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Riemers3DXNA4advterrain19gradient

Simon (darkside) Jackson edited this page Aug 25, 2020 · 1 revision

Gradient SkyDome

Now we’ve coded a cloudmap that also shifts in shape, let’s code a technique worthy of displaying this map on our skydome. This will result in a gradient skydome.

The technique is rather simple. If you take a look outside, the top of the atmosphere has a deeper color than the horizon. Let’s translate this sentence into HLSL.

As usual, let’s start with defining the output structures for our vertex and pixel shaders:

//------- Technique: SkyDome --------
struct SDVertexToPixel
{
    float4 Position         : POSITION;
    float2 TextureCoords    : TEXCOORD0;
    float4 ObjectPosition    : TEXCOORD1;
};

struct SDPixelToFrame
{
    float4 Color : COLOR0;
};

The vertex shader will need to pass the texture coordinates to the pixel shader, but also the object position of each vertex. The object position of a vertex is the position of the vertex inside the object, the skydome in this case. This position remains the same all the time, no matter whether the object is rotated, moved or scaled in the 3D world. This will allow us to define a fixed gradient in the pixel shader.

This is our vertex shader:

SDVertexToPixel SkyDomeVS( float4 inPos : POSITION, float2 inTexCoords: TEXCOORD0)
{
    SDVertexToPixel Output = (SDVertexToPixel)0;
    float4x4 preViewProjection = mul (xView, xProjection);
    float4x4 preWorldViewProjection = mul (xWorld, preViewProjection);

    Output.Position = mul(inPos, preWorldViewProjection);
    Output.TextureCoords = inTexCoords;
    Output. ObjectPosition = inPos;

    return Output;
}

You see the original position and texture coordinates are routed immediately to the ObjectPos and TextureCoords outputs respectively. Because the skydome is a 3D model that needs to be transformed to 2D screen space, we as usual need to transform the 3D position by the WorldViewProjection matrix and pass the result to the mandatory Output.Position.

The pixel shader is quite easy. I wish is was a bit more complex to end the last chapter, but it isn’t:

SDPixelToFrame SkyDomePS(SDVertexToPixel PSIn)
{
    SDPixelToFrame Output = (SDPixelToFrame)0;

    float4 topColor = float4(0.3f, 0.3f, 0.8f, 1);
    float4 bottomColor = 1;

    float4 baseColor = lerp(bottomColor, topColor, saturate((PSIn. ObjectPosition.y)/0.4f));
    float4 cloudValue = tex2D(TextureSampler, PSIn.TextureCoords).r;

    Output.Color = lerp(baseColor,1, cloudValue);

    return Output;
}

You define 2 colors: one blueish color for the top of the skydome, and white for the horizons. Next, you interpolate between both colors, based on how high the current pixel is in the skydome. The highest point in the skydome has height Y=0.5, so all pixels above 0.4 will get the blueish color. The pixels lower than 0.4 will get a gradient color between the bleuish color and white.

Finally, we look up the value in the cloud map, corresponding to the current pixel. We use this value to interpolate between our sky color and white, which adds the clouds to our skydome.

That’s it! Just add the technique definition:

technique SkyDome
{
    pass Pass0
    {
        VertexShader = compile vs_1_1 SkyDomeVS();
        PixelShader = compile ps_2_0 SkyDomePS();
    }
}

And we’re ready to change the DrawSkydome method, as it still uses the Textured technique. There’s not too much we need to change. Actually, we just need to change the name of the technique we want to use!

 currentEffect.CurrentTechnique = currentEffect.Techniques["SkyDome"];

When you run this code, you’ll see the final screen for Series 4.

Final

We’ve literary covered quite some terrain since the beginning of the 4th series. We’ve learned about first-person cameras, multi-textured terrain, moving water, billboards and perlin noise. I hope you learned a lot, and will return for a 5th series!

Our final XNA code

 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;
         RenderTarget2D cloudsRenderTarget;
         Texture2D cloudStaticMap;
         VertexPositionTexture[] fullScreenVertices;
         VertexDeclaration fullScreenVertexDeclaration;
 
         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);
            cloudsRenderTarget = 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);

            fullScreenVertices = SetUpFullscreenVertices();
            fullScreenVertexDeclaration = new VertexDeclaration(device, VertexPositionTexture.VertexElements);
        }

        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");            cloudStaticMap = CreateStaticMap(32);
        }

        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;
        }

        private Texture2D CreateStaticMap(int resolution)
        {
            Random rand = new Random();
            Color[] noisyColors = new Color[resolution * resolution];
            for (int x = 0; x < resolution; x++)
                for (int y = 0; y < resolution; y++)
                    noisyColors[x + y * resolution] = new Color(new Vector3((float)rand.Next(1000) / 1000.0f, 0, 0));

            Texture2D noiseImage = new Texture2D(device, resolution, resolution, 1, TextureUsage.None, SurfaceFormat.Color);
            noiseImage.SetData(noisyColors);
            return noiseImage;
        }

        private VertexPositionTexture[] SetUpFullscreenVertices()
        {
            VertexPositionTexture[] vertices = new VertexPositionTexture[4];

            vertices[0] = new VertexPositionTexture(new Vector3(-1, 1, 0f), new Vector2(0, 1));
            vertices[1] = new VertexPositionTexture(new Vector3(1, 1, 0f), new Vector2(1, 1));
            vertices[2] = new VertexPositionTexture(new Vector3(-1, -1, 0f), new Vector2(0, 0));
            vertices[3] = new VertexPositionTexture(new Vector3(1, -1, 0f), new Vector2(1, 0));

            return vertices;
        }

        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();
            GeneratePerlinNoise(time);

            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["SkyDome"];
                     currentEffect.Parameters["xWorld"].SetValue(worldMatrix);
                     currentEffect.Parameters["xView"].SetValue(currentViewMatrix);
                     currentEffect.Parameters["xProjection"].SetValue(projectionMatrix);
                     currentEffect.Parameters["xTexture"].SetValue(cloudMap);
                 }
                 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);
 
             bbEffect.Begin();
 
             device.Vertices[0].SetSource(treeVertexBuffer, 0, VertexPositionTexture.SizeInBytes);
             device.VertexDeclaration = treeVertexDeclaration;
             int noVertices = treeVertexBuffer.SizeInBytes / VertexPositionTexture.SizeInBytes;
             int noTriangles = noVertices / 3;
             {
                 device.RenderState.AlphaTestEnable = true;
                 device.RenderState.AlphaFunction = CompareFunction.GreaterEqual;
                 device.RenderState.ReferenceAlpha = 200;
 
                 bbEffect.CurrentTechnique.Passes[0].Begin();
                 device.DrawPrimitives(PrimitiveType.TriangleList, 0, noTriangles);
                 bbEffect.CurrentTechnique.Passes[0].End();
             }
 
             {
                 device.RenderState.DepthBufferWriteEnable = false;
 
                 device.RenderState.AlphaBlendEnable = true;
                 device.RenderState.SourceBlend = Blend.SourceAlpha;
                 device.RenderState.DestinationBlend = Blend.InverseSourceAlpha;
 
                 device.RenderState.AlphaTestEnable = true;
                 device.RenderState.AlphaFunction = CompareFunction.Less;
                 device.RenderState.ReferenceAlpha = 200;
 
                 bbEffect.CurrentTechnique.Passes[0].Begin();
                 device.DrawPrimitives(PrimitiveType.TriangleList, 0, noTriangles);
                 bbEffect.CurrentTechnique.Passes[0].End();
             }
             
             device.RenderState.AlphaBlendEnable = false;
             device.RenderState.DepthBufferWriteEnable = true;
             device.RenderState.AlphaTestEnable = false;            
 
             bbEffect.End();
         }
 
         private void GeneratePerlinNoise(float time)
         {
             device.SetRenderTarget(0, cloudsRenderTarget);
             device.Clear(ClearOptions.Target | ClearOptions.DepthBuffer, Color.Black, 1.0f, 0);
                         
             effect.CurrentTechnique = effect.Techniques["PerlinNoise"];
             effect.Parameters["xTexture"].SetValue(cloudStaticMap);
             effect.Parameters["xOvercast"].SetValue(1.1f);
             effect.Parameters["xTime"].SetValue(time/1000.0f);
             effect.Begin();
             foreach (EffectPass pass in effect.CurrentTechnique.Passes)
             {
                 pass.Begin();
 
                 device.VertexDeclaration = fullScreenVertexDeclaration;
                 device.DrawUserPrimitives(PrimitiveType.TriangleStrip, fullScreenVertices, 0, 2);
 
                 pass.End();
             }
             effect.End();
 
             device.SetRenderTarget(0, null);
             cloudMap = cloudsRenderTarget.GetTexture();
         }
     }
 }

HLSL shader

And our complete HLSL file:

//----------------------------------------------------
//--                                                --
//--             www.riemers.net                 --
//--         Series 4: Advanced terrain             --
//--                 Shader code                    --
//--                                                --
//----------------------------------------------------

//------- Constants --------
float4x4 xView;
float4x4 xReflectionView;
float4x4 xProjection;
float4x4 xWorld;
float3 xLightDirection;
float xAmbient;
bool xEnableLighting;
float xWaveLength;
float xWaveHeight;
float3 xCamPos;
float xTime;
float xWindForce;
float3 xWindDirection;
float xOvercast;

//------- Texture Samplers --------
Texture xTexture;

sampler TextureSampler = sampler_state { texture = <xTexture> ; magfilter = LINEAR; minfilter = LINEAR; mipfilter=LINEAR; AddressU = mirror; AddressV = mirror;};Texture xTexture0;

sampler TextureSampler0 = sampler_state { texture = <xTexture0> ; magfilter = LINEAR; minfilter = LINEAR; mipfilter=LINEAR; AddressU = wrap; AddressV = wrap;};Texture xTexture1;

sampler TextureSampler1 = sampler_state { texture = <xTexture1> ; magfilter = LINEAR; minfilter = LINEAR; mipfilter=LINEAR; AddressU = wrap; AddressV = wrap;};Texture xTexture2;

sampler TextureSampler2 = sampler_state { texture = <xTexture2> ; magfilter = LINEAR; minfilter = LINEAR; mipfilter=LINEAR; AddressU = mirror; AddressV = mirror;};Texture xTexture3;

sampler TextureSampler3 = sampler_state { texture = <xTexture3> ; magfilter = LINEAR; minfilter = LINEAR; mipfilter=LINEAR; AddressU = mirror; AddressV = mirror;};Texture xReflectionMap;

sampler ReflectionSampler = sampler_state { texture = <xReflectionMap> ; magfilter = LINEAR; minfilter = LINEAR; mipfilter=LINEAR; AddressU = mirror; AddressV = mirror;};Texture xRefractionMap;

sampler RefractionSampler = sampler_state { texture = <xRefractionMap> ; magfilter = LINEAR; minfilter = LINEAR; mipfilter=LINEAR; AddressU = mirror; AddressV = mirror;};Texture xWaterBumpMap;

sampler WaterBumpMapSampler = sampler_state { texture = <xWaterBumpMap> ; magfilter = LINEAR; minfilter = LINEAR; mipfilter=LINEAR; AddressU = mirror; AddressV = mirror;};
//------- Technique: Textured --------
struct TVertexToPixel
{
    float4 Position     : POSITION;    
    float4 Color        : COLOR0;
    float LightingFactor: TEXCOORD0;
    float2 TextureCoords: TEXCOORD1;
};

struct TPixelToFrame
{
    float4 Color : COLOR0;
};

TVertexToPixel TexturedVS( float4 inPos : POSITION, float3 inNormal: NORMAL, float2 inTexCoords: TEXCOORD0)
{    
    TVertexToPixel Output = (TVertexToPixel)0;
    float4x4 preViewProjection = mul (xView, xProjection);
    float4x4 preWorldViewProjection = mul (xWorld, preViewProjection);
    
    Output.Position = mul(inPos, preWorldViewProjection);    
    Output.TextureCoords = inTexCoords;
    
    float3 Normal = normalize(mul(normalize(inNormal), xWorld));    
    Output.LightingFactor = 1;
    if (xEnableLighting)
        Output.LightingFactor = saturate(dot(Normal, -xLightDirection));
    
    return Output;    
}

TPixelToFrame TexturedPS(TVertexToPixel PSIn)
{
    TPixelToFrame Output = (TPixelToFrame)0;        
    
    Output.Color = tex2D(TextureSampler, PSIn.TextureCoords);
    Output.Color.rgb *= saturate(PSIn.LightingFactor + xAmbient);

    return Output;
}

technique Textured_2_0
{
    pass Pass0
    {
        VertexShader = compile vs_2_0 TexturedVS();
        PixelShader = compile ps_2_0 TexturedPS();
    }
}

technique Textured
{
    pass Pass0
    {
        VertexShader = compile vs_1_1 TexturedVS();
        PixelShader = compile ps_1_1 TexturedPS();
    }
}

//------- Technique: Multitextured --------
struct MTVertexToPixel
{
    float4 Position         : POSITION;    
    float4 Color            : COLOR0;
    float3 Normal            : TEXCOORD0;
    float2 TextureCoords    : TEXCOORD1;
    float4 LightDirection    : TEXCOORD2;
    float4 TextureWeights    : TEXCOORD3;
    float Depth                : TEXCOORD4;
};

struct MTPixelToFrame
{
    float4 Color : COLOR0;
};

MTVertexToPixel MultiTexturedVS( float4 inPos : POSITION, float3 inNormal: NORMAL, float2 inTexCoords: TEXCOORD0, float4 inTexWeights: TEXCOORD1)
{    
    MTVertexToPixel Output = (MTVertexToPixel)0;
    float4x4 preViewProjection = mul (xView, xProjection);
    float4x4 preWorldViewProjection = mul (xWorld, preViewProjection);
    
    Output.Position = mul(inPos, preWorldViewProjection);
    Output.Normal = mul(normalize(inNormal), xWorld);
    Output.TextureCoords = inTexCoords;
    Output.LightDirection.xyz = -xLightDirection;
    Output.LightDirection.w = 1;    
    Output.TextureWeights = inTexWeights;
    Output.Depth = Output.Position.z/Output.Position.w;
    
    return Output;    
}

MTPixelToFrame MultiTexturedPS(MTVertexToPixel PSIn)
{
    MTPixelToFrame Output = (MTPixelToFrame)0;        
    
    float lightingFactor = 1;
    if (xEnableLighting)
        lightingFactor = saturate(saturate(dot(PSIn.Normal, PSIn.LightDirection)) + xAmbient);
        
    float blendDistance = 0.99f;
    float blendWidth = 0.005f;
    float blendFactor = clamp((PSIn.Depth-blendDistance)/blendWidth, 0, 1);
        
    float4 farColor;
    farColor = tex2D(TextureSampler0, PSIn.TextureCoords)*PSIn.TextureWeights.x;
    farColor += tex2D(TextureSampler1, PSIn.TextureCoords)*PSIn.TextureWeights.y;
    farColor += tex2D(TextureSampler2, PSIn.TextureCoords)*PSIn.TextureWeights.z;
    farColor += tex2D(TextureSampler3, PSIn.TextureCoords)*PSIn.TextureWeights.w;
    
    float4 nearColor;
    float2 nearTextureCoords = PSIn.TextureCoords*3;
    nearColor = tex2D(TextureSampler0, nearTextureCoords)*PSIn.TextureWeights.x;
    nearColor += tex2D(TextureSampler1, nearTextureCoords)*PSIn.TextureWeights.y;
    nearColor += tex2D(TextureSampler2, nearTextureCoords)*PSIn.TextureWeights.z;
    nearColor += tex2D(TextureSampler3, nearTextureCoords)*PSIn.TextureWeights.w;

    Output.Color = lerp(nearColor, farColor, blendFactor);
    Output.Color *= lightingFactor;
    
    return Output;
}

technique MultiTextured
{
    pass Pass0
    {
        VertexShader = compile vs_1_1 MultiTexturedVS();
        PixelShader = compile ps_2_0 MultiTexturedPS();
    }
}

//------- Technique: Water --------
struct WVertexToPixel
{
    float4 Position                 : POSITION;
    float4 ReflectionMapSamplingPos    : TEXCOORD1;
    float2 BumpMapSamplingPos        : TEXCOORD2;
    float4 RefractionMapSamplingPos : TEXCOORD3;
    float4 Position3D                : TEXCOORD4;
};

struct WPixelToFrame
{
    float4 Color : COLOR0;
};

WVertexToPixel WaterVS(float4 inPos : POSITION, float2 inTex: TEXCOORD)
{    
    WVertexToPixel Output = (WVertexToPixel)0;

    float4x4 preViewProjection = mul (xView, xProjection);
    float4x4 preWorldViewProjection = mul (xWorld, preViewProjection);
    float4x4 preReflectionViewProjection = mul (xReflectionView, xProjection);
    float4x4 preWorldReflectionViewProjection = mul (xWorld, preReflectionViewProjection);

    Output.Position = mul(inPos, preWorldViewProjection);
    Output.ReflectionMapSamplingPos = mul(inPos, preWorldReflectionViewProjection);    
    Output.RefractionMapSamplingPos = mul(inPos, preWorldViewProjection);
    Output.Position3D = mul(inPos, xWorld);        
    
    float3 windDir = normalize(xWindDirection);    
    float3 perpDir = cross(xWindDirection, float3(0,1,0));
    float ydot = dot(inTex, xWindDirection.xz);
    float xdot = dot(inTex, perpDir.xz);
    float2 moveVector = float2(xdot, ydot);
    moveVector.y += xTime*xWindForce;    
    Output.BumpMapSamplingPos = moveVector/xWaveLength;    

    
    return Output;
}

WPixelToFrame WaterPS(WVertexToPixel PSIn)
{
    WPixelToFrame Output = (WPixelToFrame)0;        
    
    float4 bumpColor = tex2D(WaterBumpMapSampler, PSIn.BumpMapSamplingPos);
    float2 perturbation = xWaveHeight*(bumpColor.rg - 0.5f)*2.0f;
    
    float2 ProjectedTexCoords;
    ProjectedTexCoords.x = PSIn.ReflectionMapSamplingPos.x/PSIn.ReflectionMapSamplingPos.w/2.0f + 0.5f;
    ProjectedTexCoords.y = -PSIn.ReflectionMapSamplingPos.y/PSIn.ReflectionMapSamplingPos.w/2.0f + 0.5f;        
    float2 perturbatedTexCoords = ProjectedTexCoords + perturbation;
    float4 reflectiveColor = tex2D(ReflectionSampler, perturbatedTexCoords);
    
    float2 ProjectedRefrTexCoords;
    ProjectedRefrTexCoords.x = PSIn.RefractionMapSamplingPos.x/PSIn.RefractionMapSamplingPos.w/2.0f + 0.5f;
    ProjectedRefrTexCoords.y = -PSIn.RefractionMapSamplingPos.y/PSIn.RefractionMapSamplingPos.w/2.0f + 0.5f;    
    float2 perturbatedRefrTexCoords = ProjectedRefrTexCoords + perturbation;    
    float4 refractiveColor = tex2D(RefractionSampler, perturbatedRefrTexCoords);
    
    float3 eyeVector = normalize(xCamPos - PSIn.Position3D);
    float3 normalVector = (bumpColor.rbg-0.5f)*2.0f;
    
    float fresnelTerm = dot(eyeVector, normalVector);    
    float4 combinedColor = lerp(reflectiveColor, refractiveColor, fresnelTerm);
    
    float4 dullColor = float4(0.3f, 0.3f, 0.5f, 1.0f);
    
    Output.Color = lerp(combinedColor, dullColor, 0.2f);    
    
    float3 reflectionVector = -reflect(xLightDirection, normalVector);
    float specular = dot(normalize(reflectionVector), normalize(eyeVector));
    specular = pow(specular, 256);        
    Output.Color.rgb += specular;
    
    return Output;
}

technique Water
{
    pass Pass0
    {
        VertexShader = compile vs_1_1 WaterVS();
        PixelShader = compile ps_2_0 WaterPS();
    }
}

//------- Technique: PerlinNoise --------
struct PNVertexToPixel
{    
    float4 Position         : POSITION;
    float2 TextureCoords    : TEXCOORD0;
};

struct PNPixelToFrame
{
    float4 Color : COLOR0;
};

PNVertexToPixel PerlinVS(float4 inPos : POSITION, float2 inTexCoords: TEXCOORD)
{    
    PNVertexToPixel Output = (PNVertexToPixel)0;
    
    Output.Position = inPos;
    Output.TextureCoords = inTexCoords;
    
    return Output;    
}

PNPixelToFrame PerlinPS(PNVertexToPixel PSIn)
{
    PNPixelToFrame Output = (PNPixelToFrame)0;    
    
    float2 move = float2(0,1);
    float4 perlin = tex2D(TextureSampler, (PSIn.TextureCoords)+xTime*move)/2;
    perlin += tex2D(TextureSampler, (PSIn.TextureCoords)*2+xTime*move)/4;
    perlin += tex2D(TextureSampler, (PSIn.TextureCoords)*4+xTime*move)/8;
    perlin += tex2D(TextureSampler, (PSIn.TextureCoords)*8+xTime*move)/16;
    perlin += tex2D(TextureSampler, (PSIn.TextureCoords)*16+xTime*move)/32;
    perlin += tex2D(TextureSampler, (PSIn.TextureCoords)*32+xTime*move)/32;    
    
    Output.Color.rgb = 1.0f-pow(perlin.r, xOvercast)*2.0f;
    Output.Color.a =1;

    return Output;
}

technique PerlinNoise
{
    pass Pass0
    {
        VertexShader = compile vs_1_1 PerlinVS();
        PixelShader = compile ps_2_0 PerlinPS();
    }
}


 //------- Technique: SkyDome --------
 struct SDVertexToPixel
 {    
     float4 Position         : POSITION;
     float2 TextureCoords    : TEXCOORD0;
     float4 ObjectPosition    : TEXCOORD1;
 };
 
 struct SDPixelToFrame
 {
     float4 Color : COLOR0;
 };
 
 SDVertexToPixel SkyDomeVS( float4 inPos : POSITION, float2 inTexCoords: TEXCOORD0)
 {    
     SDVertexToPixel Output = (SDVertexToPixel)0;
     float4x4 preViewProjection = mul (xView, xProjection);
     float4x4 preWorldViewProjection = mul (xWorld, preViewProjection);
     
     Output.Position = mul(inPos, preWorldViewProjection);
     Output.TextureCoords = inTexCoords;
     Output.ObjectPosition = inPos;
     
     return Output;    
 }
 
 SDPixelToFrame SkyDomePS(SDVertexToPixel PSIn)
 {
     SDPixelToFrame Output = (SDPixelToFrame)0;        
 
     float4 topColor = float4(0.3f, 0.3f, 0.8f, 1);    
     float4 bottomColor = 1;    
     
     float4 baseColor = lerp(bottomColor, topColor, saturate((PSIn.ObjectPosition.y)/0.4f));
     float4 cloudValue = tex2D(TextureSampler, PSIn.TextureCoords).r;
     
     Output.Color = lerp(baseColor,1, cloudValue);        
 
     return Output;
 }
 
 technique SkyDome
 {
     pass Pass0
     {
         VertexShader = compile vs_1_1 SkyDomeVS();
         PixelShader = compile ps_2_0 SkyDomePS();
     }
 }
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