# Spawn Atmospheric Fog At Runtime - Precompute Not Working

**URL:** <https://forums.unrealengine.com/t/spawn-atmospheric-fog-at-runtime-precompute-not-working/385735>\
**Category:** Blueprint\
**Tags:** spawn, Atmospheric-Fog, unreal-engine, Blueprint, question\
**Created:** [February 21, 2017, 11:16pm UTC](https://forums.unrealengine.com/t/spawn-atmospheric-fog-at-runtime-precompute-not-working/385735 "2017-02-21T23:16:00Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![anonymous\_user\_af66ec49](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_af66ec49](https://forums.unrealengine.com/u/anonymous_user_af66ec49)\
**Post date:** [February 21, 2017, 11:16pm UTC](https://forums.unrealengine.com/t/spawn-atmospheric-fog-at-runtime-precompute-not-working/385735/1 "2017-02-21T23:16:00Z")

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Hey everyone!

Back with another question. Have a class array of actors that each contain a directional light, sky light, atmospheric fog, and exponential height fog, all with a different ‘mood’ that will be chosen by a variable. At runtime, in the Level Blueprint, when the chosen actor is spawned, the Atmospheric Fog does not spawn along with it, causing the sky to remain black.

According to this [unresolved question][1], “SetPrecomputeParams” and “StartPrecompute” nodes are required. I’m using a GetComponentsByClass to snag the Atmospheric Fog, then attempting to get the atmospheric precompute params, feeding it into the SetPrecomputeParams node and then starting precompute.

 ![127205-atmosphericfogsetup.png](https://d3kjluh73b9h9o.cloudfront.net/original/4X/e/6/c/e6ce1a89500d7507ca8e4ee01c4a3e8523cc8cfb.png)

However, nothing happens at runtime. Sky is still black. Any ideas as to why this is happening?

Alternatively, is there a way to discover a few key Atmospheric Fog variables from the blueprint and using those to set a pre-existing Atmospheric Fog’s variables? That way we can keep all the work we did for each ‘mood’ without necessarrily having to run the precompute?

Any ideas are welcome!!

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**Author:** ![burak.io](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@burak.io](https://forums.unrealengine.com/u/burak.io)\
**Post date:** [February 3, 2018, 4:32pm UTC](https://forums.unrealengine.com/t/spawn-atmospheric-fog-at-runtime-precompute-not-working/385735/2 "2018-02-03T16:32:34Z")

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Any progress on this?

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**Author:** ![Derjyn](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/derjyn/32/931618_2.png) [@Derjyn](https://forums.unrealengine.com/u/Derjyn)\
**Post date:** [June 17, 2018, 3:24pm UTC](https://forums.unrealengine.com/t/spawn-atmospheric-fog-at-runtime-precompute-not-working/385735/3 "2018-06-17T15:24:17Z")

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This is still an issue in 4.19… Hoping this gets fixed ASAP, as it’s been hindering some features I’m working on, in a couple different projects. It drives me mad every time I got back to tinker with any of that part of the project.