SpriteSheet Animation with Dynamic Body

Topics: Developer Forum, Project Management Forum, User Forum
Jun 10, 2012 at 8:01 PM



I am new to farseer, i tried to create a Dynamic Body, with my spritesheet animation,

But the problem is, after that it loses it physicaly behaviour, i.e. it does not collide or bounce, it just bypass all the objects and goes down.

I am not sure how to apply spritesheet animation to a dynamic body.

Below is my code.

    class AnimatingPhysicsObject 

       protected float width;
        protected float height;
        public Body body;
        public Fixture fixture;
        protected Texture2D texture;
        protected Vector2 origin;

        int elapsedTime;
        // The time we display a frame until the next one
        int frameTime;
        // The number of frames that the animation contains
        int frameCount;
        int frameLines;
        int currentLine = 0;
        // The index of the current frame we are displaying
        int currentFrame = 0;
        // The color of the frame we will be displaying
        Color color;
        // The area of the image strip we want to display
        Rectangle sourceRect = new Rectangle();
        // The area where we want to display the image strip in the game
        Rectangle destinationRect = new Rectangle();
        // Width of a given frame
        public int FrameWidth;
        // Height of a given frame
        public int FrameHeight;
        // The state of the Animation
        public bool Active;
        // Determines if the animation will keep playing or deactivate after one run
        public bool Looping;
        // Width of a given frame
        public AnimatingPhysicsObject(World world, Vector2 position, float width, float height, float mass, Texture2D texture,int frameWidth, int frameHeight, int frameCount,int frameLines,
            int frametime, bool looping)
            this.texture = texture;
            this.origin = new Vector2(texture.Width / 2, texture.Height / 2);
            this.width = width;
            this.height = height;

            this.FrameWidth = frameWidth;
            this.FrameHeight = frameHeight;
            this.frameCount = frameCount;
            this.frameTime = frametime;
               // Set the time to zero
            elapsedTime = 0;
            currentFrame = 0;
           // bomb = Content.Load<Texture2D>("canon/bomb");

            // Set the Animation to active by default
            Active = true;

            Looping = looping;

            this.frameLines = frameLines;

            SetUpPhysics(world, position, width, height, mass);

        protected virtual void SetUpPhysics(World world, Vector2 position, float width, float height, float mass)
            fixture = FixtureFactory.CreateRectangle(world, ConvertUnits.ToSimUnits(FrameWidth), ConvertUnits.ToSimUnits(FrameHeight), mass, ConvertUnits.ToSimUnits(position));
            body = fixture.Body;
            fixture.Body.BodyType = BodyType.Dynamic;
            fixture.Restitution = 0.3f;
            fixture.Friction = 0.5f;
        public void Update(GameTime gameTime)
            // Do not update the game if we are not active
            if (Active == false)

                currentFrame = 0;
                currentLine = 0;
           // fixture.Body.Position = Position;

            // Update the elapsed time
            elapsedTime += (int)gameTime.ElapsedGameTime.TotalMilliseconds;

            // If the elapsed time is larger than the frame time
            // we need to switch frames
            if (elapsedTime > frameTime)
                // Move to the next frame

                // If the currentFrame is equal to frameCount reset currentFrame to zero
                if (currentFrame == frameCount)
                    currentFrame = 0;
                    if (currentLine == frameLines)
                        currentLine = 0;
                        // If we are not looping deactivate the animation
                            Active = false;

                // Reset the elapsed time to zero
                elapsedTime = 0;

            // Grab the correct frame in the image strip by multiplying the currentFrame index by the frame width
            sourceRect = new Rectangle(currentFrame * FrameWidth, currentLine * FrameHeight, FrameWidth, FrameHeight);

            // Grab the correct frame in the image strip by multiplying the currentFrame index by the frame width
            destinationRect = new Rectangle((int)ConvertUnits.ToDisplayUnits(body.Position.X) - (int)(FrameWidth) / 2,
            (int)ConvertUnits.ToDisplayUnits(body.Position.Y) - (int)(FrameHeight) / 2,
        public virtual void Draw(SpriteBatch spriteBatch)
            spriteBatch.Draw(texture, destinationRect, sourceRect, Color.White, body.Rotation, origin, SpriteEffects.None, 0f);



Please help, its urgent.

Jun 10, 2012 at 8:29 PM

Could be an aligment issue between the sprite and the fixture. Enable the DebugView on top of your Draw to check. See the Samples for an example.

Also you do call World.Step() in your main logic and move the body by applying forces or changing the velocity and not teleporting it, right? 

Jun 11, 2012 at 6:53 AM

Yes i am doing World.Step() in my main logic update method.

right now i am not applying forces to the body , it is coming down due to gravity of the world.


i am not sure how to check it using DebugView

Jun 11, 2012 at 10:18 AM

Do  you have issues adding the DebugView to your game? It is quite easy - check the ScreenManager/PhysicsGameScreen.cs in the Samples. You can draw the debug data together with your own graphics code. It will show you what is actually present in the physics world and what collides with what in the physics simulation.