Service

Basic info about services in AI Tree

Services are special nodes that continuously update data or perform certain actions throughout the execution of the behavior tree. Unlike tasks, which are executed once and then completed, services run in the background and can periodically update information or check conditions, providing important data to other nodes in the behavior tree.

Service image (green box)

Key Aspects of Service:

1. Periodic Execution:

   • Services are executed at regular intervals, set by the developer. For example, a service might periodically check the environment or update information about the NPC’s current target at a specific time interval.

2. Data Support:

   • Services are often used to update variables in the Blackboard. For instance, a service could update a key in the Blackboard that holds the player’s position or the NPC’s current state (e.g., in combat, patrolling, etc.).

3. Attached to Tree Branches:

   • Services are attached to specific branches of the behavior tree and only run when that branch is active. This allows for efficient management, activating services only when necessary.

4. Logic Without Tasks:

   • Unlike tasks, services don’t perform specific actions (such as attacking or moving). Instead, they support behavior logic by checking conditions and updating data, which can then be used by other nodes in the behavior tree.

5. Flexible Configuration:

   • Services can be configured through the visual Behavior Tree editor or via C#. The developer can set the service’s update frequency and the logic it will perform.

Example of Service Usage:

Suppose an NPC has a behavior tree for patrolling an area. A service can be attached to the patrol node, periodically updating the player’s position in the world so that the NPC can react if the player comes into view. As soon as the player enters the NPC’s line of sight, the service updates the relevant variable in the Blackboard, causing the NPC to switch from patrolling to attacking.

Services are also useful for implementing "smart" behavior systems where NPCs need to frequently update information about the world or environment in order to make the right decisions.

In this way, service nodes provide dynamic and continuous data updates to support more complex and flexible NPC behavior in the game.