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Conditional NPC Spawning & Behavior Tools

NPC Behavior Scheduling System

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A system for populating open worlds with reactive NPC behaviors using a limited actor pool.

Prototype captured in Unreal Engine 5

Overview

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Designed and prototyped a system to streamline the scheduling of NPC daily behaviors.

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The goal of this tool is to increase world immersion by enabling NPCs to perform believable, context-aware actions based on time of day and other stimuli—creating a world that feels active and alive without direct player involvement.

Key Features

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  • SPAWN TREES:

Custom-made Behavior Tree framework used to conditionally spawn NPCs and assign behaviors based on world state. Click here for more info on Spawn Trees.​

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  • ​STATE TREES: 

​Drive high-level NPC decision-making, allowing characters to locate and claim available Smart Objects.​

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  • SMART OBJECTS:

​Interactable objects placed throughout the world. Once claimed, they take control of the user's behavior to execute specific behaviors (e.g., working, resting, idling anims).​

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  • ​MOTION MATCHING:

​Provides natural-looking locomotion by selecting closest-match animation frames based on movement trajectory.​

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  • ​MOTION WARPING:

Provides smooth transitions between movement and interaction animations.

What I Learned​​

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  1. Gained hands-on experience with several of UE5’s newer tools, including State Trees, Smart Objects, and Motion Matching

  2. Practiced using multiple AI methodologies in tandem (State Trees + Behavior Trees) to create a single cohesive behavior setup.

What's Next​​

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  1. Introduce a second group of hostile NPCs with their own daily schedule.

  2. Enable emergent interactions: when opposing groups run into each other, they dynamically break from their schedule to engage in combat. On combat completion, they resume their schedules.

  3. Expand the system to support more dynamic behaviors. (e.g. react to weather, deliver contextual dialogue, etc.)

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