Simplest Way to Create a State Machine in Godot 4 (detailed tutorial)

Introduction

In this tutorial, you will learn how to create a finite state machine (FSM) in Godot 4, which is a vital tool for managing complex behaviors in game development. This guide will walk you through defining states, establishing transitions, and utilizing the LimboAi addon for an efficient setup. By the end of this tutorial, you’ll have a practical understanding of implementing a state machine in your game projects.

Step 1: Setting Up Godot and LimboAi

1. Download Godot 4 from the official website if you haven't already.
2. Install the LimboAi addon by following these steps:
   • Visit the LimboAi GitHub page.
   • Download the latest release and extract it into your Godot project’s addons directory.
   • Enable the addon in your project settings under Project -> Project Settings -> Plugins.

Step 2: Project Setup

1. Create a new project in Godot 4.
2. Set up the project structure by creating the following directories:
   • Scripts
   • States
   • Resources
3. Save your scene in the main project directory to avoid losing your progress.

Step 3: Initiating the State Machine

1. Create a new script in the Scripts directory for your state machine.
2. Initialize the state machine within your main script:

   var state_machine = StateMachine.new()
   

3. Connect the state machine to your Godot node to manage its behaviors.

Step 4: Defining States

1. Create individual scripts for each state you want to define. For example:
   • IdleState.gd
   • RunState.gd
   • JumpState.gd
2. Implement the _enter and _exit methods to handle state changes:

   func _enter():
       # Code for entering the state
       
   func _exit():
       # Code for exiting the state
   

Step 5: Adding States to the State Machine

1. Register each state in your state machine script:

   state_machine.add_state(IdleState.new())
   state_machine.add_state(RunState.new())
   state_machine.add_state(JumpState.new())
   

2. Set the initial state to start with:

   state_machine.change_state(IdleState)
   

Step 6: Transitioning Between States

1. Define transitions in each state script by overriding a method, for example:

   func transition_to_run():
       state_machine.change_state(RunState)
   

2. Call the transition method based on conditions, such as player input or game events.

Step 7: Saving and Accessing State Information

1. Create a resource file to save your state configurations:
   • Go to Resources and create a new resource type for your states.
2. Load the resource in your main script to access the state definitions when needed:

   var state_data = preload("res://Resources/StateData.tres")
   

Conclusion

You have now set up a basic finite state machine in Godot 4 using the LimboAi addon. This FSM setup allows for clear management of states and transitions, making your game development process more organized and efficient. As next steps, consider experimenting with adding more states, customizing transitions, or integrating the state machine with other game systems. With this knowledge, you are well on your way to implementing advanced behaviors in your game projects.