Doubt in drag and shoot code with sprite.

Hi, I am working on drag and shoot mechanics. I have created the mechanics, but i am not able to figure out the code for line renderer which rotates in opposite direction when dragged in 3D. (ex. buca, available on ios). I need the line renderer to rotate in direction of launch as i move my finger.

Here the code for drag and shoot-

Vector3 startPos, endPos;
public Vector3 direction;
Rigidbody myRigidbody;
public float Power = 4f;
public int hits=0;
private LineRenderer rend;
//public Sprite dir;

Vector3 cam = new Vector3(0,0,180);

void Start()
{
myRigidbody = GetComponent<Rigidbody> ();
//rend=GetComponent<LineRenderer>();

if(rend==null){

rend=gameObject.AddComponent<LineRenderer>();
}
rend.positionCount=2;

}

void OnMouseDown (){
if (Input.GetMouseButtonDown (0)) {
startPos = Input.mousePosition;
//startPos=Quaternion.Euler(0f, 0.0f, 90f);
myRigidbody.isKinematic=true;
rend.SetPosition(0,startPos);
rend.SetWidth(0.25f,0.45f);
rend.useWorldSpace=true;

}
}
void OnMouseUp (){
if (Input.GetMouseButtonUp (0)) {
hits = hits + 1;
myRigidbody.isKinematic = false;
endPos = Input.mousePosition;
direction = startPos - endPos;
direction = Quaternion.Euler(90.0f, 0.0f, 0.0f) * direction;
myRigidbody.AddForce (direction * Power);
}
}
}


Can you help with that?