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Instantiating an object after updating a variable isn't working as expected

Let's say I have two scripts:
SpawnManager
Enemy
In SpawnManager, I have the function SpawnEnemyWave that should instantiate 3 enemies, if the random number generator is lower than 5, then one of them should have a higher movement speed, the other shouldn't move at all.
In SpawnManager:
bool toughEnemy = true;
int waveNumber = 3;
float randomNumber = Random.Range(0, 10);
void Start()
{
SpawnEnemyWave(waveNumber);
}
void SpawnEnemyWave(int enemiesToSpawn)
{
float randomNumber = Random.Range(0, 10);
print(randomNumber);
for (int i = 0; i < enemiesToSpawn; i++)
{
if ((randomNumber < 5) && toughEnemy)
{
print("Tough");
Instantiate(enemyPrefab, GenerateSpawnPosition(), enemyPrefab.transform.rotation);
toughEnemy = false; //I make sure there is only one tough enemy per wave
}
else
{
print("Weak");
Instantiate(enemyPrefab, GenerateSpawnPosition(), enemyPrefab.transform.rotation);
}
}
}
In Enemy, I'm checking if the toughEnemy variable is set to true to modify the enemy speed before the instantiation, I put those if statements in the start function because I think than when an enemy is instantiated is when it is called.
void Start()
{
spawnManager = GameObject.Find("Spawn Manager").GetComponent<SpawnManager>();
if (spawnManager.toughEnemy)
{
speed = 1;
print("Speed " + speed);
}
else
{
speed = 0;
print("Speed " + speed);
}
}
The problem is, when the random number is 0 in the logs i see this...
random number:0
Tough (the i in the for loop is 0)
Weak (the i in the for loop is 1)
Weak (the i in the for loop is 2)
speed 0
speed 0
speed 0
And what I was expecting was something like below, because I'm modifying the variable in the SpawnManager script first before instantiating the enemy.
random number:0
Tough (the i in the for loop is 0)
speed 1
Weak (the i in the for loop is 1)
speed 0
Weak (the i in the for loop is 2)
speed 0
What am I missing here?

Timing. You’re partly correct thinking that Start will be called when the object is instantiated. But, it will be called when the next frame starts. In your current loop, you’re setting up the objects to be instantiated, then you set the toughEnemy to true. When the next frame starts, all the enemies think that a tough enemy has been set, and the output you see is correct.
If you want the manager to control the enemies, I’d personally include something like a Setup method, called by the manager. For example, in the Enemy script:
public bool isSetup { get; private set; }
public bool isTough { get; private set; }
void Setup(bool tough)
{
if ( isSetup ) return;
isSetup = true;
isTough = tough;
speed = tough ? 1 : 0;
}
Then, when you instantiate the enemy in your manager, do something like:
for (int i=0; i<enemiesToSpawn; i++)
{
var enemy = Instantiate( enemyPrefab, GenerateSpawnPosition(), enemyPrefab.transform.rotation );
var e = enemy.GetComponent<Enemy> ( );
if ((randomNumber < 5) && toughEnemy)
{
print("Tough");
toughEnemy = false; //I make sure there is only one tough enemy per wave
e.Setup(true);
}
else
{
print("Weak");
e.Setup(false);
}
}
Here’s the life cycle of a ‘frame’
Notice that the Update method processing occurs about in the middle of the frame lifecycle. You’re Instantiating 3 objects in the same Update method. THEN … the frame ends, and at the beginning of the next frame, the Start event for each of the new objects is triggered.

I would do this by putting the toughEnemy flag in the Enemy script itself. I would then add a SetTough() method to Enemy, which I would call from SpawnManager via GetComponent() after the Enemy is instantiated.

Unity Can't flip sprite from timer elapsed function

I've just started exploring unity & c# working together, and accidently I faced a next problem:
I have a fish. Fish was supposed to go from left to right, then change its direction and go from right to left. I haven't finished that moving part yet, but I was going to do it with timer. So timer is active, fish starts to move, timer stops, changing direction, timer resets, fish starts to move etc.
I want to flip my sprite, so it will face correct direction. It doesn't work from Elapsed function and I don't understand why. If you have any ideas, please share
using System.Timers;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class FishBehavior : MonoBehaviour
{
public float moveSpeed;
private int direction; //for left -1, for right 1
private Timer timer;
private SpriteRenderer img;
private Rigidbody2D rb;
void Start()
{
img = GetComponent<SpriteRenderer>();
rb = GetComponent<Rigidbody2D>();
direction = 1;
timer = new Timer();
timer.Elapsed += TimerElapsed;
ChangeTimerOptions();
}
private void Move()
{
//moving
}
private void ChangeDirection()
{
direction *= -1;
img.flipX = !img.flipX; //Doesn't work!
//stop movement
}
private void ChangeTimerOptions()
{
System.Random rand = new System.Random();
timer.Interval = rand.Next(3000, 8000);
timer.Enabled = true;
Move();
}
private void TimerElapsed(object source, ElapsedEventArgs e)
{
ChangeDirection();
ChangeTimerOptions();
}
}

The issue is that the callback for TimerElapsed is on a different thread than that of Unity. Meaning any sort of calls you make inside of it to methods that would normally work in Unity will not. I would recommend instead using a Coroutine or an Invoke.
To briefly explain what both are, a Coroutine is a special method that completes small amounts of work over multiple frames. The method can also be suspended for certain amounts of time to wait to perform code down the line. An Invoke or InvokeRepeating is a call to perform a method after a certain amount of time or to continually make a call to a method after a set start time and set amount of time.
If you are also eventually incorporating a movement and randomizing your wait time, I would consider using a Coroutine over an Invoke so you can handle all movement/flip logic from the same main call.
public float moveSpeed;
private int direction; //for left -1, for right 1
private Timer timer;
private SpriteRenderer img;
private Rigidbody2D rb;
// store the coroutine in case a duplicate call occurs somehow
private Coroutine MoveAndFlip = null;
void Start()
{
img = GetComponent<SpriteRenderer>();
rb = GetComponent<Rigidbody2D>();
direction = 1;
// detect if any coroutine is already running
CleanUpMoveAndFlipCoroutine();
MoveAndFlip = StartCoroutine(MoveAndFlipAsset());
}
private void Move()
{
//moving
}
private void ChangeDirection()
{
direction *= -1;
img.flipX = !img.flipX;
//stop movement
}
private IEnumerator MoveAndFlipAsset()
{
// instead of milliseconds, use seconds
float randomTimeInterval = Random.Range(3.0f, 8.0f);
while(true)
{
// can do movement here - depending on how you would like to apply motion it would change how
// it is implemented such as directly changing velocity, using a Vector3.Lerp, AddForce, etc.
// wait the time to flip
yield return new WaitForSeconds(randomTimeInterval);
// now flip
ChangeDirection();
}
}
private void CleanUpMoveAndFlipCoroutine()
{
if (MoveAndFlip != null)
StopCoroutine(MoveAndFlip);
}
If you would like an Invoke example to the above implementation, here is how you could approach it.
void Start()
{
img = GetComponent<SpriteRenderer>();
rb = GetComponent<Rigidbody2D>();
direction = 1;
Invoke("ChangeDirection", RandomTimeToFlip());
}
private float RandomTimeToFlip()
{
return Random.Range(3.0f, 8.0f); ;
}
private void ChangeDirection()
{
direction *= -1;
img.flipX = !img.flipX;
//stop movement
// start our method again after a set amount of time
Invoke("ChangeDirection", RandomTimeToFlip());
}
Edit: Apparently, you are able to use the TimerElapsed by changing the Timer's SynchronizingObject reference, but I am not exactly sure what to assign it to. I would still recommend using one of the two methods I described above though.

Why can't I use ParticleSystem.Emit() outside of Start() method?

I am trying to use ParticleSystem.Emit() to dynamically emit particles, and am unable to get Emit() to work outside of the Start() method.
I am able to emit particles in the Start() method, either directly or with a separate method. When attempting to do the same in Update(), LateUpdate(), or FixedUpdate() it no longer works.
There are no errors reported. I reported the number of particles in the update methods to make sure that the code there was actually running, and it reports however many particles I emit in the Start() method.
When trying to emit particles in the update methods I have tried:
Using Emit() directly in the update loop.
Using a separate method called directly in the update loop.
Using a separate method called using Invoke() in the update loop.
I'm able to check and alter particle position in Update(), so I don't think I'm having some kind of scope problem.
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class Test : MonoBehaviour
{
public ParticleSystem aSystem;
private ParticleSystem.Particle[] aParticle;
void Start()
{
aParticle = new ParticleSystem.Particle[aSystem.main.maxParticles];
// Emit particle.
DoEmit();
Debug.Log("Particle Count: " + aSystem.particleCount);
}
void Update()
{
int numParticles = aSystem.GetParticles(aParticle);
Debug.Log("Number of particles: " + numParticles);
for (int i = 0; i < numParticles; i++)
{
if (aParticle[i].position.z > 1)
{
aParticle[i].position = new Vector3(0f,0f,0f);
}
aParticle[i].velocity = new Vector3(0f, 0f, 1f);
}
aSystem.SetParticles(aParticle);
// Emit particle.
DoEmit();
}
void DoEmit()
{
// Configure render settings for particle.
ParticleSystemRenderer aRenderer = aSystem.GetComponent<ParticleSystemRenderer>();
aRenderer.renderMode = ParticleSystemRenderMode.Mesh;
aRenderer.mesh = Resources.Load<Mesh>("vector");
// Configure rest of settings and emit.
var emitParams = new ParticleSystem.EmitParams();
emitParams.startLifetime = 120;
emitParams.position = new Vector3(0.0f, 0.0f, 0.0f);
emitParams.velocity = new Vector3(0.0f, 0.0f, 0.0f);
emitParams.startSize = 1;
aSystem.Emit(emitParams, 1);
aSystem.Play(); // Continue normal emissions
Debug.Log("DoEmit() called!");
}
}
Expected result: A stream of particles moving in the +z direction.
Actual result: One particle moving in the +z direction.

I needed to do something similar and found this answer in the Unity forums gave me a great, reliable solution that I've reused and modified to my purposes many times. It's a particle pool from which you can emit one or more particles as needed, killing off the last particle made and reusing it once it reaches its max number of particles. I think it achieves exactly what you're looking for. I'll include the relevant script here for reference (complete with #Artifact-Jesse's colorful commentary for clarity).
Note that this script was written for Unity 2018.x, but still works great as of 2020.2.1
Artifact-Jesse's complete, functional example of a fairly generic particle pool:
using UnityEngine;
[RequireComponent(typeof(ParticleSystem))]
public class ParticlePool : MonoBehaviour
{
private int lastParticleIndex = 0; // keeps track of our oldest particle (for deletion)
// these will all be inited in Initialize() on Start()
private ParticleSystem particleSys; // our object's particle system
private ParticleSystem.Particle[] particles; // our reusable array of particles
private ParticleSystem.EmitParams emitParams; // reusable emitparams
private int maxParticles = 0; // total number of particles in our scene before re-using
private void Awake()
{
Initialize(); // initialize all of our member variables
}
public void CreateParticle(Vector3 position, float size, Vector3 velocity, float angularVelocity)
{
// if we're at our particle count limit, kill our oldest particle.
int activeParticles = particleSys.GetParticles(particles);
/// this thing sucks. Read the Unity docs VERY carefully to understand...
/// basically the parameter (particles) is an out parameter which will
/// write out the existing particles in the particle system to our
/// reusable array. After that, we can directly modify the particles
/// and then when we're done, write the particles back into the
/// particle system with ParticleSystem.SetParticles( particles, count )
if (activeParticles >= maxParticles)
{
// set lifetime to -1 to kill the particle
particles[lastParticleIndex].remainingLifetime = -1;
// we need to reset start lifetime to a normal value, too or the particle will still have infinite lifetime
particles[lastParticleIndex].startLifetime = 1;
lastParticleIndex++; // keep track of oldest particle
if (lastParticleIndex >= maxParticles) lastParticleIndex = 0;
// have to re-write
particleSys.SetParticles(particles, particles.Length); // write those pesky particles back into our ParticleSystem
}
// set up params for this particle, you can use whatever you want (see unity docs for EmitParams for what's available)
emitParams.angularVelocity = angularVelocity;
emitParams.position = position;
emitParams.startSize = size;
emitParams.velocity = velocity;
emitParams.startLifetime = float.MaxValue; // float.MaxValue makes the particle's lifetime infinite
particleSys.Emit(emitParams, 1);
particleSys.Play();
}
void Initialize()
{
if (particleSys == null)
particleSys = GetComponent<ParticleSystem>();
maxParticles = particleSys.main.maxParticles;
if (particles == null || particles.Length < particleSys.main.maxParticles)
particles = new ParticleSystem.Particle[particleSys.main.maxParticles];
}
}
Note: the particle system in this example is just bare mininum with a renderer. Not looping, no start on awake, simulation space set to World. MaxParticles is respected by the above script.

Move spawn object to random position

I have a spawner object. Every time a gameobject is spawned, I want that object to move randomly (wandering). The problem in my script is that the gameobject movement is very random (jittery). How can I solve this?
void Start ()
{
InvokeRepeating("SpawnNPC", Spawntime, Spawntime);
}
// Update is called once per frame
void Update () {
population = GameObject.FindGameObjectsWithTag("NPCobject");
for (int i = 0; i < population.Length; i++)
{
getNewPosition();
if (population[i].transform.position != pos)
{
population[i].transform.position = Vector3.MoveTowards(population[i].transform.position, pos, .1f);
}
}
}
void getNewPosition()
{
float x = Random.Range(-22, 22);
float z= Random.Range(-22, 22);
pos = new Vector3(x, 0, z);
}
I made the New randomize vector in different method, because I plan to change it with pathfinder function and make it in different thread/task.

You are choosing a new direction every single frame. That will always be very jittery. You wan't to only change direction after, at least, a small interval. Here is a link to one way to do that from Unity's website. https://docs.unity3d.com/ScriptReference/MonoBehaviour.InvokeRepeating.html

What about using Navigation? As you said wandering, I thought it would give you a nice result and also make your code simple.
The following screenshot is a sample with Navigation. The moving game objects are also changing their direction nicely, although it cannot be seen in the sample because the game object is capsule...
Ground game object in the sample program has NavMesh. See here to build NavMesh.
Agent game object has NavMeshAgent Component. See here to set it up.
Th Behaviour class below is for Agent game object.
using UnityEngine;
using UnityEngine.AI;
public class NavAgentBehaviour : MonoBehaviour {
public Transform[] Destinations { get; set; }
// Use this for initialization
void Start ()
{
InvokeRepeating("changeDestination", 0f, 3f);
}
void changeDestination()
{
var agent = GetComponent<NavMeshAgent>();
agent.destination = Destinations[Random.Range(0, Destinations.Length)].position;
}
}
The next Behaviour class is just for spawning the Agent and setting up the destinations. On Unity, set it to whatever game object in the scene, and allocate game objects to the fields.
using UnityEngine;
public class GameBehaviour : MonoBehaviour {
public GameObject Agent;
public Transform SpawnPoint;
public Transform Destination1;
public Transform Destination2;
public Transform Destination3;
// Use this for initialization
void Start()
{
Agent.SetActive(false);
InvokeRepeating("Spawn", 0f, 2f);
}
void Spawn() {
var newAgent = Instantiate(Agent);
newAgent.GetComponent<NavAgentBehaviour>().Destinations = new[] { Destination1, Destination2, Destination3 };
newAgent.transform.position = SpawnPoint.position;
newAgent.SetActive(true);
}
}
Increase the number of destination, to make the moves look more random. By the way, the destinations do not need to be specified by game objects, which is only for making it easy to see the sample program's behaviour.

The source of the jitteriness comes from the fact that you are updating the position to move every frame so your objects never have a consistent location to move to. I would instead suggest attaching a new script to each of your objects that individually handles their movement. In that script you could do something like the following, which has a delay to keep the target position for more than 1 frame.
float delaytimer;
Vector3 pos;
void Start () {
getNewPosition(); // get initial targetpos
}
void Update () {
delaytimer += Time.deltaTime;
if (delaytimer > 1) // time to wait
{
getNewPosition(); //get new position every 1 second
delaytimer = 0f; // reset timer
}
transform.position = Vector3.MoveTowards(transform.position, pos, .1f);
}
void getNewPosition()
{
float x = Random.Range(-22, 22);
float z= Random.Range(-22, 22);
pos = new Vector3(x, 0, z);
}

You are changing the direction they are moving in every frame, thats what is causing the jitter.
You could wait a few moments before you change the direction, perhaps something like this.
// Outside update
float betweenChanges = 2;
float lastChange = 0;
// Inside update
if(Time.realtimeSinceStartup > lastChange)
{
// Change directions
// ...
lastChange = Time.realTimeSinceStart + betweenChanges;
}
You could also solve this by using InvokeRepeating or a Coroutine.
If you dont want all the NPC's to change direction at the same time and still plan on controlling every NPC from the same class like in your example, you should perhaps add a timer for each NPC instance instead and use that to decide when to change its direction.
A better idea would be to let each NPC have its own Movement-script.

Move GameObject to new position overtime [duplicate]

I am learning Unity from a Swift SpriteKit background where moving a sprite's x Position is as straight forward as an running an action as below:
let moveLeft = SKAction.moveToX(self.frame.width/5, duration: 1.0)
let delayAction = SKAction.waitForDuration(1.0)
let handSequence = SKAction.sequence([delayAction, moveLeft])
sprite.runAction(handSequence)
I would like to know an equivalent or similar way of moving a sprite to a specific position for a specific duration (say, a second) with a delay that doesn't have to be called in the update function.

gjttt1's answer is close but is missing important functions and the use of WaitForSeconds() for moving GameObject is unacceptable. You should use combination of Lerp, Coroutine and Time.deltaTime. You must understand these stuff to be able to do animation from Script in Unity.
public GameObject objectectA;
public GameObject objectectB;
void Start()
{
StartCoroutine(moveToX(objectectA.transform, objectectB.transform.position, 1.0f));
}
bool isMoving = false;
IEnumerator moveToX(Transform fromPosition, Vector3 toPosition, float duration)
{
//Make sure there is only one instance of this function running
if (isMoving)
{
yield break; ///exit if this is still running
}
isMoving = true;
float counter = 0;
//Get the current position of the object to be moved
Vector3 startPos = fromPosition.position;
while (counter < duration)
{
counter += Time.deltaTime;
fromPosition.position = Vector3.Lerp(startPos, toPosition, counter / duration);
yield return null;
}
isMoving = false;
}
Similar Question: SKAction.scaleXTo

The answer of git1 is good but there is another solution if you do not want to use couritines.
You can use InvokeRepeating to repeatedly trigger a function.
float duration; //duration of movement
float durationTime; //this will be the value used to check if Time.time passed the current duration set
void Start()
{
StartMovement();
}
void StartMovement()
{
InvokeRepeating("MovementFunction", Time.deltaTime, Time.deltaTime); //Time.deltaTime is the time passed between two frames
durationTime = Time.time + duration; //This is how long the invoke will repeat
}
void MovementFunction()
{
if(durationTime > Time.time)
{
//Movement
}
else
{
CancelInvoke("MovementFunction"); //Stop the invoking of this function
return;
}
}

You can use co-routines to do this. To do this, create a function that returns type IEnumerator and include a loop to do what you want:
private IEnumerator foo()
{
while(yourCondition) //for example check if two seconds has passed
{
//move the player on a per frame basis.
yeild return null;
}
}
Then you can call it by using StartCoroutine(foo())
This calls the function every frame but it picks up where it left off last time. So in this example it stops at yield return null on one frame and then starts again on the next: thus it repeats the code in the while loop every frame.
If you want to pause for a certain amount of time then you can use yield return WaitForSeconds(3) to wait for 3 seconds. You can also yield return other co-routines! This means the current routine will pause and run a second coroutine and then pick up again once the second co-routine has finished.
I recommend checking the docs as they do a far superior job of explaining this than I could here