Lerp not working

[Batzuga]

I’m currently working on a menu. And I need to get it to slide.
But my Lerp is working just like normal transform.position and I don’t really
know why. Heres the code I’m using! Any ideas?

var player : Transform;

private var fp : Vector2;

private var lp : Vector2;

var startp = Vector3(0,0,-5);

var pos1 = Vector3(5,0,-5);

function Start()
{
}

function Update()
{

for (var touch : Touch in Input.touches)
{
      if (touch.phase == TouchPhase.Began)
      {
            fp = touch.position;
            lp = touch.position;
      }
      if (touch.phase == TouchPhase.Moved )
      {
            lp = touch.position;
      }
      if(touch.phase == TouchPhase.Ended)
	  { 
  
      if((fp.x - lp.x) > 0.5) // left swipe
      {
   			
   	       player.transform.position = Vector3.Lerp(startp, pos1, Time.deltaTime);
   				
      }
      else if((fp.x - lp.x) < -0.5) // right swipe
      {
           
   	       player.transform.position = Vector3.Lerp(pos1, startp, Time.deltaTime);
   				
      }
      
	 }

}

}

[rutter]

Oddly enough, I’m currently writing a blog post about this exact question. I’ll drop the first section, here, since it’s pretty much ready to go:

I see this sort of thing far too often:

transform.position = Vector3.Lerp(startPos, endPos, Time.deltaTime);

The person posting it is usually convinced that Vector3.Lerp is “broken”, but the real problem is that they’re not using it correctly.

Lerp, short for “linear interpolation” does one very simple thing: given two values, x and y, it returns a value that is t percent between them. If you expect the output to change, the arguments you pass in need to reflect that!

In the example above, it doesn’t make sense to just pass in Time.deltaTime, because that’s only the time that passed during the most recent frame. If your game is running at a constant 50fps, that’s always going to be 0.02.

We’ll get better results if we let that timer accumulate over multiple frames.

Something like this should get the point across:

public class LerpExample : MonoBehaviour {
    float lerpTime = 1f;
    float currentLerpTime;
    
    float moveDistance = 10f;
    
    Vector3 startPos;
    Vector3 endPos;
    
    protected void Start() {
        startPos = transform.position;
        endPos = transform.position + transform.up * moveDistance;
    }
    
    protected void Update() {
        //reset when we press spacebar
        if (Input.GetKeyDown(KeyCode.Space)) {
            currentLerpTime = 0f;
        }
        
        //increment timer once per frame
        currentLerpTime += Time.deltaTime;
        if (currentLerpTime > lerpTime) {
            currentLerpTime = lerpTime;
        }
        
        //lerp!
        float perc = currentLerpTime / lerpTime;
        transform.position = Vector3.Lerp(startPos, endPos, perc);
    }
}

You could create an empty scene, drop in a cube, attach this script, and see it in action.

Notice the result if you change lerpTime or moveDistance.

[Eco-Editor]

Hello @rutter
I also have a problem with Lerp, but I understood it differently.
In a line such as:

shopper.transform.forward = Vector3.Lerp(shopper.transform.forward, SceneIndex.instance.waypointTransforms[nextWayPoint].targetTransform.forward, 8f * Time.deltaTime

What will happen?
Thanks