[ODE] Bowling physics
samira S.
samila_1 at hotmail.com
Fri May 11 00:55:51 MST 2007
Ok, the forces in ODE might be more precise, but why would that sphere not
let the box fall down? I mean by positionioning the boxes in the way that
you can see in the picture the top one should fall down even without letting
a sphere fall on it. I am not quite sure if you understood my picture?
This is a simple thing of gravity. But it seems to me as if the boxes stick
to each other.
So if you (or anyone else) already implemented a bowling phisics, or
something similar, could you please send me the important parts of that
implementation? Or at least give me an idea about how to chose the
parameters like mass an gravity and force ... I tried lots of values, but
nothing looks realistic. I would really appreciate that.
Samira
>From: "Jon Watte (ODE)" <hplus-ode at mindcontrol.org>
>To: "samira S." <samila_1 at hotmail.com>
>CC: ode at ode.org
>Subject: Re: [ODE] Bowling physics
>Date: Thu, 10 May 2007 11:15:23 -0700
>
>Note that, in simulation, you can get much more precise forces than in real
>life. A sphere that falls STRAIGHT down onto a box, will just come to rest
>on that box.
>
>For bowling pins, I've preivously used a collection of three primitives:
>
>1) a capsule for the main pin part
>2) a sphere for the lower globe part
>3) a small box positioned at the bottom, to make the pin stand up
>
>Note that you can attach more than one geom to a body, and they can
>intersect without problems.
>
>Cheers,
>
>/ h+
>
>
>samira S. wrote:
>>Hello
>>
>>I need to get some realistic Bowling-Physics by using ODE.
>>Actually this should not be too hard, but I am new to physics engines and
>>I have the following problems:
>>I created two boxes which should approximate my BowlingPins. However when
>>I tried to let a sphere push them over, they just slipped away on the
>>ground (approximated by a plane)
>>I tried to change several Parameters, like friction (surface.mu,
>>surface.mu2), mass, the spheres velocity and initial force, but the boxes
>>were never pushed over, they only slide away.
>>
>>Then I tried the following:
>>Box1 is standing on the plane and Box2 is on top of it, but horizontal, in
>>such a way that it should fall down (see picture). In addition I let a
>>sphere fall on Box2 so that the Box should really fall down. However,
>>this didn´t happen. The sphere just stayed on Box2.
>>
>> O Sphere
>> ------------- Box2 is horizontal
>> l
>> l
>> l
>> l
>> l Box1 is vertical
>>
>>
>>Please, can anyone tell me what I am doing wrong in my implementation, or
>>which parameter could be wrong or missing?
>>I am using Visual Studio C# and the Tao-Framework-bindings for ODE. But
>>anyone who knows ODE should understand my Code as well:
>>
>>
>>private void main()
>> {
>> world = Ode.dWorldCreate();
>>
>> Ode.dWorldSetGravity(world, 0,0,-9.81f);
>>
>> space = Ode.dSimpleSpaceCreate(System.IntPtr.Zero);
>> contactgroup = Ode.dJointGroupCreate(0);
>>
>> floorGeom = Ode.dCreatePlane(space,0,0,1.0f,0);
>>
>> sphere_body = Ode.dBodyCreate(world);
>> sphere_geom = Ode.dCreateSphere(space,10);
>>
>> pin1_body = Ode.dBodyCreate(world);
>> pin1_geom = Ode.dCreateBox(space,10,10,100);
>>
>> pin2_body = Ode.dBodyCreate(world);
>> pin2_geom = Ode.dCreateBox(space,10,100,10);
>>
>> Ode.dGeomSetBody(sphere_geom,sphere_body);
>> Ode.dGeomSetBody(pin1_geom,pin1_body);
>> Ode.dGeomSetBody(pin2_geom,pin2_body);
>>
>> Ode.dMass sphere_mass = new Ode.dMass();
>> Ode.dMassSetSphere(ref mass, 2500, 10);
>>
>> Ode.dMass pin1_mass = new Ode.dMass();
>> Ode.dMassSetBox(ref pin1_mass,2500,10,10,100);
>>
>> Ode.dMass pin2_mass = new Ode.dMass();
>> Ode.dMassSetBox(ref pin2_mass,2500,10,100,10);
>>
>> sphere_mass.mass = 100;
>> pin1_mass.mass = 15;
>> pin2_mass.mass = 15;
>>
>> Ode.dBodySetMass(sphere_body, ref sphere_mass);
>> Ode.dBodySetMass(pin1_body,ref pin1_mass);
>> Ode.dBodySetMass(pin2_body,ref pin2_mass);
>>
>> Ode.dBodySetPosition(sphere_body,0,10,190);
>> Ode.dBodySetPosition(pin1_body,0,80,50);
>> Ode.dBodySetPosition(pin2_body,0,50,105);
>>
>> Ode.dBodySetLinearVel(sphere_body,0,0,-2000);
>>
>> float time = 0;
>>
>> float deltaTime = 0.04f;
>>
>> while(time < 2)
>> {
>> //Get the bodies position
>> Ode.dVector3 position = Ode.dBodyGetPosition(sphere_body);
>> Ode.dVector3 pin1_position =
>>Ode.dBodyGetPosition(pin1_body);
>> Ode.dVector3 pin2_position =
>>Ode.dBodyGetPosition(pin2_body);
>>
>> //Get the bodies velocity
>> Ode.dVector3 velocity = Ode.dBodyGetLinearVel(sphere_body);
>> Ode.dVector3 pin1_velocity = Ode.dBodyGetLinearVel(pin1_body);
>> Ode.dVector3 pin2_velocity = Ode.dBodyGetLinearVel(pin2_body);
>>
>> //Get the bodies Rotation
>> // convert the quaternion to an axis angle so we can put the rotation
>> Ode.dQuaternion rotation = new Ode.dQuaternion();
>> Ode.dGeomGetQuaternion(pin2_geom,ref rotation);
>>
>> float cos_a = rotation.W;
>> float angle = (float)(Math.Acos(cos_a) * 2.0f);
>> float sin_a = (float)(Math.Sqrt(1.0f - cos_a * cos_a));
>> if (Math.Abs(sin_a) < 0.0005f)
>> sin_a = 1.0f;
>> sin_a = 1.0f / sin_a;
>> float x_axis = rotation.X * sin_a;
>> float y_axis = rotation.Y * sin_a;
>> float z_axis = rotation.Z * sin_a;
>>
>>
>> // Print out the 'time', the body's position, rotation and its
>>velocity
>> Console.WriteLine("{0} sec: rot_angel={1} rot_axis=({2}, {3}, {4}))",
>> time,angle,x_axis,y_axis,z_axis);
>> Console.WriteLine("{0:0.00} sec: pos=({1:0.00}, {2:0.00},
>>{3:0.00}) vel=({4:0.00}, {5:0.00}, {6:0.00})",
>> time, position[0], position[1], position[2],
>>velocity[0], velocity[1], velocity[2]);
>>
>> Ode.dSpaceCollide(space,(IntPtr)1, new
>>Ode.dNearCallback(cbTest));
>>
>> Ode.dWorldStep(world, deltaTime);
>>
>> Ode.dJointGroupEmpty(contactgroup);
>>
>> time += deltaTime;
>> }
>> }//end main
>>
>>
>>
>>// nearCallback:
>>static void cbTest(IntPtr data, IntPtr o1, IntPtr o2)
>>{
>> IntPtr b1 = Ode.dGeomGetBody(o1);
>> IntPtr b2 = Ode.dGeomGetBody(o2);
>>
>> int MAX_COLLISIONS = 128;
>>
>> Ode.dContactGeom[] contactGeoms = new
>>Ode.dContactGeom[MAX_COLLISIONS];
>>
>> int numc = Ode.dCollide(o1,o2,MAX_COLLISIONS,contactGeoms,sizeOf());
>>
>> Ode.dContact[] contact = new Tao.Ode.Ode.dContact[numc];
>>
>> for(int i=0; i<numc; i++)
>> {
>> contact[i].surface.mode =
>>(int)Ode.dContactFlags.dContactBounce |
>>(int)Ode.dContactFlags.dContactSoftCFM;
>>
>> contact[i].surface.mu = 5;
>> contact[i].surface.mu2 = 5;
>> contact[i].surface.bounce = 0.1f;
>> contact[i].surface.bounce_vel = 0.1f;
>> contact[i].surface.soft_cfm = 0;
>>
>> contact[i].geom = contactGeoms[i];
>>
>> IntPtr joint =
>>Ode.dJointCreateContact(world,contactgroup,ref contact[i]);
>> Ode.dJointAttach(joint,b1,b2);
>> }
>>}
>>
>>Regards,
>>Samira
>>
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>>
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