How to enable Trajectory on a ball when being pulled? - unity3d

Question

So I have made a Trajectory for my ball.
This is the code...
{
[Header("Line renderer veriables")]
public LineRenderer line;
[Range(2, 30)]
public int resolution;
Rigidbody rb;
[Header("Formula variables")]
public Vector3 velocity;
public float yLimit;
private float g;
[Header("Linecast variables")]
[Range(2, 30)]
public int linecastResolution;
public LayerMask canHit;
public Rigidbody ballRigid;
private void Start()
{
rb = GetComponent<Rigidbody>();
g = Mathf.Abs(Physics.gravity.y);
}
private void Update()
{
RenderArc();
}
private void RenderArc()
{
line.positionCount = resolution + 1;
line.SetPositions(CalculateLineArray());
}
private Vector3[] CalculateLineArray()
{
Vector3[] lineArray = new Vector3[resolution + 1];
var lowestTimeValueX = MaxTimeX() / resolution;
var lowestTimeValueZ = MaxTimeZ() / resolution;
var lowestTimeValue = lowestTimeValueX > lowestTimeValueZ ? lowestTimeValueZ : lowestTimeValueX;
for (int i = 0; i < lineArray.Length; i++)
{
var t = lowestTimeValue * i;
lineArray[i] = CalculateLinePoint(t);
}
return lineArray;
}
private Vector3 HitPosition()
{
var lowestTimeValue = MaxTimeY() / linecastResolution;
for (int i = 0; i < linecastResolution + 1; i++)
{
RaycastHit rayHit;
var t = lowestTimeValue * i;
var tt = lowestTimeValue * (i + 1);
if (Physics.Linecast(CalculateLinePoint(t), CalculateLinePoint(tt), out rayHit, canHit))
return rayHit.point;
}
return CalculateLinePoint(MaxTimeY());
}
private Vector3 CalculateLinePoint(float t)
{
float x = rb.velocity.x * t;
float z = rb.velocity.z * t;
float y = (rb.velocity.y * t) - (g * Mathf.Pow(t, 2) / 2);
return new Vector3(x + transform.position.x, y + transform.position.y, z + transform.position.z);
}
private float MaxTimeY()
{
var v = rb.velocity.y;
var vv = v * v;
var t = (v + Mathf.Sqrt(vv + 2 * g * (transform.position.y - yLimit))) / g;
return t;
}
private float MaxTimeX()
{
if (IsValueAlmostZero(velocity.x))
SetValueToAlmostZero(ref velocity.x);
var x = rb.velocity.x;
var t = (HitPosition().x - transform.position.x) / x;
return t;
}
private float MaxTimeZ()
{
if (IsValueAlmostZero(velocity.z))
SetValueToAlmostZero(ref velocity.z);
var z = rb.velocity.z;
var t = (HitPosition().z - transform.position.z) / z;
return t;
}
private bool IsValueAlmostZero(float value)
{
return value < 0.0001f && value > -0.0001f;
}
private void SetValueToAlmostZero(ref float value)
{
value = 0.0001f;
}
public void SetVelocity(Vector3 velocity)
{
this.velocity = velocity;
}
}
I have a slingshot With a objectholder(which holds the ball). Also I have a robot arm that pulls the objectholder with its clawhand . The arm pulls it but The ball is in kinematic until the claw opens. The objectholder contains springs joints so its able to go back to its place and make a elastic effect and throw the ball. Now with this code when I pull the trajectory doesnt appear until i let go and it picks a target by itself and just follows the line. What i want is when I pull it the trajectory shows and the user is able to pick the target or move the trajectory. Note: (If i get rid of rb.velocity and replace it with velocity, then when i pull it it shows the trajectory and I can change the target but when i open my claw and the ball shoots, it doesnt follow the trajectory, its like the trajectory follows the ball. Can someone helps? This code makes the ball follows the line so its good I just have that problem.
My other code when clawhand opens and closes and ball is kinematic or not:
public class open2close : MonoBehaviour
{
public float speed;
private Animation anim;
[SerializeField] bool isClosed;
private bool isKinematic;
public Transform rightClaw;
public Vector3 offset;
public Rigidbody Rb2;
public Rigidbody ball_Rigid;
void Start()
{ Debug.Log(transform.position);
Console.WriteLine("test");
anim = gameObject.GetComponent<Animation>();
Rb2 = Rb2.GetComponent<Rigidbody>();
ball_Rigid = ball_Rigid.GetComponent<Rigidbody>();
//Rb2.isKinematic = true;
}
void Update()
{
// Debug.Log(transform.position);
if (Input.GetKey(KeyCode.X))
{
anim.Play("clawopen");
isClosed = false;
Rb2.isKinematic = false;
ball_Rigid.isKinematic = false;
}
if (Input.GetKey(KeyCode.Y))
{
anim.Play("clawclose");
isClosed = true;
Rb2.isKinematic = true;
ball_Rigid.isKinematic = true;
}
}
private void OnTriggerStay(Collider spring2)
{
Rigidbody colRb = spring2.attachedRigidbody;
if (isClosed && spring2.transform.gameObject.tag == "Player")
{
spring2.transform.position = rightClaw.transform.position + offset;
}
}
private void OnTriggerExit(Collider spring2)
{
Rigidbody colRb = spring2.attachedRigidbody;
if (isClosed && spring2.transform.gameObject.tag == "Player")
{
colRb.WakeUp();
}
}
}