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Rotate your terrain using the keyboard

Using XNA, it is very easy to read in the current state of your keyboard. The correct libraries, Microsoft.Xna.Framework.Input, are already linked to by default when you’ve started your XNA project, so we can immediately move on to the code that reads in the keyboard input.

Replace the line that updates your angle with the following piece of code in your Update method, which is called 60 times per second:

 KeyboardState keyState = Keyboard.GetState();
 if (keyState.IsKeyDown(Keys.Delete))
     angle += 0.05f;
 if (keyState.IsKeyDown(Keys.PageDown))
     angle -= 0.05f;

Here you put the current state of the keyboard in a variable 'keyState'. Using this variable, you can immediately read out which keys are currently being pressed! When the user presses the Delete or PageDown key, the value of the ‘angle’ variable will be adjusted.

In our Draw method, we need to make sure that this rotation is taken into account by our World matrix:

 Matrix worldMatrix = Matrix.CreateTranslation(-terrainWidth / 2.0f, 0, terrainHeight / 2.0f) * Matrix.CreateRotationY(angle);

The terrain is rotated around the Y Up axis before it is moved to the (0,0,0) 3D origin.

Et voila! When you run the code, you can rotate your terrain simply by pressing the Delete and PageDown buttons!




DirectX Tutorial 9 - Keyboard

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Click here to go to the forum on this chapter!

Or click on one of the topics on this chapter to go there:
  • Input with JOYPAD
          Hi, Thanks for your work Would it possible t...
  • Problem with LoaderLock and the keyboard
          I was going through everything fine until I got to...
  • Inline code vs end of page
          Hi Riemer! I love the tutorials. I know website m...



    You can try these exercises to practice what you've learned:
  • Add some code that reads in the Arrow keys. Adjust your world matrix so the terrain is moved into the direction of the Arrow key being pressed.
    The code for our rotating terrain:

     using System;
     using System.Collections.Generic;
     using System.Linq;
     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.Media;
     
     namespace Series3D1
     {
         public class Game1 : Microsoft.Xna.Framework.Game
         {
             GraphicsDeviceManager graphics;
             SpriteBatch spriteBatch;
             GraphicsDevice device;
     
             Effect effect;
             VertexPositionColor[] vertices;
             Matrix viewMatrix;
             Matrix projectionMatrix;
             int[] indices;
     
             private float angle = 0f;
             private int terrainWidth = 4;
             private int terrainHeight = 3;
             private float[,] heightData;
     
             public Game1()
             {
                 graphics = new GraphicsDeviceManager(this);
                 Content.RootDirectory = "Content";
             }
     
             protected override void Initialize()
             {
                 graphics.PreferredBackBufferWidth = 500;
                 graphics.PreferredBackBufferHeight = 500;
                 graphics.IsFullScreen = false;
                 graphics.ApplyChanges();
                 Window.Title = "Riemer's XNA Tutorials -- 3D Series 1";
     
                 base.Initialize();
             }
     
             protected override void LoadContent()
             {
                 spriteBatch = new SpriteBatch(GraphicsDevice);
     
                 device = graphics.GraphicsDevice;

                effect = Content.Load<Effect> ("effects");            SetUpCamera();


                Texture2D heightMap = Content.Load<Texture2D> ("heightmap");            LoadHeightData(heightMap);
                SetUpVertices();
                SetUpIndices();            
            }

            protected override void UnloadContent()
            {
            }

            private void SetUpVertices()
            {
                vertices = new VertexPositionColor[terrainWidth * terrainHeight];
                for (int x = 0; x < terrainWidth; x++)
                {
                    for (int y = 0; y < terrainHeight; y++)
                    {
                        vertices[x + y * terrainWidth].Position = new Vector3(x, heightData[x, y], -y);
                        vertices[x + y * terrainWidth].Color = Color.White;
                    }
                }
            }

            private void SetUpIndices()
            {
                indices = new int[(terrainWidth - 1) * (terrainHeight - 1) * 6];
                int counter = 0;
                for (int y = 0; y < terrainHeight - 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;
                    }
                }
            }

            private void LoadHeightData(Texture2D heightMap)
            {
                terrainWidth = heightMap.Width;
                terrainHeight = heightMap.Height;

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

                heightData = new float[terrainWidth, terrainHeight];
                for (int x = 0; x < terrainWidth; x++)
                    for (int y = 0; y < terrainHeight; y++)
                        heightData[x, y] = heightMapColors[x + y * terrainWidth].R / 5.0f;
            }

            private void SetUpCamera()
            {
                viewMatrix = Matrix.CreateLookAt(new Vector3(60, 80, -80), new Vector3(0, 0, 0), new Vector3(0, 1, 0));
                projectionMatrix = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, device.Viewport.AspectRatio, 1.0f, 300.0f);
            }

            protected override void Update(GameTime gameTime)
            {
                if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
                    this.Exit();


                 KeyboardState keyState = Keyboard.GetState();
                 if (keyState.IsKeyDown(Keys.Delete))
                     angle += 0.05f;
                 if (keyState.IsKeyDown(Keys.PageDown))
                     angle -= 0.05f;
     
                 base.Update(gameTime);
             }
     
             protected override void Draw(GameTime gameTime)
             {
                 device.Clear(Color.Black);
     
                 RasterizerState rs = new RasterizerState();
                 rs.CullMode = CullMode.None;
                 rs.FillMode = FillMode.WireFrame;
                 device.RasterizerState = rs;
     
                 Matrix worldMatrix = Matrix.CreateTranslation(-terrainWidth / 2.0f, 0, terrainHeight / 2.0f) * Matrix.CreateRotationY(angle);
                 effect.CurrentTechnique = effect.Techniques["ColoredNoShading"];
                 effect.Parameters["xView"].SetValue(viewMatrix);
                 effect.Parameters["xProjection"].SetValue(projectionMatrix);
                 effect.Parameters["xWorld"].SetValue(worldMatrix);
     
                 foreach (EffectPass pass in effect.CurrentTechnique.Passes)
                 {
                     pass.Apply();
     
                     device.DrawUserIndexedPrimitives(PrimitiveType.TriangleList, vertices, 0, vertices.Length, indices, 0, indices.Length / 3, VertexPositionColor.VertexDeclaration);
                 }
     
                 base.Draw(gameTime);
             }
         }
     }
     
     


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    Contents

    News
    Home
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    XNA 2.0 Recipes Book (8)
    XNA 3.0 Recipes Book (8)
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    Extra Reading (3)
    Matrices: geometrical
    Matrix Mathematics
    Homogenous matrices
    Community Projects (1)
    Tutorials (160)
    XNA 4.0 using C# (89)
    2D Series: Shooters (22)
    3D Series 1: Terrain (13)
    Starting a project
    The effect file
    The first triangle
    World space
    Rotation - translation
    Indices
    Terrain basics
    Terrain from file
    Keyboard
    Adding colors
    Lighting basics
    Terrain lighting
    VertexBuffer & IndexBuffer
    3D Series 2: Flightsim (14)
    3D Series 3: HLSL (18)
    3D Series 4: Adv. terrain (19)
    Short Tuts (3)
    DirectX using C# (54)
    DirectX using C++ (15)
    DirectX using VB (2)
    -- Expand all --


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