微软前段时间发布基于XNA框架Windows Phone 7游戏开发实例，看到Silverlight for phone和XNA 4.0的开发文章已经有了不少，而且质量很高。而XNA 4.0的3D开发这个领域的文章还不是很多，XNA 4.0的3D类库设计的非常好，比iPhone和Android的OpenGLES类库高出一个档次。以后学习3D开发，用XNA类库也是个不错的选择，而且Windows Phone模拟器对3D的支持也非常好。唯一的遗憾是，Windows Phone不支持C++的3D开发。
51CTO推荐专题：Windows Phone应用开发详解
程序代码编译环境Visual Stuido 2010, Windows Phone 7 SDK, XNA 4.0 Game Studio, 下载链接：http://files.cnblogs.com/aawolf/XNA_aawolf_3D.rar
如果做过Zune上XNA 3.1开发的朋友可能会记得，在XNA 3.1中是不支持3D开发的，XNA 4.0中加入的3D支持类，主要包含在Microsoft.Xna.Framework.Graphics命名空间中。如果XNA 4.0中的3D概念与OpenGLES十分相似，我们可以找到很多相对应的函数、方法等，某种意义上，XNA 4.0的3D支持是对OpenGLES 2.0的封装。
一个简单的3D程序
我们就从一个简单的3D程序开始吧，这个程序的原来介绍在下面这个链接里。
http://msdn.microsoft.com/en-us/library/bb203926.aspx
不过移植到Windows Phone 7上时，还是遇到了一些小问题，有的是文档的问题，有的是接口变化。如何在Visual Studio 2010里创建XNA 4.0的工程就不多说了，大家可以参考我写的《Windows Phone开发工具初体验》，链接如下：
http://www.cnblogs.com/aawolf/archive/2010/08/28/1811438.html
XNA 4.0的程序是派生自Microsoft.Xna.Framework.Game的类，开发者需要重载Game的四个方法：Initialize（初始化）、LoadContent（加载内容）、UnloadContent（卸载内容）、Update（更新）和Draw（绘制）等方法。
首先，我们在Game1类中加入所需要的一些私有变量：
- Matrix worldMatrix;
- Matrix viewMatrix;
- Matrix projectionMatrix;
- VertexPositionNormalTexture[] cubeVertices;
- VertexDeclaration vertexDeclaration;
- VertexBuffer vertexBuffer;
- BasicEffect basicEffect;
Martrix 的中文名叫“矩阵”，还有个翻译叫“黑客帝国”……扯远了，什么是矩阵？我们就不解释了，只要知道矩阵是一切3D线性变化的基础就可以了。我们不知道矩阵是什么，却身处其中。在Game1类中用了三个矩阵：worldMatrix用来描述世界坐标系；viewMatrix用来描述摄影机坐标系；projectionMatrix用来描述投影坐标系。这些都是3D图形学的概念，不解释了。
另外两个重要的变量是vertexBuffer和basicEffect。vertexBuffer包含了一系列的向量，这些向量构成了我们要显示的正方体的各个顶点；basicEffect用来描述一个基础的渲染效果，其中描述了坐标系、颜色和灯光等基本的要素，这些要素是3D图形显示的基础。
接下来创建一个叫InitMatrices的方法，对各个坐标系进行初始化，记得，这个InitMatrices的函数是我们自己创建的，代码如下：
- private void InitMatrices()
- {
- // Initialize the world, view, and projection matrices.
- float tilt = MathHelper.ToRadians(0); // 0 degree angle
- // Use the world matrix to tilt the cube along x and y axes.
- worldMatrix = Matrix.CreateRotationX(tilt) * Matrix.CreateRotationY(tilt);
- viewMatrix = Matrix.CreateLookAt(new Vector3(5, 5, 5), Vector3.Zero, Vector3.Up);
- projectionMatrix = Matrix.CreatePerspectiveFieldOfView(
- MathHelper.ToRadians(45), // 45 degree angle
- (float)GraphicsDevice.Viewport.Width /
- (float)GraphicsDevice.Viewport.Height,
- 1.0f, 100.0f);
- }
算了，不解释了，大家知道这段代码在干什么就好了。接下来，创建一个叫做InitEffect的函数中，对basicEffect进行初始化，代码如下：
- private void InitEffect()
- {
- // Initialize BasicEffect with transformation and light values
- basicEffect = new BasicEffect(graphics.GraphicsDevice);
- basicEffect.World = worldMatrix;
- basicEffect.View = viewMatrix;
- basicEffect.Projection = projectionMatrix;
- // primitive color
- basicEffect.AmbientLightColor = new Vector3(0.1f, 0.1f, 0.1f);
- basicEffect.DiffuseColor = new Vector3(1.0f, 1.0f, 1.0f);
- basicEffect.SpecularColor = new Vector3(0.25f, 0.25f, 0.25f);
- basicEffect.SpecularPower = 5.0f;
- basicEffect.Alpha = 1.0f;
- basicEffect.LightingEnabled = true;
- if (basicEffect.LightingEnabled)
- {
- basicEffect.DirectionalLight0.Enabled = true; // enable each light individually
- if (basicEffect.DirectionalLight0.Enabled)
- {
- // x direction
- basicEffect.DirectionalLight0.DiffuseColor = new Vector3(1, 0, 0); // range is 0 to 1
- basicEffect.DirectionalLight0.Direction = Vector3.Normalize(new Vector3(-1, 0, 0));
- // points from the light to the origin of the scene
- basicEffect.DirectionalLight0.SpecularColor = Vector3.One;
- }
- basicEffect.DirectionalLight1.Enabled = true;
- if (basicEffect.DirectionalLight1.Enabled)
- {
- // y direction
- basicEffect.DirectionalLight1.DiffuseColor = new Vector3(0, 0.75f, 0);
- basicEffect.DirectionalLight1.Direction = Vector3.Normalize(new Vector3(0, -1, 0));
- basicEffect.DirectionalLight1.SpecularColor = Vector3.One;
- }
- basicEffect.DirectionalLight2.Enabled = true;
- if (basicEffect.DirectionalLight2.Enabled)
- {
- // z direction
- basicEffect.DirectionalLight2.DiffuseColor = new Vector3(0, 0, 0.5f);
- basicEffect.DirectionalLight2.Direction = Vector3.Normalize(new Vector3(0, 0, -1));
- basicEffect.DirectionalLight2.SpecularColor = Vector3.One;
- }
- }
- }
然后要对vertexDeclaration、cubeVertices和vertexBuffer变量进行初始化，我们将这部分代码放在InitVertexBuffer函数中：
- private void InitVertexBuffer()
- {
- // Create a vertex declaration for the type VertexPositionNormalTexture
- vertexDeclaration = new VertexDeclaration(new VertexElement[]
- {
- new VertexElement(0, VertexElementFormat.Vector3, VertexElementUsage.Position, 0),
- new VertexElement(12, VertexElementFormat.Vector3, VertexElementUsage.Normal, 0),
- new VertexElement(24, VertexElementFormat.Vector2, VertexElementUsage.TextureCoordinate, 0)
- }
- );
- // Create the per vertex data
- cubeVertices = new VertexPositionNormalTexture[36];
- Vector3 topLeftFront = new Vector3(-1.0f, 1.0f, 1.0f);
- Vector3 bottomLeftFront = new Vector3(-1.0f, -1.0f, 1.0f);
- Vector3 topRightFront = new Vector3(1.0f, 1.0f, 1.0f);
- Vector3 bottomRightFront = new Vector3(1.0f, -1.0f, 1.0f);
- Vector3 topLeftBack = new Vector3(-1.0f, 1.0f, -1.0f);
- Vector3 topRightBack = new Vector3(1.0f, 1.0f, -1.0f);
- Vector3 bottomLeftBack = new Vector3(-1.0f, -1.0f, -1.0f);
- Vector3 bottomRightBack = new Vector3(1.0f, -1.0f, -1.0f);
- Vector2 textureTopLeft = new Vector2(0.0f, 0.0f);
- Vector2 textureTopRight = new Vector2(1.0f, 0.0f);
- Vector2 textureBottomLeft = new Vector2(0.0f, 1.0f);
- Vector2 textureBottomRight = new Vector2(1.0f, 1.0f);
- Vector3 frontNormal = new Vector3(0.0f, 0.0f, 1.0f);
- Vector3 backNormal = new Vector3(0.0f, 0.0f, -1.0f);
- Vector3 topNormal = new Vector3(0.0f, 1.0f, 0.0f);
- Vector3 bottomNormal = new Vector3(0.0f, -1.0f, 0.0f);
- Vector3 leftNormal = new Vector3(-1.0f, 0.0f, 0.0f);
- Vector3 rightNormal = new Vector3(1.0f, 0.0f, 0.0f);
- // Front face.
- cubeVertices[0] =
- new VertexPositionNormalTexture(
- topLeftFront, frontNormal, textureTopLeft);
- cubeVertices[1] =
- new VertexPositionNormalTexture(
- bottomLeftFront, frontNormal, textureBottomLeft);
- cubeVertices[2] =
- new VertexPositionNormalTexture(
- topRightFront, frontNormal, textureTopRight);
- cubeVertices[3] =
- new VertexPositionNormalTexture(
- bottomLeftFront, frontNormal, textureBottomLeft);
- cubeVertices[4] =
- new VertexPositionNormalTexture(
- bottomRightFront, frontNormal, textureBottomRight);
- cubeVertices[5] =
- new VertexPositionNormalTexture(
- topRightFront, frontNormal, textureTopRight);
- // Back face.
- cubeVertices[6] =
- new VertexPositionNormalTexture(
- topLeftBack, backNormal, textureTopRight);
- cubeVertices[7] =
- new VertexPositionNormalTexture(
- topRightBack, backNormal, textureTopLeft);
- cubeVertices[8] =
- new VertexPositionNormalTexture(
- bottomLeftBack, backNormal, textureBottomRight);
- cubeVertices[9] =
- new VertexPositionNormalTexture(
- bottomLeftBack, backNormal, textureBottomRight);
- cubeVertices[10] =
- new VertexPositionNormalTexture(
- topRightBack, backNormal, textureTopLeft);
- cubeVertices[11] =
- new VertexPositionNormalTexture(
- bottomRightBack, backNormal, textureBottomLeft);
- // Top face.
- cubeVertices[12] =
- new VertexPositionNormalTexture(
- topLeftFront, topNormal, textureBottomLeft);
- cubeVertices[13] =
- new VertexPositionNormalTexture(
- topRightBack, topNormal, textureTopRight);
- cubeVertices[14] =
- new VertexPositionNormalTexture(
- topLeftBack, topNormal, textureTopLeft);
- cubeVertices[15] =
- new VertexPositionNormalTexture(
- topLeftFront, topNormal, textureBottomLeft);
- cubeVertices[16] =
- new VertexPositionNormalTexture(
- topRightFront, topNormal, textureBottomRight);
- cubeVertices[17] =
- new VertexPositionNormalTexture(
- topRightBack, topNormal, textureTopRight);
- // Bottom face.
- cubeVertices[18] =
- new VertexPositionNormalTexture(
- bottomLeftFront, bottomNormal, textureTopLeft);
- cubeVertices[19] =
- new VertexPositionNormalTexture(
- bottomLeftBack, bottomNormal, textureBottomLeft);
- cubeVertices[20] =
- new VertexPositionNormalTexture(
- bottomRightBack, bottomNormal, textureBottomRight);
- cubeVertices[21] =
- new VertexPositionNormalTexture(
- bottomLeftFront, bottomNormal, textureTopLeft);
- cubeVertices[22] =
- new VertexPositionNormalTexture(
- bottomRightBack, bottomNormal, textureBottomRight);
- cubeVertices[23] =
- new VertexPositionNormalTexture(
- bottomRightFront, bottomNormal, textureTopRight);
- // Left face.
- cubeVertices[24] =
- new VertexPositionNormalTexture(
- topLeftFront, leftNormal, textureTopRight);
- cubeVertices[25] =
- new VertexPositionNormalTexture(
- bottomLeftBack, leftNormal, textureBottomLeft);
- cubeVertices[26] =
- new VertexPositionNormalTexture(
- bottomLeftFront, leftNormal, textureBottomRight);
- cubeVertices[27] =
- new VertexPositionNormalTexture(
- topLeftBack, leftNormal, textureTopLeft);
- cubeVertices[28] =
- new VertexPositionNormalTexture(
- bottomLeftBack, leftNormal, textureBottomLeft);
- cubeVertices[29] =
- new VertexPositionNormalTexture(
- topLeftFront, leftNormal, textureTopRight);
- // Right face.
- cubeVertices[30] =
- new VertexPositionNormalTexture(
- topRightFront, rightNormal, textureTopLeft);
- cubeVertices[31] =
- new VertexPositionNormalTexture(
- bottomRightFront, rightNormal, textureBottomLeft);
- cubeVertices[32] =
- new VertexPositionNormalTexture(
- bottomRightBack, rightNormal, textureBottomRight);
- cubeVertices[33] =
- new VertexPositionNormalTexture(
- topRightBack, rightNormal, textureTopRight);
- cubeVertices[34] =
- new VertexPositionNormalTexture(
- topRightFront, rightNormal, textureTopLeft);
- cubeVertices[35] =
- new VertexPositionNormalTexture(
- bottomRightBack, rightNormal, textureBottomRight);
- vertexBuffer = new VertexBuffer(
- graphics.GraphicsDevice,
- typeof(VertexPositionNormalTexture),
- cubeVertices.Length,
- BufferUsage.None
- );
- vertexBuffer.SetData(cubeVertices);
- }
请原谅我把36个顶点的代码都贴出来了，如果不贴出来，肯定会有人不补全，然后就看不到完整的正方体了。
这里就要说到***个错误点了：文章中没有列出所有36个顶点的定义，不过示例代码UseBasicEffect中列出了；另一个问题是VertexBuffer的构造函数发生了变化，原文和示例代码中的VertexBuffer构造函数是这样的：
- vertexBuffer = new VertexBuffer(
- graphics.GraphicsDevice,
- VertexPositionNormalTexture.SizeInBytes * cubeVertices.Length,
- BufferUsage.None
- );
而正确的写法应该是：
- vertexBuffer = new VertexBuffer(
- graphics.GraphicsDevice,
- typeof(VertexPositionNormalTexture),
- cubeVertices.Length,
- BufferUsage.None
- );
VertexBuffer增加了一个Type类型的参数（第二个），我们必须传入一个IVertexType接口的派生类型，构造函数会用类型和顶点列表的长度计算VertexBuffer的size，这显然比上边的实现好了许多。
分别实现了这三个初始化函数后，我们要在真正的初始化函数Initialize里调用这三个函数，注意Initialize函数不是自己添加的，在Game1类中本来就有：
- protected override void Initialize()
- {
- InitMatrices();
- InitEffect();
- InitVertexBuffer();
- base.Initialize();
- }
好了，我们在Draw函数里增加绘制方法：
- protected override void Draw(GameTime gameTime)
- {
- GraphicsDevice.Clear(Color.CornflowerBlue);
- // TODO: Add your drawing code here
- RasterizerState rasterizerState1 = new RasterizerState();
- rasterizerState1.CullMode = CullMode.None;
- graphics.GraphicsDevice.RasterizerState = rasterizerState1;
- GraphicsDevice.SetVertexBuffer(vertexBuffer);
- foreach (EffectPass pass in basicEffect.CurrentTechnique.Passes)
- {
- pass.Apply();
- graphics.GraphicsDevice.DrawPrimitives(
- PrimitiveType.TriangleList,
- 0,
- 36
- );
- }
- base.Draw(gameTime);
- }
这里包含了第二个错误点，原文没有下面这句（上文高亮标出）：
GraphicsDevice.SetVertexBuffer(vertexBuffer);
如果没有SetVertexBuffer的调用，程序在运行时会遇到下面的异常：
An unhandled exception of type 'System.InvalidOperationException' occurred in Microsoft.Xna.Framework.Graphics.dll
Additional information: A valid vertex buffer (and a valid index buffer if you are using indexed primitives) must be set on the device before any draw operations may be performed.
原文的调用方式和UseBasicEffect的实现方式完全不同，所以大家要注意一下。毕竟是Beta版，很多文档还没有***完成。
好了，到这里，其实我们编译运行该程序的话，就可以看到绘制出的立方体来了。但是，我还想再加点——让立方体旋转起来。
在Update函数中增加下面两句（高亮显示）：
- protected override void Update(GameTime gameTime)
- {
- // Allows the game to exit
- if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
- this.Exit();
- // TODO: Add your update logic here
- Matrix matrix = Matrix.CreateRotationX(0.1f);
- basicEffectbasicEffect.World = basicEffect.World * matrix;
- base.Update(gameTime);
- }
我们创建了一个沿X轴旋转0.1度的矩阵，与basicEffect中的世界坐标系相乘，就可以使我们绘制出来的立方体每次Update时，都沿着X轴旋转0.1f度。因为角度是float型，千万别忘了0.1f之后的那个f。好了，程序***的样子就是这样的。在***篇文章里，我留了很多问题，比如3D的基本概念、坐标系、灯光、材质、旋转，希望在后边能够比较从容地解释这些知识。我现在唯一的希望是，不要等到六个月后才有时间再写第二篇……
【编辑推荐】
- Windows Phone 7核心控件Panorama和Pivot月底发布
- 微软应用开发大赛曝光Windows Phone 7首批应用
- 微软发布Windows Phone 7游戏开发实例 基于XNA框架
- Windows Phone 7 平面设计师的T型台
- Windows Phone 7开发之Silverlight游戏编辑器
