Enemy patrol and chase patterns in Unity

Introduction

Enemy patrol and chase patterns make game characters move in smart ways. They help enemies look around and follow the player when close.

When you want enemies to walk back and forth on a path.

When enemies should follow the player after spotting them.

To make game levels more exciting with moving enemies.

When creating stealth or action games with enemy AI.

To add challenge by having enemies chase the player.

Syntax

Unity

using UnityEngine;

public class EnemyPatrolChase : MonoBehaviour
{
    public Transform[] patrolPoints;
    public float speed = 2f;
    public float chaseSpeed = 4f;
    public float chaseRange = 5f;
    private int currentPointIndex = 0;
    private Transform player;

    void Start()
    {
        player = GameObject.FindGameObjectWithTag("Player").transform;
    }

    void Update()
    {
        float distanceToPlayer = Vector3.Distance(transform.position, player.position);

        if (distanceToPlayer < chaseRange)
        {
            ChasePlayer();
        }
        else
        {
            Patrol();
        }
    }

    void Patrol()
    {
        Transform targetPoint = patrolPoints[currentPointIndex];
        transform.position = Vector3.MoveTowards(transform.position, targetPoint.position, speed * Time.deltaTime);

        if (Vector3.Distance(transform.position, targetPoint.position) < 0.1f)
        {
            currentPointIndex = (currentPointIndex + 1) % patrolPoints.Length;
        }
    }

    void ChasePlayer()
    {
        transform.position = Vector3.MoveTowards(transform.position, player.position, chaseSpeed * Time.deltaTime);
    }
}

Use Vector3.MoveTowards to smoothly move the enemy.

Check distance to player to switch between patrol and chase.

Examples

This moves the enemy between patrol points in order, looping back to the first point.

Unity

void Patrol()
{
    // Move between points in a loop
    Transform target = patrolPoints[currentPointIndex];
    transform.position = Vector3.MoveTowards(transform.position, target.position, speed * Time.deltaTime);
    if (Vector3.Distance(transform.position, target.position) < 0.1f)
        currentPointIndex = (currentPointIndex + 1) % patrolPoints.Length;
}

This makes the enemy chase the player at a faster speed.

Unity

void ChasePlayer()
{
    // Move enemy towards player faster
    transform.position = Vector3.MoveTowards(transform.position, player.position, chaseSpeed * Time.deltaTime);
}

Sample Program

This script makes an enemy move between set points. When the player comes close, the enemy chases the player. Otherwise, it keeps patrolling.

Unity

using UnityEngine;

public class EnemyPatrolChase : MonoBehaviour
{
    public Transform[] patrolPoints;
    public float speed = 2f;
    public float chaseSpeed = 4f;
    public float chaseRange = 5f;
    private int currentPointIndex = 0;
    private Transform player;

    void Start()
    {
        player = GameObject.FindGameObjectWithTag("Player").transform;
    }

    void Update()
    {
        float distanceToPlayer = Vector3.Distance(transform.position, player.position);

        if (distanceToPlayer < chaseRange)
        {
            ChasePlayer();
        }
        else
        {
            Patrol();
        }
    }

    void Patrol()
    {
        Transform targetPoint = patrolPoints[currentPointIndex];
        transform.position = Vector3.MoveTowards(transform.position, targetPoint.position, speed * Time.deltaTime);

        if (Vector3.Distance(transform.position, targetPoint.position) < 0.1f)
        {
            currentPointIndex = (currentPointIndex + 1) % patrolPoints.Length;
        }
    }

    void ChasePlayer()
    {
        transform.position = Vector3.MoveTowards(transform.position, player.position, chaseSpeed * Time.deltaTime);
    }
}

Important Notes

Make sure your player GameObject has the tag "Player" set.

Patrol points must be set in the Unity Editor by dragging transforms.

Adjust speeds and chase range to fit your game feel.

Summary

Enemy patrols between points using smooth movement.

Enemy chases player when close enough.

Switching between patrol and chase is based on distance.

Practice

1. What is the main purpose of an enemy patrol pattern in Unity game development?

easy

A. To make the enemy jump randomly

B. To move the enemy between set points repeatedly

C. To make the enemy disappear and reappear

D. To make the enemy shoot projectiles continuously

Solution

1. Step 1: Understand enemy patrol behavior

   Enemy patrol means moving the enemy between fixed points in a loop to simulate guarding or searching.

2. Step 2: Identify correct behavior from options

   Only moving between set points repeatedly matches patrol behavior.

3. Final Answer:

   To move the enemy between set points repeatedly -> Option B

4. Quick Check:

   Enemy patrol = moving between points [OK]

Hint: Patrol means looping between points, not random actions [OK]

Common Mistakes:

• Confusing patrol with attack or random movement
• Thinking patrol involves shooting or disappearing

2. Which of the following is the correct way to check the distance between the enemy and player in Unity C#?

easy

A. float dist = enemy.position.Distance(player.position);

B. float dist = enemy.position - player.position;

C. float dist = Vector3.Distance(enemy, player);

D. float dist = Vector3.Distance(enemy.position, player.position);

Solution

1. Step 1: Recall Vector3.Distance syntax

   The correct method to get distance between two Vector3 points is Vector3.Distance(point1, point2).

2. Step 2: Check each option

   float dist = Vector3.Distance(enemy.position, player.position); uses Vector3.Distance with positions, which is correct. Others have syntax errors or wrong usage.

3. Final Answer:

   float dist = Vector3.Distance(enemy.position, player.position); -> Option D

4. Quick Check:

   Use Vector3.Distance(point1, point2) for distance [OK]

Hint: Use Vector3.Distance with positions, not subtract vectors directly [OK]

Common Mistakes:

• Subtracting vectors without calling Distance method
• Calling Distance on a Vector3 instance incorrectly
• Passing transforms instead of positions

3. Given this code snippet for enemy chase, what will be the output if the player is 3 units away and chaseDistance is 5?

if (Vector3.Distance(transform.position, player.position) < chaseDistance) {
    Debug.Log("Chasing player");
} else {
    Debug.Log("Patrolling");
}

medium

A. No output

B. Patrolling

C. Chasing player

D. Error at runtime

Solution

1. Step 1: Calculate distance and compare

   Distance is 3, chaseDistance is 5, so 3 < 5 is true.

2. Step 2: Determine which branch runs

   Since condition is true, "Chasing player" is printed.

3. Final Answer:

   Chasing player -> Option C

4. Quick Check:

   Distance 3 < 5 triggers chase [OK]

Hint: Compare distance to chaseDistance to decide behavior [OK]

Common Mistakes:

• Confusing less than with greater than
• Assuming no output if condition true
• Thinking code causes error

4. Identify the error in this patrol code snippet:

void Patrol() {
    int currentPoint = 0;
    transform.position = Vector3.MoveTowards(transform.position, patrolPoints[currentPoint].position, speed * Time.deltaTime);
    if (transform.position == patrolPoints[currentPoint].position) {
        currentPoint++;
        if (currentPoint >= patrolPoints.Length) {
            currentPoint = 0;
        }
    }
}

medium

A. currentPoint should be declared outside the method to keep its value

B. Vector3.MoveTowards is used incorrectly

C. Time.deltaTime should not be multiplied by speed

D. The if condition should use < instead of >

Solution

1. Step 1: Check variable scope for currentPoint

   currentPoint is reset to 0 every time Patrol() runs, so it never increments properly.

2. Step 2: Understand how to fix the scope issue

   Declaring currentPoint outside the method (as a class variable) preserves its value between calls.

3. Final Answer:

   currentPoint should be declared outside the method to keep its value -> Option A

4. Quick Check:

   Keep patrol index outside method to track progress [OK]

Hint: Keep patrol index as a class variable, not local [OK]

Common Mistakes:

• Thinking MoveTowards usage is wrong
• Confusing comparison operators in if
• Misunderstanding Time.deltaTime usage

5. How can you combine patrol and chase behaviors so the enemy patrols until the player is within 4 units, then chases the player, and returns to patrol if the player moves away?

hard

A. Use a state variable to switch between patrol and chase based on distance checks

B. Call Patrol() and Chase() methods simultaneously every frame

C. Only use Chase() method and ignore patrol points

D. Use a timer to switch behaviors every 5 seconds regardless of player position

Solution

1. Step 1: Understand behavior switching logic

   The enemy needs to switch between patrol and chase based on player distance dynamically.

2. Step 2: Use a state variable to track current behavior

   A state variable (like enum or bool) can control which method runs each frame depending on distance.

3. Step 3: Implement distance check to update state

   If player is closer than 4 units, set state to chase; else set to patrol.

4. Final Answer:

   Use a state variable to switch between patrol and chase based on distance checks -> Option A

5. Quick Check:

   State variable + distance check = behavior switch [OK]

Hint: Switch states based on distance, don't run both behaviors together [OK]

Common Mistakes:

• Running patrol and chase at the same time causing conflicts
• Ignoring player distance for switching
• Using timers instead of distance checks