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Rigid body friction

I am currently working on a 3D Rigid Body simulation program. Currently, I have managed to make rigid bodies collide with the floor and bounce correctly using momentum. However, my problem is that when they bounced, they accelerate despite using the friction vector to try to slow them down.

This is the code when you hit the ground

Rvector fDirection(m_Bodies[i].Vel.x,0.0,m_Bodies[i].Vel.z);
Rvector relativeVelocities = m_Bodies[i].Vel - floorVelocity;
fDirection.normalize();


Real impulse = -(1+e) * (Rvector::dotProduct(relativeVelocities,floorNormal)) 
/ (1/m_Bodies[i].mass + floorMass);
Rvector friction = fDirection*mu*gravity.length()*m_Bodies[i].mass;

Rvector collision_forces = Rvector(0,1,0)*impulse;
collision_forces += friction ;

m_Bodies[i].Vel += (collision_forces/m_Bodies[i].mass);

thank

Edit: Here is the integration code.

void RigidBodySimulation::eulerIntegration(float dTime)
{
    Rvector newVel;
    Rvector newPos;
    Rvector zero(0.0, 0.0, 0.0);
    Real one_over_mass;
    Rvector accel;
    for( unsigned int i = 0 ; i < m_Bodies.size(); i++)
    {   
        one_over_mass = 1/m_Bodies[i].mass;
        newVel = m_Bodies[i].Vel + m_Bodies[i].force*one_over_mass*dTime;
        newPos = m_Bodies[i].Pos + m_Bodies[i].Vel*dTime;
        accel = m_Bodies[i].force / m_Bodies[i].mass;
        m_Bodies[i].acceleration = accel;
        m_Bodies[i].newPos = newPos;  
        m_Bodies[i].Vel = newVel;
        m_Bodies[i].Pos = newPos;
    }
}
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2 answers

I have to say that this is a pretty awful piece of code that you have, and I've been doing this for over 10 years now. You should get a basic tutorial on dynamics (like Hibbeler).

Real impulse = -(1+e) * (Rvector::dotProduct(relativeVelocities,floorNormal))
               / (1/m_Bodies[i].mass + floorMass);

, ( ). -, , - , . . , . , , , , , . :

Real momentum_before = Rvector::dotProduct(m_Bodies[i].Vel * m_Bodies[i].mass + floorVelocity * floorMass, floorNormal);
Real rel_vel_after = -e * Rvector::dotProduct(relativeVelocities,floorNormal);
// conservation of momentum in normal direction gives this:
Real body_vel_after = (momentum_before + floorMass * rel_vel_after) / (m_Bodies[i].mass + floorMass);
Real floor_vel_after = body_vel_after - rel_vel_after;

:

Real body_vel_after = ( (m_Bodies[i].mass - e * floorMass) * Rvector::dotProduct(m_Bodies[i].Vel, floorNormal)
                      + (1.0 + e) * floorMass * Rvector::dotProduct(floorVelocity, floorNormal) 
                      ) / (m_Bodies[i].mass + floorMass);

, , ( , ), :

Real body_rel_vel_after = -e * Rvector::dotProduct(relativeVelocities, floorNormal);
Real body_vel_after = Rvector::dotProduct(floorVelocity, floorNormal) + body_rel_vel_after;

. , , . :

Real impulse = m_Bodies[i].mass * (body_vel_after - Rvector::dotProduct(m_Bodies[i].Vel, floorNormal));

, , . "mu" , .. |Ff| = mu * |Fn|, , .. |If| = mu * |In|. , :

Real friction_impulse = mu * fabs(impulse);

. , :

Rvector tangent_rel_vel = relativeVelocities - Rvector::dotProduct(relativeVelocities, floorNormal) * floorNormal;

:

Rvector dir_rel_vel = tangent_rel_vel;
dir_rel_vel.normalize();

( , , )

( , - , ):

Rvector tangent_rel_vel_after = tangent_rel_vel - dir_rel_vel * friction_impulse / m_Bodies[i].mass;

, , ? , , , , , ( ). , . , :

Real tang_rel_vel_change = friction_impulse / mBodies[i].mass;
Rvector tangent_rel_vel_after = tangent_rel_vel - dir_rel_vel * tang_rel_vel_change;

if ( tang_rel_vel_change > tangent_rel_vel.length() ) 
    tangent_rel_vel_after = Rvector(0.0, 0.0, 0.0);   // stop relative motion.

, , :

m_Bodies[i].Vel = floorVelocity + tangent_rel_vel_after + body_rel_vel_after * floorNormal;

, , ( ). , : , ( ). , , - , . , " ", , ( , ). , , .

+6

, ?

 Rvector fDirection(m_Bodies[i].Vel.x,0.0,m_Bodies[i].Vel.z);

. , ( )

collision_forces += friction ;
 m_Bodies[i].Vel += (collision_forces/m_Bodies[i].mass);

, .

:
  : (1/m_Bodies[i].mass + floorMass) 1/ . (1/(m_Bodies[i].mass + floorMass))

, , . , acceleration ?

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