatrix = Matrix.Identity; viewMatrix = Matrix.Identity; projectionMatrix = Matrix.Identity; } /// <summary> /// Allows the game component to perform any initialization it needs to before starting /// to run. This is where it can query for any required services and load content. /// </summary> public override void Initialize() { Vector3 topLeftFront=new Vector3(-1,1,1); Vector3 topRightFront = new Vector3(1, 1, 1); Vector3 bottomLeftFront = new Vector3(-1, -1, 1); Vector3 bottomRightFront = new Vector3(1, -1, 1); Vector3 topLeftBack = new Vector3(-1, 1, -1); Vector3 topRightBack = new Vector3(1, 1, -1); Vector3 bottomLeftBack = new Vector3(-1, -1, -1); Vector3 bottomRightBack = new Vector3(1, -1, -1); box = new VertexPositionNormalTexture[]{ new VertexPositionNormalTexture(topLeftFront,new Vector3(0,0,-1),new Vector2(0.33f,0.25f)), //front new VertexPositionNormalTexture(topRightFront,new Vector3(0,0,-1),new Vector2(0.66f,0.25f)), new VertexPositionNormalTexture(bottomLeftFront,new Vector3(0,0,-1),new Vector2(0.33f,0.5f)), new VertexPositionNormalTexture(bottomLeftFront,new Vector3(0,0,-1),new Vector2(0.33f,0.5f)), new VertexPositionNormalTexture(topRightFront,new Vector3(0,0,-1),new Vector2(0.66f,0.25f)), new VertexPositionNormalTexture(bottomRightFront,new Vector3(0,0,-1),new Vector2(0.66f,0.5f)), new VertexPositionNormalTexture(bottomRightFront,new Vector3(0,0,-1),new Vector2(0.66f,0.5f)), //bottom new VertexPositionNormalTexture(bottomRightBack,new Vector3(0,0,-1),new Vector2(0.66f,0.75f)), new VertexPositionNormalTexture(bottomLeftBack,new Vector3(0,0,-1),new Vector2(0.33f,0.75f)), new VertexPositionNormalTexture(bottomLeftBack,new Vector3(0,0,-1),new Vector2(0.33f,0.75f)), new VertexPositionNormalTexture(bottomLeftFront,new Vector3(0,0,-1),new Vector2(0.33f,0.5f)), new VertexPositionNormalTexture(bottomRightFront,new Vector3(0,0,-1),new Vector2(0.66f,0.5f)), new VertexPositionNormalTexture(bottomRightFront,new Vector3(0,0,-1),new Vector2(0.66f,0.5f)), //right new VertexPositionNormalTexture(topRightFront,new Vector3(0,0,-1),new Vector2(0.66f,0.25f)), new VertexPositionNormalTexture(topRightBack,new Vector3(0,0,-1),new Vector2(1.0f,0.25f)), new VertexPositionNormalTexture(topRightBack,new Vector3(0,0,-1),new Vector2(1.0f,0.25f)), new VertexPositionNormalTexture(bottomRightBack,new Vector3(0,0,-1),new Vector2(1.0f,0.5f)), new VertexPositionNormalTexture(bottomRightFront,new Vector3(0,0,-1),new Vector2(0.66f,0.5f)), new VertexPositionNormalTexture(bottomRightBack,new Vector3(0,0,-1),new Vector2(0.66f,0.75f)), //back new VertexPositionNormalTexture(topRightBack,new Vector3(0,0,-1),new Vector2(0.66f,1.0f)), new VertexPositionNormalTexture(topLeftBack,new Vector3(0,0,-1),new Vector2(0.33f,1.0f)), new VertexPositionNormalTexture(topLeftBack,new Vector3(0,0,-1),new Vector2(0.33f,1.0f)), new VertexPositionNormalTexture(bottomLeftBack,new Vector3(0,0,-1),new Vector2(0.33f,0.75f)), new VertexPositionNormalTexture(bottomRightBack,new Vector3(0,0,-1),new Vector2(0.66f,0.75f)), new VertexPositionNormalTexture(bottomLeftBack,new Vector3(0,0,-1),new Vector2(0.0f,0.5f)), //left new VertexPositionNormalTexture(topLeftBack,new Vector3(0,0,-1),new Vector2(0.0f,0.25f)), new VertexPositionNormalTexture(topLeftFront,new Vector3(0,0,-1),new Vector2(0.33f,0.25f)), new VertexPositionNormalTexture(topLeftFront,new Vector3(0,0,-1),new Vector2(0.33f,0.25f)), new VertexPositionNormalTexture(bottomLeftFront,new Vector3(0,0,-1),new Vector2(0.33f,0.5f)), new VertexPositionNormalTexture(bottomLeftBack,new Vector3(0,0,-1),new Vector2(0.0f,0.5f)), new VertexPositionNormalTexture(topLeftFront,new Vector3(0,0,-1),new Vector2(0.33f,0.25f)), //top new VertexPositionNormalTexture(topLeftBack,new Vector3(0,0,-1),new Vector2(0.33f,0.0f)), new VertexPositionNormalTexture(topRightBack,new Vector3(0,0,-1),new Vector2(0.66f,0.0f)), new VertexPositionNormalTexture(topRightBack,new Vector3(0,0,-1),new Vector2(0.66f,0.0f)), new VertexPositionNormalTexture(topRightFront,new Vector3(0,0,-1),new Vector2(0.66f,0.25f)), new VertexPositionNormalTexture(topLeftFront,new Vector3(0,0,-1),new Vector2(0.33f,0.25f)) }; basicEffect = new BasicEffect(Game.GraphicsDevice); texture = Game.Content.Load<Texture2D>(@"Images\skybox"); base.Initialize(); } /// <summary> /// Allows the game component to update itself. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> public override void Update(GameTime gameTime) { base.Update(gameTime); } public override void Draw(GameTime gameTime) { GraphicsDevice.SamplerStates[0] = SamplerState.LinearClamp; DepthStencilState depthState = new DepthStencilState(); depthState.DepthBufferWriteEnable = false; GraphicsDevice.DepthStencilState = depthState; RasterizerState rasterizerState = new RasterizerState(); rasterizerState.CullMode = CullMode.CullClockwiseFace; GraphicsDevice.RasterizerState = rasterizerState; basicEffect.TextureEnabled = true; basicEffect.Texture = texture; basicEffect.World = worldMatrix; basicEffect.View = viewMatrix; basicEffect.Projection = projectionMatrix; foreach (EffectPass pass in basicEffect.CurrentTechnique.Passes) { pass.Apply(); Game.GraphicsDevice.DrawUserPrimitives<VertexPositionNormalTexture>(PrimitiveType.TriangleList, box, 0, box.Length/3); } base.Draw(gameTime); DepthStencilState depthState2 = new DepthStencilState(); depthState2.DepthBufferWriteEnable = true; GraphicsDevice.DepthStencilState = depthState2; } } ~~~ ——歡迎轉載，請注明出處 [http://blog.csdn.net/caowenbin](http://blog.csdn.net/caowenbin) ——