Unity Animation Rigging IK 체인 구성 완전 가이드

개요

Unity Animation Rigging 패키지는 런타임 IK와 컨스트레인트를 구현합니다. 애니메이션 클립과 독립적으로 동작하여 표면 적응, 조준, 손 위치 보정 등을 실시간으로 처리할 수 있습니다.

설치: Package Manager → com.unity.animation.rigging

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1. 기본 설정

캐릭터 오브젝트 구조:
  Character
  ├── Rig 1 (Rig 컴포넌트 + RigBuilder 컴포넌트를 Character에 추가)
  │   ├── TwoBoneIK_RightHand
  │   ├── TwoBoneIK_LeftHand
  │   └── AimIK_Head
  └── Armature
      └── (스켈레톤 본)

RigBuilder 설정: Character 오브젝트에 Rig Builder 컴포넌트 추가 → Rigs 리스트에 Rig 오브젝트 추가

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2. Two Bone IK — 손/팔 IK

// 에디터 설정 후 런타임 제어
using UnityEngine;
using UnityEngine.Animations.Rigging;

public class HandIKController : MonoBehaviour
{
    [Header("IK 컨스트레인트")]
    [SerializeField] private TwoBoneIKConstraint rightHandIK;
    [SerializeField] private TwoBoneIKConstraint leftHandIK;

    [Header("무기 그립 위치")]
    [SerializeField] private Transform rightGrip;
    [SerializeField] private Transform leftGrip;

    private float _ikWeight = 0f;
    private bool _isHoldingWeapon = false;

    void Update()
    {
        // IK 무게 스무스 전환
        float targetWeight = _isHoldingWeapon ? 1f : 0f;
        _ikWeight = Mathf.MoveTowards(_ikWeight, targetWeight, Time.deltaTime * 5f);

        rightHandIK.weight = _ikWeight;
        leftHandIK.weight = _ikWeight;

        // 손 위치를 무기 그립으로 이동
        if (rightGrip != null)
            rightHandIK.data.target.position = rightGrip.position;
        if (leftGrip != null)
            leftHandIK.data.target.position = leftGrip.position;
    }

    public void PickUpWeapon(Transform weaponRightGrip, Transform weaponLeftGrip)
    {
        rightGrip = weaponRightGrip;
        leftGrip = weaponLeftGrip;
        _isHoldingWeapon = true;
    }
}

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3. AimConstraint — 조준 시스템

public class AimSystem : MonoBehaviour
{
    [SerializeField] private MultiAimConstraint spineAim;  // 척추 조준
    [SerializeField] private MultiAimConstraint headAim;   // 머리 조준
    [SerializeField] private Transform aimTarget;           // 조준점

    [SerializeField] private float aimSmoothSpeed = 10f;

    private Vector3 _targetPosition;
    private bool _isAiming;

    void Update()
    {
        if (_isAiming)
        {
            // 조준 무게 증가
            spineAim.weight = Mathf.Lerp(spineAim.weight, 1f, Time.deltaTime * aimSmoothSpeed);
            headAim.weight  = Mathf.Lerp(headAim.weight, 0.8f, Time.deltaTime * aimSmoothSpeed);

            // 조준점 이동
            aimTarget.position = Vector3.Lerp(
                aimTarget.position, _targetPosition, Time.deltaTime * aimSmoothSpeed);
        }
        else
        {
            spineAim.weight = Mathf.Lerp(spineAim.weight, 0f, Time.deltaTime * 5f);
            headAim.weight  = Mathf.Lerp(headAim.weight, 0f, Time.deltaTime * 5f);
        }
    }

    public void SetAimTarget(Vector3 worldPosition)
    {
        _targetPosition = worldPosition;
        _isAiming = true;
    }

    public void StopAiming() => _isAiming = false;
}

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4. 발 IK — 지형 적응

public class FootIKSystem : MonoBehaviour
{
    [SerializeField] private TwoBoneIKConstraint leftFootIK;
    [SerializeField] private TwoBoneIKConstraint rightFootIK;
    [SerializeField] private Transform leftFootTarget;
    [SerializeField] private Transform rightFootTarget;

    [SerializeField] private float footHeightOffset = 0.1f;
    [SerializeField] private LayerMask groundMask;

    void LateUpdate()
    {
        AdaptFootToGround(leftFootTarget, leftFootIK);
        AdaptFootToGround(rightFootTarget, rightFootIK);
    }

    void AdaptFootToGround(Transform footTarget, TwoBoneIKConstraint constraint)
    {
        Ray ray = new Ray(footTarget.position + Vector3.up * 0.5f, Vector3.down);

        if (Physics.Raycast(ray, out RaycastHit hit, 1.5f, groundMask))
        {
            // 발을 지면에 붙임
            Vector3 targetPos = hit.point + Vector3.up * footHeightOffset;
            footTarget.position = Vector3.Lerp(
                footTarget.position, targetPos, Time.deltaTime * 15f);

            // 법선 방향으로 발 회전
            Quaternion targetRot = Quaternion.FromToRotation(
                footTarget.up, hit.normal) * footTarget.rotation;
            footTarget.rotation = Quaternion.Lerp(
                footTarget.rotation, targetRot, Time.deltaTime * 15f);

            constraint.weight = 1f;
        }
        else
        {
            constraint.weight = Mathf.Lerp(constraint.weight, 0f, Time.deltaTime * 5f);
        }
    }
}

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5. OverrideTransform — 본 직접 제어

public class HeadLookAt : MonoBehaviour
{
    [SerializeField] private OverrideTransform headConstraint;
    [SerializeField] private Transform lookAtTarget;

    void Update()
    {
        // 머리가 바라볼 방향 계산
        Vector3 direction = lookAtTarget.position - headConstraint.transform.position;

        headConstraint.data.target.rotation = Quaternion.LookRotation(direction);
        headConstraint.weight = 0.7f;  // 70% 영향 (애니메이션 30% 유지)
    }
}

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6. 런타임 Rig 가중치 제어

public class RigController : MonoBehaviour
{
    [SerializeField] private Rig combatRig;
    [SerializeField] private Rig idleRig;

    private RigBuilder _rigBuilder;

    void Awake()
    {
        _rigBuilder = GetComponent<RigBuilder>();
    }

    public void SwitchToCombat()
    {
        combatRig.weight = 1f;
        idleRig.weight = 0f;
    }

    public void SwitchToIdle()
    {
        StartCoroutine(BlendRigs());
    }

    IEnumerator BlendRigs()
    {
        float t = 0f;
        while (t < 1f)
        {
            t += Time.deltaTime * 3f;
            combatRig.weight = 1f - t;
            idleRig.weight = t;
            yield return null;
        }
    }
}

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정리

컨스트레인트	용도
TwoBoneIKConstraint	팔/다리 2본 IK
ChainIKConstraint	꼬리/촉수 다본 IK
MultiAimConstraint	본이 타겟을 바라봄
OverrideTransform	본 위치/회전 직접 덮어쓰기
MultiParentConstraint	여러 부모의 영향 혼합

참고 자료

• Unity Docs — Animation Rigging