How to center on a moving rectangle that represents a scrolling sprite.

@willmotil wrote:

So this is going to be linked to and for future reference.

You will need to replace the texture2d i used with you're own.

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;

namespace HowToCameraScrollOnaGameObject
{
    /// <summary>
    /// This is the main type for your game.
    /// </summary>
    public class Game1 : Game
    {
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;
        Texture2D texture;

        public static Vector3 camera2DScrollPosition = new Vector3(0, 0, 0);
        public static float camera2dRotationZ = 0f;
        public static float cameraScale = 1f;

        Matrix cameraTransform = Matrix.Identity;

        Rectangle objectPositionBlue = new Rectangle(0, 0, 300, 300);
        Rectangle objectPositionGreen = new Rectangle(100, 100, 300, 300);
        Rectangle objectPositionRed = new Rectangle(200, 200, 300, 300);


        public Game1()
        {
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";
            graphics.GraphicsProfile = GraphicsProfile.HiDef;
            Window.AllowUserResizing = true;
            this.IsMouseVisible = true;
        }

        protected override void Initialize()
        {
            graphics.PreferredBackBufferWidth = 800;
            graphics.PreferredBackBufferHeight = 800;
            graphics.ApplyChanges();

            base.Initialize();
        }

        protected override void LoadContent()
        {
            spriteBatch = new SpriteBatch(GraphicsDevice);
            texture = Content.Load<Texture2D>("blue-square-button-editted-md");
        }

        protected override void UnloadContent()
        {
        }

        public void SetCameraToCenterOnGameObjectsCenter(Rectangle gameObjectRectangle)
        {
            var c = gameObjectRectangle.Center;
            camera2DScrollPosition.X = -c.X + GraphicsDevice.Viewport.Width / 2;
            camera2DScrollPosition.Y = -c.Y + GraphicsDevice.Viewport.Height / 2;
            CreateCameraTransform();
        }

        public void CreateCameraTransform()
        {
            // There is two pretty easy ways to do it.
            // Depending on how you want your camera to behave when you are moving under world rotation. 

            // 1)

            //cameraTransform =
            //    Matrix.CreateTranslation(camera2DScrollPosition) *
            //    Matrix.CreateScale(cameraScale) *
            //    Matrix.CreateRotationZ(camera2dRotationZ)
            //    ;

            // Or using the 3d create world function.

            // 2)

            cameraTransform = Matrix.CreateWorld(camera2DScrollPosition, Vector3.Forward, Matrix.CreateRotationZ(camera2dRotationZ).Up) * Matrix.CreateScale(cameraScale);
        }

        protected override void Update(GameTime gameTime)
        {
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed || Keyboard.GetState().IsKeyDown(Keys.Escape))
                Exit();

            // Some code to move a sprite around with the arrow keys.
            if (Keyboard.GetState().IsKeyDown(Keys.Left))
                objectPositionRed.X = objectPositionRed.X - 1;
            if (Keyboard.GetState().IsKeyDown(Keys.Right))
                objectPositionRed.X = objectPositionRed.X + 1;
            if (Keyboard.GetState().IsKeyDown(Keys.Up))
                objectPositionRed.Y = objectPositionRed.Y - 1;
            if (Keyboard.GetState().IsKeyDown(Keys.Down))
                objectPositionRed.Y = objectPositionRed.Y + 1;

            // Set the sprite to be what the camera follows.
            SetCameraToCenterOnGameObjectsCenter(objectPositionRed);

            base.Update(gameTime);
        }

        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(Color.CornflowerBlue);

            spriteBatch.Begin(SpriteSortMode.Immediate,null, null, null, null, null, cameraTransform);
            
            Rectangle source = new Rectangle(0, 0, texture.Width, texture.Height);
     
            spriteBatch.Draw(texture, objectPositionBlue, source, Color.Blue);
            spriteBatch.Draw(texture, objectPositionGreen, source, Color.ForestGreen);
            spriteBatch.Draw(texture, objectPositionRed, source, Color.Red);

            spriteBatch.End();

            base.Draw(gameTime);
        }
    }
}

Posts: 1

Participants: 1

Read full topic