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Respawn AI after destroy

I'm new, and I've got hard time to respawn my AI (right now he just a cube that follow my player) after he been destroy. I believe its because the script sits on the object that get destroyed. but what I need to do to respawn it?
(although I'm sure my respawn code is not good :\ (It's mobile-android project) )
using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class EnemyTesting : MonoBehaviour
{
[SerializeField]
public GameObject player;
public GameObject enemy;
private Rigidbody body;
Vector3 accelerationDir;
// Use this for initialization
void Start()
{
body = GetComponent<Rigidbody>();
}
private void Update()
{
accelerationDir = Input.acceleration;
if (accelerationDir.sqrMagnitude>=5)
{
EnemyDead();
}
}
void EnemyDead()
{
Destroy(enemy);
Invoke("Respawn", 5);
}
void Respawn()
{
enemy = (GameObject)Instantiate(enemy);
enemy.transform.position = transform.position;
}
// Update is called once per frame
void FixedUpdate()
{
Vector3 toTarget = player.transform.position - transform.position;
float speed = 1.5f;
transform.Translate(toTarget * speed * Time.deltaTime);
}
}
Thanks very much!

I am supposing that your enemy GameObject is inside the scene holding your EnemyTesting MonoBehaviour instance (correct me if I'm wrong).
If this is the case, you cannot instantiate a gameObject that is destroyed.
As #derHugo pointed out, you should not use Destroy and Instantiate for your use case. It would be better to set inactive the enemy GameObject, move it to the position that you want, an (re)set it active. It will look like the enemy respawned.
If you want to dig the subject later, look at the object pooling game optimization pattern.
Otherwise, if you still want to use Instantiate for respawning, I would create a prefab of your enemy GameObject. The enemy GameObject referenced in the EnemyTesting field (in the Inspector view), would be your prefab from the project hierarchy instead of a GameObject inside the scene.
This way, you would be able to instantiate an enemy GameObject as many times as you want (and use it in other scenes!). Don't forget to hold a reference to the instantiated enemy GameObject so you can know which one you want to destroy. It would looke like this :
enemy = Instantiate(enemyPrefab, transform.position, transform.rotation);
You can replace transform with the transform of your choice, for example the transform of an empty enemyRespawnPoint GameObject in your Scene.
Do you see any error in the console ?

Bug in Unity 2D gravity?

I'm writing a script in C# in Unity that essentially functions as a switch to turn gravity on or off for a 2D Rigidbody. When the game starts, gravity should be 0 for the Rigidbody. Then when the user taps the space bar, gravity is supposed to increase to 3 (which is does). Then, however, when the player collides with a gameObject labeled 'InvisGoal', the player should teleport to another location and then gravity should be 0 again. However, the player always falls after coming in contact with InvisGoal and teleporting and I can't figure out why. This is my first project in C# so sorry for any obvious errors.. The script is here:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class BallLaunch : MonoBehaviour {
private Rigidbody2D myRigidBody;
public GameObject Ball;
// Use this for initialization
void Start ()
{
myRigidBody = GetComponent<Rigidbody2D> ();
GetComponent<Rigidbody2D>().gravityScale = 0f;
}
// Update is called once per frame
void Update ()
{
if (Input.GetButtonDown ("Jump"))
{
GetComponent<Rigidbody2D> ().gravityScale = 3f;
}
}
void OnTriggerEnter2D(Collider2D other){
if (other.tag == "InvisGoal")
{
Ball.gameObject.GetComponent<Rigidbody2D>().gravityScale = 0f;
transform.position = new Vector3 (0.61f, 1.18f, 0f);
return;
}
}
}

Ball.gameObject.GetComponent<Rigidbody2D>().gravityScale = 0f;
This is likely what is causing the problem.
It sounds like the RigidBody2D you are referencing to in this line is not the same as the one you retrieved beforehand with GetComponent().
GetComponent returns the component of the GameObject you call it from. Therefore in the code I mentioned above,
Ball.gameObject.GetComponent<RigidBody2D>()
and
GetComponent<RigidBody2D>()
would give you an two different RigidBody2D component if the field Ball does not refer to the same GameObject your BallLaunch script is attached to.
[
Supposing BallLaunch script is attached to the Ball you want to set the gravity of (As picture above)
Simply change:
Ball.gameObject.GetComponent<Rigidbody2D>().gravityScale = 0f;
To
GetComponent<Rigidbody2D>().gravityScale = 0f;
Also, since you already referenced your RigidBody2D in your Start method to the field myRigidBody, you can replace all subsequent GetComponent with myRigidBody.
GetComponent<Rigidbody2D>().gravityScale = 0f;
To
myRigidBody.gravityScale = 0f;

Move Object Along Raycast

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);
}
}

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.

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;
}
}

Using the LookAt() function in Unity

So I have an assignment that I have to do for school where an enemy shoots at the player in a gun type game. I have read about the LookAt() function in the Unity tutorials and used it to my knowledge of it. However it doesn't seem to be working. The following code is what I have so far:
public class EnemyControl : MonoBehaviour {
private Rigidbody rb;
public GameObject Bullet_Emitter2;
public GameObject EnemyBullet;
public float speedOfBullet;
private int score;
public Text countText;
public Text winText;
private GameObject Temporart_Bullet_Handler2;
public Transform player;
public Transform enemy;
void Start()
{
rb = GetComponent<Rigidbody>();
score = 0;
}
private void Update()
{
enemy.LookAt(player);
}
// Update is called once per frame
void FixedUpdate () {
int fire = Random.Range(0, 100);
if(fire == 0 || fire == 1 || fire == 5)
{
Temporart_Bullet_Handler2 = Instantiate(EnemyBullet, Bullet_Emitter2.transform.position, Bullet_Emitter2.transform.rotation) as GameObject;
Temporart_Bullet_Handler2.transform.Rotate(Vector3.right * 90);
Rigidbody Temporary_Rigid_Body;
Temporary_Rigid_Body = Temporart_Bullet_Handler2.GetComponent<Rigidbody>();
Temporary_Rigid_Body.AddForce(transform.up * speedOfBullet);
Destroy(Temporart_Bullet_Handler2, 20.0f);
}
}
}
The problem is my enemy now just looks at the ground instead of me and then just shoots downwards. Is there a way I can fix this? I have attached an image of what it looks like to a player playing the game?
Before putting in the LookAt() function my spaceman would just be stationary and fire bullets in a straight line but I need the AI to track the player instead of stationary. Is there another way to do this without using LookAt() or am I using this function wrong?
Thanks for the help in advance?

I would post this in comments but I can't yet because of low reputation
As Serlite pointed out, LookAt() only faces the GameObject's trasnform.forward (which is desired to be (0, 0, 1) when the object is not rotated) towards the target passed as argument.
To 'fix' this simply add an empty GameObject to your Hirarchy and set your AI object as its child
Empty GameObject
- AI GameObject (with your script)
Now you can set a global rotation for your object (Rotate the parent) in a way that the AI's forwards faces z+.

Tank does not shoot instantiated bullet

I started making a simple game in Unity3d: a tank to shoot at a wall (see image).
A GameObject is attached to the turret of the tank, and to this GameObject is attached the following script :
using UnityEngine;
using System.Collections;
public class Shooter : MonoBehaviour {
public Rigidbody bullet;
public float power = 1500f;
void Update () {
if (Input.GetButtonDown ("Fire1")) {
Rigidbody bulletRB = Instantiate (bullet, transform.position, transform.rotation) as Rigidbody;
Vector3 fwd = transform.TransformDirection(Vector3.forward);
bulletRB.AddForce(fwd*power);
}
}
}
When I press on the Fire1 button the bullet does not shoot. I put (for test) a Debug.Log("BULLET SHOOT") after bulletRB.addForce(). The message is displayed, so the script reached this point. What is wrong with my code?

Based on this somewhat similar question on Unity Answers, you should probably be instantiating the GameObject of the bullet prefab/instance, rather than its Rigidbody directly. Then, access the Rigidbody component of that new bullet and add the force.
Your adjusted Update() method would then look like:
void Update () {
if (Input.GetButtonDown ("Fire1")) {
GameObject newBullet = Instantiate (bullet.gameObject, transform.position, transform.rotation) as GameObject;
RigidBody bulletRB = newBullet.GetComponent<Rigidbody>();
Vector3 fwd = transform.TransformDirection(Vector3.forward);
bulletRB.AddForce(fwd*power);
}
}
Another thing you may want to change is using transform.forward (aka. Forward vector of the turret) rather than Vector3.forward (global forward vector Vector3(0, 0, 1), which may not match the direction of the turret).
Hope this helps! Let me know if you have any questions.

Force can be applied only to an active rigidbody. If a GameObject is inactive, AddForce has no effect.
Wakes up the Rigidbody by default. If the force size is zero then the Rigidbody will not be woken up.
The above description is taken from Unity
Therefore, I would suggest to check if the GameObject is active first.
You can test it by doing the following:
if (newBullet.activeInHierarchy === true)
{
//active
}else{
//inactive
}