2d Trajectory Line Prediction not acurate

Question

I'm current facing a problem where in my trajectory line is very inaccurate

Please see the attached image below

Here's where it goes

Here's my code so far

private void Start()
    {
        line = new GameObject[maxDots];
        for (int i = 0; i < line.Length; i++)
        {
            var go = GameObject.CreatePrimitive(PrimitiveType.Sphere);
            go.transform.localScale = new Vector3(0.5f, 0.5f, 0.5f);
            line[i] = go;
        }

        startPos = transform.position;
    }

on my OnMouseUp is for shooting the ball

    //TEMPORARY
    private void OnMouseUp()
    {
        // Disable IsKenematic
        GetComponent<Rigidbody2D>().isKinematic = false;

        // Add the Force
        Vector2 dir = startPos - (Vector2)transform.position;
        GetComponent<Rigidbody2D>().AddForce(dir * force);
        //Remove the script (not the gameobject)
        Destroy(this);
    }

And on my OnMouseDrag is for the ball to keep in radius cause I set a limit for the dragging of the ball

    private void OnMouseDrag()
    {
        DisplayLine();
        //Convert mouse potision to world position
        Vector2 p = Camera.main.ScreenToWorldPoint(Input.mousePosition);

        //Keep it in a certain radius
        float radius = 1.8f;
        Vector2 dir = p - startPos;

        if (dir.sqrMagnitude > radius)
        {
            dir = dir.normalized * radius;

            //Set position
            transform.position = startPos + dir;
        }
    }

Here's my method of displaying the line

    void DisplayLine()
    {
        line[0].transform.position = transform.position;
        Vector3 v3 = transform.position;
        float y = (forces * (home - transform.position)).y;
        float t = 0.0f;
        v3.y = 0.0f;

        for(int i = 1; i < line.Length; i++)
        {
            v3 += forces * (home - transform.position) * spacing;
            t += spacing;
            v3.y = y * t + 0.5f * Physics2D.gravity.y * t * t + transform.position.y;
            line[i].transform.position = v3;
        }
    }

What I am trying to do is that create a trajectory prediction line for my game I know I am almost there but still couldn't get the exact output that I want. Could someone help me. Thank you.

Answer 1

Use the same function to calculate both. Then you won't have the problem also any change on trajectory calculation results in only one change not two.

Answer 2

Solved it

line[0].transform.position = transform.position;
        Vector2 v2 = transform.position;
        float y = (force *( startPos - (Vector2)transform.position)).y;
        float t = 0.0f;
        v2.y = 0.0f;

        for(int i = 1; i < line.Length; i++)
        {
            v2 += force * (startPos - (Vector2)transform.position) * spacing;
            t += spacing;
            v2.y = y * t + 0.5f * Physics2D.gravity.y * t * t + transform.position.y;
            line[i].transform.position = v2;
        }

I need to change from vector3 to vector2 so I need to cast (vector2) between those transform.positions.y