Bone Driven Controller

The Bone Driven Controller allows a "Driver" bone to dynamically affect the motion of one or more "Driven" bones. This is useful for characters that have accessories attached as you can use this to avoid geometry from intersecting during an animation, even when a lot of blending is being used.

You can either set the "Driver" value directly with a Multiplier, remap it to a whole new range, or use a Curve asset to drive the motion. Using a Curve is usually the best approach as it lest you define the response naturally and interactively tweak points/tangents while seeing the changes reflected in real-time.

In the example below, the attached accessory (green) has no authored animations, and is being driven in two axes as a function of the character's thigh bone. This is all calculated at runtime, so a blend of animations ends up working quite well here, even without hand-authored tweaking.

Bone Driven Controller

Property Description

Source (Driver)

Source Bone The Bone to use as the controller input.
Source Component The Transform component to use as input.


Driving Curve Curve used to map from the source attribute to the driven attributes if present (otherwise the Multiplier will be used).
Remap Source Whether or not to clamp the driver value and remap it before scaling it.
Multiplier Multiplier to apply to the input value (Ignored when a Curve is used).

Destination (Driven)

Target Bone Bone to drive using controller input.
Target Component Space The Parent Bone Space used.
Value Effect
Translation The XYZ component of translation on the target bone.
Rotation The XYZ component of rotation on the target bone.
Scale The XYZ component of scale on the target bone.
Modification Mode Set the type of modification to make to the destination component(s).
Value Effect
Add to Input Add the driven value to the input component value(s).
Replace Component Replace the input component value(s) with the driven value.
Add to Ref Pose Add the driven value to the reference pose value.


(As Pin) Alpha Enable/Disable the display of the Alpha pin on the node.
Alpha Scale Bias Set the minimal and maximal input scaling values.

Bone Driven Controller nodes are also affected by the LOD Threshold system introduced in 4.11. You can find the setting for this in the Details Panel for the Bone Driven Controller node.


Property Description
LOD Threshold This is the max Level of Detail (LOD) that this node is permitted to run on. For example: if you have LOD Threshold set to 2, it will run until LOD 2, but disable itself once the component's LOD becomes 3.