How to Make a Simple Behavior Tree in Unreal Engine 5 - Advanced AI

Introduction

In this tutorial, you will learn how to create a simple AI using Behavior Trees in Unreal Engine 5. This technique is essential for developing more advanced AI systems in games, enabling characters to make decisions based on their environment. By the end of this guide, you’ll have a foundational understanding of Behavior Trees and how to implement them in your projects.

Step 1: Setting Up the Project

1. Open Unreal Engine 5 and create a new project.
2. Select a project template (e.g., Third-Person template) that suits your needs.
3. Make sure to enable the necessary plugins:
   • Go to Edit > Plugins.
   • Search for Behavior Tree and ensure it is enabled.
4. Once your project is set up, navigate to the Content Browser.

Step 2: Creating the AI Character

1. Add a new Character Blueprint:
   • Right-click in the Content Browser.
   • Select Blueprint Class and choose Character.
   • Name it (e.g., AICharacter).
2. Set up the AI Controller:
   • Create a new Blueprint Class based on AIController.
   • Name it (e.g., AIController).
3. Assign the AI Controller to your AI Character:
   • Open the AICharacter Blueprint.
   • In the details panel, set the AI Controller Class to your newly created AIController.

Step 3: Creating the Behavior Tree

1. Create the Behavior Tree:
   • Right-click in the Content Browser.
   • Select Artificial Intelligence > Behavior Tree and name it (e.g., AIBehaviorTree).
2. Create a corresponding Blackboard:
   • Right-click again and select Artificial Intelligence > Blackboard.
   • Name it (e.g., AIBlackboard).
3. Open the Blackboard and add relevant keys:
   • Add a Vector key for storing the target location.
   • Add an Object key for the target player character.

Step 4: Designing the Behavior Tree

1. Open the Behavior Tree you created.
2. Add nodes to define the AI's behavior:
   • Start with a Selector node to manage different behaviors.
   • Under the Selector, add a Sequence node for actions the AI will perform.
3. Add tasks within the Sequence:
   • Use Move To node to navigate towards the player.
   • Include a condition check (e.g., is the player in range).
4. Connect the nodes logically to define the flow of actions.

Step 5: Implementing the AI Logic

1. Open the AI Controller Blueprint.
2. Implement the logic to run the Behavior Tree:
   • In the Event Begin Play node, add the following:

     Run Behavior Tree (AIBehaviorTree)
     

   • Set the blackboard key values:

     Get Blackboard Component -> Set Value As Object (Target Key)
     

3. Add functionality to update the target location based on the player's position.

Conclusion

In this tutorial, you learned how to set up a simple AI using Behavior Trees in Unreal Engine 5. We covered everything from creating the AI character and controller to designing the Behavior Tree and implementing AI logic. As a next step, consider experimenting with different nodes and behaviors to enhance your AI's complexity and capabilities. Happy developing!