itch.io

using UnityEngine.Rendering.PostProcessing;

is the namespace:

    public PostProcessVolume postProcessVolume;   
  private Vignette vignette;

is the volume

if (!postProcessVolume.profile.TryGetSettings(out vignette))

        {

            Debug.LogError("Vignette is not found in the Post-Process Volume!");

            this.enabled = false;

            return;

        }

gets the vignette settings

then vignette.intensity.value controls it