Twist bones are included in some rigs for the purpose of better controlling limb rotation. Using twist bones allows for more natural limb deformation.
For a twist bone to properly work in a Cascadeur rig, it should be attached to the parent of the joint which it is supposed to control:
If a twist bone continues the limb joint, like on the image below, this mean it cannot be used for controlling rotation: Cascadeur rig doesn't currently support this kind of 'reverse' hierarchy.
For cases thike these we recommend either altering the rig (if you need to use twist bones), or simply to ignore twist bones.
Generally, twist bones should not be rigged using rigid bodies.
However, if you want to be able to control the twist bones during animation, you can rig them with Box Controllers:
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 Set button:
After creating a twist, you can adjust its parameters in the Outliner window, under the Proto box tab:
The twist joint from which rotation is transfered to the twist box.
Defines how much the twist bone is influenced by the joint from which it derives its rotation. Defaul value is 0.750.
These three numbers define the axis used to transfer rotation from the twist joint to the twist box. Other axes are ignored.
Parameters described above can only be set during rigging. After the rig is finalized, they are no longer available.
However, twist joints can still be customized even after rigging. For this, a different set of parameters is used.
To access these paramaters:
1. Select the box controller associated with the twist bone.
2. In the Outliner, open the Twist tab.
Set the axis of the "parent" joint from which the twis should derive its rotation
Sets the rotational axis for the twist bone
Set the strength of the effect