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rig.rechain

Recreates a virtual FK chain hierarchy over disconnected or constrained nodes.

This modifier allows you to rebuild an FK-style hierarchy virtually, useful for setups like FK joints constrained to rivets, where real parenting is not possible. It supports both a legacy and a new, more explicit method.

Options​

  • name (str, optional): Base name used to generate the IDs of the virtual nodes.
  • weight (bool, optional): Adds a weight attribute to enable/disable the transformation constraint (default: true).
  • ctrls (list[node]): List of controller nodes representing the FK chain.
  • roots (list[node], optional): Corresponding roots for each controller (only needed if controller matrices aren't complete).
  • nodes (list[node]): List of nodes to be constrained, typically the roots following each controller.

⚠️ Only the local matrix is connected in this method. If using transform hierarchies instead of FK controllers, specify the roots list.

⚠️ When using default.bones templates, make sure the nodes list only includes root nodes. The modifier will not work with other types.

⚠️ For riveted joints, make sure the hierarchy is broken and nodes are reparented to avoid unwanted scale propagation.

DAG graph how rechain works

Examples​

Multiple subchains driven by a main chain​

To animate multiple subchains using a main chain, start by breaking the original hierarchy:

# Disconnect subchain controllers and parent them to the main chain hooks
#> n: [0, 1, 2, 3, 4]
parent: subchain.L::roots.<n> chain::hooks.<n>

Then use rechain to rebuild the desired FK behavior:

rig.rechain:
  roots:
    - subchain.L::roots.0
    - subchain.L::roots.1
    - subchain.L::roots.2
    - subchain.L::roots.3
  ctrls:
    - subchain.L::skin.0
    - subchain.L::skin.1
    - subchain.L::skin.2
    - subchain.L::skin.3
  nodes:
    - subchain.L::roots.1
    - subchain.L::roots.2
    - subchain.L::roots.3
    - subchain.L::roots.4

viewport example

Virtual hierarchy between riveted joints​

Here, joint1 controls joint2, and joint2 controls joint3:

rig.rechain:
  ctrls:
    - joint1::skin.0
    - joint2::skin.0
  nodes:
    - joint2::roots.0
    - joint3::roots.0

viewport example