Farseer Physics Engine

New Post: How to move forward?

wmfwlr — Tue, 08 Jul 2008 19:05:54 GMT

Have you tried ApplyImpulse() instead?

New Post: How to move forward?

Lemunde — Tue, 08 Jul 2008 02:57:25 GMT

That looks similar to the method I use but I see some numbers there and I'm not sure what their purpose is. Anyway the system I'm using is working so if you want to dissect this small snippet of code and see if there's any differences, have at it. The first two 'if' chunks are just to show the rotation I'm using is unmodified and you can ignore most of it. I also use two functions, fSin and fCos, but their basically just shorter versions of what you're using cause I got sick of typing out all the conversions. Hope this helps.

            if (iPlayerControlType == iTypeShip)
            {
                fSpeed1 = Math.Abs(ShipBody[iPlayer].LinearVelocity.X) + Math.Abs(ShipBody[iPlayer].LinearVelocity.Y);
                fThrust = fShipThrust[iPlayer];
                fTorqueAmount = fShipTorqueAmount[iPlayer];
                fRotationAngle = ShipBody[iPlayer].Rotation;
                fMaxSpeed = fShipMaxSpeed[iPlayer];
            }
            if (iPlayerControlType == iTypeCar)
            {
                fSpeed1 = Math.Abs(CarBody[iPlayer].LinearVelocity.X) + Math.Abs(CarBody[iPlayer].LinearVelocity.Y);
                fThrust = fCarThrust[iPlayer];
                fTorqueAmount = fCarTorqueAmount[iPlayer];
                fRotationAngle = CarBody[iPlayer].Rotation;
                fMaxSpeed = fCarMaxSpeed[iPlayer];
            }

            if (fSpeed1 > fMaxSpeed) fThrust = 0;
            //---------Get Forces
            if (KState.IsKeyDown(Keys.W))
            {
                vForce.X = fSin(fRotationAngle) * fThrust;
                vForce.Y = fCos(fRotationAngle) * fThrust * -1;
            }
            else if (KState.IsKeyDown(Keys.S))
            {
                vForce.X = fSin(fRotationAngle + MathHelper.ToRadians(180)) * fThrust;
                vForce.Y = fCos(fRotationAngle + MathHelper.ToRadians(180)) * fThrust * -1;
            }
            if (KState.IsKeyDown(Keys.A)) { fTorque -= fTorqueAmount; }
            if (KState.IsKeyDown(Keys.D)) { fTorque += fTorqueAmount; }

            //---------Apply Forces
            if (iPlayerControlType == iTypeShip)
            {
                ShipBody[iPlayer].ApplyForce(vForce);
                ShipBody[iPlayer].ApplyTorque(fTorque);
            }
            if (iPlayerControlType == iTypeCar)
            {
                CarBody[iPlayer].ApplyForce(vForce);
                CarBody[iPlayer].ApplyTorque(fTorque);
            }

Edit: Here's those two functions in case you want to use them:

        float fSin(float num1)
        {
            float fResult = (float)Math.Sin((double)num1);
            return fResult;
        }
        float fCos(float num1)
        {
            float fResult = (float)Math.Cos((double)num1);
            return fResult;
        }

New Post: How to move forward?

lostlogic — Tue, 08 Jul 2008 01:03:00 GMT

Normally to move objects in space on a vector I calculate the vector and adjust the position accordingly. Such as:

float forcex = (float)(Math.Cos(MathHelper.ToRadians(Players[i].GetRot()))*2);
float forcey = (float)(Math.Sin(MathHelper.ToRadians(Players[i].GetRot()))*2);

When I do this with Farseer and apply torque in the same manner my object doesn't move "forward":

ApplyForce(new Vector2(-75*forcex, -75*forcey));

Is there a call I can use to tell Farseer to apply forward velocity or some such thing to get the effect I want?

New Post: Implementing Fluid

LedZepp — Sun, 06 Jul 2008 21:53:37 GMT

For the past couple of days I've been trying to get some fluid into a little game I'm making with XNA. I can deploy the demo just fine and run it with no errors, but the fluid just doesn't work or show up on the screen. Here's the code I have so far for it, maybe someone here can help me with it.

recBody = BodyFactory.Instance.CreateRectangleBody(physicsSimulator, 100, 100, 1);
rectangleGeom = GeomFactory.Instance.CreateRectangleGeom(physicsSimulator, recBody, 100, 100);
waterAABB = new AABB(new Vector2(150, 240), new Vector2(50, 140));
waterContainer = new AABBFluidContainer(waterAABB);
fluidDragController = new FluidDragController();
fluidDragController.AddGeom(rectangleGeom);
fluidDragController.Initialize(waterContainer, .5f, 3.3f, 1, new Vector2(0, 100)); // Demo's Gravity is (0,200)
physicsSimulator.ControllerList.Add(fluidDragController);

New Post: Circles Colliding and Becoming One

ChurroLoco — Sun, 06 Jul 2008 17:18:30 GMT

I have tried making the marble larger. It works, but sadly I really do need the marbles the size they are.

Adjusting the Time Step... that sounds like it might work. I see two problems with that though. One- I don't know how. Two- If I use that work around I'm afriad how this might react on other slower machines. I'm running a pretty fast rig here and I'm afraid others just won't get the same results. So unless Farseer has a time step setting that is set way below what is is capable of.... well I don't.

I'll go subdivided my balls and see what happens. (lol)

New Post: Circles Colliding and Becoming One

Treacles — Sun, 06 Jul 2008 13:16:58 GMT

Have you tried making the marbles bigger? And you should try giving it more vertices, Or making the Time step smaller or larger

New Post: Circles Colliding and Becoming One

ChurroLoco — Sun, 06 Jul 2008 12:24:33 GMT

I have a game with marbles that collided into each other and I have noticed a problem that I have I put off fixing for a while. If marble collided with too much speed they get absorbed into each other.

I pretty much know how it happens. I assume that since the marble is going so fast that from one frame to another the marble ends up inside the other. Based on the engine it can't expell the other because they are the same size and shape.

Does anybody have an idea how to fix this?

For now, I have just limited the speed of the marbles, but I would really like them to go fast. I haven't tried adding more vertices. I don't know if that would help.

New Post: Object movement against angular platform

Treacles — Sun, 06 Jul 2008 11:35:33 GMT

Hmmm... the code doesnt seem to paste so ill have to do it a different way

Import "source/Engine.bmx"

Graphics 1200, 900
SetClsColor(30, 60, 90)
SetBlend(AlphaBlend)

Global Physics:TPhysicsSimulator = TPhysicsSimulator.Create(Vector2.Create(0, 100))
Global View:TPhysicsSimulatorView = TPhysicsSimulatorView.Create(Physics)
Physics.EnableDiagnostics = True

Global Player:TBody = TBodyFactory.CreateCircleBody(Physics, 30, 1)
Global PlayerG:TGeom = TGeomFactory.CreateCircleGeom(Physics, Player, 30, 20)
Position(Player, 600, 450)
Friction(PlayerG, 0.4)
Restitution(PlayerG,0.4)
LinearDrag(Player, 0.4)

Global Floor1:TBody = TBodyFactory.CreateRectangleBody(Physics, 1200, 50, 1)
Global Floor1G:TGeom = TGeomFactory.CreateRectangleGeom(Physics, Floor1, 1200, 50)
Position(Floor1, 600, 850)
Floor1.SetRotation(0.5)
Disable(Floor1)

Global Floor2:TBody = TBodyFactory.CreateRectangleBody(Physics, 1200, 50, 1)
Global Floor2G:TGeom = TGeomFactory.CreateRectangleGeom(Physics, Floor2, 1200, 50)
Position(Floor2, 600, 850)
Floor2.SetRotation(-0.5)
Disable(Floor2)

Repeat
Update()
Cls
Draw()
Flip
Until KeyDown(Key_Escape)

Function Update()
Physics.Update(0.01)
HandleInput()
End Function

Function Draw()
View.Draw()
End Function

Function HandleInput()
Speed:Float = 3000
Force:Vector2 = Vector2.Zero()
If KeyDown(Key_Up)
  Force.Y = -Speed
End If
If KeyDown(Key_Down)
  Force.Y = +Speed
End If
If KeyDown(Key_Left)
  Force.X = -Speed
End If
If KeyDown(Key_Right)
  Force.X = +Speed
End If
If Force.X > 300
  Force.X = 300
End If
If Force.X < -300
  Force.X = -300
End If
Player.ApplyForce(Force)
End Function

Had to put it through Notepad firt so that it wouldnt come out with weird yellow and white lettering

New Post: NaN Difficulties

pyroneil — Sun, 06 Jul 2008 01:04:49 GMT

I was having some problems in that several things such as angular velocity, and body positions are (seemingly spontaneously) becoming floats with value NaN (not a number) upon collisions, has anyone else had a problem similar to this. Any ideas how to fix it?

New Post: Object movement against angular platform

Knuttz — Sun, 06 Jul 2008 00:06:19 GMT

My horizontal force is 3000.0f. My max horizontal speed is something like 300.0f. I basically wanted the object to reach max speed as quickly as possible, but limit it.

Perhaps you could post a code example (physics values) and compare it to see whether those values will work on my end.

Thanks

New Post: Negative position allowed?

lostlogic — Sat, 05 Jul 2008 15:59:55 GMT

I'm using Farseer on a 2D plane but with 3D graphics. In this, I have a scene centered around 0,0,0 and have various bodies around the scene. Although I have Vector2(-450,0) for one of my collision objects, it seems to put itself at (0,0) position wise. Does Farseer assume everything is on a positive axis?

New Post: Farseer + Silverlight = Fragile - game freezes with too many geom/body objects

Treacles — Sat, 05 Jul 2008 12:57:16 GMT

Late reply i know but... Have you changed the collision group of the tiles to be all the same? That way they wont be colliding with each over but will collide with the Player

New Post: Documentation/Wiki

Treacles — Sat, 05 Jul 2008 12:46:54 GMT

Thanks for making the post on your Blog Jeff... We still need more help with it though, A tutorial or even just a small amount of information in the 2 other sections could help

New Post: Object movement against angular platform

Treacles — Sat, 05 Jul 2008 12:00:11 GMT

Well, My attempts seem to be working fine? Maybe the force isnt high enough... What are you using atm?

New Post: Object movement against angular platform

Treacles — Fri, 04 Jul 2008 21:45:26 GMT

Apparently, People have stopped using Farseer and not many people are here to help... Ill see if i can try to recreate what youve done in BlitzMax to try and figure out the problem myself...

New Post: Object movement against angular platform

Knuttz — Fri, 04 Jul 2008 16:35:39 GMT

Does anyone have any idea? Perhaps I didn't explain the problem well enough. Need more details or code?

Currently, the body/geom for the object is just stuck against the platform and can't move across it when I apply a horizontal force. I even tried applying a small upward vertical force to help, but it didn't make any difference. Any ideas?

I appreciate any help in advance.

New Post: Vector2 compilation error

Knuttz — Fri, 04 Jul 2008 16:16:46 GMT

Have you tried just building the project that you download from the site rather than pulling it apart and adding it to your own? The project as it is from the package should compile with no issues. You can then just include the binaries built from that project.

If you include a copy of LineBrush into your own project and it won't compile because of ambiguous references, then just remove any reference to the Farseer Vector2 class in that file and replace it with the XNA Vector2. I think those are only in there because of Silverlight.

New Post: Vector2 compilation error

1amowery — Thu, 03 Jul 2008 20:38:35 GMT

Okay, I've got my windows version of Farseer and my game set to x86 and Release. I add the farseer 360 project to my solution, I then create a 360 copy of my game. I then change the solution platform to Xbox 360. The farseer portion builds ok but the 360 version of my game bombs with the same 'ambiguous reference' error. I'm getting errors about the Vector2 thing in the LineBrush class that I copied from the demos. Simply changing the target platform is not working for me.

New Post: Movement direction and velocity of geom/body

wmfwlr — Thu, 03 Jul 2008 18:40:35 GMT

hey,

You have to set the LinearVelocity to a new Vector2, not set the properties of the exposed LinearVelocity property independently.

// copy the velocity so it can be modified
Vector2 desiredSpeed = body.LinearVelocity;

// constrain like so ...
if(desiredSpeed.X > maxX)
{
desiredSpeed.X = maxX;
}

// ... or like so
desiredSpeed.Y = Math.Min(maxY, desiredSpeed.Y);

// apply the restricted velocity
body.LinearVelocity = desiredSpeed;

New Post: Movement direction and velocity of geom/body

lostlogic — Thu, 03 Jul 2008 02:27:46 GMT

rgaino wrote:
Hi Dicki. The attribute LinearVelocity on the Body object gives you a vector that defines the velocity it is moving in X and Y. You can also set it to whatever you want to limit the speed like

if (body.LinearVelocity.X > maxSpeed)
body.LinearVelocity.X = maxSpeed

Hope it helps.

I tried your code above and it tells me the return value LinearVelocity cannot be modified because it is not a variable? How do you go about limiting the velocity if that is the case?