Move Object Along Raycast

Question

I have made a Raycast that goes from my camera to the point of the object clicked. However, I am trying to make an object (in this case a bullet) to fly along the path of the ray. At the moment it flies straight forwards from the camera no matter where on the object you click because of the vector 3. How would I get it to follow the Ray?

C#

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class RaycastShot : MonoBehaviour {

public Camera camera;
private Ray ray;
private RaycastHit hit;
public GameObject bullet;
private GameObject createBullet;
private Collider collider;

void Update () {
    if (Input.GetMouseButtonDown (0)) {
        ray = camera.ScreenPointToRay (Input.mousePosition);

        createBullet = Instantiate (bullet, camera.transform.position, bullet.transform.rotation);
        createBullet.AddComponent<Rigidbody>();
        createBullet.GetComponent<Rigidbody>().AddRelativeForce (new Vector3(0, 1500, 0));
        createBullet.GetComponent<Rigidbody>().useGravity = false;
        collider = createBullet.GetComponent<Collider> ();
        Destroy (collider);

        if (Physics.Raycast (ray, out hit)) {

        }
    }
    Debug.DrawLine (ray.origin, hit.point, Color.red);
}
}

Answer 1

You would want to use ray.direction property instead of (0,1500,0) as the direction of the force.

The add force should occur in FixedUpdate, and should only occur if the Ray hits something. Where you have it now is probably not the best spot.

Of course, make sure the bullet gets instantiated at the camera's location first.

Ray.direction gives you the vector3 direction of the ray object. If you need the distance at which it hit, you could also use ray.distance.

Edit: I'm near my computer now, so here's a more detailed answer relating to your comments.

First off: Here's the way I set up the test Project:

I Created a prefab bullet. This is just a sphere with a rigidbody, with my "BulletController" script attached to it. The point of prefabs is to avoid all of those lines where you have to add components. For testing purposes I set the rigibody to ignore gravity and its mass to 0.1.

Next, I created the BulletController script, which will be attached to the bullet prefab.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class BulletController : MonoBehaviour {

    Rigidbody rb;
    public float bulletForce;
    bool firstTime = false;
    Vector3 direction;

    // Use this for initialization
    void Start () {
        rb = GetComponent<Rigidbody> ();
    }


    public void SetDirection (Vector3 dir) {
        direction = dir;
        firstTime = true;
    }

    void OnCollisionEnter () {
        //code for when bullet hits something
    }

    void FixedUpdate () {
        if (firstTime) {
            rb.AddForce (direction * bulletForce);
            firstTime = false;
        }
    }   
}

This script is is charge of controlling bullets. The (later on) script that will create the bullets doesn't really care what happens to them afterwards, since its job is just to create bullets. This BulletController script is in charge of dealing with bullets once they're created.

The main parts are the SetDirection method which tells the bullet which direction to travel in. Also it adds a one-time force in its FixedUpdate method that pushes it in the direction you just set. FixedUpdate is used for physics changes like adding forces. Don't use Update to do this kind of thing. It multiplies the force by a force that you set called "bulletForce".

Finally the BulletListener Script, which is simply attached to an empty game object in the scene. This script is in charge of listening for mouse clicks and creating bullets towards them.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class BulletListener : MonoBehaviour {

    public Camera mainCamera;
    public BulletController bulletPrefab;

    void Update () {
        if (Input.GetMouseButtonDown (0)) {

            //create ray from camera to mousePosition
            Ray ray = mainCamera.ScreenPointToRay (Input.mousePosition);

            //Create bullet from the prefab
            BulletController newBullet = Instantiate (bulletPrefab.gameObject).GetComponent<BulletController> ();

            //Make the new bullet start at camera
            newBullet.transform.position = mainCamera.transform.position;

            //set bullet direction
            newBullet.SetDirection (ray.direction);

        }

    }
}

In the inspector for this empty game object, I added this script, and then dragged the camera, and the bulletPrefab into the appropriate fields. Be sure to drag the prefab from the FOLDER, not from the SCENE. Since this will use the prefab, not an object in the scene.

Now click around and you'll see the bullets flying! Note that using a low force is good to test, and then increase it later.

The main things to take away from this is to split up your logic. A script should only be in charge of one thing. For example, your enemies might also fire bullets. You can now reuse your bulletController script for those bullets as well. Also, say you have different sized or shaped bullets, you can just drag the bulletcontroller script onto the different prefabs you've made for your bullets. This will not affect your listener script which will still create bullets where you click.

Answer 2

If you have the end point then you can move along the vector with MoveTowards:

Vector3 target = hit.point;
StartCoroutine(MoveAlong(target));


private IEnumerator MoveAlong(Vector3 target){
    while(this.transform.position != target){
         this.transform.position = MoveTowards(this.transform.position, target, step);
         yield return null;
    }
}