How can I optimize this code?

Questions & Answers
1

Here is my Fixed Update code… It has very poor performance on mobile devices. There is anywhere from 100-500 objects in the scene running this code at any given time. I was hoping maybing someone could give me some insight on how this code could potentionally be optimized. Once the game reaches about 300+ of these objects on a high end mobile device frame rate drops to around 15 fps.

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void FixedUpdate()
    {
        if (GetComponent<Chicken>().isFollowing)
        {
            transform.LookAt(GetComponent<Chicken>().GetFollowingPlayer());
            GetComponent<Rigidbody>().velocity = Vector3.Slerp(GetComponent<Rigidbody>().velocity, transform.forward * GetComponent<Chicken>().followSpeed, Time.deltaTime * turnSpeed);
        }
        else
        {
            Wander();
        }
    }

    public void Wander()
    {
        transform.LookAt(wanderDestination);
        GetComponent<Rigidbody>().velocity = Vector3.Slerp(GetComponent<Rigidbody>().velocity, transform.forward * speed, Time.deltaTime * turnSpeed);
        distanceToDestination = wanderDestination - GetComponent<Rigidbody>().position;
        if (distanceToDestination.magnitude < 1)
        {
            SetRandomDestination();
        }
    }

    public void SetRandomDestination()
    {
        wanderDestination = RandomNavSphere(transform.position, wanderRadius, -1);
    }

    public static Vector3 RandomNavSphere(Vector3 origin, float dist, int layermask)
    {
        NavMesh.SamplePosition((Random.insideUnitSphere * dist) + origin, out navHit, dist, layermask);
        return navHit.position;
    }
2

The biggest piece of advice here:

CACHE YOUR COMPONENT CALLS!

Every time you call GetComponent(), you’re making a very complex check for a component on your GameObject. If you cache the results of those into each object, that alone will save a ton of unnecessary calculation work.

As an example of how to approach this:

Rigidbody rb;
Chicken ckn;

void Start()
{
	rb = GetComponent<Rigidbody>();
	ckn = GetComponent<Chicken>();
}

void FixedUpdate()
{
	if (ckn.isFollowing)
	// etc.
}
3

Separate Physics updates from your ai/decision making code and run these in batches:

using System.Collections;
using System.Collections.Generic;
using System.Threading.Tasks;

using UnityEngine;

[RequireComponent(typeof(Rigidbody))]
public class Mob : MonoBehaviour
{

    static List<Mob> _instances = new List<Mob>(100);

    [SerializeField] [HideInInspector] Rigidbody _rigidbody;
    Vector3 _targetVelocity;

    #if UNITY_EDITOR
    void OnValidate ()
    {
        if( _rigidbody==null ) { _rigidbody = GetComponent<Rigidbody>(); }
    }
    void OnDrawGizmos ()
    {
        Vector3 position = transform.position; 
        Gizmos.color = Color.blue;
        Gizmos.DrawLine( position , position + _targetVelocity );
        Gizmos.color = Color.cyan;
        Gizmos.DrawLine( position , position + _rigidbody.velocity );
    }
    #endif

    void OnEnable ()
    {
        //register instance:
        if( _instances.Count==_instances.Capacity )
        {
            _instances.Capacity *= 2;
        }
        _instances.Add( this );
    }

    void OnDisable ()
    {
        //unregister instance:
        _instances.Remove( this );
    }

    void FixedUpdate ()
    {
        //NO AI CODE, simple operations only
        _rigidbody.velocity = Vector3.Lerp( _rigidbody.velocity , _targetVelocity , Time.fixedDeltaTime );
    }
    
    async Task AiTick ()
    {
        //AI CODE GOES HERE
        if( Random.value>0.5f )
        {
            Vector2 vec = Random.insideUnitCircle;
            _targetVelocity = new Vector3( vec.x , 0f , vec.y );
        }
        else
        {
            _targetVelocity = Vector3.zero;
        }
        await Task.CompletedTask;
    }

	[RuntimeInitializeOnLoadMethod]
    static async void MobAi ()
    {
        List<Mob> batch = new List<Mob>();
        while( Application.isPlaying )
        {
            //grab new batch:
            batch.Clear();
            batch.AddRange( _instances );

            //process batch:
            foreach( Mob mob in batch )
            {
                //execute ai code:
                await mob.AiTick();
            }

            //await:
            await Task.Delay( 1000/4 );
        }
    }

}