Lerp not working inside Coroutine.

Questions & Answers
1

Hello everyone, I’m trying to somehow understand what’s going on my code. It’s supposed to make a circle increase in size(localScale) after it’s created. It has a start and ending size, the lerp is inside a coroutine which starts only ONCE. If I debug the Vector3.Lerp it returns the same (0.7,0.7,0.7) every frame while the IEnumerator coroutine is working. Please if you can point out the error I’d be really glad. The circle gets to the ending size after the coroutine has finished, but there’s no transition visible

This snippet of code brings sets the parameters of the function EnlargeCircle

    Vector3 initialSize = new Vector3(0.0f,0.0f,0.0f);
    Vector3 endingSize = new Vector3(spread*2.0f,spread*2.0f,spread*2.0f);
    StartCoroutine(EnlargeCircle(initialSize,endingSize));

Here is the function.That starts only once.

    IEnumerator EnlargeCircle(Vector3 initialSize,Vector3 endingSize)
    	{
    		float t = 0;
    		while(t < 5)
    		{
    			t += Time.deltaTime;
    			circle.localScale = Vector3.Lerp (initialSize, endingSize,  Time.deltaTime);
    			yield return null;
    		}
    		circle.localScale = endingSize;
    	}
2

There are hundreds of questions and answers about how to use Lerp correctly, and it’s also explained in the manual: Unity - Scripting API: Vector3.Lerp, but here’s one more time…:

circle.localScale = Vector3.Lerp (initialSize, endingSize,  Time.deltaTime);

This line means:

“Set circle.localScale to be Time.deltaTime of the fraction between initialSize and endingSize.”

Time.deltaTime is the time it took to render the last frame - a value somewhere around 0.02 (if your game runs at 50FPS). So, on every frame of your coroutine, you’re just setting the localScale to an arbitrary fluctuating value. You need to increase the third parameter to Lerp from 0 to 1. The easiest way to do this is:

circle.localScale = Vector3.Lerp (initialSize, endingSize, t / 5.0f);