Twist Bones

Twist bones are included in some rigs for the purpose of better controlling limb rotation. Using twist bones allows for more natural limb deformation.

Generally, twist bones should not be rigged using rigid bodies.

If a twist bone is attached to the joint, this bone should be ignored:

If a twist bone continues the limb joint, create one set of rig elements for it and for the limb joint.
​See Complex Skeletons to learn more about this topic.

Rigging Twist Bones

If you want to be able to control the twist bones during animation, you should create rig elements for them as well.

  1. Select the twist bone
  2. Create a box controller for it (enable Only box controller and click Add rig element)
  3. Select this box controller
  4. Select the joint from which the twist bone should receive its rotation
  5. Click the Add button

Twist Bone Parameters

After creating a twist, you can adjust its parameters in the Outliner window, under the Proto box tab:

Twist_strength
Defines how much the twist bone is influenced by the joint from which it derives its rotation. Defaul value is 0.750.

Other Parameters

Currently, these parameters are only available after the rig is finalized.
This will change in the future versions.

To access these paramaters:

input_rotation_axis
Set the axis of the "parent" joint from which the twis should derive its rotation 

Output_rotation_axis
Sets the rotational axis for the twist bone

Strength
Set the strength of the effect

 

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