Easy 2D trajectory line for Unity 2D.

trajectoryline.cs

//************** REAL GAMES STUDIO ***************
//************************************************
//realgamesss.weebly.com
//gamejolt.com/@Real_Game
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//************************************************

using UnityEngine;

public class trajectoryline : MonoBehaviour
{
    public float power = 5f;

    LineRenderer lr;
    Rigidbody2D rb;

    Vector2 startDragPos;

    void Start()
    {
        lr = GetComponent<LineRenderer>();
        rb = GetComponent<Rigidbody2D>();
    }

    void Update()
    {
        if (Input.GetMouseButtonDown(0))
            startDragPos = Camera.main.ScreenToWorldPoint(Input.mousePosition);

        if (Input.GetMouseButton(0))
        {
            lr.enabled = true;

            Vector2 endDragPos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
            Vector2 _velocity = (endDragPos - startDragPos) * power;

            Vector2[] trajectory = Plot(rb, (Vector2)transform.position, _velocity, 500);

            lr.positionCount = trajectory.Length;

            Vector3[] positions = new Vector3[trajectory.Length];

            for(int i = 0; i < trajectory.Length; i++)
            {
                positions[i] = trajectory[i];
            }

            lr.SetPositions(positions);
        }
        else
        {
            lr.enabled = false;
        }

        if (Input.GetMouseButtonUp(0))
        {
            Vector2 endDragPos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
            Vector2 _velocity = (endDragPos - startDragPos) * power;

            rb.velocity = _velocity;
        }
    }

    public Vector2[] Plot(Rigidbody2D rigidbody, Vector2 pos, Vector2 velocity, int steps)
    {
        Vector2[] results = new Vector2[steps];

        float timestep = Time.fixedDeltaTime / Physics2D.velocityIterations;
        Vector2 gravityAccel = Physics2D.gravity * rigidbody.gravityScale * timestep * timestep;

        float drag = 1f - timestep * rigidbody.drag;
        Vector2 moveStep = velocity * timestep;

        for (int i = 0; i < steps; i++)
        {
            moveStep += gravityAccel;
            moveStep *= drag;
            pos += moveStep;
            results[i] = pos;
        }

        return results;
    }
}

This is exactly what I have been trying to do for months. Thank you so much!