How to make distance meter in unity3d

Question

I am trying to make a distance meter. But I am not getting what I wanted. so I uploaded a picture. I want curved distance but I am getting straight something like displacement.

Here is my Code:

using UnityEngine;
using System.Collections;
using UnityEngine.UI;

public class DistanceMeter : MonoBehaviour {

    public GameObject current;
    public GameObject destination;
    private float beginPos;
    private float targetPos;
    private float currPos;
    public Text dist;

    void Start()
    {
        beginPos = current.transform.position.x;
        targetPos = destination.transform.position.x;
    }

    void Update()
    {
        currPos = current.transform.position.x - targetPos;
        int Distance = Mathf.Abs(Mathf.RoundToInt (currPos));
        dist.text = Distance.ToString()+ " meters";
    }
}

Answer 1

You can accumulate the traveled distance to find out the traveled distance on the curve:

public class DistanceMeter : MonoBehaviour
{
    public GameObject current;
    public GameObject destination;
    private float beginPos;
    private float targetPos;
    private float currPos;
    private float displacement;
    public Text dist;

    void Start()
    {
        beginPos = current.transform.position.x;
        targetPos = destination.transform.position.x;
    }

    void Update()
    {
        float currDelta = current.transform.position.x - currPos;
        currPos = current.transform.position.x;
        displacement += Mathf.Abs(currDelta);
        dist.text = displacement.ToString() + " meters";
    }
}

But in order to find out the remaining distance (or displacement which has not traveled yet) you need to at least know the radius of the curve:

I assumed that the curve is part of a circle

If the curve is half of a circle, the displacement is radius × pi

Else if the angel is known, the displacement is radius × angel (in radians)

if angel is unknown but radius and distance is known, the displacement is 2 × radius × arcsin(distance/2 × radius)