Gravity force not set when mass changes

[Stillmoon]

In the project I'm working on, we occasionally need to change the mass of rigid bodies. We call btRigidBody::setMassProps with the new mass and inertia while the simulation is running.

However, setMassProps does not recalculate the force due to gravity, which of course, depends on the mass.

This was easy enough to fix by calling

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someBody->setGravity(someBody->getGravity());

after setMassProps.

Is this something setMassProps should handle internally? If so, adding

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m_gravity = m_gravity_acceleration * mass;

to the end of setMassProps should do the trick.

This may also help solve some of the "slow-motion" gravity issues I read about, if the rigid bodies' mass is being set after it's added to the dynamics world.

[Erwin Coumans]

Good point. We should add this indeed,

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m_gravity = acceleration * (btScalar(1.0) / m_inverseMass);

Here is the new issue: http://code.google.com/p/bullet/issues/detail?id=364

Thanks for the feedback,
Erwin