State machines for AI behavior in Unity - Mini Project: Build & Apply

State machines for AI behavior

📖 Scenario: You are creating a simple AI for a game character in Unity. This AI will have three states: Idle, Patrol, and Chase. The character will start by idling, then patrol between points, and chase the player if the player is close enough.

🎯 Goal: Build a basic state machine in Unity C# script to control AI behavior switching between Idle, Patrol, and Chase states based on player distance.

📋 What You'll Learn

Create an enum called AIState with values Idle, Patrol, and Chase

Create a variable called currentState of type AIState and set it to AIState.Idle

Create a float variable called chaseDistance and set it to 5f

Write a method called UpdateState that changes currentState to Chase if the player is within chaseDistance, otherwise to Patrol

Print the current state in the Update method

💡 Why This Matters

🌍 Real World

State machines are used in games to control AI characters' behavior in a clear and organized way.

💼 Career

Understanding state machines is important for game developers and AI programmers to create responsive and maintainable AI systems.

1

Create AIState enum and currentState variable

Create an enum called AIState with values Idle, Patrol, and Chase. Then create a variable called currentState of type AIState and set it to AIState.Idle inside the AIBehavior class.

Unity

using UnityEngine;

public class AIBehavior : MonoBehaviour
{
    // Create AIState enum and currentState variable
    // Your code here
}

Need a hint?

Use enum AIState { Idle, Patrol, Chase } and declare public AIState currentState = AIState.Idle; inside the class.

2

Add chaseDistance variable

Add a public float variable called chaseDistance and set it to 5f inside the AIBehavior class.

Unity

using UnityEngine;

public class AIBehavior : MonoBehaviour
{
    public enum AIState { Idle, Patrol, Chase }
    public AIState currentState = AIState.Idle;

    // Add chaseDistance variable
    // Your code here
}

Need a hint?

Declare public float chaseDistance = 5f; inside the class.

3

Write UpdateState method to change currentState

Write a public method called UpdateState that takes a float parameter called playerDistance. Inside this method, if playerDistance is less than or equal to chaseDistance, set currentState to AIState.Chase. Otherwise, set currentState to AIState.Patrol.

Unity

using UnityEngine;

public class AIBehavior : MonoBehaviour
{
    public enum AIState { Idle, Patrol, Chase }
    public AIState currentState = AIState.Idle;
    public float chaseDistance = 5f;

    // Write UpdateState method
    // Your code here
}

Need a hint?

Use an if statement to compare playerDistance with chaseDistance and set currentState accordingly.

4

Print currentState in Update method

In the Update method, call UpdateState with a test float value of 3f to simulate player distance. Then print the current state using Debug.Log with the message "Current State: " followed by currentState.

Unity

using UnityEngine;

public class AIBehavior : MonoBehaviour
{
    public enum AIState { Idle, Patrol, Chase }
    public AIState currentState = AIState.Idle;
    public float chaseDistance = 5f;

    public void UpdateState(float playerDistance)
    {
        if (playerDistance <= chaseDistance)
        {
            currentState = AIState.Chase;
        }
        else
        {
            currentState = AIState.Patrol;
        }
    }

    // Add Update method to call UpdateState and print currentState
    // Your code here
}

Need a hint?

Call UpdateState(3f) inside Update() and print the current state with Debug.Log("Current State: " + currentState);.