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update suspension to correctly use Hooke's Law #4758

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update suspension to correctly use Hooke's Law #4758

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7 changes: 3 additions & 4 deletions src/BulletDynamics/Vehicle/btRaycastVehicle.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -385,8 +385,6 @@ void btRaycastVehicle::updateSuspension(btScalar deltaTime)
{
(void)deltaTime;

btScalar chassisMass = btScalar(1.) / m_chassisBody->getInvMass();

for (int w_it = 0; w_it < getNumWheels(); w_it++)
{
btWheelInfo& wheel_info = m_wheelInfo[w_it];
Expand All @@ -400,7 +398,7 @@ void btRaycastVehicle::updateSuspension(btScalar deltaTime)
btScalar current_length = wheel_info.m_raycastInfo.m_suspensionLength;

btScalar length_diff = (susp_length - current_length);

// assume stiffness is in N/m
force = wheel_info.m_suspensionStiffness * length_diff * wheel_info.m_clippedInvContactDotSuspension;
}

Expand All @@ -417,12 +415,13 @@ void btRaycastVehicle::updateSuspension(btScalar deltaTime)
{
susp_damping = wheel_info.m_wheelsDampingRelaxation;
}
// assume damping is in N/(m/s)
force -= susp_damping * projected_rel_vel;
}
}

// RESULT
wheel_info.m_wheelsSuspensionForce = force * chassisMass;
wheel_info.m_wheelsSuspensionForce = force;
if (wheel_info.m_wheelsSuspensionForce < btScalar(0.))
{
wheel_info.m_wheelsSuspensionForce = btScalar(0.);
Expand Down