Make existing static/kinematic body behave like dynamic one

[B_old]

Hi,
I would like to make an existing (already added to the simulation) static or kinematic shape behave like a dynamic one at a certain point. Here is what I tried:

Code: Select all

float mass = 500.0f;

btVector3 localInertia(btScalar(0), btScalar(0), btScalar(0));

m_body->getCollisionShape()->calculateLocalInertia(btScalar(mass), localInertia);

m_body->setMassProps(mass, localInertia);

m_body->setCollisionFlags(0);

m_body->setGravity(btVector3(btScalar(0), btScalar(-9.8), btScalar(0)));

m_body->forceActivationState(0);
m_body->activate();

One problem I have, is that the body will only collide with dynamic bodies but not with static/kinematic ones. Didn't I fix that with the collisionflags?
Also I wonder about the gravity. Is there an elegant way to give the body the same gravity as specified in the dynamicsWorld? I haven't yet checked how bullet handles gravity. Maybe if I manually set the gravity for all (dynamic/kinematic/static) bodies when I add them to the world it won't change their behavior but they will automatically have the gravity ready once they become dynamic. What do you think?

Thanks for any help.

[pico]

Hi,

you need to remove and add again the body to make it work.

bltWorld->removeCollisionObject(body);
.. do your stuff here ..
bltWorld->addRigidBody(body,filterGroup,filterMask);

regards

[B_old]

Hi,

you need to remove and add again the body to make it work.

bltWorld->removeCollisionObject(body);
.. do your stuff here ..
bltWorld->addRigidBody(body,filterGroup,filterMask);

regards

I almost thought so. Is that the only way to do it? Would have preferred it otherwise, but I can live with it. I suppose, that would solve my gravity problem though. Thanks for the help!

I have another question about the mass. Static/Kinematic objects have a mass of 0. But when I make them dynamic I need a mass. That mass is read from a file during scene creation time. So when I make a body dynamic, I either have to read it again (not an option) or I have to store it somewhere. Could I store it in the btRigidBody regardless of kinematic/dynamic behavior or will setting a mass != 0 always make the body dynamic? It would only save me one float, but still.