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Hand IK Retargeting

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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.



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



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.


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.




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.