Unreal Engine 5 Enemy AI #3 – Chasing the Player & Forgetting System

Unreal Engine 5 Enemy AI #3 – Chasing the Player & Forgetting System

Published: August 01, 2025 • Series: Enemy AI Series • Level: beginner

unreal ue5 enemy ai blueprints ai perception patrol chasing forgetting gamedev

Welcome back to the Unreal Engine 5 Enemy AI Series!

  • In Part 1, we created an enemy character with AI Sight.
  • In Part 2, we added patrol paths with NavMesh and fixed sliding animations.
  • Now in Part 3, we’ll make the enemy chase the player, then forget after a few seconds and return to patrol.

This is one of the most important mechanics for believable AI: enemies shouldn’t chase forever, but they also shouldn’t instantly forget you. We’ll configure Unreal’s AI Perception, tweak project settings, and wire everything in Blueprints only.

🎯 What You’ll Learn

  • Fine-tuning AI sight, lose-sight radius, and vision angle
  • Understanding Max Age and Unreal’s Forget Stale Actors system
  • Making the AI chase the player with increased speed
  • Returning to patrol speed when the player is forgotten
  • Debugging with print strings and text format
  • Fixing “sticky” Blueprint cache issues that can break AI logic
  • Visualizing AI vision cones in UE5.6

📝 Chapters

  • 00:00 – Intro & What’s Coming
  • 01:10 – AI Sight: Configuring Perception
  • 02:28 – Max Age & Forgetting Explained
  • 03:10 – Project Settings: Forget Stale Actors
  • 03:45 – Patrol Speed Setup
  • 04:23 – Blueprint: Chasing the Player
  • 06:41 – Blueprint: Forget & Resume Patrol
  • 08:16 – Binding Forget Events
  • 09:54 – Debugging & Troubleshooting Cache Issues
  • 10:46 – Fixing Persistent Bugs (Intermediate & Cache Folders)
  • 11:27 – Testing in Editor + Visual Debug Tips
  • 12:12 – Outro & Next Steps

⚙️ Step 1: Configure AI Perception (Sight)

Open BP_EnemyGuard and select the AI Perception component.
In Details → Sight Config:

  • Sight Radius = 600 (6m) → balanced detection range.
  • Lose Sight Radius = 800 → gives AI a buffer before forgetting.
  • Peripheral Vision Half Angle = 60° → allows sneaking from behind.
  • Max Age = 5s → AI memory span (forget after 5s).

💡 Important Gotcha:
Max Age is not directly readable in Blueprints (it won’t update live). Instead, we rely on Unreal’s internal forget system.

⚙️ Step 2: Enable Forget Stale Actors (Project Settings)

Go to Edit → Project Settings → Engine → AI System.
Enable: Forget Stale Actors ✅

Without this, enemies never truly forget targets, no matter the Max Age. This single setting makes the whole system work.

⚙️ Step 3: Patrol Speed vs. Chase Speed

Select Character Movement component in BP_EnemyGuard:

  • Max Walk Speed = 300 (patrol speed)
  • Max Walk Speed Crouch = 250 (extra realism if crouching AI)

Later, when chasing the player, we’ll temporarily set this to 500.

⚙️ Step 4: Blueprint – Chasing the Player

  1. Select AI Perception component → scroll to Events → click On Target Perception Updated (+).
  2. A new event node appears.
  3. From Actor pin, drag off → Cast to Player Blueprint (e.g. BP_ThirdPersonCharacter).
  4. Drag Character Movement component into graph → connect to Set Max Walk Speed = 500.
  5. Add AI Move To:
    • Pawn = Self
    • Target Actor = Player cast reference

👉 Now, when AI sees the player:

  • Speed increases to 500
  • AI runs towards player

⚙️ Step 5: Blueprint – Forgetting the Player

  1. Select AI Perception component → On Target Perception Forgotten (+).
  2. Add event node.
  3. From Actor pin → Cast to Player Blueprint (same as above).
  4. Set Max Walk Speed = 300 (return to patrol pace).
  5. Connect execution to Get All Actors with Tag (patrol logic from Part 2).

⚙️ Step 6: Binding the Forget Event

Unreal doesn’t auto-bind the Forget event.

  • Right-click → search Assign On Target Perception Forgotten.
  • Place node near Event BeginPlay.
  • Connect AI Perception component as target.
  • Hook event pin to custom Forget logic.

⚙️ Step 7: Debugging the Forget System

Add debug print:

  1. After Forget event fires → Format Text node.
    • Format string: AI forgot {Actor}.
  2. Connect Actor pin.
  3. Pipe into Print String.

👉 Now when AI forgets the player, you’ll see a message in the viewport and log.

⚠️ Step 8: Troubleshooting AI Bugs

Sometimes AI doesn’t update after changes. Common causes:

  1. Old actors in level

    • Delete BP_EnemyGuard instances.
    • Drag fresh copies into level.
    • Reassign tags (path1, path2).

  2. Stale cache folders

    • Close Unreal.
    • Delete Intermediate and DerivedDataCache from project folder.
    • Reopen project (Unreal rebuilds them).

💡 This fixes 90% of “AI stuck” issues after changing perception or Blueprint logic.

🎥 Testing

  • Hit Play.
  • Approach AI → it sees you → chase speed (500).
  • Run out of sight → after 5 seconds → Forget event fires → AI slows to patrol (300) and resumes route.
  • Press ' (apostrophe) + Numpad 4 → open Perception Debugger.
  • Green cone shows vision → helps test radius and FOV.

👉 Note: In UE5.6, sometimes only one AI shows in visualizer (quirk). Behavior still works fine.

✅ Summary

By now, your AI can:

  • Patrol between points (from Part 2)
  • Detect player with AI Perception (Sight)
  • Chase player at higher speed (500)
  • Forget after 5 seconds → return to patrol speed (300)
  • Debug forget events in real time

This is the foundation of believable AI—not too robotic, not too dumb.

📦 Project Files → GitHub Repo
🌐 More Tutorials → rambod.net
💬 Drop questions in comments → I reply to all.
🔔 Subscribe for Part 4: Sound Sensing & Chasing Upgrades

📺 Watch the full tutorial:
👉 https://www.youtube.com/watch?v=1U19AJxCpNw