Group Opacity Controller | Child Opacity Controller | 2D & 3D | C# | Unity Game Engine

GroupOpacityController.cs (using Update)

using UnityEngine;

[ExecuteAlways]
public class GroupOpacityController : MonoBehaviour
{
    [Range(0f, 1f)]
    public float opacity = 1f;  
    Renderer[] renderers;
    SpriteRenderer[] spriteRenderers;

    float _previousOpacity;

    void Start()
    {
        renderers = GetComponentsInChildren<Renderer>();
        spriteRenderers = GetComponentsInChildren<SpriteRenderer>();
        SetOpacity(opacity);
    }

    void Update()
    {
        if(opacity != _previousOpacity)
        {
            SetOpacity(opacity); 
            _previousOpacity = opacity;
        }
    }

    void SetOpacity(float opacity)
    {
        if (renderers != null)
        {
            foreach (Renderer renderer in renderers)
            {
                for (int i = 0; i < renderer.sharedMaterials.Length; i++)
                {
                    Color color= renderer.sharedMaterials[i].color;
                    color.a = opacity;
                    MaterialPropertyBlock matBlock = new MaterialPropertyBlock();
                    matBlock.SetColor("_Color", color);
                    renderer.SetPropertyBlock(matBlock, i);
                }
            }
        }

        if (spriteRenderers != null)
        {
            foreach (SpriteRenderer spriteRenderer in spriteRenderers)
            {
                Color color = spriteRenderer.color;
                color.a = opacity;
                spriteRenderer.color = color;
            }
        }
    }
}

GroupOpacityController.cs (using Property)

using UnityEngine;

[ExecuteAlways]
public class GroupOpacityController : MonoBehaviour
{
    [SerializeField, Range(0f, 1f)]
    float _opacity = 1f;
    public float Opacity
    {
        get { return _opacity; }
        set
        {
            _opacity = Mathf.Clamp01(value);
            SetOpacity(_opacity);
        }
    }    

    Renderer[] renderers;
    SpriteRenderer[] spriteRenderers;
	
#if UNITY_EDITOR
    void OnValidate()
    {
        SetOpacity(_opacity);
    }
#endif

    void Start()
    {
        renderers = GetComponentsInChildren<Renderer>();
        spriteRenderers = GetComponentsInChildren<SpriteRenderer>();
        SetOpacity(_opacity);
    }

    void SetOpacity(float opacity)
    {
        if (renderers != null)
        {
            foreach (Renderer renderer in renderers)
            {
                for (int i = 0; i < renderer.sharedMaterials.Length; i++)
                {
                    Color color= renderer.sharedMaterials[i].color;
                    color.a = opacity;
                    MaterialPropertyBlock matBlock = new MaterialPropertyBlock();
                    matBlock.SetColor("_Color", color);
                    renderer.SetPropertyBlock(matBlock, i);
                }
            }
        }

        if (spriteRenderers != null)
        {
            foreach (SpriteRenderer spriteRenderer in spriteRenderers)
            {
                Color color = spriteRenderer.color;
                color.a = opacity;
                spriteRenderer.color = color;
            }
        }
    }
}