Changing a dynamic object to a static object.

[steveh]

Is it possible to turn a dynamic object into a static object (mass = 0)?

I've tried:

pRBody->setMassProps(0.0f,btVector3(0.0f,0.0f,0.0f));

But this just makes my rigid body disappear!

Any ideas?

Thanks,

Steve.

[steveh]

On the same topic, am I correct in assuming that:

myMotionState->m_graphicsWorldTrans contains uninitialised data for static objects? So when my renderer comes to use the matrix from the physics, I have to check to see if the object is static first?

Thanks,

Steve

[Erwin Coumans]

If you use the motionState, make sure to initialize the m_graphicsWorldTransform before constructing the rigidbody. Then the rigidbody will pick this transform as initial transform. If you use 'btDefaultMotionState' as motionstate it should be initialized by the constructor.

Before changing a dynamic object into a static object, remove it from the dynamics world, make the change, and add it back to the dynamics world.

Please let us know if that helps,
Erwin

[ola]

I'm trying out this.

Is the only way to set static/dynamic objects done with setting the mass to either 0 or >0?

The reason I'm asking is that in my application I do this switch for some objects rather often. When it's done with the mass then I need to store the object's mass information somewhere else during the time the object is static. It's sure quite doable this way but something like a setStatic()/setDynamic() function would seem a bit more elegant to me.

Best regards,
Ola

[ola]

Switching between dynamic and static works well now that I remove the the objects from the dynamics world before modifying the mass and then adding them again.

With the vechicle, there's trouble when I do this. I get an assertion failed:

Code: Select all

src/BulletDynamics/ConstraintSolver/btJacobianEntry.h:53: btJacobianEntry::btJacobianEntry(const btMatrix3x3&, const btMatrix3x3&, const btVector3&, const btVector3&, const btVector3&, const btVector3&, btScalar, const btVector3&, btScalar): Assertion `m_Adiag > btScalar(0.0)' failed

I recon it happens because the car mass is zero and the vehicle constraint is still active. What do you think, Erwin? Should I fix this in my end (remove the constraint and re-add it later as well, I guess) or should Bullet be able to handle this case? I can offer to try to make a patch if you opt for the latter.

Best regards,
Ola