btMultiBody unstability problems when using colliders
Posted: Mon Sep 12, 2016 3:43 am
I am a researcher working with motion capture data and complex multi-body characters having 50+ DOFs.
Recently, I tried to port my characters to use the btMultiBody class,
and it worked well until I added colliders to some links.
Without using colliders, the simulation worked perfectly.
Also, the simulation works well for simple models (<10DOFs) which have colliders.
However, it does not when I use more complex models. The simulation simply explodes.
Strangely, this stability issue appear even when non of the colliders actually collide.
For example, a 56DOF ragdoll free-falled well when I attached no collider.
But if I attach a small box to a foot of the ragdoll, the ragdoll simulation explodes within a few hundreds frames even though the ragdoll is falling from very high above the ground, and there there was no contacts involved.
I googled about this issue, and I found one technical paper which reports the same problem.
https://homes.cs.washington.edu/~todoro ... ICRA15.pdf
"We implemented a comparison instance that uses the new Featherstone functionality in Bullet, but this functionality is not yet fully debugged and exhibits unexpected behavior
in some simulations, so we were able to use this new functionality only in tests without contact."
Is this a known problem for the bullet team? Is there any easy way to fix it?
Recently, I tried to port my characters to use the btMultiBody class,
and it worked well until I added colliders to some links.
Without using colliders, the simulation worked perfectly.
Also, the simulation works well for simple models (<10DOFs) which have colliders.
However, it does not when I use more complex models. The simulation simply explodes.
Strangely, this stability issue appear even when non of the colliders actually collide.
For example, a 56DOF ragdoll free-falled well when I attached no collider.
But if I attach a small box to a foot of the ragdoll, the ragdoll simulation explodes within a few hundreds frames even though the ragdoll is falling from very high above the ground, and there there was no contacts involved.
I googled about this issue, and I found one technical paper which reports the same problem.
https://homes.cs.washington.edu/~todoro ... ICRA15.pdf
"We implemented a comparison instance that uses the new Featherstone functionality in Bullet, but this functionality is not yet fully debugged and exhibits unexpected behavior
in some simulations, so we were able to use this new functionality only in tests without contact."
Is this a known problem for the bullet team? Is there any easy way to fix it?