Lerp in Coroutine (Crazy Behavior)

Question

Hey my friends i have a problem that i strugle on it for days now , i make an obstacle that goes up and stay some time and return down and stay for some times also, i make it move with the Vector3.lerp function, and to make it stop i use the coroutine yield thing , all work great, but when the time goes and with some duplicante, the obstacles began to move in unsynchronized movements and move with crazy behavior , please help me, it blocks me from advancing in my project this is the code :

  IEnumerator Move()
 {
     //float timeToStart = Time.deltaTime;
     while (isAlive) {


         if (tail.transform.position == currentPoint.position)
         {


             pointSelection++;
             yield return new WaitForSeconds (waitTime);


             if (pointSelection == points.Length) {
                 pointSelection = 0;
                 waitTime = waitTimeDown;
                 yield return null;
             } else {

                 waitTime = waitTimeUp;
                 yield return null;

             }

             currentPoint = points[pointSelection];
             PlaySound (pointSelection);
         }

         tail.transform.position=Vector3.Lerp(tail.transform.position,currentPoint.position,speed );
     
         yield return null;
     }

 }

Answer 1

Hello there,

If you know how long you want the object to be travelling for, you could use something like this:

     //SerializeField means you can assign them in the inspector
     [SerializeField] private float f_moveDuration = 4.0f;
     [SerializeField] private float f_timeToStayUp = 2.0f;
     [SerializeField] private float f_timeToStayDown = 3.0f;
     [SerializeField] private Transform tr_upTarget = null;
     [SerializeField] private Transform tr_downTarget = null;
 
     private Coroutine moveCoroutine = null;
 
     private void Start()
     {
         StartMovingObject();
     }
 
     // Call to start perpetual movement
     public void StartMovingObject()
     {
         moveCoroutine = StartCoroutine(MoveObjectCoroutine());
     }
 
     // Call to stop movement
     public void StopMovingObject()
     {
         if (moveCoroutine != null)
             StopCoroutine(moveCoroutine);
     }
 
     private IEnumerator MoveObjectCoroutine()
     {
         //Assuming your object starts DOWN
         bool isDown = true;
         yield return new WaitForSeconds(f_timeToStayDown);
         while(true)
         {
             float timer = 0.0f;
             Vector3 startPosition = gameObject.transform.position;
             Vector3 targetPosition = isDown ? tr_upTarget.position : tr_downTarget.position;
 
             // Object Starts Moving here
             while (timer < f_moveDuration)
             {
                 timer += Time.deltaTime;
                 float t = timer / f_moveDuration;
 
                 //Smoothing
                 t = t * t * t * (t * (6f * t - 15f) + 10f);
                 gameObject.transform.position = Vector3.Lerp(startPosition, targetPosition, t);
                 yield return null;
             }
 
             //Object has reached destination here
             isDown = !isDown;
             yield return new WaitForSeconds(isDown ? f_timeToStayDown : f_timeToStayUp);
         }
 
         yield return null;
     }

Throw that script onto your object, assign its variables, and you're good to go. It'll go up, stay a while, go down, stay a while, and start again. You can control exactly how long the objects spend moving, waiting up, and waiting down with f_moveDuration, f_timeToStayUp, and f_timeToStayDown (in seconds).

I threw a smoothing algorithm in there, but if you don't like it you can pick any other from this page

I hope that helps!

Cheers,

~LegendBacon

Answer 2

Your problem is probably in speed

 tail.transform.position=Vector3.Lerp(tail.transform.position,currentPoint.position,speed );

Lerp as a function goes from point A to point B, by a value from 0 to 1.

In addition to speed, try at least to give it a smoothed DeltaTime conversion

 tail.transform.position=Vector3.Lerp(tail.transform.position,currentPoint.position, speed * Time.DeltaTime );

That will make the speed factor seem more natural. However the progress will not be linear.

If you wish for the movement to be linear, I would suggest remembering the starting Vector3 position at the beggining of the movement

 var startPos = tail.transform.position;
 float progress = 0f;

 while(whatever){
    tail.transform.position=Vector3.Lerp(startPos ,currentPoint.position, progress);
    progress = Mathf.clamp(progress + speed * Time.DeltaTime, 0f, 1f);
    yield return null;
 }

Lastly your condition

 if (tail.transform.position == currentPoint.position)

might never be sated, because a Lerp never reaches destination unless the coeffecient (third parameter) is 1 or greater. I would suggest testing destination reached based on distance delta.

 if( (tail.transform.position -currentPoint.position).magnitude < 0.05f )

Lerp in Coroutine (Crazy Behavior)

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