Moving a platform from one point to another indefinitely HELP please

Hi, can anybody help me? I've searched in 2D, in Scripting and even in the Answers and I don't figure out how to move an object up and down indefinitely.

I have this code

float dist = (Time.time)*speed;
float fraccion = dist / length;
transform.position = Vector3.Lerp (inicio, fin, fraccion);

The movement goes smoothly from the upper point(inicio) to the lower one(fin), but I don't know how to invert it.

I understood that "fraccion" must be a value between 0 and 1, 0 is for "inicio" and 1 is for "fin", the problem here is that "dist" is obtained multiplying by time and the time goes ahead, after it reaches 1 it keeps on. Here I need to alternate "fraccion" between 0 and 1 indefinitely.

I tried with "for" but the problem with the instruccion "for" is that it executes completely in every frame and the movement is not at all smooth.

 

I made this script a while ago to have some object floating in a 2D game. It might suit your need.

Code (csharp):

1.  
2. using UnityEngine;
3. using System.Collections;
4.  
5. public class FloatingScript : MonoBehaviour
6. {
7.     public Vector2 randomSpeedRange;
8.     public float speed;
9.  
10.     public Vector2 randomAmplitudeRange;
11.     public float amplitude;
12.  
13.     Vector3 startPos;
14.     bool isFloating = false;
15.  
16.     void Awake()
17.     {
18.         if(speed == 0)
19.             speed = Random.Range(randomSpeedRange.x, randomSpeedRange.y);
20.  
21.         if(amplitude == 0)
22.             amplitude = Random.Range(randomAmplitudeRange.x, randomAmplitudeRange.y);
23.     }
24.  
25.     public void Reset()
26.     {
27.         transform.position = startPos;
28.     }
29.  
30.     void Start()
31.     {
32.         startPos = transform.position;
33.         StartFloat();
34.     }
35.  
36.     void StartFloat()
37.     {
38.         isFloating = true;
39.     }
40.  
41.     void Update()
42.     {
43.         if(isFloating)
44.             transform.position = new Vector3(transform.position.x, (startPos.y + amplitude * Mathf.Sin(speed * Time.time)), transform.position.z);
45.             // Since Sin ranges from -1 to +1, you'll have the object floating from -amplitude to +amplitude around the y0 coordinate,
46.             // and the time to complete one cycle is 2 * PI * speed - about 6.3 seconds if speed is 1.
47.     }
48. }

 

Ahhhh ok, I undestand, "Sin" helps you to alternate, to go forwards and towards and "speed" as its name says indicates how fast is the movement, ok, thank you, it helps me a lot. As I see, "for" is useless in "update" and "fixedupdate".