Look.cs Optimization

//You can simply copy and paste this entire script if you want to skip the tutorial
//Just do a Ctrl + A on your Visual Studio, and paste (Ctrl + V)

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Look : MonoBehaviour
{
    public GameObject target;               //reference to the Target gameobject
    public GameObject face;                 //reference to the character's face
    public GameObject nearestObject;        //current nearest object
    public float smoothTime = 1;            //the smoothing timing
    public List<GameObject> objectsInSight;

    private Vector3 currentVelocity;

    private void Update()
    {
        MoveTargetLookAt();
    }

    private void OnTriggerEnter(Collider other)
    {
        if (other.CompareTag("Wall")) return;

        if(nearestObject == null)
        {
            nearestObject = other.gameObject;
        }

        if(!objectsInSight.Contains(other.gameObject))
        {
            objectsInSight.Add(other.gameObject);
        }
    }

    private void OnTriggerExit(Collider other)
    {
        if(objectsInSight.Contains(other.gameObject))
        {
            objectsInSight.Remove(other.gameObject);
        }

        if(other.gameObject == nearestObject)
        {
            FindNearestObject();
        }
    }

    private void MoveTargetLookAt()
    {
        if(nearestObject != null)
        {
            target.transform.position = Vector3.SmoothDamp(target.transform.position,
                nearestObject.transform.position, ref currentVelocity, smoothTime * Time.deltaTime);
        }
        else
        {
            target.transform.position = Vector3.SmoothDamp(target.transform.position,
                face.transform.position + new Vector3(0, 1.5f, 1f), ref currentVelocity, smoothTime * Time.deltaTime);
        }
    }

    //Note: Original code from the tutorial.
    //To quickly uncomment this code, select all lines in green and press Ctrl + K + U
    //To comment it again, select all and press Ctrl + K + C
    //private void FindNearestObject()
    //{
    //  if (objectsInSight.Count == 0)
    //  {
    //      nearestObject = null;
    //  }
    //  else if (objectsInSight.Count == 1)
    //  {
    //      nearestObject = objectsInSight[0];
    //  }
    //  else
    //  {
    //      nearestObject = objectsInSight[0];
    //      for (int i = 1; i < objectsInSight.Count; i++)
    //      {
    //          if (Vector3.Distance(face.transform.position, objectsInSight[i].transform.position)
    //              < Vector3.Distance(face.transform.position, nearestObject.transform.position))
    //          {
    //              nearestObject = objectsInSight[i];
    //          }
    //      }
    //  }
    //}

    //Optimized version
    private void FindNearestObject()
    {
        if(objectsInSight.Count == 0)
        {
            nearestObject = null;
        }
        else if(objectsInSight.Count == 1)
        {
            nearestObject = objectsInSight[0];
        }
        else
        {
            //This is just a variable to hold our current nearest object (caching)
            nearestObject = objectsInSight[0];
            var nearestObjectDistance = getDistance(face.transform.position,
                                            nearestObject.transform.position);

            for (int i = 1; i < objectsInSight.Count; i++)
            {

                //Optimized version: We don't need to recalculate distance between
                //the current nearest object and the character's face if the current nearest object
                //is still the same object

                if (getDistance(face.transform.position, objectsInSight[i].transform.position)
                    < nearestObjectDistance)
                {
                    nearestObject = objectsInSight[i];

                    nearestObjectDistance = getDistance(face.transform.position,
                                            nearestObject.transform.position);
                }
            }
        }
    }

    //Optimized version: We've replaced Vector3.Distance with sqrMagnitude.
    //Apparently, Vector3.Distance uses square root function which is more costly.
    //I don't quite understand that myself, so let's just follow the pros!
    private float getDistance(Vector3 a, Vector3 b)
    {
        return (a - b).sqrMagnitude;
    }
}