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Making our water move – adding a wind direction

Now our water is graphically OK, it still misses a lot of realism because it isn’t moving. So that’s what we’re going to fix in this chapter.

Remember what’s the origin of the ripples in our water? The bump map of the water indicates for each pixel exactly how much to perturbate the sampling coordinates of the reflection and refraction map. If you’re unsure about this, take a quick look at the Ripples chapter.

This means that simply translating the texture coordinates of this bump map will already make our water move in one direction. Remember, these texture coordinates were attached to the 6 vertices of the 2 giant triangles that make up our water. So one way to change the vertices would be in the XNA app, but a MUCH better place would be to change them in the vertex shader. Always try to offload CPU workload to the GPU.

We’ll simply pass a xTime variable to our shader, which the vertex shader will use to update the bump map texture coordinates:

float xTime;
float3 xWindDirection;
float xWindForce;

The xWindForce variable will control how fast the ripples scroll through our water, while we obviously also want to be able to control the direction of our ripples.

This is the simple code that should be added to the vertex shader:

float2 moveVector = float2(0, xTime*xWindForce);
Output.BumpMapSamplingPos = (inTex + moveVector)/xWaveLength;

You see we scroll our bump map along the Y direction, as the waves in the image are horizontal so you need to scroll them vertically. The scrolling speed depends on the xWindForce value.

Of course, we still need to set the XNA-to-HLSL variables from within our XNA app. Because we’ll also need the wind direction for our moving clouds later on in this series, we’ll add this as a class variable:

 Vector3 windDirection = new Vector3(1,0,0);

And add these lines to our DrawWater method:

 effect.Parameters["xTime"].SetValue(time);
 effect.Parameters["xWindForce"].SetValue(20.0f);
 effect.Parameters["xWindDirection"].SetValue(windDirection);

That’s it! Running the code should make your water move.

However, there is one factor we still cannot control: the direction of the wind, and thus the direction of the waves. We’ve already specified the xWindDirection variable, but as you see our vertex shader never uses it. So changing this value from within our XNA application would have no impact.

Obviously, there needs to be a way to allow us to change the direction of the waves, and it immediately is a nice exercise on vectors. Take a look at the image below:



The square indicates our original texture coordinates, or you can think of it as our complete water plane. The red arrow indicates the direction we want our water to move. The green arrow is nothing more than the direction perpendicular to the red arrow.

Take a look at the right image. For each pixel in the black square, we need to find a new X and Y texture coordinate. There is a constraint on each of them:

  • All pixels on the red arrow must have the same X texture coordinate.
  • All pixels on the green arrow must have the same Y texture coordinate.

    This way of writing applies only to the pixels that are exactly on the arrows. But if you understand the 2 constraints above, this is the more generalized way:

  • Imagine any line parallel to the red arrow. All pixels on this line must have the same X texture coordinate.
  • Imagine any line parallel to the green arrow. All pixels on this line must have the same Y texture coordinate.

    For each pixel in the black quad, this gives constraints on the X and Y texture coordinate. The question that remains, is which X and Y texture coordinates for all pixels?

    In the right image, take a look at the upper-left pixel of the black square. The Y texture coordinate is found by taking the corresponding portion of the red arrow, as displayed by the thick red line. The length of this thick red line will be the Y texture coordinate for this pixel. Even more, all pixels on the long dotted line have the same thick red line, and thus the same Y texture coordinate. This fulfils the second constraint!

    Exactly the same, the X texture coordinate is found by projecting the pixel on the green arrow, and finding the length of the thick green line. All pixels on the short dotted line will have the same thick green line, and thus the same X texture coordinate!

    It’s very easy to find the length of the thick red and green lines, as it’s the dot product between the pixel vector (the thin black line) and the red and green vectors respectively.

    So in order to obtain the X and Y texture coordinates, we should first find the red and green arrows. The red one is easy, as it is the normalized version of the xWindVariable vector. The green arrow is perpendicular to the red arrow and the Up direction, so it can be found by taking their cross product:

    float3 windDir = normalize(xWindDirection);    
    float3 perpDir = cross(xWindDirection, float3(0,1,0));

    Next, we find the X and Y texture coordinates by taking the dot product of the pixel vector and both arrows:

    float ydot = dot(inTex, xWindDirection.xz);
    float xdot = dot(inTex, perpDir.xz);
    float2 moveVector = float2(xdot, ydot);

    What we obtain are the fixed texure coordinates, rotated so the waves are perpendicular to our xWindDirection, exactly as they should be. All we need to do, is increase the Y texture coordinate the make the texture scroll vertically, and pass the result to the pixel shader:

    moveVector.y += xTime*xWindForce;    
    Output.BumpMapSamplingPos = moveVector/xWaveLength;    

    This little extra HLSL code allows you to fully control the direction of your waves!




    DirectX Tutorial 13 - Moving water

    If you appreciate the amount of time I spend creating and updating
    these pages, feel free to donate -- any amount is welcome !



    Click here to go to the forum on this chapter!

    Or click on one of the topics on this chapter to go there:
  • Infinite Water
          Anyone know , how can make the water infinite ? M...
  • XNA 4.0
           ******************************** **************...
  • Refactoring, the Series
          Minor updates to terrain.cs. First, the wind fact...
  • Strange water movements
          I'm trying to make water move, but without any su...
  • Wind Force Typo
          There is a typo in the tutorial where we define th...
  • Water Error
          Hi Reimer and all, I've been working through t...
  • Sadly, water is not moving ...
          Hi, before I will describe my problem, here is ...
  • poor frame rate
          I added this project to my engine, and got frame r...
  • Error in shader file?
          Hi, i'm new to XNA D3D and shader development ...
  • Problem with water reflection
          I am having a weird display issue with the water. ...
  • Glitch in the code?
          Hi ho, I've noticed a small distortion of the ...
  • Adding heightmap files
           I want to load up 9 height maps. so I redid all t...
  • Collision Detection
          Hi there, im new to this, so im having trouble wit...
  • Ugly edges
          First of all: A big thanks to what your doing here...
  • Last Typo, and a Problem:
          The typo: elapsedTime = gameTime.TotalGam...
  • RenderTarget2D initialization values
          Firstly, I must agree with the majority vote on th...
  • Are the tutorials stopped?
          Are the tutorials stopped? We want more! We need m...
  • rendering larger bodies of water
          Hello. First a quick thanks for the tutorials, ...
  • LOD- Level of detail tutorial
          Is there any way you could add some LOD tutorial, ...
  • A small requst that could be cool
          Well, im new to XNA programing, and i really liked...
  • RunTime Problem
          Was wondering if you could help me find a starting...
  • Water rendering performance
          Loving the look,and it really works well. just ...


    With your water moving, there’s one last effect we’ll add to it: specular lighting.

    Our XNA code thus far:

     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;
     
             Effect effect;
             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;
             
             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");
                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);
            }

            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");        }

            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);
            }

            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.Black, 1.0f, 0);
                DrawSkyDome(viewMatrix);
                DrawTerrain(viewMatrix);
                DrawWater(time);

                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);
                DrawTerrain(reflectionViewMatrix);
                DrawSkyDome(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();
             }
         }
     }

    …and our 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;


    //------- 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 = float3(0,1,0);
        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);
        
        return Output;
    }

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



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    ©2003 - 2011 Riemer Grootjans
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    Microsoft MVP Award



    2007 - 2011 MVP Award
    DirectX - XNA

    Contents

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    XNA 4.0 using C# (89)
    2D Series: Shooters (22)
    3D Series 1: Terrain (13)
    3D Series 2: Flightsim (14)
    3D Series 3: HLSL (18)
    3D Series 4: Adv. terrain (19)
    Starting code
    Mouse camera
    Textured terrain
    Multitexturing
    Adding detail
    Skydome
    The water technique
    Refraction map
    Reflection map
    Perfect mirror
    Ripples
    The Fresnel term
    Moving water
    Specular highlights
    Billboarding
    Region growing
    Billboarding renderstates
    Perlin noise
    Gradient skybox
    Short Tuts (3)
    DirectX using C# (54)
    DirectX using C++ (15)
    DirectX using VB (2)
    -- Expand all --


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