Moving a particular sprite up and down on an axis regardless of rotation

I am making a spike which pops a needle every t interval. I am able to make this to work. But when I try to rotate my game object, say, sideways leftwards, the popping of needle literally goes up and down not sideways as I expect. I need it to move up and down on an axis. Currently, in my game the game object is facing the green line (y-axis). I want my needle to go up and down on this axis.

Here is what I currently have:

Code (CSharp):

1.     void Pop(float elapsed)
2.     {
3.         float step = elapsed * speed;
4.         transform.position = Vector3.MoveTowards (transform.position, popped, step);
5.         transform.
6.     }
7.  
8.     void Unpop(float elapsed)
9.     {
10.         float step = elapsed * speed;
11.         transform.position = Vector3.MoveTowards(transform.position, relax, step);
12.     }
13.  

Here is how I initialize the target positions:

Code (CSharp):

1.     void Start ()
2.     {
3.         relax  = new Vector3 (transform.position.x, transform.position.y, transform.position.z);
4.         popped = new Vector3 (transform.position.x, transform.position.y + 0.8f, transform.position.z);
5.  
6.         StartCoroutine (PopNeedles ());
7.     }
8.  

What I am expecting is that the needle to pop out leftwards, since I made it face leftwards (via rotation)! I can circumvent this by making an object and appropriate scripts but that is very stupid and rubbish.

I want it all done in a single game object.

Thanks!

 

I think the problem is that you set your vectors relaxed and poped only once during start method. When you rotate your object update those vectors too.

 

I believe I don't have to? I want it to move to a specific axis. To its local axes. I was able to make this to work by using
this method transform.Translate. But it goes on and on without stopping.

 

all of your code is working on global position/axis. Probably want to look at localPosition etc.

 

Thanks, actually I gave up, it doesn't fit quite well into the game so I decided to ditch the idea. Thanks you very much! I look into it when I come back to that idea again. Maybe I am able to make this work next time.

 

As I said just recalculate relax and popped when rotating.
Firstly you can simplify those lines:
relax = transform.localPosition;
popped = relax + transform.up * 0.8f;
And make sure they get updated, so put them in to your PopNeedles() coroutine.
It works

Code (CSharp):

1. using UnityEngine;
2. using System.Collections;
3.  
4. public class NeedleExample : MonoBehaviour
5. {
6.     float speed = 2f;
7.     float waitTime = 0.5f;
8.     Vector3 relax;
9.     Vector3 popped;
10.  
11.     void Start()
12.     {
13.         StartCoroutine(PopNeedles());
14.     }
15.     void Pop()
16.     {
17.         transform.position = Vector3.MoveTowards(transform.position, popped, Time.deltaTime * speed);
18.     }
19.     void Unpop()
20.     {
21.         transform.position = Vector3.MoveTowards(transform.position, relax, Time.deltaTime * speed);
22.     }
23.     IEnumerator PopNeedles()
24.     {
25.         while(true)
26.         {
27.             relax = transform.localPosition;
28.             popped = relax + transform.up * 0.8f;
29.             Pop();
30.             yield return new WaitForSeconds(0.5f);
31.             Unpop();
32.             yield return new WaitForSeconds(0.5f);
33.         }
34.     }
35. }
36.