Hand IK Retargeting

The Hand IK Retargeting control is a solver that can be used to handle retargeting of IK bone chains. The solver moves an IK bone chain to meet FK hand bones, based on the Hand FKWeight value (to favor either side). For example, 0 would favor the left hand, 1 would favor the right hand and 0.5 would be equal weight.


Below, Hand IK Retargeting and Two Bone IK controls are used to affect how a character holds a weapon.

While the Two Bone IK nodes drive the position of the left and right hands, the Hand FKWeight property (driven by the variable Hand Favoring) determines which hand to favor while holding the weapon. Above, we slowed the animation down to illustrate how the weapon shifts in the character's hands based on the weight value provided.

See the Animation map inside the Content Examples project (available for free via the Learn tab in the Epic Games Launcher) for this sample.

Property Description

Hand IKRetargeting

Right Hand FK The Bone for Right Hand FK
Left Hand FK The Bone for Left Hand FK
Right Hand IK The Bone for Right Hand IK
Left Hand IK The Bone for Left Hand IK
IKBones to Move The IK Bones affected
Pin Description

Input Pins

Hand FKWeight Which hand to favor. 0.5 is equal weight for both, 1 = right hand, 0 = left hand.
Component Pose The incoming pose.
Alpha The current strength of the control.

Hand IK Retargeting 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 Hand IK Retargeting 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.