Quaternion

Unity Engine
1

Hi every one.
I just loocking to optimize my code.
The give code use rotate camera around specfic target(Gameobject) so when target rotate about x or y axis but not z-axis the camera also rotate.
The code work very well but is there any way to optimize expression in line 21 so I don’t want to use Quaternion.Euler and target.eulerAngles I just want to use any other Quaternion operation and target.rotation to get to same result

using UnityEngine;
using System.Collections;
public class cam : MonoBehaviour
{
	public Transform target;
	public float s, sd;
	Transform t;
	Vector2 delta_ang = new Vector2 (0f, 0f);
	float d = 0;
	void Start ()
	{
		t = GetComponent<Transform> ();
	}
	void LateUpdate ()
	{
		if (Input.GetMouseButton (0))
			delta_ang.x += s * Input.GetAxis ("Mouse Y");
		if (Input.GetMouseButton (1))
			delta_ang.y -= s * Input.GetAxis ("Mouse X");
		d = Mathf.Clamp (d - sd * Input.GetAxis ("Mouse ScrollWheel"), 7f, 20f);
		Quaternion ang = Quaternion.Euler (target.eulerAngles.x + delta_ang.x, target.eulerAngles.y + delta_ang.y, 0);
		t.position = target.position + ang * Vector3.back * d;
		t.rotation = ang;
		
	}
}
2

Under the assumption that the z angle of the target is zero, you can use an alternative approach. First, create a quaternion for the delta_ang:

In order to combine the rotations, you can just multiply them. But keep in mind: It only works if the z angle of the target is zero!