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[Solved] Position of object not changing.

Topics: Developer Forum
Apr 26, 2010 at 3:17 AM

I have created a very simple XNA 3.1 project that loads a rectangle sprite and creates a rectangle object in the Physics world. I first manually set a position for my object in the physics world. I have setup gravity along with other forces to try and make the box move. However, when I draw my sprite from the Body object's position, it doesn't appear to move. I have included the Farseer source folder in my own solution and referenced the .dll from my project. There are no compilation errors. The program runs but my box just sits stagnant.

I'm guessing whatever I am doing wrong is something stupid but this is my first stab at using farseer. Thanks for any help in advanced.


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;
using Microsoft.Xna.Framework.Net;
using Microsoft.Xna.Framework.Storage;

using FarseerGames.FarseerPhysics;
using FarseerGames.FarseerPhysics.Dynamics;
using FarseerGames.FarseerPhysics.Collisions;
using FarseerGames.FarseerPhysics.Factories;
using FarseerGames.FarseerPhysics.Interfaces;
using FarseerGames.FarseerPhysics.Mathematics;
using FarseerGames.FarseerPhysics.Controllers;

namespace TestBed
    /// <summary>
    /// This is the main type for your game
    /// </summary>
    public class Game1 : Microsoft.Xna.Framework.Game
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;

        // Rectangle Sprite
        Texture2D myTexture;
        Vector2 spritePosition = Vector2.Zero;

        // Physics Stuff
        Body rectBody;
        Geom rectGeom;
        PhysicsSimulator physicsSimulator;

        public Game1()
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";

        /// <summary>
        /// Allows the game to perform any initialization it needs to before starting to run.
        /// This is where it can query for any required services and load any non-graphic
        /// related content.  Calling base.Initialize will enumerate through any components
        /// and initialize them as well.
        /// </summary>
        protected override void Initialize()
            // TODO: Add your initialization logic here
            // Farseer Physics Stuff
            physicsSimulator = new PhysicsSimulator(new Vector2(0, 500f));
            rectBody = BodyFactory.Instance.CreateRectangleBody(256, 256, 1);
            rectBody.Position = new Vector2(150f, 130f);
            rectGeom = GeomFactory.Instance.CreateRectangleGeom(physicsSimulator, rectBody, 256, 256);


        /// <summary>
        /// LoadContent will be called once per game and is the place to load
        /// all of your content.
        /// </summary>
        protected override void LoadContent()
            // Create a new SpriteBatch, which can be used to draw textures.
            spriteBatch = new SpriteBatch(GraphicsDevice);

            // Load the Rectangle Texture
            myTexture = Content.Load<Texture2D>("floor_tile");

        /// <summary>
        /// UnloadContent will be called once per game and is the place to unload
        /// all content.
        /// </summary>
        protected override void UnloadContent()
            // TODO: Unload any non ContentManager content here

        /// <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)
            // Physics Logic
            rectBody.LinearVelocity.X = 400f;
            rectBody.ApplyForce(new Vector2(0,10.0f));
            physicsSimulator.Update(gameTime.ElapsedGameTime.Milliseconds / 1000f);


        /// <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)
            // Clear the Buffer

            // Draw the sprite.
            spriteBatch.Draw(myTexture, rectBody.Position, Color.White);


Apr 26, 2010 at 5:04 AM

Solved: I was missing the PhysicsSimulator in my BodyFactory call.