IKControl.cs

using UnityEngine;

[RequireComponent(typeof(Animator))]

public class IKControl : MonoBehaviour {

    protected Animator animator;

    public bool ikActive = false;
    public Transform leftHandObj = null;
    public Transform rightHandObj = null;
    public Transform headObj = null;
    public Transform hipsObj = null;

    void Start() {
        animator = GetComponent<Animator>();
    }

    private void LateUpdate() {
        if (headObj != null) {
            Transform head = animator.GetBoneTransform(HumanBodyBones.Head);
            head.rotation = headObj.rotation;
            //head.position = headObj.position;
        }
        if (hipsObj != null) {
            Transform hips = animator.GetBoneTransform(HumanBodyBones.Hips);
            //hips.rotation = hipsObj.rotation;
            Vector3 oldPosition = gameObject.transform.position;
            gameObject.transform.position = new Vector3(hipsObj.position.x, oldPosition.y, hipsObj.position.z);
            Quaternion oldRotation = gameObject.transform.rotation;
            gameObject.transform.rotation = Quaternion.Euler(oldRotation.eulerAngles.x, hipsObj.rotation.eulerAngles.y, oldRotation.eulerAngles.z);

            // offset to avoid showing mouth parts in view
            gameObject.transform.position += gameObject.transform.forward * -0.1f;
        }
    }

    //a callback for calculating IK
    void OnAnimatorIK() {
        if (animator) {

            //if the IK is active, set the position and rotation directly to the goal. 
            if (ikActive) {
                if (leftHandObj != null) {
                    animator.SetIKPositionWeight(AvatarIKGoal.LeftHand, 1);
                    animator.SetIKRotationWeight(AvatarIKGoal.LeftHand, 1);
                    animator.SetIKPosition(AvatarIKGoal.LeftHand, leftHandObj.position);
                    animator.SetIKRotation(AvatarIKGoal.LeftHand, leftHandObj.rotation);
                }

                // Set the right hand target position and rotation, if one has been assigned
                if (rightHandObj != null) {
                    animator.SetIKPositionWeight(AvatarIKGoal.RightHand, 1);
                    animator.SetIKRotationWeight(AvatarIKGoal.RightHand, 1);
                    animator.SetIKPosition(AvatarIKGoal.RightHand, rightHandObj.position);
                    animator.SetIKRotation(AvatarIKGoal.RightHand, rightHandObj.rotation);
                }
            }

            //if the IK is not active, set the position and rotation of the hand and head back to the original position
            else {
                animator.SetIKPositionWeight(AvatarIKGoal.LeftHand, 0);
                animator.SetIKRotationWeight(AvatarIKGoal.LeftHand, 0);
                animator.SetIKPositionWeight(AvatarIKGoal.RightHand, 0);
                animator.SetIKRotationWeight(AvatarIKGoal.RightHand, 0);
            }
        }
    }
}