Problems with Color.Lerp in a Coroutine

It reaches the end of the coroutine but no color changes seem to occur at all now, not even a single frame switch to the ending color. The logic you laid out sounds like it should work so there must be something off with the color.lerp function... Perhaps something is off with the time?

Hi =).

Color.Lerp should work fine. You can confirm this (and confirm the coroutine is yielding) by using Debug.Log to print out the colour Color.Lerp returns each frame. You should find it changes.

My guess would be that something else is going on. What is SR.color and where is it defined? Does anything else change it? Are multiple objects calling and running your coroutines at the same time?

Could you post your full script so we can see if anything else is going on? =)

As a quick litmus test though, to confirm the above works properly try this:

• Create an empty scene and put a cube in it.

• Create a script called ColorLerp and attach it to the cube.

• Press play and then space, you should see the colour correctly change. (Let me know if you don't!)

The code to put in ColorLerp:

 using UnityEngine;
 using System.Collections;
 
 public class ColorLerp : MonoBehaviour
 {
     public Color StartColor = Color.green;
     public Color EndColor = Color.red;
     public float TransitionTime = 5f;
     
     private Material _myMaterial;
     // Just to make sure we don't try to lerp if we're already doing so
     private bool _transitioning = false;
     
     private void Awake()
     {
         _myMaterial = GetComponent<Renderer>().material;
     }
     
     private void Update()
     {
         if(Input.GetKeyDown(KeyCode.Space) && !_transitioning)
         {
             StartCoroutine(DoLerp());
         }
     }
     
     private IEnumerator DoLerp()
     {
         _transitioning = true;
         
         float timeElapsed = 0f;
         float totalTime = TransitionTime;
         
         Color startColor = StartColor;
         Color endColor = EndColor;
         
         while(timeElapsed < totalTime)
         {
             timeElapsed += Time.deltaTime;
             _myMaterial.color = Color.Lerp(startColor, endColor, timeElapsed/totalTime);
             yield return null;
         }
         
         _transitioning = false;
     }
 }

I haven't had the chance to quickly test that in Unity, so a couple of typos may have slipped through, just so you know!

The above test should be able to confirm that Color.Lerp with coroutines works okay. So you know the problem must be something else.

As I say, put up the rest of your code so we can take a look =).

One thought, just re-looking. Coroutines are run on MonoBehaviours, so will stop (be destroyed) if that MonoBehaviour is destroyed. Do you see "Ending Infestation!" show up in the console? If not, I think this might be the problem.

In OnCollision2D, you destroy a GameObject. Is that the same GameObject that the coroutine is running on? (i.e. this script?)

If so, then that's the problem. With your original version, the colour lerped to the end before the call to destroy, resulting in something that instantly jumped to the end colour. In the new version, the coroutine only gets to run one frame before it is destroyed along with the MonoBehaviour, resulting in code that would work but doesn't get a chance and so the starting colour stays.

Try making sure either the destruction happens after the coroutine is finished, or run the coroutine on an object that doesn't get destroyed (whichever object is changing colour would make the most sense). Let me know if you need help setting that up (I don't know what the rest of your code looks like).

I think that might be your problem anywho.

The red cell, that has this script, is the one that changes color and the virus that bumps it is destroyed and kicks off the infection process. I've put up the script with your advice added in, there is still no color change although all the debug.logs get printed just fine so the whole coroutine is gone through at least.

Hmm. That's odd. =S

Couldn't see anything else weird in your script.

Can you try replacing: Color.Lerp(Red, Green, (ElapsedTime/TotalTime))

with: Color.Lerp(Red, Green, 1f) just to confirm the SpriteRender goes green okay (should be instant again).

Let me know what happens.