Archive 17/01/2023.

Static RigidBody enters sleeping state after being still for a while

WangKai

Hi guys,

I just found that if RigidBody with zero mass stops moving for a while, it will become “deactivated” and stops all collisions.

github.com

urho3d/Urho3D/blob/6802a83fcd259430098426480d6c045114c0786c/Source/ThirdParty/Bullet/src/BulletDynamics/Dynamics/btRigidBody.h#L499



		return m_inverseMass + normal.dot(vec);
	}

	SIMD_FORCE_INLINE btScalar computeAngularImpulseDenominator(const btVector3& axis) const
	{
		btVector3 vec = axis * getInvInertiaTensorWorld();
		return axis.dot(vec);
	}

	SIMD_FORCE_INLINE void updateDeactivation(btScalar timeStep)
	{
		if ((getActivationState() == ISLAND_SLEEPING) || (getActivationState() == DISABLE_DEACTIVATION))
			return;

		if ((getLinearVelocity().length2() < m_linearSleepingThreshold * m_linearSleepingThreshold) &&
			(getAngularVelocity().length2() < m_angularSleepingThreshold * m_angularSleepingThreshold))
		{
			m_deactivationTime += timeStep;
		}
		else

It seems we need to set active to DISABLE_DEACTIVATION and add as an interface to RigidBody.

github.com

urho3d/Urho3D/blob/6802a83fcd259430098426480d6c045114c0786c/Source/ThirdParty/Bullet/src/BulletDynamics/Dynamics/btRigidBody.h#L518


		}
		else
		{
			m_deactivationTime = btScalar(0.);
			setActivationState(0);
		}
	}

	SIMD_FORCE_INLINE bool wantsSleeping()
	{
		if (getActivationState() == DISABLE_DEACTIVATION)
			return false;

		//disable deactivation
		if (gDisableDeactivation || (gDeactivationTime == btScalar(0.)))
			return false;

		if ((getActivationState() == ISLAND_SLEEPING) || (getActivationState() == WANTS_DEACTIVATION))
			return true;

		if (m_deactivationTime > gDeactivationTime)

Please correct me if this is not accurate.