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InertiaBones

InertiaBones is a Unity Editor tool for VRChat avatars that allows you to create (mainly) rotational PhysBone jiggle on any bones and any avatars of your choosing.

It features:

  • Consistent and stable PhysBone controller chain generation
  • Safe SkinnedMeshRenderer weight rewriting
  • Session (non-destructive) iteration mode
  • Persistent mesh baking
  • Influence loss protection
  • Automatic baked mesh cleanup

The tool is designed to serve as a framework for current and future methods included in the tool, so that you can easily add PhysBone dynamics wherever you want.

Info

With a tool like this, and as this is the first release, there are likely edge-cases I haven't found yet. So remember to follow recommended workflows to minimize issues and if you find any bugs or similar, head to the Contact section to send me a bug-report!

Get started → Configuration →

Important Notes

While the underlying techniques used by InertiaBones are technically achievable manually, performing them correctly inside Unity is time-consuming, error-prone, and difficult to iterate safely — especially when modifying mesh weights directly.

InertiaBones streamlines this entire workflow.

It allows you to generate complex controller setups in seconds, iterate and tune them in a non-destructive environment, and only finalize your configuration once you are satisfied. When ready, you can bake the result into clean mesh assets so your avatar remains prefab-safe and export-ready.

The tool is built with multiple guardrails to ensure predictable behavior and safe experimentation, allowing you to explore advanced setups without risking mesh corruption or structural instability.

The tool:

  • Never overwrites mesh assets in place
  • Always rebuilds from pristine backup
  • Never mutates baked assets
  • Protects against removing still-influencing controllers
  • Ensures bindpose integrity

Core Workflow Model

For each source bone, InertiaBones creates:

PBCTRL_SourceBone
└── SourceBone_Sim
    └── SourceBone_Jiggle

Mesh weights are redirected:

Source Bone → Jiggle Bone

All persistent output is generated from a hidden pristine backup stored under the avatar.