Problem with "btGeneric6DofConstraint"

[Youne]

Hi,

Sorry, I forgot to ask the question.


In the ConstraintDemo the slider is between a rigid body and a fixed body. In my model "Hydraulic jack", I have to create a slider between two rigid bodies (Capsules). So the description of the slider is as follows :


btRigidBody* Body1;
btRigidBody* Body2;

btlocalA.setIdentity(); localB.setIdentity();
localA.setOrigin(btVector3(btScalar(0), btScalar(0.), btScalar(0)));
localB.setOrigin(btVector3(btScalar(0.), btScalar(0), btScalar(0)));
slider = new btGeneric6DofConstraint(*Body1, *Body2, localA, localB, true);
slider->setLinearLowerLimit(btVector3(0,-1,0));
slider->setLinearUpperLimit(btVector3(0,1,0));
slider->setAngularLowerLimit(btVector3(0,0,0));
slider->setAngularUpperLimit(btVector3(0,0,0));
m_ownerWorld->addConstraint(slider, true);

The problem is the silder does not respect these limits and it goes in all directions when it moves slightly. So do you have any idea how to Correct this Instability.

Thanks

Y

[Erwin Coumans]

The problem is the silder does not respect these limits and it goes in all directions when it moves slightly. So do you have any idea how to Correct this Instability.

We will provide a sample that shows a slider constraint between two dynamic rigid bodies, and make sure there is no instability.

You can follow progress here:
http://code.google.com/p/bullet/issues/list

Thanks for the feedback,
Erwin

[Youne]

Hi Erwin,

Just to know !

Do you know when approximately that will be done?
Do you know when the bullet 2.67 version will be available?

Thanhs very much

Y

[Erwin Coumans]

Hi Erwin,

Just to know !

Do you know when approximately that will be done?

When its done.

Do you know when the bullet 2.67 version will be available?

Bullet 2.67 is available for download right now: http://code.google.com/p/bullet/
Enjoy,
Erwin

[Youne]

Hi to all,

Do you have any idea how to Correct this Instability of the slider.

Thanks

[rponomarev]

I'm working on that right now
Hope it will be resolved soon

As a temporary solution you can add string:

m_linearLimits.m_accumulatedImpulse.setValue(0.f, 0.f, 0.f);

at the beginning of function btGeneric6DofConstraint::buildJacobian()

file .../src/BulletDynamics/ConstraintSolver/btGeneric6DofConstraint.cpp
line 380

Hope this will help

--Roman

[Youne]

Hi Roman,

Thank you very much for the solution

have a nice day

[amirishere]

thanks rponomarev this solved my problem.
Note that the constriant demo app has this problem that after a while of fidgeting around with it, its boundaries become unstable. your solution solves this.