Objects freezing in midair when joint anchors get pushed apart

[nstoddard]

Hi, I'm seeing some weird behavior in a game I'm working on and I'm not sure if it's a bug or not. Sometimes, when a revolute joint receives a sharp impact, the joint anchors will get pushed apart. For some reason, this causes the attached rigid bodies to freeze in midair for a while (with only a bit of movement), until the anchors are pulled back together, which sometimes takes several seconds. This is really disruptive to gameplay, because even if the objects were moving/rotating fast before this happens, they'll just freeze in midair for a while.

Has anyone else seen this, or have any ideas for how to fix it? I've been able to reduce the incidence of this behavior by increasing some integration parameters (num_solver_iterations etc) but that's probably expensive and doesn't entirely fix the problem.

Edit: I see that multibody joints were recommended in another related discussion (#722). Unfortunately they don't seem suitable for my use case, since I need to support loops and multibody joints apparently don't support those. It's hard to be sure, though, since there's essentially no documentation for them (this describes them as "An joint attached to two bodies based on the reduced coordinates formalism.", which isn't especially helpful). Is there better documentation somewhere?

[ThierryBerger]

Concerning multibody joints docs, dimforge/rapier.rs#132 may answer a few questions.

A minimal reproduction code would be helpful to investigate your issue further ; you're right that impulse joints can be sensitive to configuration and scene.