Behavior Tree System - Modular Entity AI & Mob Controller
Kiss.My.Assets
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A hierarchical node-based framework for NPC logic. It enables reactive, modular, and scalable AI behaviors by prioritizing tasks through conditional branches and state management.A Behavior Tree is a mathematical model of plan execution used extensively in game development to create complex, lifelike AI. Unlike traditional Finite State Machines (FSMs), which become a "spaghetti" of transitions as complexity grows, BTs are inherently modular.The tree functions through a Ticking system: the root sends a signal down the branches at regular intervals. Each node performs its logic and returns one of three statuses:Success: The task was completed (e.g., the NPC reached the door).Failure: The task couldn't be completed (e.g., the door is locked).Running: The task is still in progress (e.g., the NPC is currently walking).This structure allows for sophisticated decision-making. For instance, a "Combat" branch can be prioritized over a "Patrol" branch; if a "Decorator" node senses an enemy, it immediately interrupts lower-priority tasks to trigger an attack sequence. Because nodes are self-contained, developers can reuse the same "Find Path" or "Reload Weapon" logic across entirely different NPC types without rewriting code.The logic is built on a combination of four node types:Composite: Controls the flow of execution.Selection (S): Executes child nodes until one returns Success. Analogous to a logical "OR."Sequence (Q): Executes nodes one by one until all return Success. Analogous to a logical "AND."Decorator: Filter nodes. They check conditions (e.g., "Does a mob see the player?") or invert the result of a child node.Leaf/Action: Endpoints that execute specific code (play an animation, move to a point, deal damage).Blackboard: Shared AI memory that stores variables (target, health, coordinates) accessed by tree nodes.
