3D系列4.16 在指定区域放置树木

本章我们要添加许多树。要获得最好的结果, 我们要在地形上添加一些树林而不是随机放置。

本章要处理的主要问题是:如何创建这些树林的边界?解决方法是使用一张噪点贴图。本系列的最后一章中,你会学习如何自己创建噪点贴图。本章使用的噪点贴图如下所示:

噪点贴图

解决方法很简单:如果噪点贴图上的像素的白色值大于某个临界值,我们就会在地形上添加一棵树。因此首先将treeMap.jpg导入到项目中。

然后,看一下GenerateTreePositions方法并做适当变化。第一个变化是方法定义,我们需要将噪点贴图作为参数:

private List<Vector3> GenerateTreePositions(Texture2D treeMap, VertexMultitextured[] terrainVertices) 

方法内部的代码变化如下所示:

Color[] treeMapColors = new Color[treeMap.Width * treeMap.Height]; 
treeMap.GetData(treeMapColors); 
int[,] noiseData = new int[treeMap.Width, treeMap.Height]; 

for (int x = 0; x < treeMap.Width; x++) 
    for (int y = 0; y < treeMap.Height; y++) 
        noiseData[x, y] = treeMapColors[y + x * treeMap.Height].R; 
List<Vector3> treeList = new List<Vector3> (); 
Random random = new Random(); 
for (int x = 0; x < terrainWidth; x++) 
{
    for (int y = 0; y < terrainLength; y++) 
    { 
        //add trees 
    }
}
return treeList; 

首先将图像转换为一个1D的颜色数组:首先创建一个1D数组,然后使用GetData方法将纹理中的数据复制到这个数组中。然后,这个1D数组被重新排列为一个整数2D数组。对每个像素,获取它的红色分量(它的值介于0和255之间)。因为当前噪点贴图是一张灰度图,所以红色通道的值与绿色和蓝色通道是相同的。

准备好2D数组后,我们创建一个Vector3集合,它也是这个方法的返回值,还有一个随机函数生成器用来使树木不会排成一行。

最后的两个循环遍历地形网格,对每个顶点,我们判断是否需要放置树木,所以需要进行以下检测:

让我们一个接一个解决上面的问题。

第一个问题很简单:我们只需获取当前位置的高度,检查它是否在可接受的范围之内。所以在循环中用下面的代码替换掉注释:

float terrainHeight = heightData[x, y]; 
if ((terrainHeight > 8) && (terrainHeight < 14)) { } 

这会让树木只放置在地形高度为8至14之间的位置。然后是地形的坡度。我们可以添加一些复杂的算法检测邻近顶点的高度,但事实上我们有更好的东西:每个顶点的法线。法线表示每个顶点垂直于地形的方向。所以在水平的地面上,法线是向上的。这就是我们想要检测的:法线与UP向量靠得有多近,这可以通过点乘这两个向量获得。所以在if-check中放置以下代码:

float flatness = Vector3.Dot(terrainVertices[x + y * terrainWidth].Normal, new Vector3(0, 1, 0)); 

如果顶点的法线和(0,1,) Up向量是相同的,点乘的结果为1。如果两者垂直则为0。因为点乘结果就是两个向量间夹角的余弦值,下面的代码可以检测地形的坡度不超过15度:

float minFlatness = (float)Math.Cos(MathHelper.ToRadians(15)); 
if (flatness> minFlatness) { } 

15度对应的点乘结果为0.966,所以我们检测地形的坡度是否比它小。最后,我们还需检测噪点贴图是否允许在当前位置放置树木。所以,我们需要采用对应当前位置的噪点贴图上的点。在if-check中添加以下代码:

float relx = (float)x / (float)terrainWidth; 
float rely = (float)y / (float)terrainLength; 
float noiseValueAtCurrentPosition = noiseData[(int)(relx * treeMap.Width), (int)(rely * treeMap.Height)]; 
float treeDensity; 
if (noiseValueAtCurrentPosition > 200) 
    treeDensity = 5; 
else if  (noiseValueAtCurrentPosition > 150) 
    treeDensity = 4; 
else if (noiseValueAtCurrentPosition > 100) 
    treeDensity = 3; 
else treeDensity = 0; 

因为我们想让地形的分辨率与噪点贴图的分辨率无关,所以使用相对坐标。Relx和rely的值介于0和1之间,让我们可以在正确的位置采样噪点贴图。当前位置的噪点值存储在noiseValueAtCurrentPosition变量中,这个变量的值介于0和255之间。

从这个值我们可以决定当前位置应该添加多少树木。如果这个值很大,说明在树林中间,在这个地形顶点周围添加5棵树!这个数量对应当前的噪点值,当噪点值小于某个临界值时树木数量为0。

这样,我们就可以确实知道当前地形顶点上应该放置多少树木。下面的代码生成新树木的位置:

for (int currDetail = 0; currDetail < treeDensity; currDetail++) 
{
    float rand1 = (float)random.Next(1000) / 1000.0f; 
    float rand2 = (float)random.Next(1000) / 1000.0f; 
    Vector3 treePos = new Vector3((float)x - rand1, 0, -(float)y - rand2); 
    treePos.Y = heightData[x, y]; treeList.Add(treePos); 
} 

首先生成两个随机数,并缩放到[0,1]区间,使用这两个随机数添加当前顶点的X和Z坐标,使用地形高度作为Y坐标。最后,将新位置添加到集合中。

在LoadVertices方法中,我们还需要加载treeMap.jpg纹理,将它传递到GenerateTreePositions方法!所以,使用以下代码替换掉LoadVertices方法底部的代码:

Texture2D treeMap = Content.Load<Texture2D> ("treeMap");
List<Vector3> treeList = GenerateTreePositions(treeMap, terrainVertices);
CreateBillboardVerticesFromList(treeList); 

好了,CreateBillboardVerticesFromList和DrawBillboard方法前面已经定义了,绘制树木的两个三角形是定义在GenerateTreePositions方法中的。现在运行代码!程序截图如下。如果移动相机,你会发现两个缺陷:

这个因为没有在DrawReflectionMap方法中绘制树木,所以,在调用DrawSkyDome方法之后,添加以下调用:

DrawBillboards(reflectionViewMatrix); 

这样你就可以看到水面上树木的反射了。

程序截图

本章只有XNA代码有变化,红色代码为相对于上一章改变的部分:

using System;
 using System.Collections.Generic;
 using Microsoft.Xna.Framework;
 using Microsoft.Xna.Framework.Audio;
 using Microsoft.Xna.Framework.Content;
 using Microsoft.Xna.Framework.GamerServices;
 using Microsoft.Xna.Framework.Graphics;
 using Microsoft.Xna.Framework.Input;
 using Microsoft.Xna.Framework.Net;
 using Microsoft.Xna.Framework.Storage;
 
 namespace XNAseries4
 {
     public struct VertexMultitextured
     {
         public Vector3 Position;
         public Vector3 Normal;
         public Vector4 TextureCoordinate;
         public Vector4 TexWeights;
 
         public static int SizeInBytes = (3 + 3 + 4 + 4) * sizeof(float);
         public static VertexElement[] VertexElements = new VertexElement[]
          {
              new VertexElement( 0, 0, VertexElementFormat.Vector3, VertexElementMethod.Default, VertexElementUsage.Position, 0 ),
              new VertexElement( 0, sizeof(float) * 3, VertexElementFormat.Vector3, VertexElementMethod.Default, VertexElementUsage.Normal, 0 ),
              new VertexElement( 0, sizeof(float) * 6, VertexElementFormat.Vector4, VertexElementMethod.Default, VertexElementUsage.TextureCoordinate, 0 ),
              new VertexElement( 0, sizeof(float) * 10, VertexElementFormat.Vector4, VertexElementMethod.Default, VertexElementUsage.TextureCoordinate, 1 ),
          };
     }
 
     public class Game1 : Microsoft.Xna.Framework.Game
     {
         GraphicsDeviceManager graphics;
         GraphicsDevice device;
 
         int terrainWidth;
         int terrainLength;
         float[,] heightData;
 
         VertexBuffer terrainVertexBuffer;
         IndexBuffer terrainIndexBuffer;
         VertexDeclaration terrainVertexDeclaration;
 
         VertexBuffer waterVertexBuffer;
         VertexDeclaration waterVertexDeclaration;
 
         VertexBuffer treeVertexBuffer;
         VertexDeclaration treeVertexDeclaration;
 
         Effect effect;
         Effect bbEffect;
         Matrix viewMatrix;
         Matrix projectionMatrix;
         Matrix reflectionViewMatrix;
 
         Vector3 cameraPosition = new Vector3(130, 30, -50);
         float leftrightRot = MathHelper.PiOver2;
         float updownRot = -MathHelper.Pi / 10.0f;
         const float rotationSpeed = 0.3f;
         const float moveSpeed = 30.0f;
         MouseState originalMouseState;
 
         Texture2D grassTexture;
         Texture2D sandTexture;
         Texture2D rockTexture;
         Texture2D snowTexture;
         Texture2D cloudMap;
         Texture2D waterBumpMap;
         Texture2D treeTexture;
         Texture2D treeMap;
 
         Model skyDome;
 
         const float waterHeight = 5.0f;
         RenderTarget2D refractionRenderTarget;
         Texture2D refractionMap;
         RenderTarget2D reflectionRenderTarget;
         Texture2D reflectionMap;
 
         Vector3 windDirection = new Vector3(0, 0, 1);
 
         public Game1()
         {
             graphics = new GraphicsDeviceManager(this);
             Content.RootDirectory = "Content";
         }
 
         protected override void Initialize()
         {
             graphics.PreferredBackBufferWidth = 500;
             graphics.PreferredBackBufferHeight = 500;
 
             graphics.ApplyChanges();
             Window.Title = "Riemer's XNA Tutorials -- Series 4";
 
             base.Initialize();
         }
 
         protected override void LoadContent()
         {
             device = GraphicsDevice;
 

            effect = Content.Load<Effect> ("Series4Effects");
            bbEffect = Content.Load<Effect> ("bbEffect");            UpdateViewMatrix();
            projectionMatrix = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, device.Viewport.AspectRatio, 0.3f, 1000.0f);

            Mouse.SetPosition(device.Viewport.Width / 2, device.Viewport.Height / 2);
            originalMouseState = Mouse.GetState();


            skyDome = Content.Load<Model> ("dome"); skyDome.Meshes[0].MeshParts[0].Effect = effect.Clone(device);
            PresentationParameters pp = device.PresentationParameters;
            refractionRenderTarget = new RenderTarget2D(device, pp.BackBufferWidth, pp.BackBufferHeight, 1, device.DisplayMode.Format);
            reflectionRenderTarget = new RenderTarget2D(device, pp.BackBufferWidth, pp.BackBufferHeight, 1, device.DisplayMode.Format);

            LoadVertices();
            LoadTextures();
        }

        private void LoadVertices()
        {

            Texture2D heightMap = Content.Load<Texture2D> ("heightmap"); LoadHeightData(heightMap);
            VertexMultitextured[] terrainVertices = SetUpTerrainVertices();
            int[] terrainIndices = SetUpTerrainIndices();
            terrainVertices = CalculateNormals(terrainVertices, terrainIndices);
            CopyToTerrainBuffers(terrainVertices, terrainIndices);
            terrainVertexDeclaration = new VertexDeclaration(device, VertexMultitextured.VertexElements);

            SetUpWaterVertices();
            waterVertexDeclaration = new VertexDeclaration(device, VertexPositionTexture.VertexElements);



            Texture2D treeMap = Content.Load<Texture2D> ("treeMap");
            List<Vector3> treeList = GenerateTreePositions(treeMap, terrainVertices);            CreateBillboardVerticesFromList(treeList);

         }
 
         private void LoadTextures()
         {

            grassTexture = Content.Load<Texture2D> ("grass");
            sandTexture = Content.Load<Texture2D> ("sand");
            rockTexture = Content.Load<Texture2D> ("rock");
            snowTexture = Content.Load<Texture2D> ("snow");
            cloudMap = Content.Load<Texture2D> ("cloudMap");
            waterBumpMap = Content.Load<Texture2D> ("waterbump");
            treeTexture = Content.Load<Texture2D> ("tree");
            treeMap = Content.Load<Texture2D> ("treeMap");        }

        private void LoadHeightData(Texture2D heightMap)
        {
            float minimumHeight = float.MaxValue;
            float maximumHeight = float.MinValue;

            terrainWidth = heightMap.Width;
            terrainLength = heightMap.Height;

            Color[] heightMapColors = new Color[terrainWidth * terrainLength];
            heightMap.GetData(heightMapColors);

            heightData = new float[terrainWidth, terrainLength];
            for (int x = 0; x < terrainWidth; x++)
                for (int y = 0; y < terrainLength; y++)
                {
                    heightData[x, y] = heightMapColors[x + y * terrainWidth].R;
                    if (heightData[x, y] < minimumHeight) minimumHeight = heightData[x, y];
                    if (heightData[x, y] > maximumHeight) maximumHeight = heightData[x, y];
                }

            for (int x = 0; x < terrainWidth; x++)
                for (int y = 0; y < terrainLength; y++)
                    heightData[x, y] = (heightData[x, y] - minimumHeight) / (maximumHeight - minimumHeight) * 30.0f;
        }

        private VertexMultitextured[] SetUpTerrainVertices()
        {
            VertexMultitextured[] terrainVertices = new VertexMultitextured[terrainWidth * terrainLength];

            for (int x = 0; x < terrainWidth; x++)
            {
                for (int y = 0; y < terrainLength; y++)
                {
                    terrainVertices[x + y * terrainWidth].Position = new Vector3(x, heightData[x, y], -y);
                    terrainVertices[x + y * terrainWidth].TextureCoordinate.X = (float)x / 30.0f;
                    terrainVertices[x + y * terrainWidth].TextureCoordinate.Y = (float)y / 30.0f;

                    terrainVertices[x + y * terrainWidth].TexWeights.X = MathHelper.Clamp(1.0f - Math.Abs(heightData[x, y] - 0) / 8.0f, 0, 1);
                    terrainVertices[x + y * terrainWidth].TexWeights.Y = MathHelper.Clamp(1.0f - Math.Abs(heightData[x, y] - 12) / 6.0f, 0, 1);
                    terrainVertices[x + y * terrainWidth].TexWeights.Z = MathHelper.Clamp(1.0f - Math.Abs(heightData[x, y] - 20) / 6.0f, 0, 1);
                    terrainVertices[x + y * terrainWidth].TexWeights.W = MathHelper.Clamp(1.0f - Math.Abs(heightData[x, y] - 30) / 6.0f, 0, 1);

                    float total = terrainVertices[x + y * terrainWidth].TexWeights.X;
                    total += terrainVertices[x + y * terrainWidth].TexWeights.Y;
                    total += terrainVertices[x + y * terrainWidth].TexWeights.Z;
                    total += terrainVertices[x + y * terrainWidth].TexWeights.W;

                    terrainVertices[x + y * terrainWidth].TexWeights.X /= total;
                    terrainVertices[x + y * terrainWidth].TexWeights.Y /= total;
                    terrainVertices[x + y * terrainWidth].TexWeights.Z /= total;
                    terrainVertices[x + y * terrainWidth].TexWeights.W /= total;
                }
            }

            return terrainVertices;
        }

        private int[] SetUpTerrainIndices()
        {
            int[] indices = new int[(terrainWidth - 1) * (terrainLength - 1) * 6];
            int counter = 0;
            for (int y = 0; y < terrainLength - 1; y++)
            {
                for (int x = 0; x < terrainWidth - 1; x++)
                {
                    int lowerLeft = x + y * terrainWidth;
                    int lowerRight = (x + 1) + y * terrainWidth;
                    int topLeft = x + (y + 1) * terrainWidth;
                    int topRight = (x + 1) + (y + 1) * terrainWidth;

                    indices[counter++] = topLeft;
                    indices[counter++] = lowerRight;
                    indices[counter++] = lowerLeft;

                    indices[counter++] = topLeft;
                    indices[counter++] = topRight;
                    indices[counter++] = lowerRight;
                }
            }

            return indices;
        }

        private VertexMultitextured[] CalculateNormals(VertexMultitextured[] vertices, int[] indices)
        {
            for (int i = 0; i < vertices.Length; i++)
                vertices[i].Normal = new Vector3(0, 0, 0);

            for (int i = 0; i < indices.Length / 3; i++)
            {
                int index1 = indices[i * 3];
                int index2 = indices[i * 3 + 1];
                int index3 = indices[i * 3 + 2];

                Vector3 side1 = vertices[index1].Position - vertices[index3].Position;
                Vector3 side2 = vertices[index1].Position - vertices[index2].Position;
                Vector3 normal = Vector3.Cross(side1, side2);

                vertices[index1].Normal += normal;
                vertices[index2].Normal += normal;
                vertices[index3].Normal += normal;
            }

            for (int i = 0; i < vertices.Length; i++)
                vertices[i].Normal.Normalize();

            return vertices;
        }

        private void CopyToTerrainBuffers(VertexMultitextured[] vertices, int[] indices)
        {
            terrainVertexBuffer = new VertexBuffer(device, vertices.Length * VertexMultitextured.SizeInBytes, BufferUsage.WriteOnly);
            terrainVertexBuffer.SetData(vertices);

            terrainIndexBuffer = new IndexBuffer(device, typeof(int), indices.Length, BufferUsage.WriteOnly);
            terrainIndexBuffer.SetData(indices);
        }

        private void SetUpWaterVertices()
        {
            VertexPositionTexture[] waterVertices = new VertexPositionTexture[6];

            waterVertices[0] = new VertexPositionTexture(new Vector3(0, waterHeight, 0), new Vector2(0, 1));
            waterVertices[2] = new VertexPositionTexture(new Vector3(terrainWidth, waterHeight, -terrainLength), new Vector2(1, 0));
            waterVertices[1] = new VertexPositionTexture(new Vector3(0, waterHeight, -terrainLength), new Vector2(0, 0));

            waterVertices[3] = new VertexPositionTexture(new Vector3(0, waterHeight, 0), new Vector2(0, 1));
            waterVertices[5] = new VertexPositionTexture(new Vector3(terrainWidth, waterHeight, 0), new Vector2(1, 1));
            waterVertices[4] = new VertexPositionTexture(new Vector3(terrainWidth, waterHeight, -terrainLength), new Vector2(1, 0));

            waterVertexBuffer = new VertexBuffer(device, waterVertices.Length * VertexPositionTexture.SizeInBytes, BufferUsage.WriteOnly);
            waterVertexBuffer.SetData(waterVertices);
        }


        private void CreateBillboardVerticesFromList(List<Vector3> treeList)        {
            VertexPositionTexture[] billboardVertices = new VertexPositionTexture[treeList.Count * 6];
            int i = 0;
            foreach (Vector3 currentV3 in treeList)
            {
                billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(0, 0));
                billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(1, 0));
                billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(1, 1));

                billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(0, 0));
                billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(1, 1));
                billboardVertices[i++] = new VertexPositionTexture(currentV3, new Vector2(0, 1));
            }

            treeVertexBuffer = new VertexBuffer(device, billboardVertices.Length * VertexPositionTexture.SizeInBytes, BufferUsage.WriteOnly);
            treeVertexBuffer.SetData(billboardVertices);
            treeVertexDeclaration = new VertexDeclaration(device, VertexPositionTexture.VertexElements);
        }



        private List<Vector3> GenerateTreePositions(Texture2D treeMap, VertexMultitextured[] terrainVertices)        {
            Color[] treeMapColors = new Color[treeMap.Width * treeMap.Height];
            treeMap.GetData(treeMapColors);

            int[,] noiseData = new int[treeMap.Width, treeMap.Height];
            for (int x = 0; x < treeMap.Width; x++)
                for (int y = 0; y < treeMap.Height; y++)
                    noiseData[x, y] = treeMapColors[y + x * treeMap.Height].R;


            List<Vector3> treeList = new List<Vector3> ();                        Random random = new Random();

            for (int x = 0; x < terrainWidth; x++)
            {
                for (int y = 0; y < terrainLength; y++)
                {
                    float terrainHeight = heightData[x, y];
                    if ((terrainHeight > 8) && (terrainHeight < 14))
                    {
                        float flatness = Vector3.Dot(terrainVertices[x + y * terrainWidth].Normal, new Vector3(0, 1, 0));
                        float minFlatness = (float)Math.Cos(MathHelper.ToRadians(15));
                        if (flatness > minFlatness)
                        {
                            float relx = (float)x / (float)terrainWidth;
                            float rely = (float)y / (float)terrainLength;

                            float noiseValueAtCurrentPosition = noiseData[(int)(relx * treeMap.Width), (int)(rely * treeMap.Height)];
                            float treeDensity;
                            if (noiseValueAtCurrentPosition > 200)
                                treeDensity = 5;
                            else if (noiseValueAtCurrentPosition > 150)
                                treeDensity = 4;
                            else if (noiseValueAtCurrentPosition > 100)
                                treeDensity = 3;
                            else
                                treeDensity = 0;

                            for (int currDetail = 0; currDetail < treeDensity; currDetail++)
                            {
                                float rand1 = (float)random.Next(1000) / 1000.0f;
                                float rand2 = (float)random.Next(1000) / 1000.0f;
                                Vector3 treePos = new Vector3((float)x - rand1, 0, -(float)y - rand2);
                                treePos.Y = heightData[x, y];
                                treeList.Add(treePos);
                            }
                        }
                    }
                }
            }

            return treeList;
        }

 
         protected override void UnloadContent()
         {
         }
 
         protected override void Update(GameTime gameTime)
         {
             if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
                 this.Exit();
 
             float timeDifference = (float)gameTime.ElapsedGameTime.TotalMilliseconds / 1000.0f;
             ProcessInput(timeDifference);
 
             base.Update(gameTime);
         }
 
         private void ProcessInput(float amount)
         {
             MouseState currentMouseState = Mouse.GetState();
             if (currentMouseState != originalMouseState)
             {
                 float xDifference = currentMouseState.X - originalMouseState.X;
                 float yDifference = currentMouseState.Y - originalMouseState.Y;
                 leftrightRot -= rotationSpeed * xDifference * amount;
                 updownRot -= rotationSpeed * yDifference * amount;
                 Mouse.SetPosition(device.Viewport.Width / 2, device.Viewport.Height / 2);
                 UpdateViewMatrix();
             }
 
             Vector3 moveVector = new Vector3(0, 0, 0);
             KeyboardState keyState = Keyboard.GetState();
             if (keyState.IsKeyDown(Keys.Up) || keyState.IsKeyDown(Keys.W))
                 moveVector += new Vector3(0, 0, -1);
             if (keyState.IsKeyDown(Keys.Down) || keyState.IsKeyDown(Keys.S))
                 moveVector += new Vector3(0, 0, 1);
             if (keyState.IsKeyDown(Keys.Right) || keyState.IsKeyDown(Keys.D))
                 moveVector += new Vector3(1, 0, 0);
             if (keyState.IsKeyDown(Keys.Left) || keyState.IsKeyDown(Keys.A))
                 moveVector += new Vector3(-1, 0, 0);
             if (keyState.IsKeyDown(Keys.Q))
                 moveVector += new Vector3(0, 1, 0);
             if (keyState.IsKeyDown(Keys.Z))
                 moveVector += new Vector3(0, -1, 0);
             AddToCameraPosition(moveVector * amount);
         }
 
         private void AddToCameraPosition(Vector3 vectorToAdd)
         {
             Matrix cameraRotation = Matrix.CreateRotationX(updownRot) * Matrix.CreateRotationY(leftrightRot);
             Vector3 rotatedVector = Vector3.Transform(vectorToAdd, cameraRotation);
             cameraPosition += moveSpeed * rotatedVector;
             UpdateViewMatrix();
         }
 
         private void UpdateViewMatrix()
         {
             Matrix cameraRotation = Matrix.CreateRotationX(updownRot) * Matrix.CreateRotationY(leftrightRot);
 
             Vector3 cameraOriginalTarget = new Vector3(0, 0, -1);
             Vector3 cameraOriginalUpVector = new Vector3(0, 1, 0);
             Vector3 cameraRotatedTarget = Vector3.Transform(cameraOriginalTarget, cameraRotation);
             Vector3 cameraFinalTarget = cameraPosition + cameraRotatedTarget;
             Vector3 cameraRotatedUpVector = Vector3.Transform(cameraOriginalUpVector, cameraRotation);
 
             viewMatrix = Matrix.CreateLookAt(cameraPosition, cameraFinalTarget, cameraRotatedUpVector);
 
             Vector3 reflCameraPosition = cameraPosition;
             reflCameraPosition.Y = -cameraPosition.Y + waterHeight * 2;
             Vector3 reflTargetPos = cameraFinalTarget;
             reflTargetPos.Y = -cameraFinalTarget.Y + waterHeight * 2;
 
             Vector3 cameraRight = Vector3.Transform(new Vector3(1, 0, 0), cameraRotation);
             Vector3 invUpVector = Vector3.Cross(cameraRight, reflTargetPos - reflCameraPosition);
 
             reflectionViewMatrix = Matrix.CreateLookAt(reflCameraPosition, reflTargetPos, invUpVector);
         }
 
         protected override void Draw(GameTime gameTime)
         {
             float time = (float)gameTime.TotalGameTime.TotalMilliseconds / 100.0f;
 
             DrawRefractionMap();
             DrawReflectionMap();
 
             device.Clear(ClearOptions.Target | ClearOptions.DepthBuffer, Color.White, 1.0f, 0);
             DrawSkyDome(viewMatrix);
             DrawTerrain(viewMatrix);
             DrawWater(time);
             DrawBillboards(viewMatrix);
 
             base.Draw(gameTime);
         }
 
         private void DrawTerrain(Matrix currentViewMatrix)
         {
             effect.CurrentTechnique = effect.Techniques["MultiTextured"];
             effect.Parameters["xTexture0"].SetValue(sandTexture);
             effect.Parameters["xTexture1"].SetValue(grassTexture);
             effect.Parameters["xTexture2"].SetValue(rockTexture);
             effect.Parameters["xTexture3"].SetValue(snowTexture);
 
             Matrix worldMatrix = Matrix.Identity;
             effect.Parameters["xWorld"].SetValue(worldMatrix);
             effect.Parameters["xView"].SetValue(currentViewMatrix);
             effect.Parameters["xProjection"].SetValue(projectionMatrix);
 
             effect.Parameters["xEnableLighting"].SetValue(true);
             effect.Parameters["xAmbient"].SetValue(0.4f);
             effect.Parameters["xLightDirection"].SetValue(new Vector3(-0.5f, -1, -0.5f));
 
             effect.Begin();
             foreach (EffectPass pass in effect.CurrentTechnique.Passes)
             {
                 pass.Begin();
 
                 device.Vertices[0].SetSource(terrainVertexBuffer, 0, VertexMultitextured.SizeInBytes);
                 device.Indices = terrainIndexBuffer;
                 device.VertexDeclaration = terrainVertexDeclaration;
 
                 int noVertices = terrainVertexBuffer.SizeInBytes / VertexMultitextured.SizeInBytes;
                 int noTriangles = terrainIndexBuffer.SizeInBytes / sizeof(int) / 3;
                 device.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, noVertices, 0, noTriangles);
 
                 pass.End();
             }
             effect.End();
         }
 
         private void DrawSkyDome(Matrix currentViewMatrix)
         {
             device.RenderState.DepthBufferWriteEnable = false;
 
             Matrix[] modelTransforms = new Matrix[skyDome.Bones.Count];
             skyDome.CopyAbsoluteBoneTransformsTo(modelTransforms);
 
             Matrix wMatrix = Matrix.CreateTranslation(0, -0.3f, 0) * Matrix.CreateScale(100) * Matrix.CreateTranslation(cameraPosition);
             foreach (ModelMesh mesh in skyDome.Meshes)
             {
                 foreach (Effect currentEffect in mesh.Effects)
                 {
                     Matrix worldMatrix = modelTransforms[mesh.ParentBone.Index] * wMatrix;
                     currentEffect.CurrentTechnique = currentEffect.Techniques["Textured"];
                     currentEffect.Parameters["xWorld"].SetValue(worldMatrix);
                     currentEffect.Parameters["xView"].SetValue(currentViewMatrix);
                     currentEffect.Parameters["xProjection"].SetValue(projectionMatrix);
                     currentEffect.Parameters["xTexture"].SetValue(cloudMap);
                     currentEffect.Parameters["xEnableLighting"].SetValue(false);
                 }
                 mesh.Draw();
             }
             device.RenderState.DepthBufferWriteEnable = true;
         }
 
         private Plane CreatePlane(float height, Vector3 planeNormalDirection, Matrix currentViewMatrix, bool clipSide)
         {
             planeNormalDirection.Normalize();
             Vector4 planeCoeffs = new Vector4(planeNormalDirection, height);
             if (clipSide)
                 planeCoeffs *= -1;
 
             Matrix worldViewProjection = currentViewMatrix * projectionMatrix;
             Matrix inverseWorldViewProjection = Matrix.Invert(worldViewProjection);
             inverseWorldViewProjection = Matrix.Transpose(inverseWorldViewProjection);
 
             planeCoeffs = Vector4.Transform(planeCoeffs, inverseWorldViewProjection);
             Plane finalPlane = new Plane(planeCoeffs);
 
             return finalPlane;
         }
 
         private void DrawRefractionMap()
         {
             Plane refractionPlane = CreatePlane(waterHeight + 1.5f, new Vector3(0, -1, 0), viewMatrix, false);
             device.ClipPlanes[0].Plane = refractionPlane;
             device.ClipPlanes[0].IsEnabled = true;
             device.SetRenderTarget(0, refractionRenderTarget);
             device.Clear(ClearOptions.Target | ClearOptions.DepthBuffer, Color.Black, 1.0f, 0);
             DrawTerrain(viewMatrix);
             device.ClipPlanes[0].IsEnabled = false;
 
             device.SetRenderTarget(0, null);
             refractionMap = refractionRenderTarget.GetTexture();
         }
 
         private void DrawReflectionMap()
         {
             Plane reflectionPlane = CreatePlane(waterHeight - 0.5f, new Vector3(0, -1, 0), reflectionViewMatrix, true);
             device.ClipPlanes[0].Plane = reflectionPlane;
             device.ClipPlanes[0].IsEnabled = true;
             device.SetRenderTarget(0, reflectionRenderTarget);
             device.Clear(ClearOptions.Target | ClearOptions.DepthBuffer, Color.Black, 1.0f, 0);
             DrawSkyDome(reflectionViewMatrix);
             DrawTerrain(reflectionViewMatrix);
             DrawBillboards(reflectionViewMatrix);
             device.ClipPlanes[0].IsEnabled = false;
 
             device.SetRenderTarget(0, null);
             reflectionMap = reflectionRenderTarget.GetTexture();
         }
 
         private void DrawWater(float time)
         {
             effect.CurrentTechnique = effect.Techniques["Water"];
             Matrix worldMatrix = Matrix.Identity;
             effect.Parameters["xWorld"].SetValue(worldMatrix);
             effect.Parameters["xView"].SetValue(viewMatrix);
             effect.Parameters["xReflectionView"].SetValue(reflectionViewMatrix);
             effect.Parameters["xProjection"].SetValue(projectionMatrix);
             effect.Parameters["xReflectionMap"].SetValue(reflectionMap);
             effect.Parameters["xRefractionMap"].SetValue(refractionMap);
             effect.Parameters["xWaterBumpMap"].SetValue(waterBumpMap);
             effect.Parameters["xWaveLength"].SetValue(0.1f);
             effect.Parameters["xWaveHeight"].SetValue(0.3f);
             effect.Parameters["xCamPos"].SetValue(cameraPosition);
             effect.Parameters["xTime"].SetValue(time);
             effect.Parameters["xWindForce"].SetValue(0.002f);
             effect.Parameters["xWindDirection"].SetValue(windDirection);
 
             effect.Begin();
             foreach (EffectPass pass in effect.CurrentTechnique.Passes)
             {
                 pass.Begin();
 
                 device.Vertices[0].SetSource(waterVertexBuffer, 0, VertexPositionTexture.SizeInBytes);
                 device.VertexDeclaration = waterVertexDeclaration;
                 int noVertices = waterVertexBuffer.SizeInBytes / VertexPositionTexture.SizeInBytes;
                 device.DrawPrimitives(PrimitiveType.TriangleList, 0, noVertices / 3);
 
                 pass.End();
             }
             effect.End();
         }
 
         private void DrawBillboards(Matrix currentViewMatrix)
         {
             bbEffect.CurrentTechnique = bbEffect.Techniques["CylBillboard"];
             bbEffect.Parameters["xWorld"].SetValue(Matrix.Identity);
             bbEffect.Parameters["xView"].SetValue(currentViewMatrix);
             bbEffect.Parameters["xProjection"].SetValue(projectionMatrix);
             bbEffect.Parameters["xCamPos"].SetValue(cameraPosition);
             bbEffect.Parameters["xAllowedRotDir"].SetValue(new Vector3(0, 1, 0));
             bbEffect.Parameters["xBillboardTexture"].SetValue(treeTexture);
             
             device.RenderState.AlphaBlendEnable = true;
             device.RenderState.SourceBlend = Blend.SourceAlpha;
             device.RenderState.DestinationBlend = Blend.InverseSourceAlpha;
 
             bbEffect.Begin();
             foreach (EffectPass pass in bbEffect.CurrentTechnique.Passes)
             {
                 pass.Begin();
                 device.Vertices[0].SetSource(treeVertexBuffer, 0, VertexPositionTexture.SizeInBytes);
                 device.VertexDeclaration = treeVertexDeclaration;
                 int noVertices = treeVertexBuffer.SizeInBytes / VertexPositionTexture.SizeInBytes;
                 int noTriangles = noVertices / 3;
                 device.DrawPrimitives(PrimitiveType.TriangleList, 0, noTriangles);
                 pass.End();
             }
             bbEffect.End();
 
             device.RenderState.AlphaBlendEnable = false;
         }
     }
 }

发布时间:2009/12/31 下午12:43:31  阅读次数:7898

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