Create a string with slider constraint

[Vince]

Hi,

I would like to create a spring between two rigid bodies by using the slider constraint (btSliderConstraint). I have tried different things but I cannot achieve the spring effect.

Any ideas which parameters is the most suitable to have a spring between two RBs?

Thanks

[rponomarev]

Hello,

Unfortunately spring is not supported for the slider joint for now.
But you can use the 6DOF joint with spring, this will give the same effect

Try the following code:

Code: Select all

	{ // create a generic 6DOF constraint with springs 

		btTransform tr;
		tr.setIdentity();
		tr.setOrigin(btVector3(btScalar(-10.), btScalar(0.), btScalar(0.)));
		tr.getBasis().setEulerZYX(0,0,0);
		btRigidBody* pBodyA = localCreateRigidBody( 0.0, tr, shape);
		pBodyA->setActivationState(DISABLE_DEACTIVATION);

		tr.setIdentity();
		tr.setOrigin(btVector3(btScalar(0.), btScalar(0.), btScalar(0.)));
		tr.getBasis().setEulerZYX(0,0,0);
		btRigidBody* pBodyB = localCreateRigidBody(1.0, tr, shape);
		pBodyB->setActivationState(DISABLE_DEACTIVATION);

		btTransform frameInA, frameInB;
		frameInA = btTransform::getIdentity();
		frameInA.setOrigin(btVector3(btScalar(10.), btScalar(0.), btScalar(0.)));
		frameInB = btTransform::getIdentity();
		frameInB.setOrigin(btVector3(btScalar(0.), btScalar(0.), btScalar(0.)));

		btGeneric6DofSpringConstraint* pGen6DOFSpring = new btGeneric6DofSpringConstraint(*pBodyA, *pBodyB, frameInA, frameInB, true);
		pGen6DOFSpring->setLinearUpperLimit(btVector3(5., 0., 0.));
		pGen6DOFSpring->setLinearLowerLimit(btVector3(-5., 0., 0.));

		pGen6DOFSpring->setAngularLowerLimit(btVector3(0.f, 0.f, 0.f));
		pGen6DOFSpring->setAngularUpperLimit(btVector3(0.f, 0.f, 0.f));

		m_dynamicsWorld->addConstraint(pGen6DOFSpring, true);
		pGen6DOFSpring->setDbgDrawSize(btScalar(5.f));
		
		pGen6DOFSpring->enableSpring(0, true);
		pGen6DOFSpring->setStiffness(0, 39.478f);
		pGen6DOFSpring->setDamping(0, 0.5f);
		pGen6DOFSpring->setEquilibriumPoint();
	}

See also Demos/ConstraintDemo.cpp

Hope this will help,
Roman Ponomarev