How to start the lerp over again automatic each time the value reached to the end/start?

Question

using System.Collections;
using System.Collections.Generic;
using TMPro;
using UnityEngine;
using UnityEngine.UI;

public class DistanceCheck : MonoBehaviour
{
    float lerpDuration = 3;
    public GameObject descriptionTextImage;
    public TextMeshProUGUI text;

    private Animator anim;
    private bool slowDownOnExit = false;

    private float timeElapsed = 0;
    private float startValue = 1;
    private float endValue = 0;
    private float valueToLerp = 0;

    // Start is called before the first frame update
    void Start()
    {
        anim = transform.GetComponent<Animator>();
    }

    // Update is called once per frame
    void Update()
    {
        if (slowDownOnExit)
        {
            if (timeElapsed < lerpDuration)
            {
                valueToLerp = Mathf.Lerp(startValue, endValue, timeElapsed / lerpDuration);
                anim.SetFloat("Forward", valueToLerp);
                timeElapsed += Time.deltaTime;
            }
            anim.SetFloat("Forward", valueToLerp);
            descriptionTextImage.SetActive(true);
            text.text = "I can't move that far by foot. I need to find some transportation to move any further.";
        }
        else
        {
            text.text = "";
            descriptionTextImage.SetActive(false);
        }
    }

    private void OnTriggerExit(Collider other)
    {
        if(other.name == "CrashLandedShipUpDown")
        {
            slowDownOnExit = true;
        }
    }
}

Now the startValue is 1 and the endValue is 0 i want that when the lerp is finish and decreasing slowing down the speed by changing the float value to 0 that it will start increasing the float back to 1 then when reaching to 1 to slow down again and so on nonstop.

also how can i display the text when the endValue is at 0 no the text show once it's start slow down and i want to display the text when it's reaching to 0 stopped.

Answer 1

You could add one more varible currentValue and lerp that like following

private float startValue = 1;
private float endValue = 0;
private float targetValue;
private float currentValue;

private void Awake() {
    targetValue = startValue;
}

private void Update() {
    currentValue = Mathf.Lerp(currentValue, targetValue, lerpTime);

    if (currentValue == startValue) {
        targetValue = endValue;
    }

    if (currentValue == endValue) {
        targetValue = startValue;
    }
}

Here we check for currentValue and update the target accordingly so it will continue to ping pong from 0 to 1