Adjusting material properties in coroutine strange problem

Questions & Answers
1

Hi guys,

this is my first question here and I hope it’s not to noobish.

I try to adjust a material property to achieve a white flashing effect on a sprite.
It works fine if i do this:

private IEnumerator DoFlash()
    {
        thisRenderer.material.SetFloat("_FlashAmount", 1f);        
        Debug.Log("FlashOn");
        yield return new WaitForSeconds(0.2f);
        thisRenderer.material.SetFloat("_FlashAmount", 0f);        
        Debug.Log("FlashOff");                
    }

This does flash one time, so thats working fine. But if I want it to flash continuously like this:

private IEnumerator DoFlash()
    {
        thisRenderer.material.SetFloat("_FlashAmount", 1f);        
        Debug.Log("FlashOn");
        yield return new WaitForSeconds(0.2f);
        thisRenderer.material.SetFloat("_FlashAmount", 0f);        
        Debug.Log("FlashOff");
        StartCoroutine("DoFlash");         
    }

… the _FlashAmount gets set to 1 and then it seems to simply stop working. The strange thing is that the Debug Statements showing up fine in the console, just like it should.

I just cant wrap my head around this. So if anyone has an idea I would greatly appreciate it.

here’s the whole script:

[RequireComponent(typeof(Movement))]
[RequireComponent(typeof(Rigidbody2D))]

public class KnockBack : MonoBehaviour {

    private Rigidbody2D thisRigidbody;
    private SpriteRenderer thisRenderer; 
    private Movement movementscript;
    private SlowMotion slowMoScript;
	
    private Vector2 direction;
  					
	void Awake ()
	{
        thisRigidbody = GetComponent<Rigidbody2D>();
        movementscript = GetComponent<Movement>(); 		
        thisRenderer = GetComponentInChildren<SpriteRenderer>();   
        slowMoScript = Camera.main.GetComponent<SlowMotion>();
	}
       
    public void StartKnockback(Vector2 _direction) 
	{              		
        direction = _direction;
		StartCoroutine("DoKnockback");             
	}

    private IEnumerator DoKnockback()
    {
        StartCoroutine("DoFlash");
        gameObject.layer = LayerMask.NameToLayer("Invincible");

        movementscript.SetCanMove(false);
        thisRigidbody.AddForce(direction * 8f, ForceMode2D.Impulse);
        GameManager.instance.SetPlayerIsInKnockBack(true);
            
        yield return new WaitForSeconds(0.3f);
        movementscript.SetCanMove(true);

        yield return new WaitForSeconds(2f);
        gameObject.layer = LayerMask.NameToLayer("Player");
        GameManager.instance.SetPlayerIsInKnockBack(false);
        StopCoroutine("DoFlash");
    }

    private IEnumerator DoFlash()
    {
        thisRenderer.material.SetFloat("_FlashAmount", 1f);        
        Debug.Log("FlashOn");
        yield return new WaitForSeconds(0.2f);
        thisRenderer.material.SetFloat("_FlashAmount", 0f);        
        Debug.Log("FlashOff");
        StartCoroutine("DoFlash");         
    }   
                  
}
2

After you set flash amount to 0 you’re immediately starting the coroutine again, which immediately (maybe after one frame?) sets flash amount back to 1. You need to add a WaitForSeconds after setting the amount to 0 so it gets to spend some time at 0 before changing it back to 1.