unity lerp scale doesn't work - unity3d

Question

I am trying to make an object scale from zero to it's normal size when I instantiate it, so it will look like it popped to the screen.
So when the object start I get it's normal size then update it to zero, and then in update I am scaling it.
This is my code:
void Start()
{
normalScale = transform.localScale;
transform.localScale *= 0.1f;
}
void Update()
{
transform.localScale = Vector3.Lerp(transform.localScale * 0.1f, transform.localScale, 5f * Time.deltaTime);
// destroy item
if (transform.localScale == normalScale)
{
transform.localScale = transform.localScale * 0.1f;
}
}
Thank you.

Answer 1

With this you're always changing from it's current scale, which of course you changed last update
transform.localScale = Vector3.Lerp(transform.localScale * 0.1f, transform.localScale, 5f * Time.deltaTime);
What you need to do is create two Vector3 outside of the update function, one for the start size, one for the final size
Vector3 start = Vector3.zero;
Vector3 end = new Vector3(1,1,1);
You'll also need a timer:
float lerpTime = 0;
Altogether you get
transform.localScale = Vector3.Lerp(start, end, lerpTime);
lerpTime += Time.deltaTime // times whatever multiplier you want for the speed

Answer 2

There are a couple of issues with your code that are likely to be causing problems. The first is the start/end values you're passing in to the lerp:
Vector3.Lerp(transform.localScale * 0.1f, transform.localScale, 5f * Time.deltaTime);
On your second frame, .localScale is roughly (0.1, 0.1, 0.1). The max value of the lerp on your second frame is the value from your first frame. That means that your current code is endlessly shrinking the target - the opposite of what you wanted.
The other problem is the way you're handling the time. You're passing 5f * Time.deltaTime, which is (probably) always going to be less than 1. This means you will never reach the maximum value.
So, to fix these, you need two things: first, you need to make sure your min/max values are actually min/max values, not arbitrary values in between. Second, you need to make sure your third parameter progresses smoothly from 0 to 1 over a defined time.
Something like this:
public float ScaleTime = 5f; // the time it'll take to grow, settable in the inspector
public float ScaleTime = 5f; // the time it'll take to grow, settable in the inspector
Vector3 _targetScale;
Vector3 _startScale;
float _currentLerp = 0f;
void Start()
{
_targetScale = this.localScale;
_startScale = _targetScale * 0.1f;
}
void Update()
{
_currentLerp += Time.deltaTime * ScaleTime;
if (_currentLerp < 1)
{
transform.localScale = Vector3.Lerp(_startScale, _targetScale, _currentLerp);
}
else
{
transform.localScale = _targetScale; // make sure we definitely hit the target size
... do whatever else you need to do here...
}
}

Answer 3

As per https://docs.unity3d.com/ScriptReference/Vector3.Lerp.html your 3rd parameter in
transform.localScale = Vector3.Lerp(transform.localScale * 0.1f, transform.localScale, 5f * Time.deltaTime);
is supposed to indicate the "fracJourney", in other words it should change from 0f to 1f to indicate the progress of your animation, but Time.deltaTime will give you the time since the last frame so that you probably see it jump around 0.005 (or whatever your frame rate is).
You need to add another variable to indicate the progress of your animation:
public float speed = 1.0F;
private float startTime;
void Start() {
startTime = Time.time;
normalScale = transform.localScale;
}
void Update()
{
float distCovered = (Time.time - startTime) * speed;
transform.localScale = Vector3.Lerp(Vector3.zero, normalScale, distCovered);
// destroy item
if (transform.localScale >= normalScale)
{
startTime = Time.time; // Reset the animation
}
}