Physbones more jittery and unstable than they used to be | Voters

Physbones more jittery and unstable than they used to be

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lackofbindings

I've been noticing and increasing number of issues with physbones over the past couple of months. 
1.
 Immobile used to work with Gravity, but now bones with gravity always shake violently while the avatar is moving quickly, completely ignoring immobile. 
Example:
 avtr_ba3daad5-0c64-4fb4-8593-38265acd9ad3 avatar uses that to determine the up vector for the cat, walking around causes the cat to jump around, it never used to in older versions.
2.
 Physbones resting on or inside colliders vibrate, sometimes even to the point where they seem to struggle to stay inside inside-out colliders. This used to be stable with no vibration. In minor cases this can sometimes be mitigated with "physbones as spheres", but it never used to be necessary.
Example:
 avtr_04a9d322-e228-4934-93b1-6e20b62cfded The boxing gloves on this avatar are long physbones with squish that are held back by inside-out colliders, they now vibrate violently at all times, they used to stay calmly in place.

October 11, 2025

Rokk

This got much worse recently.

lackofbindings

Here's another where the effect is very prominent on the foot claws and shoulder pads: avtr_b504b4b9-db85-467f-bc81-e7a10ede8c8f

lackofbindings

Please note avtr_ba3daad5-0c64-4fb4-8593-38265acd9ad3 has been replaced by avtr_5c972960-700e-41e8-9cb3-136a2c081853 , please use this new ID for testing against.

I got sick of waiting for a fix on this and since it affects live products I can't just leave this forever. I manged to find a workaround for the jitter in this case by world constraining the physbone so it never actually moves, which of course only works because the physbone is invisible and im only measuring the angle. The new ID is an upload of the old version before the fix.

Dor․

Point #2 is more prominent now but has started after the update 2024.1.2 with the change "Improved PhysBone simulation at low framerates when the avatar is moving at high speeds." which seemingly changed the update rate of physbones and colliders so that they now mismatch.
This is supposedly intentional according to pi when I brought this up on Discord (https://discord.com/channels/189511567539306508/449386885299830794/1362820391998849074) when different updates claimed to address issues that were seemingly caused by this, like the update 2025.2.1 "Fixes have been made to PhysBones to address jitter" aiming to fix skirt flow bones, which is primarily where I complained about the issue since it was first introduced, while the update improved the jitter it still did not solve it.
For a reproduction avatar (private): avtr_298fd935-0429-4b2d-93b5-61248cc7d3eb, the avatar has a skirt with flow bones, and colliders on the thighs, we didn't want the skirt to flop up with any touch of the stick, so we used world immobile 1, and it worked perfectly, the skirt would be static with stick movement but still flowed nicely with physical movement/animations, just a month or so after development the 2024.1.2 update came out and the skirt would get kicked up by the thigh colliders randomly.

lackofbindings

Here's an even better example. This avatar's shoulder pads vibrate violently all the time, whereas they used to be perfectly stable and smooth. The effect is very obvious: avtr_2bb7c911-7856-4740-960d-ff22204456a3

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