Why moving platform script is not working?

Question

I have some code attached to a moving platform:

public Transform pos1, pos2;
public float speed;
public Transform startPos;

Vector3 nextPos;
// Start is called before the first frame update
void Start()
{
    nextPos = startPos.position;
}

// Update is called once per frame
void Update()
{
    if (transform.position == pos1.position)
    {
        nextPos = pos2.position;
    }
    else if (transform.position == pos2.position)
    {
        nextPos = pos1.position;
    }
    transform.position = Vector3.MoveTowards(transform.position, nextPos, speed * Time.deltaTime);
}

private void OnDrawGizmos()
{
    Gizmos.DrawLine(pos1.position, pos2.position);
}

But my platform does not go to the pos2 when it reaches the pos1. What is wrong here?

When do you tell your platform to move toward pos1? All I see is it moving toward startPos. If startPos does not coincide with pos1, then your platdorm never moves to the position that the first if condition is checking for — DMGregory
– DMGregory ♦, Commented Oct 25, 2019 at 13:27

crueltear · Accepted Answer · 2019-10-23 08:18:41Z

1

I'm not sure how "MoveTowards" method works, but if you're working on floats then most likely you'll never have exact match of positions.

When doing path followers, I always check the distance between current position and target (pseudocode):

if (VectorLength(transform.position-pos1.position) < speed*Time.deltaTime)
{
    nextPos = pos2.position;
}

answered Oct 23, 2019 at 8:18

crueltear

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1

\$\begingroup\$ Unity already takes floating point precision into account when comparing vectors, and also does what your code snippet does in MoveTowards. \$\endgroup\$

Ed Marty
– Ed Marty

2019-10-23 13:48:06 +00:00
Commented Oct 23, 2019 at 13:48

Add a comment |

FSic · Accepted Answer · 2019-10-23 08:31:59Z

I agree with @crueltear's answer, I just wanted to provide some code that you might add in your script:

Since it is likely that the transform.position pos1.position will not perfectly match, try and add a bit of "discrepancy" so that instead of waiting for the positions to match perfectly you just have to wait for them to be within a certain distance.

Try and introduce a float, e.g. public float gapDistance and replace in your if statements

(transform.position == pos1.position)

With

(Vector3.Distance(transform.position , pos1.position) <= gapDistance)

Do the same for pos2.position. If you are using 2D Vectors instead of 3D, just change Vector3 with Vector2

Ed Marty · Accepted Answer · 2019-10-23 13:54:03Z

I would recommend adding a few debug logs in update to see what it’s doing.

// Update is called once per frame
void Update()
{
    if (transform.position == pos1.position)
    {
        nextPos = pos2.position;
        Debug.Log("Starting move to pos2 at " +  nextPos);
    }
    else if (transform.position == pos2.position)
    {
        nextPos = pos1.position;
        Debug.Log("Starting move to pos1 at " +  nextPos);
    }
    transform.position = Vector3.MoveTowards(transform.position, nextPos, speed * Time.deltaTime);
    Debug.Log("move towards " + nextPos + "; new position is " + transform.position);
}

Check the console to see what is getting logged.

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