Real-Time Physics Simulation Forum

From erwin on the bullet svn :

Log message
remove rigid body gpu pipeline, the latest version is at
https://github.com/erwincoumans/bullet3

I played a bit with it , using convex hulls , and seems to work pretty well, the only noticable thing about it, is the same as the linear friction, the behaviour doesn't seem to give linear feedback based on the value. Low values will have very little effect but when reaching higher values the effec...

Just finished updating the bullet tree in our plugin, and implementing the rolling friction now, it is missing from the rigidBodyConstructionInfo though ? Any chance to get that in there ? struct btRigidBodyConstructionInfo { ... ///best simulation results when friction is non-zero btScalar m_fricti...

Thanks for implementing that !
I'll update our code base and see how it behaves.

Is it something that will stay in there or is it just
some kind of experiment ?

Is there a way to actually fake the rotation friction on contacts ?
We do get lots of spinning when using a high friction (probably normal
since all the energy is converted in rotation), would be nice
to be able to reduce that effect a bit.

Francois

forgot to mention the demo seems to be leaking memory a whole lot !

not really a big deal since it's really just a test but should
keep it in mind

The NVidia one was faster but was getting pretty good performance with both, can't test right now , but i'll post some numbers tonight. Edit : Just did some quick performance test for the 3 demos, the machine used is a Core i7 2.8GHz w/ NVidia 285 NVidia OpenCL 1 - 55ms for 11340 particles 2 - 70ms ...

nice work !

Tested and works with NVidia OpenCL & Intel OpenCL too.

Just wondering if anyone would have an idea on how to detect the faces that are colliding. The contacts points being reduced to very few per object, it doesn't give enough information to know which faces are actually colliding. I'm implementing some basic FEM to drive fracture / glue features, and n...

I believe I did patch this in my bullet version
it was a fairly simple patch in the capsule shape code,
you should just change it there and make sure the set margin method
works as expected
I don't have access to my code right now so can't tell exactly

For fun someone actually wrote a quadcopter running within maya using bullet. We used 4 maya fields parenters to where the "motors" would be which basically apply a variable up force to the object. If you want to make it outside of maya, you can just build a small rig with a 4 calls to app...

Hey Erwin,

What is the penalty of transferring the data back to main memory ?
15fps for 110k bodies is impressive but in our case we need the data
back in the memory..

F

no

we wrote our own maya plugin which is a fair bit more evolved
than dynamica for our fx purposes here.

I haven't looked at dynamica in a quite a while though, so not
sure what is in there now...

F

In our implementation of bullet for maya we do dynamic fracturing with voronoi. Can't tell you much about it, but the idea is to take the contact points from the callback check if the collision momentum is strong enough to shatter an object and then spread points in space starting from the contact p...

you could also use the collision mask/group (can't remember the exact name)
and use it to determine what object the collider is.
Or you can also attach a name to the rigid body and check the name...