# Why does my spot light + volume fog always have something like a Mosaic

**URL:** <https://forums.unrealengine.com/t/why-does-my-spot-light-volume-fog-always-have-something-like-a-mosaic/462754>\
**Category:** Rendering\
**Tags:** light, unreal-engine, Lighting, volumetric-fog, question\
**Created:** [March 23, 2020, 7:01am UTC](https://forums.unrealengine.com/t/why-does-my-spot-light-volume-fog-always-have-something-like-a-mosaic/462754 "2020-03-23T07:01:46Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![41LAB](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@41LAB](https://forums.unrealengine.com/u/41LAB)\
**Post date:** [March 23, 2020, 7:01am UTC](https://forums.unrealengine.com/t/why-does-my-spot-light-volume-fog-always-have-something-like-a-mosaic/462754/1 "2020-03-23T07:01:46Z")

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Why does my spot light + volume fog always have something like a Mosaic and motion blur when changing position

 ![298275-微信截图-20200321134333.jpg](https://d3kjluh73b9h9o.cloudfront.net/original/4X/7/4/b/74bd3fddcfa6472f4507eea3ade9c230d75eb7d1.jpeg)

 ![298277-微信截图-20200321134423.jpg](https://d3kjluh73b9h9o.cloudfront.net/original/4X/5/3/f/53f34927cfd1357caf5a9d8aacde16cdd0a8db4a.jpeg)

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**Author:** ![anon84199231](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anon84199231](https://forums.unrealengine.com/u/anon84199231)\
**Post date:** [March 23, 2020, 7:40am UTC](https://forums.unrealengine.com/t/why-does-my-spot-light-volume-fog-always-have-something-like-a-mosaic/462754/2 "2020-03-23T07:40:01Z")

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You should try this command “r.VolumetricFog.GridPixelSize” and “r.VolumetricFog.HistoryMissSupersampleCount”.  
GridPixelSize is xy pixel size per cell.(I recommend set to 2)  
HistoryMissSupersampleCount is decrease noise when camera pan and camera cut,but increase cost.

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**Author:** ![LorenzoSalvara](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@LorenzoSalvara](https://forums.unrealengine.com/u/LorenzoSalvara)\
**Post date:** [March 26, 2024, 11:54am UTC](https://forums.unrealengine.com/t/why-does-my-spot-light-volume-fog-always-have-something-like-a-mosaic/462754/3 "2024-03-26T11:54:00Z")

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did you find a solution for this? im having the exact same problem but neither of those commands seem to do anything

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**Author:** ![Koshari\_Studios](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Koshari\_Studios](https://forums.unrealengine.com/u/Koshari_Studios)\
**Post date:** [January 3, 2025, 2:07pm UTC](https://forums.unrealengine.com/t/why-does-my-spot-light-volume-fog-always-have-something-like-a-mosaic/462754/4 "2025-01-03T14:07:19Z")

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These steps worked for me.

1. make sure to turn on cast volumetric shadows on whatever light you used.
2. Type in the console command exactly this “r.VolumetricFog.GridPixelSize 2”
3. then type in this exactly (warning it is pretty expensive and will use up quite alot of ram) “r.VolumetricFog.GridSizeZ 256” (increse that number if there is still some flicker or jitter.

ALSO, take a look at [this post](https://forums.unrealengine.com/t/volumetric-light-ghost-trail-issue-still-no-fix-for-it/492710/5)