mathf.Lerp triggering instantly

Questions & Answers
1

I am trying to fade the alpha of 3d text over time. I tried color.lerp already, but it is having the exact same issue.

Here is my current code:

public Color fontColor;
public Color newColor;
public float fadeRate = 1;

// Use this for initialization
void Start () {

	fontColor = renderer.material.color;
	//newColor = new Color(fontColor.r, fontColor.g, fontColor.b, 0); 

}

// Update is called once per frame
void Update () {

	var alphaValue = Mathf.Lerp(fontColor.a, 0, fadeRate * Time.deltaTime);
	newColor = new Color(fontColor.r, fontColor.g, fontColor.b, alphaValue);
	renderer.material.color = newColor;
}

}

Any insights appreciated!

2

Your code says that alpha value will always equal fadeRate * deltaTime. It doesn’t matter how many time Update runs, because it’s always generating the same value (give or take the difference of the length of a frame).

You probably want to use a coroutine, or increase some value as a function of fadeRate * deltaTime. Ex:

var lerpValue : float = 0;

void Update()
{
    lerpValue += fadeRate * Time.deltaTime;
    if (lerpValue <= 1)
    {
        // do your lerp
    }
}

But that solution has obvious drawbacks. You can only cycle the lerp once, and without additional logic, only in one direction. That’s where a coroutine comes in.

#pragma strict

var lowerLimit : float = 1;
var upperLimit : float = 3;

function Start ()
{
    CycleRandomColors();
}

function CycleRandomColors()
{
    while (true)
    	yield ChangeColor(GetRandomColor(), Random.Range(lowerLimit, upperLimit));
}

function ChangeColor(targetValue : Color, duration : float)
{
    var startTime : float = Time.time;
    var endTime : float = startTime + duration;
    var initialValue : Color = renderer.material.color;
    var currentValue : Color = initialValue;
    var lerpValue : float = 0;
    
    Debug.Log(String.Format("Changing to {0} over {1} seconds.", targetValue, duration));
    while (endTime >= Time.time)
    {
        lerpValue += Time.deltaTime / duration;
        renderer.material.color = Color.Lerp(initialValue, targetValue, lerpValue);
        yield;
    }
}

function GetRandomColor() : Color
{
    return new Color(Random.value, Random.value, Random.value, Random.value);
}
3