Getting the impulse force from a collision?

[Adversus]

I can get a list of btCollisionObject pairs that have collided but how do I find a way of getting the force of that collision?

Cheers.

[Erwin Coumans]

Each contact points stores the applied impulse (m_appliedImpulse).

You can check how to iterate over contact points (and manifolds) in Bullet/Demos/CollisionInterfaceDemo
Hope this helps,
Erwin

[Adversus]

Thanks Erwin,

Cheers, that worked.

However what's the best way to get the resultant collision normal?

I suspect I have to iterate over the points using getPositionWorldOnA and getPositionWorldOnB however I'm not sure.

[justin]

hi, is getAppliedImpulse still working?
I used this method in my callbacks, but found this always returned 0.

I googled, and there's a saying in 2009 that this method is not used any more.
And I lookuped btPersistentManifold and found the impulse variables still exists.
So, I'm confused.

And my scenario using this method is to get the force (or impulse) between feet and ground when walking.

[Flix]

is getAppliedImpulse still working?

Yes, as far as I know it's not available in the callbacks (e.g. "custom material callback"), but it works when you manually iterate the contact manifold for contact points.

[almatea]

It would be wonderful to be possibly get impulse before collision process (inside gContactAddedCallback for example).

[justin]

It would be wonderful to be possibly get impulse before collision process (inside gContactAddedCallback for example).

Just the opposite in my opinion, because they belong to different stages.