We Keep Coding

Unsure how to script my AI GameObject to aim at player with bullet, taking into account for gravity and drag (UNITY)

I'm currently working on a unity project where I'm testing out how to create a projectile trajectory calculation method, which'll be applied to my overall larger Unity project. Inside of this sub-project is simply a ground plane, a square target GameObject, and my AI Enemy GameObject. For reference, here's what the hierarchy of my enemy GameObject looks like:
Enemy (capsule)
GunPivot (empty, is an anchor to rotate the Gun GameObject)
Gun (square)
BulletSpawn (empty, is the spawn point for any instantiated bullet)
Now how my bullet works inside of this scene is that my bullet has a rigidbody, and moves through the scene using the Unity's physics engine, and my gun GameObject has the script that spawns, aligns, and shoots the bullet forward. It just uses AddForce() and a FirePower variable, which can be set in the unity editor. Below is what the code looks like:
public class EnemyGunController : MonoBehaviour
{
//
// Properties & Fields
//
public GameObject BulletPrefab;
public GameObject BulletSpawn;
public float FireRate;
public float FirePower;
public bool CanFire;
//
// Method(s)
//
void Update()
{
StartCoroutine(Fire());
}
// Fires a bullet.
IEnumerator Fire()
{
if (CanFire)
{
CanFire = false;
// Instantiate a bullet. Set the rotation to be looking forwards relative to BulletSpawn
GameObject bullet = Instantiate(BulletPrefab, BulletSpawn.transform.position,
Quaternion.LookRotation(BulletSpawn.transform.up));
// Set bullet so that it ignores collisions with the gun.
Physics.IgnoreCollision(bullet.GetComponent<Collider>(), GetComponent<Collider>());
// Apply force to the bullet.
bullet.GetComponent<Rigidbody>().AddForce(BulletSpawn.transform.forward * FirePower, ForceMode.Impulse);
// Wait for the fire rate before firing again.
yield return new WaitForSeconds(FireRate);
CanFire = true;
}
}
}
Now here's where the issue now lies. I want my Enemy GameObject to hold a method that'll calculate at what rotational value GunPivot needs to be at in order for the Bullet to hit the target GameObject. I already know that Quaternion.LookAt() will rotate the gun to where the target is, but that only solves half of the issue. That rotates the gun horizontally to where the gun is (y-axis I believe), but now I need to check at which rotational value GunPivot needs to be at so that the bullet, which is a rigidbody and has non-zero values for its mass and drag, will hit the target GameObject.
I did look into this a bit and found out the Physics.Simulate() method and how I can calculate this in a separate scene, however when I ran the unity editor, it just froze and then crashed. I attached it to a separate GameManager GameObject, and here's the code for it below:
public class BulletPredictor : MonoBehaviour
{
//
// Properties & Fields
//
public GameObject BulletPrefab;
Scene _mainScene;
Scene _bulletPredictorScene;
PhysicsScene _mainPhysicsScene;
PhysicsScene _bulletPredictorPhysicsScene;
//
// Method(s)
//
void Start()
{
// Disable auto simulation.
Physics.autoSimulation = false;
// Set the main scene and main physics scene fields.
_mainScene = SceneManager.GetSceneByName("MainScene");
_mainPhysicsScene = _mainScene.GetPhysicsScene();
// Set the bullet predictor scene and bullet predictor physics scene fields.
CreateSceneParameters bulletPredictorSceneParameters = new(LocalPhysicsMode.Physics3D);
_bulletPredictorScene = SceneManager.CreateScene("BulletPredictorScene", bulletPredictorSceneParameters);
_bulletPredictorPhysicsScene = _bulletPredictorScene.GetPhysicsScene();
}
// FixedUpdate is called once per frame (fixed at 50 fps).
void FixedUpdate()
{
// Main scene physics need to work, so simulate main scene normally. Needs to be within a fixed update because variable fps can effect the physics simulation.
if (_mainPhysicsScene.IsValid())
{
_mainPhysicsScene.Simulate(Time.fixedDeltaTime);
}
}
// Simulates various shot trajectories to find an optimal shooting angle to hit target, then rotates enemy's gun in main scene to that angle.
public Quaternion ShootBullet(GameObject shooter, GameObject target, Vector3 shooterPos, Vector3 targetPos)
{
// Checks if the main or bullet predictor physics scene is valid. If it isn't just return a default rotation.
if (!_mainPhysicsScene.IsValid() || !_bulletPredictorPhysicsScene.IsValid())
return Quaternion.identity;
// Clone shooter, and move it to the bullet predictor scene.
GameObject shooterClone = Instantiate(shooter, shooterPos, Quaternion.identity);
SceneManager.MoveGameObjectToScene(shooterClone, _bulletPredictorScene);
// Also clone target, and move it to the bullet predictor scene.
GameObject targetClone = Instantiate(target, targetPos, Quaternion.identity);
SceneManager.MoveGameObjectToScene(targetClone, _bulletPredictorScene);
// Get a reference to shooterClone's GunPivot gameobject.
GameObject gunPivot = shooterClone.transform.Find("GunPivot").gameObject;
// Rotate gunPivot to face targetClone.
gunPivot.transform.LookAt(targetClone.transform);
while (gunPivot.transform.rotation.x > -90)
{
// Instantiate a bullet, and move it to the bullet predictor scene. Set the rotation to be the shooterClone's BulletSpawn's rotation.
GameObject bullet = Instantiate(BulletPrefab, gunPivot.transform.position, Quaternion.LookRotation(gunPivot.transform.up));
// Add force to the bullet.
bullet.GetComponent<Rigidbody>().AddForce(gunPivot.transform.forward * bullet.GetComponent<BulletBehavior>().InitialSpeed, ForceMode.Impulse);
// Loop for 200 iterations, and simulate the bullet.
for (int i = 0; i < 200; i++)
{
// Simulate bullet predictor scene.
_bulletPredictorPhysicsScene.Simulate(Time.fixedDeltaTime);
}
// if the bullet is destroyed, break.
if (bullet == null)
{
break;
}
Destroy(bullet);
gunPivot.transform.Rotate(-0.1f, 0, 0);
}
return gunPivot.transform.rotation;
}
}
For debugging purposes, I just added a variable that referenced the GunPivot on my Gun GameObject, and called the ShootBullet() before I actually started the Fire() method, but my unity editor ended up crashing every single time I ran with this code. I'm not entirely sure why this didn't work, although I believe that this happened since I was using Simulate() in a numerical calculation, which probably is VERY VERY computationally expensive.
I'd really appreciate any insight or tips on how to either improve the simulate code I have above or perhaps try out a different approach from it what I'm doing. Also FYI, you can assume that the target isn't moving, so that might make things easier I suppose?

Unity OnBecameInvisible() fires though object is still visible

I have a Mesh Renderer and a script assigned to a rotating sphere with a hole in it. The sphere has no specific or special place in hierarchy, its just next to the camera. The script part looks like this:
void OnBecameInvisible() {
Destroy(gameObject);
}
Problem is, that when I pass the sphere with my ball, even though the sphere is still half visible, it gets deleted. I have no other camera in the scene, and the one Im using is marked as the main camera.
Video

Instead of using OnBecameInvisible for culling objects you've passed, just check if it's sufficiently behind the camera in Update:
Camera mainCam;
[SerializeField] float maxBehindDistance = 0.5f;
void Awake() { mainCam = Camera.main; }
void Update()
{
Vector3 relPos = mainCam.transform.InverseTransformPoint(transform.position);
if (relPos.z < -maxBehindDistance)
{
Destroy(gameObject);
}
}

How can I get a character to walk on a moving platform in Unity

I have a moving platform in a 2D Sidescroller built in Unity 2020.1
The Moving Platform translates between two points using the MoveTo method. It does not have a RigidBody2D component.
I attach the Player to the platform by making it the child of the platform using OnCollisionEnter2D and OnCollisionExit2D to parent the Player to the parent and reset to null respectively. Works great.
I'm using the CharacterController from Standard Assets.
The problem:
The player just walks in place when I try to move him back and forth on the platform.
What I've tried so far:
Changing the current velocity of the player by adding a constant to the x dimension of it's move vector.
Works kinda sorta but that constant needs to be huge to get it to move even a little bit. It's a huge kluge that violates every sense of coding propriety.
Put a RigidBody2D on the platform. Make it kinematic so it doesn't fall to the ground when I land on it. Move the platform via "rb.velocity = new Vector2(speed, rb.velocity.y)";
2a) Attempt to make the Player a child of the kinematic platform.
Player is made a child, but it doesn't move with the platform as expected. I believe that this is because both objects have RigidBody2D components, which I gather don't play well together based on what I've read.
2b) Attempt to add the platform's moving vector to the player's movement vector to make him stay in one place. Player stays stationary to make sure he stays fixed on the platform.
No dice.
I'm all out of ideas. Perusing videos on making player's stick to moving platforms all use the platform to move the player from place to place, without expecting that the game may want the player to move back and forth on the platform as the platform is moving.
I can't believe that this isn't a solved problem, but my Google foo isn't getting me any answers.
Thanks.

I'm a fairly newbie to Unity and C# but I wanted to help so I tried simulating your game for a solution and I didn't run into any problems using this script as the Player movement (you can modify variables as u like, add a separate variable for jump speed to make it smoother etc)
public class Player : MonoBehaviour {
Rigidbody2D rb;
float speed = 7f;
Vector3 movement;
public bool isOnGround;
public bool isOnPlatform;
// Start is called before the first frame update
void Start()
{
rb = GetComponent<Rigidbody2D>();
}
// Update is called once per frame
void Update()
{
movement = new Vector3(Input.GetAxis("Horizontal"), 0f, 0f);
transform.position += movement * speed * Time.deltaTime;
Jump();
}
void Jump()
{
if (Input.GetButtonDown("Jump") && isOnGround || Input.GetButtonDown("Jump") && isOnPlatform)
{
rb.AddForce(transform.up * speed, ForceMode2D.Impulse);
}
}
}
Also add an empty child object to your Player gameObject and add a BoxCollider2D at his feet, narrow it down on Y axis like this
also attach this script to that child gameObject to check if player is on the ground(tag ground collider objects with new tag "Ground") so u don't jump infinitely while in the air OR if the player is on the platform(tag platform collider objects with "Platform") so you're still able to jump off it
public class GroundCheck : MonoBehaviour {
Player player;
MovingPlatform mp;
// Start is called before the first frame update
void Start()
{
player = FindObjectOfType<Player>();
mp = FindObjectOfType<MovingPlatform>();
}
private void OnCollisionEnter2D(Collision2D other)
{
if (other.gameObject.tag == "Ground")
{
player.isOnGround = true;
}
if (other.gameObject.tag == "Platform")
{
player.isOnPlatform = true;
transform.parent.SetParent(other.transform);
mp.MoveThePlatform();
}
}
private void OnCollisionExit2D(Collision2D other)
{
if (other.gameObject.tag == "Ground")
{
player.isOnGround = false;
}
if (other.gameObject.tag == "Platform")
{
transform.parent.SetParent(null);
}
}
}
and finally for platform movement (no RigidBody2Ds, just a collider)
public class MovingPlatform : MonoBehaviour {
bool moving;
public Transform moveHere;
// Update is called once per frame
void Update()
{
if (moving)
{
gameObject.transform.position = Vector2.MoveTowards(transform.position, moveHere.position, 2f * Time.deltaTime);
}
}
public void MoveThePlatform()
{
moving = true;
}
}
additional images
Player, Platform
P.s. Forgot to add - on Player's RigidBody2D, under Constraints, check the "Freeze Rotation Z" box.

Move Object to the last position or position just outside the collision area

I am using a Player rigid body object and there are walls around the Player. These walls are restricting the Player to go through. The Player gets collided with these walls and then falls. The Player uses teleport function to jump from one area to next. Is there a way to make the Player jump to a position just outside the collision area after the Player is collided with these walls?
That is, Player A gets collided with the wall and does not jump to last position, but the position before the collision happened?
public GameObject Player;
public Vector3 PlayerPos;
public bool RecordPos = true;
// Start is called before the first frame update
void Start()
{
}
// Update is called once per frame
void Update()
{
if(RecordPos == true)
{
PlayerPos = Player.transform.position;
}
}
public void OnTriggerEnter(Collider col)
{
if(col.gameObject.name == "Cube(3)" )
{
RecordPos = false;
Player.transform.position = PlayerPos;
}
}
In this script, the Player moves to last position it teleported from.

The "last" position before colliding is 1 frame before the collision. If you capture this position, the character will probably just fall on the obstacle again. Imagine you have a platform ___...___ and an obstacle. The easiest solution is to have 1 trigger at the left side of the obstacles and 1 trigger at the right side. If the player hasn't overcome the obstacle yet, he will be teleported to a chosen destination by you (before the obstacle) and if he's already overcome the obstacle, he will be teleported at the right side. __S_..._S__ (S stands for save/checkpoint trigger)
You need the following script on the gameobject with the Trigger collider. You also need to create a child object to the gameobject with the trigger:
private void OnTriggerEnter2D(Collider2D collision)
{
SaveManager.Instance.LastCheckpointOnHit = transform.GetChild(0).position;
}
And I suppose you have some sort of a singleton for data persistance. Now you can move the child gameobject whereever you want to teleport the player. And BTW I named the property LastCheckpointOnHit, because I was thinking of Holow Knight where if you get hit by spikes it instantly teleports you.
Then you just move the player: Player.transform.position = SaveManager.Instance.LastCheckpointOnHit;

In general when dealing with Rigidbody you shouldn't apply positions through the Transform component but rather through the Rigidbody.
I could imagine something like if you collide with a wall you get pushed away from the wall a bit in the direction where you came from like e.g.
[SerializeField] private float someDistanceThreshold = 0.01f;
[SerializeField] private Rigidbody _rigidbody;
private void Start()
{
if(!_rigidbody) _rigidbody = Player.GetComponent<Rigidbody>();
}
private void FixedUpdate()
{
PlayerPos = _rigidbody.position;
}
public void OnTriggerEnter(Collider col)
{
// instead of the name I would rather use a tag later to cover all obstacles
if(col.gameObject.name == "Cube(3)")
{
_rigidbody.position -= (_rigidbody.position - PlayerPos).normalized * someDistanceThreshold;
// For stopping the player here
_rigidbody.velocity = Vector3.zero;
}
}

Ball slows down in unity2D game

I have a blockbreaker type game coded using C# that mainly works fine but upon play testing i have found the ball will slow right down in certain situations! i.e if it wedges between to game object bricks the force of the ball rapidly slows down! 8 times out of ten this will not happen but other times it does and im unsure why! i will post the Ball script i think you will need to help solve this but should you need anymore information then please ask.
public class Ball : MonoBehaviour {
private Paddle paddle;
private bool hasStarted = false;
private Vector3 paddleToBallVector;
void Start () {
paddle = GameObject.FindObjectOfType<Paddle> ();
paddleToBallVector = this.transform.position - paddle.transform.position;
}
// Update is called once per frame
void Update () {
if (!hasStarted) {
//lock ball relative to the paddle
this.transform.position = paddle.transform.position + paddleToBallVector;
//wait for mouse press to start
if (Input.GetMouseButtonDown (0)) {
//if (Input.GetTouch(0).phase == TouchPhase.Ended){
hasStarted = true;
this.GetComponent<Rigidbody2D> ().velocity = new Vector2 (2f, 10f);
}
}
}
void OnCollisionEnter2D(Collision2D collision){
Vector2 tweak = new Vector2 (Random.Range(0f,0.2f),Random.Range(0f,0.2f));
if (hasStarted) {
GetComponent<AudioSource> ().Play ();
GetComponent<Rigidbody2D>().velocity += tweak;
}
}
}

You are adding directly to the velocity of the ball. The velocity variable defines a direction and speed, not just a speed as you are thinking here.
So, when the ball collides with a block it has a velocity of (+x, +y). After the collision and bounce is has a velocity of (+x, -y). So by adding a random positive value to the velocity when it has the -y velocity means that it will slow down the ball.
This does not happen every time because you are moving the ball in your Update() method. Change that to 'FixedUpdated()'. Fixed Update handles all physics calculations.
Also, I would recommend having a RigidBody2D on your Ball object. Moving physics objects should always have RigidBodies. With this, you can then use AddForce in the forward direction of your ball and that should solve your problem.
EDIT: I see you have a RigidBody2D already. I missed that the first time. Instead of having GetComponent<RigidBody2D>().velocity try GetComponent<RigidBody2D>().AddForce( transform.forward * impulseAmount, ForceMode.Impluse );