Houdini 19.0 Nodes VOP nodes Two Bone IK

Two Bone IK VOP node

Perform a simple two-bone IK solve

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Since 18.5

This node takes operates on a three joint chain, performing a simple IK solve to achieve the Goal position. If connected the Twist position will control the orientation of the plane on which the solve takes place.

Typically the Root, Mid and Tip inputs will be connected to the outputs of three Get Point Transform VOPs, although any 4×4 matrices can be used.


The Root, Mid and Tip inputs represent the starting point, or rest pose for the solve. If you having difficulty with performing the solve on a hyper-extended chain (e.g. a leg where the knee is bent backwards slightly) then you can supply a static pose on another input to the Rig Attribute VOP, with the knee bent in the desired direction and use this input as the source for these transforms. Note that when using this method you will have to supply a Root Driver input in order to update the root of the chain.



The world space transform of the root joint of the chain.


The world space transform of the mid joint in the chain.


The world space transform of the last joint in the chain.

Root Driver (Optional)

If connected this will set the animated position of the Root of the chain. If disconnected, the Root transform will be used.

Twist (Optional)

If connected this will set the pole vector for the solve. If disconnected, the Mid transform will be used.


The goal position for the ik solve.


If enabled the solve will allow the chain to stretch to achieve the Goal position. The Root and Mid joints will be scaled with volume preservation.

Twist Offset

An additional twist rotation to apply post-solve.


Control how much of the result to blend with the input transforms.

Orient Tip

Control whether or not to orient the Tip joint to the Goal transform.





See also

Two Bone IK