fade from outside of your screen to the center

Hallo,

I need somehelp with a script I'm making. I created a script that creates a screenfade to black if something happend.

The fade I've now goes from nothing to black over the entire screen. Like every normal fade will do.

But I want a fade like this : https://www.youtube.com/watch?v=IPmr7M3-6Zw (Don't worry its a youtube link ;] )

Question 1: Is this possible?

Question 2: Can I create this with my script or with shaders (if yess, how do I set this up)?

ScreenFade script:

 using UnityEngine;
 using System.Collections;
 
 public class ScreenFade : MonoBehaviour
 {
     public float fadeTime = 2.0f;
 
     public Color fadeColor = new Color(0.01f, 0.01f, 0.01f, 1.0f);
 
     public Shader fadeShader = null;
 
     private Material fadeMaterial = null;
     private bool isFading = false;
 
     void Awake()
     {
         // create the fade material
         fadeMaterial = (fadeShader != null) ? new Material(fadeShader) : new Material(Shader.Find("Transparent/Diffuse"));
     }
 
     void OnDestroy()
     {
         if (fadeMaterial != null)
         {
             Destroy(fadeMaterial);
         }
     }
 
 /*    IEnumerator FadeIn()
     {
         float elapsedTime = 0.0f;
         Color color = fadeMaterial.color = fadeColor;
         isFading = true;
         while (elapsedTime < fadeTime)
         {
             yield return new WaitForEndOfFrame();
             elapsedTime += Time.deltaTime;
             color.a = 1.0f - Mathf.Clamp01(elapsedTime / fadeTime);
             fadeMaterial.color = color;
         }
         isFading = false;
     }    */
 
 #if UNITY_ANDROID && !UNITY_EDITOR
     void OnCustomPostRender()
 #else
     void OnPostRender()
 #endif
     {
         if (isFading)
         {
             fadeMaterial.SetPass(0);
             GL.PushMatrix();
             GL.LoadOrtho();
             GL.Color(fadeMaterial.color);
             GL.Begin(GL.QUADS);
             GL.Vertex3(0f, 0f, -12f);
             GL.Vertex3(0f, 1f, -12f);
             GL.Vertex3(1f, 1f, -12f);
             GL.Vertex3(1f, 0f, -12f);
             GL.End();
             GL.PopMatrix();
         }
     }
     
     public void StartFadeOutAndLoadLevel(int level)
     {
         StartCoroutine(FadeOutAndLoadLevel(level));
     }
     
     IEnumerator FadeOutAndLoadLevel(int level)
     {
         float elapsedTime = 0.0f;
         Color color = fadeMaterial.color = new Color(0.01f, 0.01f, 0.01f, 0.0f);
         isFading = true;
         while (elapsedTime < fadeTime)
         {
             yield return new WaitForEndOfFrame();
             elapsedTime += Time.deltaTime;
             color.a = Mathf.Clamp01(elapsedTime / fadeTime);
             fadeMaterial.color = color;
         }
         Debug.Log("Fade Ended");
     }
 }

NOTE: Where the Debug is would normaly be a "application.loadlevel".

EDIT: I can create muliple area's where the fade happend with (GL.Vertex3).

Thank you for your replay.