Unity3d:Projectile(Arrow of Bow) is not rotating as per trajectory.

Hi,

Thank you very much for your response.

I have followed your suggestion, but transform.rotation is not working .

I have done with this functionality after a very long & deeply study about physics and maths and lots of reserach.

$$anonymous$$y code is as follows:-

 using UnityEngine;
 using System.Collections;
 
 // calculate drag and set the speed
 // fire projectile(Arrow) in its +ve X direction.
 //Rotate as in gideros.
 
     public class bowScript : $$anonymous$$onoBehaviour {
     public GameObject bulletPrefab;
     //Clone of the bullet
     GameObject Clone;
 
     Vector2 mousePos;
     Vector3 screenPos;
     bool  isDragged;
     bool fired;
     public float hSliderValue = 0.0f;
 
     void Start()
     {
         mousePos = new Vector2 ();
         screenPos = new Vector3 ();
         fired = false;
         isDragged = false;
     }
 
     void  Update (){
         if(Input.Get$$anonymous$$ouseButtonDown(0))
         {
             Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
             RaycastHit hit;
             if (Physics.Raycast(ray, out hit, 100))
             {
                 if(hit.transform.gameObject.name == "bow")
                 {
 
                     if(!isDragged)
                     {
                         isDragged = true;
                     }
                 }
             }
         }
         if(Input.Get$$anonymous$$ouseButtonUp(0))
         {
 
                     if(isDragged)
                     {
                         isDragged = false;
                         FireBullet();
                     }
                 
         }
         if(isDragged)
         {
             mousePos = Input.mousePosition;
             screenPos = Camera.main.ScreenToWorldPoint(new Vector3(mousePos.x, mousePos.y, transform.position.z - Camera.main.transform.position.z));
 
             float temp_Z = $$anonymous$$athf.Atan2((screenPos.y - transform.position.y), (screenPos.x - transform.position.x))*$$anonymous$$athf.Rad2Deg;
             if(temp_Z>=-10 && temp_Z<=90)
             {
                 transform.eulerAngles = new Vector3(0, 0, temp_Z);
             }
         }
         if (fired && !Clone.GetComponent<stick$$anonymous$$e>().isSticked) {
             Debug.Log("Done");
 
             Vector3 vel =  Clone.rigidbody.velocity;
             float angle = $$anonymous$$athf.Atan2(vel.y,vel.x)*$$anonymous$$athf.Rad2Deg;
 
             print(angle);
             Clone.transform.eulerAngles = new Vector3(0, 0, angle);
             }
     }
 
 
     void OnGUI() {
         hSliderValue = GUILayout.VerticalSlider(hSliderValue, 10.0f, 20.0f);
         GUILayout.Label("Force : "+hSliderValue.ToString());
     }
 
     public void FireBullet(){
 
         fired = true;
         Clone = Instantiate(bulletPrefab, transform.position + new Vector3(0f,0f,2f), transform.rotation) as GameObject;
         Clone.rigidbody.velocity = transform.TransformDirection(Vector3.right * hSliderValue);
         
     }
 
 }

Your code is a bit strange. Your rotation on the 'z' axis, the use of Atan2() and the use of Vector3.right indicate this is a 2D application played on XY plane. Yet you are using Rigidbody rather than Rigidbody2D. The code I gave you was for a typical 3D application. For a typical 2D application with right side of your object considered front, you can do this:

  Vector3 dir = rigidbody.velocity;
  float angle = $$anonymous$$athf.Atan2(dir.y, dir.x) * $$anonymous$$athf.Rad2Deg;
  transform.rotation = Quaternion.AngleAxis(angle, Vector3.forward);

This needs to be done every frame. I suggest you put it in a script on the arrow, not put the logic with the firing code as you've done here.

So helpful robert, thanks.