FarseerPhysics Forum Rss Feed

New Post: How can I use the ContactListener?

benblo — Tue, 21 May 2013 08:49:31 GMT

Here's how I do it:

    // do this on whatever constructor / init function you have
    void Start()
    {
        // get the world singleton somehow
        World world = FSWorldComponent.PhysicsWorld;

        // register
        world.ContactManager.BeginContact += onBeginContact;
        world.ContactManager.EndContact += onEndContact;
        world.ContactManager.PreSolve += onPreSolve;
        world.ContactManager.PostSolve += onPostSolve;

        // NOTE: you should probably unregister on destructor or wherever is relevant...
    }

    bool onBeginContact( Contact _contact )
    {
        // ...
        return true; // or false to ignore the contact
    }
    void onEndContact( Contact _contact )
    {
        // ...
    }

    void onPreSolve( Contact _contact, ref Manifold _oldManifold )
    {
        // ...
    }
    void onPostSolve( Contact _contact, ContactVelocityConstraint _impulse )
    {
        // ...
    }

I use the Unity port of Farseer so your mileage may vary.

New Post: Games That Use Farseer Physics Engine 3.x

nkast — Tue, 21 May 2013 07:54:53 GMT

Pinball league: The World of Dr. Pickaxe

Pinball game for Windows Phone & Windows Store.
Developed on XNA/monoGame.

Dr Pickaxe for Windows Phone:
http://tainicom.net/games/pinball-league-the-world-of-dr-pickaxe.aspx

Dr Pickaxe for Windows 8/RT:
http://tainicom.net/games/pinball-league-the-world-of-dr-pickaxe-hd.aspx

New Post: How can I create polygons in Farseer 3.3.1?

streikbrecher — Tue, 21 May 2013 07:47:18 GMT

Look at the specs! Its (data, width, holeDetection), so change it to

Vertices  verts = PolygonTools.CreatePolygon(data, polygonTexture.Width, true);

But I highly recommend to look at the farseer samples project. There, AdvancedDemo1 greatly explains how to make an physical object out of a texture.

New Post: How can I create polygons in Farseer 3.3.1?

Wizard999 — Tue, 21 May 2013 07:35:38 GMT

Thanx. But I still have difficulties with this line:

 //Find the vertices that makes up the outline of the shape in the texture
          Vertices  verts = PolygonTools.CreatePolygon(data, polygonTexture.Width, polygonTexture.Height, true);

No overload for method 'CreatePolygon' takes 4 arguments

What should I change in this line?

New Post: How can I create polygons in Farseer 3.3.1?

streikbrecher — Mon, 20 May 2013 23:15:50 GMT

Try changing

List<Fixture> compund = FixtureFactory.CreateCompoundPolygon(world, _list, 1);
compund[0].Body.BodyType = BodyType.Dynamic;

Body body = BodyFactory.CreateCompoundPolygon(world, _list, 1);
body.BodyType = BodyType.Dynamic;

New Post: How can I use the ContactListener?

streikbrecher — Mon, 20 May 2013 23:08:43 GMT

Maybe you can solve your issue with the EventHandlers, that exist for Separation and Collision.
This one for example, fires on collision and allows you to accept or deny to collision by returning true or false.
In the EventHandler, you also have access to the contact.

        public void LoadContent()
        {
           //Add Event
           body.OnCollision += new OnCollisionEventHandler(body_OnCollision); //IntelliSense loves them
        }

        bool body_OnCollision(Fixture fixtureA, Fixture fixtureB, Dynamics.Contacts.Contact contact)
        {
            return true;
        }

New Post: How can I use the ContactListener?

Wizard999 — Mon, 20 May 2013 22:56:27 GMT

I want to implement this ContactListener in my code, but I don't know how to do that because this is a box2d example and not a Farseer example. I want to use the PreSolve method in the ContactListener.
box2d manual(9.4 ContactListener): http://www.box2d.org/manual.html#_Toc258082975

class MyContactListener : public b2ContactListener

{

public:

  void BeginContact(b2Contact* contact)

  { /* handle begin event */ }

 

  void EndContact(b2Contact* contact)

  { /* handle end event */ }

 

  void PreSolve(b2Contact* contact, const b2Manifold* oldManifold)

  { /* handle pre-solve event */ }

 

  void PostSolve(b2Contact* contact, const b2ContactImpulse* impulse)

  { /* handle post-solve event */ }

};

Is it possible to use a similar ContactListener in Farseer? How can I do that?

New Post: How can I use the ContactListener?

streikbrecher — Mon, 20 May 2013 22:17:35 GMT

Hello,
you might want to access the contactList of a certain body.
So here's an example in which I use the contactList to cycle through the contacts of myBody:

            Dynamics.Contacts.ContactEdge cEdge = myBody.ContactList;
                do
                {
                    //Do sth with the bodies in contact
                    //Use cEdge.Contact.FixtureA.Body or cEdge.Contact.FixtureB.Body to access individual bodies

                    cEdge  = cEdge.Next;
                }
                while (cEdge != null);

New Post: Balls not bouncing!!!

mheydlauf — Mon, 20 May 2013 18:37:15 GMT

Experiment with the friction and restitution on both bodies... Restitution controls the "bounciness" but you need friction as well.

Hope that helps,
Mike.

New Post: How can I create polygons in Farseer 3.3.1?

Wizard999 — Mon, 20 May 2013 17:54:51 GMT

I tried the example in the documentation but it isn't working. I always get these two error messages:
No overload for method 'CreatePolygon' takes 4 arguments
'FarseerPhysics.Factories.FixtureFactory' does not contain a definition for 'CreateCompoundPolygon'

What is wrong? How can I create polygons?

//Create an array to hold the data from the texture
            uint[] data = new uint[polygonTexture.Width * polygonTexture.Height];
            //Transfer the texture data to the array
            polygonTexture.GetData(data); 
            //Find the vertices that makes up the outline of the shape in the texture
          Vertices  verts = PolygonTools.CreatePolygon(data, polygonTexture.Width, polygonTexture.Height, true);
            //For now we need to scale the vertices (result is in pixels, we use meters)
            Vector2 scale = new Vector2(3.50f, 1.50f);
            verts.Scale(ref scale);  
            //Since it is a concave polygon, we need to partition it into several smaller convex polygons
            _list = BayazitDecomposer.ConvexPartition(verts);   
            //Create a single body with multiple fixtures
            List<Fixture> compund = FixtureFactory.CreateCompoundPolygon(world, _list, 1);
            compund[0].Body.BodyType = BodyType.Dynamic;

New Post: How can I use the ContactListener?

Wizard999 — Mon, 20 May 2013 08:55:01 GMT

I downloaded Farseer Physics Engine 3.3.1 Samples XNA(Recommended Download), but I can not find a class named ContactListener in the Farseer folder. How can I use the ContactListener when there is no ContactListener class in the Farseer folder?

New Post: How can I create triangles?

Beringela — Mon, 20 May 2013 06:53:30 GMT

I used pyramids in one game, but I'm sure you could adapt this to more generic triangles.

So I have a create pyramid method:

private static Vertices CreateSimplePyramid(float width, float height)
{
    Vertices vertices = new Vertices();
    vertices.Add(new Vector2(0f, -height * .5f));
    vertices.Add(new Vector2(-width * .5f, height * .5f));
    vertices.Add(new Vector2(width * .5f, height * .5f));
    return vertices;
}

Then I create my pyramid as you would normally in Farseer, so code something like:

_body = BodyFactory.CreateBody(_world, ConvertUnits.ToSimUnits(_position), this);
Vertices vertices = CreateSimplePyramid(ConvertUnits.ToSimUnits(bDef.blockWidth), ConvertUnits.ToSimUnits(bDef.blockHeight));
vertices.ForceCounterClockWise();
_shape = new PolygonShape(vertices, density);
_fixture = _body.CreateFixture(_shape);
... etc

Maybe also of use, I remember Farseer has some "decomposer" routines that will split larger shapes into triangles, that was either in the samples or there was a class like eg EarclipDecomposer.

New Post: Games That Use Farseer Physics Engine 3.x

vitaliy_gorlov — Sun, 19 May 2013 21:03:14 GMT

http://www.windowsphone.com/s?appid=1d4a2c7f-b5e4-4e66-9b60-d8e2718e8c99

New game that using FPE

New Post: Games That Use Farseer Physics Engine 3.x

Beringela — Sun, 19 May 2013 16:41:49 GMT

Gerbil Physics is now available for Android devices, phones and tablets from the Google Play store, and coming soon to the Kindle Fire via Amazon's App Store.

This is a port from the WP7 version to Android using MonoGame. I don't think I needed to make any changes for Farseer to work under MonoGame, it Just Worked.

Thanks to all behind Farseer for making this possible.

New Post: Trouble with the Camera2D Class

ASlave2Gravity — Sat, 18 May 2013 21:39:25 GMT

Whoops never mind I solved it. Very silly mistake.

   graphics.PreferredBackBufferWidth =  1024;
            graphics.PreferredBackBufferHeight = 768;
            graphics.ApplyChanges();
            
            cam2D = new Cam2d(GraphicsDevice);

NOT

cam2D = new Cam2d(GraphicsDevice);
 graphics.PreferredBackBufferWidth =  1024;
            graphics.PreferredBackBufferHeight = 768;
            graphics.ApplyChanges();

As you can see it's just about creating the new cam class after a resolution change.

New Post: Trouble with the Camera2D Class

ASlave2Gravity — Sat, 18 May 2013 21:23:42 GMT

Hey all,

I really need some help with camera tracking. I apply the cam track like so

 cam2D.TrackingBody = player.playerBody;
 cam2D.EnableTracking = true;

But for some reason the player is not the centre of the screen?

Like so:

I have no idea why this is happening

All the best,

ASlave2Gravity

New Post: Mario jumps not correctly

johnnysayasane — Fri, 17 May 2013 17:26:49 GMT

Oh thank you for the Link. I'm looking for it too. :D

New Post: How can I create triangles?

Wizard999 — Fri, 17 May 2013 14:19:51 GMT

How can I create triangles in Farseer? I have no clue how to do that.

New Post: Balls not bouncing!!!

cristianormd — Thu, 16 May 2013 18:15:10 GMT

I created a fixture called Bolinha1 (Ball1), and gave it some speed by applying impulse onto it in the inicialization:

Bolinha1 = FixtureFactory.AttachCircle(TelaParaMundo(128,pixelspormetro)/2, 1f, CorpoBolinha1);

        Bolinha1.Restitution = 0.98f;
        Bolinha1.Friction = 0f;
        Bolinha1.Body.LinearDamping = 0f;
        Bolinha1.Body.FixedRotation = true;
        Bolinha1.Body.LinearDamping = 0f;                                                  
        Bolinha1.Body.AngularDamping = 0f;
        Bolinha1.Body.Inertia = 0;
        Bolinha1.Body.ApplyLinearImpulse(new Vector2(500, 0));

After That, i inicialize four edges, to delimit the screen:

for (int i = 0; i < 4; i++)

        {
            SideBody[i] = BodyFactory.CreateBody(world);
            SideBody[i].BodyType = BodyType.Static;
            SideBody[i].Restitution = 0.95f;
            SideBody[i].Friction = 0f;
            SideBody[i].LinearDamping = 0f;

        }

        Side[0] = FixtureFactory.AttachEdge(new Vector2(0, 0), new Vector2(0, 45), CorpoBorda[0]);
        Side[1] = FixtureFactory.AttachEdge(new Vector2(0, 45), new Vector2(80, 45), CorpoBorda[1]);
        Side[2] = FixtureFactory.AttachEdge(new Vector2(80, 45), new Vector2(80, 0), CorpoBorda[2]);
        Side[3] = FixtureFactory.AttachEdge(new Vector2(80, 0), new Vector2(0, 0), CorpoBorda[3]);

        for (int i = 0; i < 4; i++)
        {
            Side[i].Restitution = 0.98f;
            Side[i].Friction = 0f;
            Side[i].Body.LinearDamping = 0f;
            Side[i].Body.AngularDamping = 0f;
        }

, and then use only

        world.Step((float)gameTime.TotalGameTime.TotalMilliseconds * 0.01f);
        world.ClearForces();

as my update code.The point is, the ball sticks to the side, no matter which angle of module i assign to the impulse, and if the impulse is great enough the ball "rolls" along the edge. I also tried tinkering with its density, but had no positive results. Can anyone help me??

New Post: Mario jumps not correctly

mheydlauf — Wed, 15 May 2013 15:11:45 GMT

johnnysayasane is right, you need an additional "foot sensor" body to use for your collision detection. I found this article very helpful when solving a similar problem: http://www.iforce2d.net/b2dtut/jumpability

Cheers,
Mike.