Hand IK Applier for Unity

HandIKApplier.cs

using System;
using UnityEngine;
using UnityEngine.Animations;
using UnityEngine.Playables;

public struct IKTarget
{
    public Vector3 pos;
    public Quaternion rot;
    public Vector3 hint;
}

public struct HandIKJob : IAnimationJob
{
    public IKTarget left;
    public IKTarget right;
    public PropertySceneHandle leftWeightHandle;
    public PropertySceneHandle rightWeightHandle;

    public void ProcessRootMotion(AnimationStream stream){}

    public void ProcessAnimation(AnimationStream stream)
    {
        AnimationHumanStream humanStream = stream.AsHuman();

        left.pos = humanStream.GetGoalPosition(AvatarIKGoal.LeftHand);
        left.rot = humanStream.GetGoalRotation(AvatarIKGoal.LeftHand);
        left.hint = humanStream.GetHintPosition(AvatarIKHint.LeftElbow);
        right.pos = humanStream.GetGoalPosition(AvatarIKGoal.RightHand);
        right.rot = humanStream.GetGoalRotation(AvatarIKGoal.RightHand);
        right.hint = humanStream.GetHintPosition(AvatarIKHint.RightElbow);

        float weightL = leftWeightHandle.GetFloat(stream);
        float weightR = rightWeightHandle.GetFloat(stream);

        if(weightL>0)
        {
            humanStream.SetGoalPosition(AvatarIKGoal.LeftHand, left.pos);
            humanStream.SetGoalRotation(AvatarIKGoal.LeftHand, left.rot);
            humanStream.SetHintPosition(AvatarIKHint.LeftElbow, left.hint);
            humanStream.SetGoalWeightPosition(AvatarIKGoal.LeftHand, weightL);
            humanStream.SetGoalWeightRotation(AvatarIKGoal.LeftHand, weightL);
            humanStream.SetHintWeightPosition(AvatarIKHint.LeftElbow, weightL);
        }
        if(weightR>0)
        {
            humanStream.SetGoalPosition(AvatarIKGoal.RightHand, right.pos);
            humanStream.SetGoalRotation(AvatarIKGoal.RightHand, right.rot);
            humanStream.SetHintPosition(AvatarIKHint.RightElbow, right.hint);
            humanStream.SetGoalWeightPosition(AvatarIKGoal.RightHand, weightR);
            humanStream.SetGoalWeightRotation(AvatarIKGoal.RightHand, weightR);
            humanStream.SetHintWeightPosition(AvatarIKHint.RightElbow, weightR);
        }
        if(weightL>0 || weightR>0) humanStream.SolveIK();
    }
}

public class HandIKApplier : MonoBehaviour
{
    public bool _drawGizmo = false;
    public PlayableDirector _director;
    [Range(0,1)]
    public float _leftWeight;
    [Range(0,1)]
    public float _rightWeight;

    Animator _animator;
    AnimationScriptPlayable _playable;
    IKTarget _left;
    IKTarget _right;

    void OnEnable()
    {
        for(Transform current = this.transform; _animator==null && current!=null; current = current.parent)
            _animator = current.GetComponent<Animator>();
        if(_animator==null) throw new System.Exception("Animator has not in the parent");

        if(_director && _director.playableGraph.IsValid()) CreateJob(_director.playableGraph);
    }

    void OnDisable()
    {
        if (_playable.IsValid()) _playable.Destroy();
    }

    void CreateJob(PlayableGraph graph) // PlayableDirector's graph
    {
        for(int i=0; i<graph.GetOutputCountByType<AnimationPlayableOutput>(); i++)
        {
            AnimationPlayableOutput output = (AnimationPlayableOutput) graph.GetOutputByType<AnimationPlayableOutput>(i);
            if(output.GetTarget() == _animator && output.IsOutputValid())
            {
                var job = new HandIKJob()
                {
                    leftWeightHandle = _animator.BindSceneProperty(transform, typeof(HandIKApplier), "_leftWeight"),
                    rightWeightHandle = _animator.BindSceneProperty(transform, typeof(HandIKApplier), "_rightWeight")
                };

                _playable = AnimationScriptPlayable.Create(graph, job, 1);
                _playable.SetInputWeight(0, 1);

                var timeline = output.GetSourcePlayable();
                var source = timeline.GetInput(i);
                graph.Disconnect(timeline, i);
                graph.Connect(source, 0, _playable, 0);
                graph.Connect(_playable, 0, timeline, i);
                break;
            }
        }
        //Debug.Log("CreateJob : " + _animator + " // " + _playable);
    }

    void OnAnimatorIK()// Animation Controller events
    {
        _animator.SetIKPositionWeight(AvatarIKGoal.LeftHand, _leftWeight);
        _animator.SetIKRotationWeight(AvatarIKGoal.LeftHand, _leftWeight);
        _animator.SetIKHintPositionWeight(AvatarIKHint.LeftElbow, _leftWeight);
        _animator.SetIKPositionWeight(AvatarIKGoal.RightHand, _rightWeight);
        _animator.SetIKRotationWeight(AvatarIKGoal.RightHand, _rightWeight);
        _animator.SetIKHintPositionWeight(AvatarIKHint.RightElbow, _rightWeight);
    }

    void Update()
    {
        if(_director && _director.playableGraph.IsValid() && !_playable.IsValid()) CreateJob(_director.playableGraph);
    }

    void LateUpdate()
    {
        if (_playable.IsValid())
        {
            var job = _playable.GetJobData<HandIKJob>();
            _left = job.left;
            _right = job.right;
        }
    }

#if UNITY_EDITOR
    void OnDrawGizmosSelected()
    {
        if (_drawGizmo && _playable.IsValid())
        {
            Vector3 scale = new Vector3(1,1,1);
            Gizmos.color = Color.magenta;
            Gizmos.matrix = Matrix4x4.TRS(_left.pos, _left.rot, scale);
            Gizmos.DrawWireSphere(Vector3.zero, 0.05f);
            Gizmos.matrix = Matrix4x4.TRS(_right.pos, _right.rot, scale);
            Gizmos.DrawWireSphere(Vector3.zero, 0.05f);
            Gizmos.matrix = Matrix4x4.identity;
            Gizmos.DrawWireSphere(_left.hint, 0.05f);
            Gizmos.DrawWireSphere(_right.hint, 0.05f);
        }
    }
#endif
}

see http://ossan-engineer.blogspot.com/2022/07/handikappier-for-unity.html