# \[Critical\] Extreme lag / performance problems on UEFN islands with creatures & wildlife while building enabled

**URL:** <https://forums.unrealengine.com/t/critical-extreme-lag-performance-problems-on-uefn-islands-with-creatures-wildlife-while-building-enabled/1585206>\
**Category:** Issues and Bug Reporting\
**Tags:** fortnite-creative, unreal-editor-for-fortnite, fortnite\
**Created:** [January 3, 2024, 6:00pm UTC](https://forums.unrealengine.com/t/critical-extreme-lag-performance-problems-on-uefn-islands-with-creatures-wildlife-while-building-enabled/1585206 "2024-01-03T18:00:49Z")\
**Posts on this page:** 1\
**Showing post:** 31

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**Author:** ![Jimbohalo10](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/jimbohalo10/32/961440_2.png) [@Jimbohalo10](https://forums.unrealengine.com/u/Jimbohalo10)\
**Post date:** [August 27, 2024, 12:33pm UTC](https://forums.unrealengine.com/t/critical-extreme-lag-performance-problems-on-uefn-islands-with-creatures-wildlife-while-building-enabled/1585206/31 "2024-08-27T12:33:24Z")

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hi @im_a_lama ,  
The main documentation is  
[Understanding NPC Behaviors | Unreal Editor for Fortnite Documentation](https://dev.epicgames.com/documentation/en-us/uefn/understanding-npc-behaviors-in-unreal-editor-for-fortnite)

The Colors in  
[What does the different colors of the debug navmesh mean?](https://forums.unrealengine.com/t/what-does-the-different-colors-of-the-debug-navmesh-mean/1301729/7)

The main Documentation is in

> **[AI and NPCs | Unreal Editor for Fortnite Documentation | Epic Developer...](https://dev.epicgames.com/documentation/en-us/uefn/ai-and-npcs-in-unreal-editor-for-fortnite)**
>
> Learn how to use NPCs and create custom AI logic and behaviors for your islands!

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