Generate 4 vectors rotated in cardinal directions from a central vector

Question

There is some unit vector, which is a coordinate in a spherical space. It is necessary to obtain from it 4 vectors diverted in different directions (right, left, forward, backward) by a certain number of degrees. For these actions I use the following code:

Vector3 center = point;
Vector3 left = Quaternion.Euler(-30, 0, 0) * center;
Vector3 right = Quaternion.Euler(30, 0, 0) * center;
Vector3 back = Quaternion.Euler(0, 0, -30) * center;
Vector3 front = Quaternion.Euler(0, 0, 30) * center;

The problem is that this works when point is equal or close to Vector3.up. When deviating from the vertical position, the lateral vectors begin to "stick together".

Here is a visualization of what I need:

Test code is attached:

using System.Collections;
using UnityEngine;

public class Test : MonoBehaviour
{
    public GameObject centerGO;
    public GameObject leftGO;
    public GameObject rightGO;
    public GameObject backGO;
    public GameObject frontGO;

    ArrayList list = new ArrayList();

    void Start()
    {
        SetCenterPoint(Vector3.up);
    }

    void Update()
    {
        DrawDebugRays();

        Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
        RaycastHit hit;

        if (Physics.Raycast(ray, out hit))
        {
            SetCenterPoint(hit.point);
        }
    }

    void SetCenterPoint(Vector3 point)
    {
        Vector3 center = point;
        Vector3 left = Quaternion.Euler(-30, 0, 0) * center;
        Vector3 right = Quaternion.Euler(30, 0, 0) * center;
        Vector3 back = Quaternion.Euler(0, 0, -30) * center;
        Vector3 front = Quaternion.Euler(0, 0, 30) * center;

        centerGO.transform.position = center;
        leftGO.transform.position = left;
        rightGO.transform.position = right;
        backGO.transform.position = back;
        frontGO.transform.position = front;

        list.Clear();
        list.Add(center);
        list.Add(left);
        list.Add(right);
        list.Add(front);
        list.Add(back);
    }

    void DrawDebugRays()
    {
        for (int i = 0; i < list.Count; i++)
        {
            Color color = Color.red;
            switch (i)
            {
                case 0:
                    color = Color.green;
                    break;
                case 1:
                case 2:
                    color = Color.blue;
                    break;
            }
            Debug.DrawRay(Vector3.zero, (Vector3)list[i], color);
        }
    }
}

Answer 1

Pick a local coordinate system that puts your center direction along the local z+ axis, then rotate the other 4 relative to those coordinates:

Quaternion localSpace = Quaternion.LookRotation(centerDirection);

Vector3 backDirection = localSpace * Quaternion.Euler(-30, 0, 0) * Vector3.forward;
Vector3 frontDirection = localSpace * Quaternion.Euler(30, 0, 0) * Vector3.forward;
Vector3 rightDirection = localSpace * Quaternion.Euler(0, -30, 0) * Vector3.forward;
Vector3 leftDirection = localSpace * Quaternion.Euler(0, 30, 0) * Vector3.forward;