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I am working on a game project on unity and I am stuck at a camera problem

It has two camera angles. First person for engaging gameplay and top-down for 2D game experience. But in top down camera view I can't figure out the rotation of the camera with respect to player.
I wrote the following script for the main(top-down) camera view.
public class FollowPlayer : MonoBehaviour
{
public GameObject player;
private Vector3 offset = new Vector3(0f, 24.953f, -0f);
// Start is called before the first frame update
void Start()
{
}
// Update is called once per frame
void LateUpdate()
{
transform.position = player.transform.position + offset;
}
}`
I tried
transform.rotation = player.transform.rotation;
but it didn't work since camera is on top of player. If I could somehow do
transform.rotation = player.transform.rotation + X axis 90 degree;
That would be perfect but I don't know how to do that.

If I understand you correctly, you want to follow the player from above with your second camera. Leaving some flexibility, the best option I think would be Unity's built in Transform.LookAt(target) method (LookAt), which automatically rotates an object (in your case the camera) so that it faces the target.
Therefore, you could do something like this in your Update, assuming your script is attached to the Camera. Otherwise substitute transform with Camera.main.transform:
transform.LookAt(player);
Note: If you plan to have your camera fixed above your player at all times, it is sufficient if you perform the LookAt once, e.g. in Start and then attach the camera as a child to the player. If your camera does not move with your player in the world but you want it to focus the player anyway, do do it in Update. Hope I addressed your problem:)

My problem has been resolved. I was trying to rotate the wrong axis. My bad.
mouseInput = Input.GetAxis("Mouse X");
transform.Rotate(Vector3.forward * speed * -mouseInput);
I needed to get mouse input from user and change the Z-axis according to it. Game is working fine now.

Bullet not moving

I'm trying my first test-game with Unity, and struggling to get my bullets to move.
I have a prefab called "Bullet", with a RigidBody component, with these properties:
Mass: 1
Drag: 0
Angular drag: 0,1
Use grav: 0
Is Kinematic: 0
Interpolate: None
Coll. Detection: Discrete
On the bullet prefab, I have this script:
public float thrust = 10;
private Rigidbody rb;
void Start()
{
rb = GetComponent<Rigidbody>();
rb.AddForce(transform.forward * 100, ForceMode.Impulse);
}
On my playerController script (not the best place for this, I know):
if (Input.GetAxisRaw("Fire1") > 0)
{
var proj = Instantiate(projectile, transform.position, Quaternion.identity);
}
When I click my mouse, the bullet gets created, but doesn't move. I've added velocity to the rigidbody, which works, but I can't get it to move in the right direction. After googling around, it seems I need to be using rigidBody.AddForce(), which I did, but still can't get my bullet to move.
I've seen the other solution, but this did not work for me either.
Any advice would be appreciated.
Screenshot:

When you're working with 2D in Unity, the main camera basically becomes an orthographic camera (no perspective effects) looking sideways at the game scene along the z-axis. Incidentally, the "forward" direction of a non-rotated object is also parallel to the z-axis.
This means that when you apply a force along transform.forward, you're sending the object down the z-axis - which will not be visible to an orthographic camera looking in the same direction. The quick fix here would be to use a direction that translates to an x/y-axis movement, like transform.up or transform.right.
As derHugo also mentioned in the comments, you might want to look into using Rigidbody2D. There are some optimizations that will allow it to behave better for a 2D game (though you may not notice them until you scale up the number of objects).

Moving a GameObject using tags not working Unity

I know this is quite the noob question, but whatever, there's only one way to learn.
I've created an empty GameObject in Unity, attached a script that is supposed to move a cube(my player) and gave my cube the tag "Player". After creating the cube, I was hoping to be able to move the cube without having to put the script on the cube itself. When the script is on the cube, it moves without a problem (I know this is how it probably should be done, but for trying to learn new things I wanted to do it this way).
Player Controller script
Cube properties
After failing to find the answer through Google, any insight at all is greatly appreciated!
Thank you
Update!
Here's the code as text now, since it was asked for.
public class GameCoreController : MonoBehaviour {
private GameObject PlayerMove;
public Rigidbody rb;
void Start ()
{
PlayerMove = GameObject.FindGameObjectWithTag("Player");
rb = GetComponent<Rigidbody>();
}
void Update()
{
// character movement
if (Input.GetKey(KeyCode.W))
{
PlayerMove.transform.Translate(0, 0, 0.25f);
}
if (Input.GetKey(KeyCode.S))
{
PlayerMove.transform.Translate(0, 0, -0.25f);
}
if (Input.GetKey(KeyCode.A))
{
PlayerMove.transform.Translate(-0.25f, 0, 0);
}
if (Input.GetKey(KeyCode.D))
{
PlayerMove.transform.Translate(0.25f, 0, -0);
}
}
I've updated the code from before to include PlayerMove.transform.Translate but I still have the same issue with the cube note moving. I've also included screenshots of my scene with the cube and the GameCoreController; the empty GameObject holding the script that is supposed to control the cube.
Thanks again for the help guys.
Update 2!
After deleting the cube and re-insert it into the scene it now moves. Thanks for the help everyone.

The reason that the cube won't move because in your code you didn't move its transform but you move the transform of the gameobject that you attached this script to.
transform.Translate move the transform of the gameobject that this script attach to. So if you want to move the cube, all you need to do is change from transform.Translate to PlayerMove.transform.Translate which will move the transform of PlayerMove gameobject which is your cube with "Player" tag on it

^ All of the above. Plus, in the screenshot, your rigidbody is not set to "is kinomatic". This means that physics will still be applied to it (like gravity). Rule of thumb: If you have a moving object where collision is important, it will need a rigidbody and a collider. If the object is not moved with physics commands (eg rigidbody.AddForce()) but rather manipulating the transform as you are, set the rigidbody "isKinomatic" property to true.

Unity C#, Camera facing sprite and rigidbody not working together

I have a small piece of code to make a sprite (in a 3D world) always face the camera (It has to be in 3D space).
public class CS_CameraFacingBillboard : MonoBehaviour {
private Camera m_Camera;
private void Start()
{
m_Camera = Camera.main;
}
void Update()
{
transform.LookAt(transform.position + m_Camera.transform.rotation *
Vector3.forward, m_Camera.transform.rotation * Vector3.up);
}
}
This code ensures the sprite is always facing the camera, causing it to lean backwards as the camera in above the sprite facing down in a 45 degree agle. When I put a rigidbody on the sprite, the sprite moves on its own towards the direction its leaning. The rigidbody works fine without this code attached.
How can I have a sprite that always faces the camera, and has a rigidbody attached?

It seems you've left the rigidbody as Dynamic, you should set it to Kinematic.
EDIT: After you comments, I checked myself inside Unity, and probably I've recreated the behaviour you described. It happens to me too IF I use a Box Collider on the sprite without locking its rigidbody rotation.
So you have three possible solutions:
Use a Box Collider and under Constraints of the rigidbody freeze the rotation:
Use a Sphere Collider (or another one that doesn't behave like the box one, you can check them out in play mode).
Split the components over two game object, a parent and a child. The parent will have all the components except the sprite renderer and the camera script, which will be on the child. This option is the most flexible and less restraining. You can have the box collider without freezing rotations, etc.
Another thing, you can avoid the use of the LookAt method, by simply using:
transform.rotation = m_Camera.transform.rotation;
they have the same outcome.

Unity3d flappy bird tutorial - space button not working

I am a total beginner at Unity3d. I have some background in android programming, but no C# experience whatsoever. The first thing I am trying to do is to create a clone of flappy bird game, called flappy plane, according to this tutorial
http://anwell.me/articles/unity3d-flappy-bird/
The problem is, when I tried to write a script that allows player to move (player.cs) with the code
using UnityEngine;
using System.Collections;
public class player: MonoBehaviour {
public Vector2 jumpForce = new Vector2(0,300);
public Vector2 jumpForce2 = new Vector2(0,-300);
// Use this for initialization
// Update is called once per frame
void Update () {
if (Input.GetKeyUp("space")){
Rigidbody2D.velocity = Vector2.zero;
Rigidbody2D.AddForce(jumpForce);
}
}
}
I get an error "An Object reference is required to access non-static member 'UnityEngine.Rigidbody2D.velocity'". I have googled that and it is suggested to access Rigidbody2d with GetComponent().velocity,
so I changed
Rigidbody2D.velocity = Vector2.zero;
Rigidbody2D.AddForce(jumpForce);
with
GetComponent<Rigidbody2D>().velocity = Vector2.zero;
GetComponent<Rigidbody2D>().AddForce(jumpForce);
The error is gone and I am able to add the script to the object, still I don`t get the desired action - after I hit play the object turns invisible and just falls down, does not react to spacebar button. What am I doing wrong?
Thanks for the answer.

It's possible that you're not adding enough force to have the object move upwards.
There's technically nothing wrong with your code. (Although you do have somethings mixed up in your question). The problem is in the fact that you're not adding ANY force upwards every single frame.
Essentially, at the moment, your player object is in free-fall the instant you hit the play button, and you're adding a minuscule force to the player only on the frames that the space bar is pressed.
To solve this, here's what you should be doing
Add an upward force to counter-act the force of gravity every frame. You can do this in two ways.
a. Set the rigidbody's velocity.y to 0 BEFORE detecting the space bar (this is really a hacky way, but it'll suffice and doesn't need any more code)
b. Add an upward force to the player which will nullify the effect of gravity. Just use F = mg to get the value of force you'd need to add.
You could, alternatively set the isKinematic property to true by default on the Player's rigidbody, set it to false on pressing the space bar, and back to true after a few frames (5 - 6 frames)

make sure your player object and the ground both have BoxCollider2D colliders to keep above ground.
you could keep a reference stored for the rigidBody like Rigidbody2D myRigidbody;
then in start put myRigidbody = GetComponent<Rigidbody2D>(); then you would use like myRigidbody.AddForce(jumpForce); your jumpForce2 though is shooting your player downward you should not need it in a jump as the physics and gravity will apply with the rigidbody.
incase your input is not set up in the project settings try to fire the jump with
Input.GetKeyDown(KeyCode.Space);