Camera.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Graphics;

namespace Sidescroller
{
    class Camera
    {
        #region Members
        //The viewport that we want to use (to hold dimensions)
        public Viewport View
        {
            get;
            private set;
        }

        //Where to position the camera (0x0 will be the center of the viewport
        public Vector2 Position
        {
            get;
            private set;
        }

        //The zoom scalar (1.0f = 100% zoom level)
        public float Zoom
        {
            get;
            private set;
        }

        //Camera's transform matrix
        public Matrix Transform
        {
            get;
            private set;
        }

        //Center of the focus for the camera
        public Vector2 FocusPoint
        {
            get;
            private set;
        }
        #endregion

        #region Methods
        //Constructor
        public Camera(Viewport view, Vector2 position)
        {
            View = view;
            Position = position;
            Zoom = 1.0f;
            FocusPoint = new Vector2(view.Width / 2, view.Height / 2);
        }

        //Update Method
        public void Update(KeyboardState keyboardState)
        {
            //Resets the camera, incase the map is moved off the viewport and becomes lost.
            if (keyboardState.IsKeyDown(Keys.R))
                Reset();

            //Zooms the camera in and out with Z and X, respectivly
            if (keyboardState.IsKeyDown(Keys.Z))
                Zoom += 0.002f;
            if (keyboardState.IsKeyDown(Keys.X))
                Zoom -= 0.002f;

            //Moving the camera with WASD
            Vector2 Movement = Vector2.Zero;
            if (keyboardState.IsKeyDown(Keys.W))
                Movement.Y -= 5.0f / Zoom;
            if (keyboardState.IsKeyDown(Keys.S))
                Movement.Y += 5.0f / Zoom;
            if (keyboardState.IsKeyDown(Keys.A))
                Movement.X -= 5.0f / Zoom;
            if (keyboardState.IsKeyDown(Keys.D))
                Movement.X += 5.0f / Zoom;

            //Apply the movement vector
            Position = Vector2.Add(Position, Movement);

            /* Create a transform matrix through position, scale, rotation, and translation to the focus point
             * We use Math.Pow on the zoom to speed up or slow down the zoom.  Both X and Y will have the same zoom levels
             * so there will be no stretching.
             */
            Transform = Matrix.CreateScale(new Vector3((float)Math.Pow(Zoom, 10), (float)Math.Pow(Zoom, 10), 0)) *
                Matrix.CreateTranslation(new Vector3(FocusPoint.X, FocusPoint.Y, 0));

        }

        //Reset Method
        private void Reset()
        {
            Position = Vector2.Zero;
            Zoom = 1.0f;
        }
        #endregion
    }
}