Friction seems to occasionally either go to 0, or 100%. Unity 2019.4 LTS. Recent regression?

Unity Engine
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1

I’ve started noticing this happening in the editor probably somewhere in one of the last few 2019.4 LTS releases. Basically, after performing an LoadScene command, all of the physics in the scene will occasionally behave in one of the following two ways:

  • It’s as if every rigidbody’s friction was set to 0.
  • Or, it’s as if every rigidbody’s friction was set to 1.

So, I’ll either either start ice skating, or I’ll be barely able to move if I’m touching the ground. Upon reloading the scene again, sometimes it either works fine again, or it stays the same kind of broken, or it swaps to the other kind of broken (that is, no friction goes to 100% friction, or vice versa).

This only seems to be happening in Editor right now, not in a build. And once it starts, I need to close the editor and restart it, otherwise it keeps happening, even if I leave and reenter playmode.

This isn’t something I can reproduce. It just kind of happens from time to time. I was wondering if anyone else had experienced anything similar. Restarting the editor always clears this up, and usually for quite a while. But maybe every day or two I notice it getting into this state.

2

I had noticed weird behaviors in the past when using the Temporal Gauss Seidel solver. I don’t know if this may be related with your problem, but surely it worth a test.

3

Good to know. It looks like I’m still on Projected Gauss Seidel, so hopefully what I’m seeing isn’t related.

The issue I’m seeing isn’t that big of a deal. I think of it as kind of a “soft crash”, where the physics engine gets screwy in-editor until I close and reopen Unity. Luckily I haven’t see this in a build yet.