Drag an object in one line

[Richarrd82]

I am trying to make a draging effect. I have a project where u are supposed to pull a bone out of meat. The draging is working, but when i grab the bone i can move it in all directions. What i would like to achieve is that i can only drag it in one direction. On the images below i mean the red line. I tried many things but nothing worked so far. Any help is appreciated.

I used these functions for the draging

 void OnMouseDown()
{
    offset = this.transform.position -      Camera.main.ScreenToWorldPoint(new Vector2(transform.position.x, Input.mousePosition.y));
}

void OnMouseDrag()
{
    Vector3 curScreenPoint = new Vector2(transform.position.x, Input.mousePosition.y);
    Vector3 curPosition = Camera.main.ScreenToWorldPoint(curScreenPoint) + offset;
    transform.position = curPosition;
}

[StyleA77660]

Maybe you can try transform.up, like this:

private Vector3 Offset;       
private Vector3 MouseDownPosition;

    void OnMouseDown()
    {
        Offset = this.transform.position;
        MouseDownPosition = Input.mousePosition;
    }

    void OnMouseDrag()
    {
        transform.position = Camera.main.ScreenToWorldPoint(Input.mousePosition - MouseDownPosition + new Vector3(0, Screen.height / 2f)).y * transform.up + Offset; //The coordinates are in 2d with (0,0) being the bottom-left.
    }