Game1.cs

using FarseerPhysics.Dynamics;
using FarseerPhysics.Factories;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using System;

namespace FarseerPhysics.HelloWorld
{
	/// <summary>
	/// This is the main type for your game
	/// </summary>
	public class Game1 : Game
	{
		private GraphicsDeviceManager _graphics;
		private SpriteBatch _batch;
		private SpriteFont _font;
		Texture2D texture, caracter;
		private Color _alphaColor = Color.Gray;
		bool jumpReleased;
		private World _world;

		private Body _circleBody;
		private Body _groundBody;

		private Texture2D _circleSprite;
		private Texture2D _groundSprite;

		// Simple camera controls
		private Matrix _view;
		private Vector2 _cameraPosition;
		private Vector2 _screenCenter;

		// Farseer expects objects to be scaled to MKS (meters, kilos, seconds)
		// 1 meters equals 64 pixels here
		// (Objects should be scaled to be between 0.1 and 10 meters in size)
		private const float MeterInPixels = 64f;

		public Game1 ()
		{
			_alphaColor.A = 100;
			_graphics = new GraphicsDeviceManager (this);
			//_graphics.PreferredBackBufferWidth = 800;
			//_graphics.PreferredBackBufferHeight = 480;
			
			Content.RootDirectory = "Content";
			
			_world = new World (new Vector2 (0, 20));
		}

		/// <summary>
		/// LoadContent will be called once per game and is the place to load
		/// all of your content.
		/// </summary>
		protected override void LoadContent ()
		{
			// Initialize camera controls
			_view = Matrix.Identity;
			_cameraPosition = Vector2.Zero;
			
			
			_screenCenter = new Vector2 (_graphics.GraphicsDevice.Viewport.Width / 2f, _graphics.GraphicsDevice.Viewport.Height / 2f);
			
			_batch = new SpriteBatch (_graphics.GraphicsDevice);
			_font = Content.Load<SpriteFont> ("SpriteFont1");
			
			
			// Load sprites
			
			_circleSprite = Content.Load<Texture2D> ("circleSprite");
			//  96px x 96px => 1.5m x 1.5m
			_groundSprite = Content.Load<Texture2D> ("groundSprite");
			// 512px x 64px =>   8m x 1m			
			texture = Content.Load<Texture2D> ("gamepad");
			
			/* Circle */
			// Convert screen center from pixels to meters
			Vector2 circlePosition = (_screenCenter / MeterInPixels) + new Vector2 (0, -1.5f);
			
			// Create the circle fixture
			_circleBody = BodyFactory.CreateCircle (_world, 96f / (2f * MeterInPixels), 1f, circlePosition);
			_circleBody.BodyType = BodyType.Dynamic;
			
			// Give it some bounce and friction
			_circleBody.Restitution = 0.3f;
			_circleBody.Friction = 0.5f;
			
			/* Ground */
			Vector2 groundPosition = (_screenCenter / MeterInPixels) + new Vector2 (0, 1.25f);
			
			// Create the ground fixture
			_groundBody = BodyFactory.CreateRectangle (_world, 512f / MeterInPixels, 64f / MeterInPixels, 1f, groundPosition);
			
			//_groundBody.Rotation = .1f;
			_groundBody.IsStatic = true;
			_groundBody.Restitution = 0.3f;
			_groundBody.Friction = 0.5f;
			
			
			// Set the virtual GamePad
			ButtonDefinition BButton = new ButtonDefinition ();
			BButton.Texture = texture;
			BButton.Position = new Vector2 (200, 350);
			BButton.Type = Buttons.B;
			BButton.TextureRect = new Rectangle (72, 77, 36, 36);
			
			ButtonDefinition AButton = new ButtonDefinition ();
			AButton.Texture = texture;
			AButton.Position = new Vector2 (150, 350);
			AButton.Type = Buttons.A;
			AButton.TextureRect = new Rectangle (73, 114, 36, 36);
			
			GamePad.ButtonsDefinitions.Add (BButton);
			GamePad.ButtonsDefinitions.Add (AButton);
			
			ThumbStickDefinition thumbStick = new ThumbStickDefinition ();
			thumbStick.Position = new Vector2 (180, 400);
			thumbStick.Texture = texture;
			thumbStick.TextureRect = new Rectangle (2, 2, 68, 68);
			
			GamePad.LeftThumbStickDefinition = thumbStick;
			
		}

		/// <summary>
		/// Allows the game to run logic such as updating the world,
		/// checking for collisions, gathering input, and playing audio.
		/// </summary>
		/// <param name="gameTime">Provides a snapshot of timing values.</param>
		protected override void Update (GameTime gameTime)
		{
			//Use the joystick to move the camera;
			GamePadState gamepadStatus = GamePad.GetState (PlayerIndex.One);
			_cameraPosition.Y += (int)(gamepadStatus.ThumbSticks.Left.Y * 4);
			_cameraPosition.X += (int)(gamepadStatus.ThumbSticks.Left.X * -4);
			
			_view = Matrix.CreateTranslation (new Vector3 (_cameraPosition - _screenCenter, 0f)) * Matrix.CreateTranslation (new Vector3 (_screenCenter, 0f));

			//Move based on Accelerometer
			var accel = Accelerometer.GetState ();			
			if (Math.Abs (accel.Acceleration.X) > 0.10f)
			{
				if (accel.Acceleration.X > 0.0f)
					_circleBody.ApplyTorque (accel.Acceleration.X * 4);
				else
					_circleBody.ApplyTorque (accel.Acceleration.X * -4);
			}
			
			//Jump
			if (GamePad.GetState (PlayerIndex.One).Buttons.A == ButtonState.Pressed && jumpReleased)
				_circleBody.ApplyLinearImpulse (new Vector2 (0, -10));
			
			//Reset
			if (GamePad.GetState (PlayerIndex.One).Buttons.B == ButtonState.Pressed)
			{
				_circleBody.Position = (_screenCenter / MeterInPixels) + new Vector2 (0, -1.5f);
				_circleBody.ResetDynamics ();
			}
			
			
			jumpReleased = gamepadStatus.IsButtonUp (Buttons.A);
			//We update the world
			_world.Step ((float)gameTime.ElapsedGameTime.TotalMilliseconds * 0.001f);
			
			base.Update (gameTime);
		}

		/// <summary>
		/// This is called when the game should draw itself.
		/// </summary>
		/// <param name="gameTime">Provides a snapshot of timing values.</param>
		protected override void Draw (GameTime gameTime)
		{
			GraphicsDevice.Clear (Color.CornflowerBlue);
			
						/* Circle position and rotation */
			// Convert physics position (meters) to screen coordinates (pixels)
			Vector2 circlePos = _circleBody.Position * MeterInPixels;
			float circleRotation = _circleBody.Rotation;
			
						/* Ground position and origin */
			Vector2 groundPos = _groundBody.Position * MeterInPixels;
			Vector2 groundOrigin = new Vector2 (_groundSprite.Width / 2f, _groundSprite.Height / 2f);
			
			// Align sprite center to body position
			Vector2 circleOrigin = new Vector2 (_circleSprite.Width / 2f, _circleSprite.Height / 2f);
			
			_batch.Begin (SpriteSortMode.Deferred, SpriteBlendMode.AlphaBlend, SaveStateMode.None, _view);
			
			//Draw circle
			_batch.Draw (_circleSprite, circlePos, null, Color.White, circleRotation, circleOrigin, 1f, SpriteEffects.None, 0f);
			
			
			//Draw ground
			_batch.Draw (_groundSprite, groundPos, null, Color.White, _groundBody.Rotation, groundOrigin, 1f, SpriteEffects.None, 0f);
			
			_batch.End ();
			
			_batch.Begin ();
			
			// Display instructions
			
			_batch.DrawString (_font, circlePos.ToString (), Vector2.One, Color.Black);
			
			GamePad.Draw (gameTime, _batch);
			_batch.End ();
			
			base.Draw (gameTime);
		}
	}
}