Unity - coroutines got inaccurate with timing, want to get around

Question

I wish to move an object over time using coroutines. I wanted to get an object from point A to point B over say 2 seconds. To achieve this I used the following code:

IEnumerator _MoveObjectBySpeed()
{
    while (TheCoroutine_CanRun)
    {
        if(myObject.transform.position.y <= UpperBoundary.position.y)
        {
            myObject.transform.position = new Vector3(myObject.transform.position.x,
                myObject.transform.position.y + Step, myObject.transform.position.z);

        }
        yield return new WaitForSeconds(_smoothness);
    }
    TheCoroutine_CanRun = true;
    moveAlreadyStarted = false;
}

and the Step is calculated like

    private void CalculateSpeed()
{
    Step = _smoothness * allDistance / timeToReachTop;
}

where allDistance is the distance between the bottom and the top boundary.

_smoothness is a fix value. The thing is, the bigger I get this value, the more accurate the time gets to get from bottom to up. Note that a small value here means smoother movement. This smoothness is the time the coroutine waits in between moving the myObject. The time is measured like this:

    void FixedUpdate()
{
    DEBUG_TIMER();
}

#region DEBUG TIME

public float timer = 0.0f;
bool allowed = false;
public void DEBUG_TIMER()
{

    if (Input.GetButtonDown("Jump"))
    {
        StartTimer();
    }
    if (myObject.transform.position.y >= UpperBoundary.position.y)
    {
        StopTimer();
        Debug.Log(timer.ToString());
        //timer = 0.0f;
    }
    if (allowed)
    {
        timer += Time.fixedDeltaTime;
    }
}
void StartTimer()
{
    timer = 0;
    allowed = true;
}
void StopTimer()
{
    allowed = false;
}
#endregion

The results were:

When I wanted the object to reach the top under 1 second and set the _smoothness to 0.01, the time the myObject took to get to the top was 1.67 seconds. When _smoothness was 0.2s, the time to actually reach the top was 1.04s.

So why is this so inaccurate and how to make it work fine?

Check the `MoveObject` function in the answer from the duplicated question. Oh and `Time.deltaTime` should be used not `Time.fixedDeltaTime;` or `WaitForSeconds`. — Programmer, Jan 27 '17 at 20:04

score 1 · Accepted Answer · answered Jan 27 '17 at 20:00

This smoothness is the time the coroutine waits in between moving the myObject

The mistake you're making is assuming that a co-routine waits the perfect time before executing. Rather, it probably executes on the next frame after the timeout has finished.

Assuming you want smooth motion, you want to move the object every frame (e.g. in Update or co-routine that uses 'yield return null').

Note: Each frame may take a different duration (consider 144fps vs 15fps), and you can discover this in Time.deltaTime . https://docs.unity3d.com/520/Documentation/ScriptReference/Time-deltaTime.html

Unity - coroutines got inaccurate with timing, want to get around

1 Answers1