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Rotating Sphere with Euler integration


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#1 Irlan   Members   -  Reputation: 1843

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Posted 09 February 2013 - 08:15 PM

Hi everyone. I'm doing my class project and i'm having troubles with Euler integration (witch seems to be the basic)...
The main loop:
 
 
        torque = position.cross(force);
        
        momentum += dt * force;
        //velocity = momentum * (1.0f / mass);
 
        position += velocity * dt;
 
        ang_momentum += torque * dt;
        m_inertia_inverse = MakeMatrixFromQuaternion(orientation).transpose() * g_inertia * MakeMatrixFromQuaternion(orientation);
        ang_vel = multvm(ang_momentum, m_inertia_inverse); //multiplies a vector by a matrix
 
        orientation += (Quaternion(0, ang_vel.x, ang_vel.y, ang_vel.z) * orientation) * (0.5f * dt);
        orientation.normalize();

 

"g_inertia" is the following matrix3

 

Ix = Iy = Iz = 0.4f * mass * Mathematics::sqrt(radius);
 
        inertia.m11 = Ix;            inertia.m12 = 0;        inertia.m13 = 0;
        inertia.m21 = 0;            inertia.m22 = Iy;        inertia.m23 = 0;

        inertia.m31 = 0;            inertia.m32 = 0;        inertia.m33 = Iz; 

 

and i'm rotating like this:

 

 

orientation.angleAxis(angle, axis); //quaternion to angle axis
    
        glTranslatef(position.x, position.y, position.z);
        glRotatef( angle / Mathematics::pi * 180.0f, axis.x, axis.y, axis.z );

 

The code is right?

Seems like i'm having trouble with the numbers. They out of range... especially with the angular velocity!


Edited by irlanrobson, 11 February 2013 - 08:26 AM.

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#2 Irlan   Members   -  Reputation: 1843

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Posted 10 February 2013 - 06:38 PM

someone have a similar code ??? 


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#3 DT....   Members   -  Reputation: 487

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Posted 11 February 2013 - 11:14 AM

m_inertia_inverse = MakeMatrixFromQuaternion(orientation).transpose() * g_inertia * MakeMatrixFromQuaternion(orientation);

 

 

Would this work?

 

m_inertia_inverse = MakeMatrixFromQuaternion(orientation).transpose() * g_inertia.Inverse() * MakeMatrixFromQuaternion(orientation);



#4 Irlan   Members   -  Reputation: 1843

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Posted 11 February 2013 - 11:49 AM

m_inertia_inverse = MakeMatrixFromQuaternion(orientation).transpose() * g_inertia * MakeMatrixFromQuaternion(orientation);

 

 

Would this work?

 

m_inertia_inverse = MakeMatrixFromQuaternion(orientation).transpose() * g_inertia.Inverse() * MakeMatrixFromQuaternion(orientation);

thanks but i've already done this in the constructor 


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#5 DT....   Members   -  Reputation: 487

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Posted 12 February 2013 - 12:17 PM

  torque = position.cross(force);

 

 

 

What about:

 

r           =  some point on sphere  -  sphere position;

 

torque  =  r.cross( force );



#6 Irlan   Members   -  Reputation: 1843

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Posted 13 February 2013 - 06:51 AM

  torque = position.cross(force);

 

 

 

What about:

 

r           =  some point on sphere  -  sphere position;

 

torque  =  r.cross( force );

thanks but the only force that actually i have, is the gravity force that is on the constructor ,,, 


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