思路都是：

每一幀以兩指坐標生成一個向量Vector2，不同幀比較向量的角度變化Vector2.Angle()。

簡化版：參考EasyTouch的實現

public class TouchTest : MonoBehaviour{	Touch oldTouch1;  //上次觸摸點1(手指1)	Touch oldTouch2;  //上次觸摸點2(手指2)	void Update()	{		if (Input.touchCount <= 1) {			return;		}		Touch touch1 = Input.GetTouch(0);		Touch touch2 = Input.GetTouch(1);		//啟用雙指，尚未旋轉		if (touch2.phase == TouchPhase.Began) {			oldTouch2 = touch2;			oldTouch1 = touch1;			return;		}		if (touch1.phase == TouchPhase.Moved || touch2.phase == TouchPhase.Moved) {			Vector2 curVec = touch2.position - touch1.position;			Vector2 oldVec = oldTouch2.position - oldTouch1.position;			float angle = Vector2.Angle(oldVec, curVec);			angle *= Mathf.Sign(Vector3.Cross(oldVec, curVec).z);			transform.Rotate(new Vector3(0, 0, angle));			oldTouch1 = touch1;			oldTouch2 = touch2;		}	}}
另一種寫法，參考的博客已失效，這里貼一下
const float pinchTurnRatio = Mathf.PI / 2;	//用這個數值來判定旋轉的最小角度，自己決定大小	const float minTurnAngle = 0;	/// <summary>	///   The delta of the angle between two touch points	/// </summary>	static public float turnAngleDelta;	/// <summary>	///   The angle between two touch points	/// </summary>	static public float turnAngle;	/// <summary>	///   Calculates Pinch and Turn - This should be used inside LateUpdate	/// </summary>	static public void Calculate()	{		//pinchDistance = pinchDistanceDelta = 0;		turnAngle = turnAngleDelta = 0;		// if two fingers are touching the screen at the same time ...		if (Input.touchCount == 2) {			Touch touch1 = Input.touches[0];			Touch touch2 = Input.touches[1];			// ... if at least one of them moved ...如果有一根手指有移動			if (touch1.phase == TouchPhase.Moved || touch2.phase == TouchPhase.Moved) {				// ... or check the delta angle between them ...				//當前兩手指與X軸的角				turnAngle = Angle(touch1.position, touch2.position);				//之前兩手指與X的角度				float PRevTurn = Angle(touch1.position - touch1.deltaPosition,									   touch2.position - touch2.deltaPosition);				//旋轉的偏移量， 增量角				turnAngleDelta = Mathf.DeltaAngle(prevTurn, turnAngle);				// ... if it's greater than a minimum threshold, it's a turn!				//增量角如果大于設定值				if (Mathf.Abs(turnAngleDelta) > minTurnAngle) {					turnAngleDelta *= pinchTurnRatio;				} else {					turnAngle = turnAngleDelta = 0;				}			}		}		//鼠標判斷事件，這個只是個測試#if UNITY_EDITOR		MouseRotateEvent();#endif	}	/// <summary>	/// 取兩個向量之間的角度 與X軸	/// </summary>	/// <param name="pos1"></param>	/// <param name="pos2"></param>	/// <returns></returns>	static private float Angle(Vector2 pos1, Vector2 pos2)	{		//取兩個向量相減		Vector2 from = pos2 - pos1;		//X軸		Vector2 to = new Vector2(1, 0);		//與X軸夾角		float result = Vector2.Angle(from, to);		//向量的叉乘		Vector3 cross = Vector3.Cross(from, to);		//如果超出360度		if (cross.z > 0) {			//用360來減這個角度			result = 360f - result;		}		return result;	}#if UNITY_EDITOR	static bool isPress = false;	static float preAngle = 0;	/// <summary>	/// 鼠標右鍵旋轉事件，并非完美實現，因為沒有判斷角度為正還是為負。	/// </summary>	static public void MouseRotateEvent()	{		if (Input.GetMouseButton(1)) {			//第一次按下			if (!isPress) {				//上一幀的角度				preAngle = Angle(Input.mousePosition, Vector2.zero);				isPress = true;			} else {				//轉動的角度				turnAngle = Angle(Input.mousePosition, Vector2.zero);				//旋轉的偏移量， 增量角				turnAngleDelta = Mathf.DeltaAngle(preAngle, turnAngle);				Log.log("增量角："+turnAngleDelta);				//增量角如果大于設定值				if (Mathf.Abs(turnAngleDelta) > minTurnAngle) {					turnAngleDelta *= pinchTurnRatio;				} else {					turnAngle = turnAngleDelta = 0;				}				//更新為這一幀				preAngle = Angle(Input.mousePosition, Vector2.zero);			}		} else {			isPress = false;		}	}#endif	/// <summary>	/// 繞點旋轉，或者是Z軸旋轉？	/// </summary>	public bool isRotateAround = false;	//目標	public Transform target;	//圍繞點	protected Vector3 axis {		get {			return new Vector3(target.position.x, transform.position.y, target.position.z);		}	}	//void Start()	//{	//	if (target == null) {	//		Debug.Log("target is null!");	//		enabled = false;	//	}	//}	void Update()	{		Calculate();		if (Mathf.Abs(turnAngleDelta) > 0) {			if (isRotateAround) {				//圍點旋轉				transform.RotateAround(axis, Vector3.up, -turnAngleDelta);				//目視對方				transform.LookAt(target);			} else {				Quaternion desiredRotation = transform.rotation;				Vector3 rotationDeg = Vector3.zero;				//z軸旋轉				rotationDeg.z = -turnAngleDelta;				desiredRotation *= Quaternion.Euler(rotationDeg);				transform.rotation = desiredRotation;			}		}	}