Question Enemy jitters when camera follows the player

I have an enemy that follows or retreats from player based on the distance.

It all works fine until i make camera follow the player. When it does, enemy starts jittering while moving.

Here's the scripts

Player Movement:

Code (CSharp):

1. public class Movement : MonoBehaviour
2. {
3.     public float moveSpeed = 5;
4.  
5.     private Rigidbody2D rb;
6.     [SerializeField] private Camera cam;
7.  
8.     private Vector2 movement;
9.     private Vector2 mousePos;
10.  
11.     private void Start()
12.     {
13.         rb = GetComponent<Rigidbody2D>();
14.         cam = FindObjectOfType<Camera>();
15.     }
16.  
17.     private void Update()
18.     {
19.         movement.x = Input.GetAxisRaw("Horizontal");
20.         movement.y = Input.GetAxisRaw("Vertical");
21.  
22.         mousePos = cam.ScreenToWorldPoint(Input.mousePosition);
23.     }
24.  
25.     private void FixedUpdate()
26.     {
27.         rb.AddForce(movement * moveSpeed, ForceMode2D.Impulse);
28.  
29.         Vector2 lookDir = mousePos - rb.position;
30.         float angle = Mathf.Atan2(lookDir.y, lookDir.x) * Mathf.Rad2Deg - 90;
31.         rb.rotation = angle;
32.     }
33. }
34.  

Camera follow:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class CamScript : MonoBehaviour
6. {
7.     private Camera cam;
8.     private Transform playerPos;
9.  
10.     private void Start()
11.     {
12.         cam = GetComponent<Camera>();
13.         playerPos = GameObject.FindGameObjectWithTag("Player").transform;
14.     }
15.  
16.     private void Update()
17.     {
18.         transform.position = new Vector3(playerPos.position.x, playerPos.position.y, -10);
19.     }
20. }
21.  

Enemy movement:

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class Enemy : MonoBehaviour
6. {
7.     [SerializeField] float speed = 3;
8.     public bool isAggro = false;
9.  
10.     private Rigidbody2D rb;
11.     public Transform player;
12.  
13.     [Header("Distances")]
14.     [SerializeField] float followDistance;
15.     [SerializeField] float retreatDistance;
16.     private float distance;
17.  
18.     private void OnEnable()
19.     {
20.         rb = GetComponent<Rigidbody2D>();
21.     }
22.  
23.     private void FixedUpdate()
24.     {
25.         if (!isAggro) return;
26.  
27.         distance = Vector2.Distance(transform.position, player.position);
28.  
29.         if (distance > followDistance)
30.         {
31.             rb.MovePosition(Vector2.MoveTowards(transform.position, player.position, speed * Time.deltaTime));
32.         }
33.         else if (distance < retreatDistance)
34.         {
35.             rb.MovePosition(Vector2.MoveTowards(transform.position, player.position, -speed * Time.deltaTime));
36.         }
37.     }
38. }
39.  

 

Camera stuff is pretty tricky... you may wish to consider using Cinemachine from the Unity Package Manager.

There's even a dedicated forum: https://forum.unity.com/forums/cinemachine.136/

If you insist on doing it yourself, be sure you follow physics objects from FixedUpdate() or LateUpdate().

Here's why:

Here is some timing diagram help:

https://docs.unity3d.com/Manual/ExecutionOrder.html

Two good discussions on Update() vs FixedUpdate() timing:

https://jacksondunstan.com/articles/4824

https://johnaustin.io/articles/2019/fix-your-unity-timestep

 

Have you turned on Interpolation in the rigidbody settings for your enemy?

 

I installed cinamachine and set it to follow the player from inspector, but the enemy still jitters, does that mean the problem is in the enemy movement?

 

Yes, i tried also switching it to extrapolate but it only helped a little

 

Ok so i spent 3 hours trying everything and of course the solution was super simple.

Turns out the player himself didn't have any interpolation, set it to Interpolate and everything is fixed!