# Object and characters leave the trail

**URL:** <https://forums.unrealengine.com/t/object-and-characters-leave-the-trail/1812240>\
**Category:** Rendering\
**Tags:** unreal-engine, Rendering, Lighting, question\
**Created:** [April 20, 2024, 8:17am UTC](https://forums.unrealengine.com/t/object-and-characters-leave-the-trail/1812240 "2024-04-20T08:17:18Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![TheKJ](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@TheKJ](https://forums.unrealengine.com/u/TheKJ)\
**Post date:** [April 20, 2024, 9:08am UTC](https://forums.unrealengine.com/t/object-and-characters-leave-the-trail/1812240/2 "2024-04-20T09:08:19Z")

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Lumen is temporal, it works by tracing(the expensive part) a fraction of pixels and rotates through the fraction over time every frame to save performance. If we trace all pixels for lighting every frame, the GPU would have a hard time remaining responsive.

It then uses TAA to smooth any noise from alternating tracing _ **directions** _ as well.  
It’s “normal”, but the [Lumen devs](https://forums.unrealengine.com/t/lumen-gi-and-reflections-feedback-thread/501108) have no solution as of now.

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