Problems with Vector3.Lerp() and moving platforms

Unity Engine
1

Hi everybody,

I’m trying to create a moving platform (or elevator) that moves back and forth between two positions, which are stored in vectors. I want to use Vector3.Lerp() to move them so that everything is really smooth.

Here’s the code I have (C#):

using UnityEngine;
using System.Collections;

public class Elevator : MonoBehaviour 
{
    // Declare variables
    public Vector3 origin;
    public Vector3 destination;
    public float speed = 0f;

    // Update is called once per frame
    void Update () 
    {
        MoveElevator();
    }

    void MoveElevator()
    {
        Vector3 newPosition = destination;

        // When elevator meets end position, reverse direction
        if (origin.x >= destination.x  origin.y >= destination.y  origin.z >= destination.z)
        {
            newPosition = origin;
        }else if (destination.x <= origin.x  destination.y <= origin.y  destination.z <= origin.z)
        {
            newPosition = destination;
        }

        // Move platform
        transform.position = Vector3.Lerp(transform.position, newPosition, Time.deltaTime * speed);
    }
}

Now, the problem I’m having is that when the platform reaches its destination target, it slows to a crawl and won’t reach the full integer, and thus it won’t flip the values and reverse the destination!

For example, I have the origin vector set at X:-5, Y:1.5, Z:-0.5, and the destination vector set at X:5, Y:3.5, Z:0.5, but the platform will never reach the full integer; it will stop at something like X:4.99985, Y:3.49998, Z:0.4997. Is there anyway I can fix this, or a better way to use Vector3.Lerp() to get the desired results?

2

What you could do is

Use Vector3.MoveTowards or
Set the final position when the the current position is within a certain range

If you want to have to smoothness of lerp than choose the setting of the the final position cause movetowards gives you a linear movement.

3

MoveTowards at least makes it completely reach the final destination, but then it never actually flips the direction… Gonna try something real quick to see if that does something else…

EDIT: OK, it appears that my checks for if the platform reaches its destination are never performed?

EDIT 2: I just figured out what was wrong, and I fixed it! Here’s the updated code…

using UnityEngine;
using System.Collections;

public class Elevator : MonoBehaviour 
{
    // Declare variables
    public Vector3 origin;
    public Vector3 destination;
    public float speed;
    Vector3 newPosition;

    void Start()
    {
        newPosition = destination;
    }

    // Update is called once per frame
    void FixedUpdate () 
    {
         // When elevator meets end position, reverse direction
        if (transform.position.x >= destination.x  transform.position.y >= destination.y  transform.position.z >= destination.z)
        {
            newPosition = origin;
            Debug.Log("New Target Set At " + newPosition);
        }else if (transform.position.x <= origin.x  transform.position.y <= origin.y  transform.position.z <= origin.z)
        {
            newPosition = destination;
            Debug.Log("New Target Set At " + newPosition);
        }
        
        // Move platform
        transform.position = Vector3.MoveTowards(transform.position, newPosition, Time.deltaTime * speed);
    }
}

You see, instead of checking the current position against the target destination, I was checking the “origin” vector, which would NEVER change, hence the problem! Everything works perfectly now. :slight_smile:

4

Why dont you just do this

if (transform.position == destination)
newPosition = origin;

With the movetowards it will stop exactly at the destination so you dont have to worry that it overshoots or never reaches

5

Ah, I didn’t know that. Good to know! Nice to know I never have to do all those checks like that ever again! :slight_smile: