(VRIK) Best way to re-target generic hand model animations to Humanoid character hands

What I want to achieve is to be able to re-target generic hand model animations to Humanoid character hands.

I am currently testing this with the hand model provided by Oculus (hand_skeletal_lowres) and a character model called racer from Mixamo. Ideally you would be able to do this with any custom hand model (E.g hand model with 3 fingers) and any custom character model.

After some research I have found out that in order to achieve this you either create hand animation using humanoid character and add a layer with hand mask in the animation controller (VR Chat has done this)
or apply the rotation of each finger bones to and then apply some rotation offset again like this guy

https://forum.unity.com/threads/oculus-handtracking-with-custom-hand-model.810678/

I have tried both methods and the second method ended up giving me the better result

Here is the helper class I created for second method

public class HandSkeletonHelper : MonoBehaviour

    {

  

        [System.Serializable]

        public class Retargetable

        {

            public Transform source;

            public Transform destination;

            public Vector3 offset;

  

            public Retargetable(Transform source, Transform destination, Vector3 offset)

            {

                this.source = source;

                this.destination = destination;

                this.offset = offset;

            }

        }

  

        [System.Serializable]

        public class Finger

        {

            public Retargetable bone1;

            public Retargetable bone2;

            public Retargetable bone3;

            public Retargetable bone4;

  

            public Finger(Retargetable bone1, Retargetable bone2, Retargetable bone3, Retargetable bone4)

            {

                this.bone1 = bone1;

                this.bone1 = bone2;

                this.bone1 = bone3;

                this.bone4 = bone4;

            }

        }

  

        public Retargetable wrist;

        public Finger[] fingers;

  

        // Update is called once per frame

        void Update()

        {

            for (int fingerIndex = 0; fingerIndex < fingers.Length; fingerIndex++)

            {

                Finger finger = fingers[fingerIndex];

                //finger.bone1.destination.localRotation = finger.bone1.source.localRotation;

                finger.bone1.destination.rotation = finger.bone1.source.rotation;

                finger.bone1.destination.Rotate(finger.bone1.offset);

                //finger.bone2.destination.localRotation = finger.bone2.source.localRotation;

                finger.bone2.destination.rotation = finger.bone2.source.rotation;

                finger.bone2.destination.Rotate(finger.bone2.offset);

                //finger.bone3.destination.localRotation = finger.bone3.source.localRotation;

                finger.bone3.destination.rotation = finger.bone3.source.rotation;

                finger.bone3.destination.Rotate(finger.bone3.offset);

                //finger.bone4.destination.localRotation = finger.bone4.source.localRotation;

                finger.bone4.destination.rotation = finger.bone4.source.rotation;

                finger.bone4.destination.Rotate(finger.bone4.offset);

  

            }

  

            //wrist.destination.position = wrist.source.position;

            //wrist.destination.localRotation = wrist.source.localRotation;

        }

    }

The results look like this

using LocalRotation without offset

using LocalRotation with offset

using Rotation without offset

using Rotation with offset

Obviously using rotation with offset achieves what I want but is this really the best way to do it?
It feels quite hacky and if I were to use different character model, I would have to set the offset for each finger bone all over again.

If someone knows any better solutions to achieve this, please post it here.

 

@minsuthekoiwi Did you ever find a better solution? I'm looking todo something similar.

 

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