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

Part 3 of the UE5 Enemy AI Series. Learn how to make enemies chase the player using AI Perception (Sight), speed changes, and Unreal’s forget system—then return to patrol automatically.

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