Unity, Visual Effects Graph - how can I programatically play + stop an effect?

Question

I want to use the Visual Effect Graph to make a particle explosion. I am trying to activate and stop this explosion programmatically.

I first create a Particles prefab object, and attach a Visual Effect Graph object to it:

Then I make the spawn rate an exposed parameter. So when the explosion activates it will set this parameter to 100. To stop the explosion, the spawn rate will be set to 0:

Now this parameter is visible in the particle prefab:

Then I instantiate the Particles prefab:

var effect = Instantiate(particlesPrefab, position), Quaternion.identity);

The particle effect shows up on the screen, but the problem is I can't find the spawn rate attribute.

How can I programmatically change this attribute's value?

Answer 1

1. Get the VisualEffect from the Particles GameObject:

   // In a MonoBehaviour attached to the Particles GameObject
   
   using UnityEngine.Experimental.VFX;
   
   ...
   
   // As a field in the MonoBehaviour
   public VisualEffect myEffect;
   
   ... 
   
   myEffect = GetComponent<VisualEffect>();
   

2. Use SetInt to set the exposed integer called "spawn rate":

   // As class field
   
   public static readonly string SPAWN_RATE_NAME = "spawn rate";
   
   // Wherever you want to stop explosion
   
   myEffect.SetInt(SPAWN_RATE_NAME, 0);
   
   // Wherever you want to start explosion
   
   myEffect.SetInt(SPAWN_RATE_NAME, 100);