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Lumen, volumetric fog and flashlights.

polycounter lvl 10
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GlowingPotato polycounter lvl 10


My scene consists of a dark environment, a flashlight and fog. pretty clichê.

I’m using lumen for lightning.

My issue is, when the flashlight is on, is has a nice effect on the fog, but it has a light trail when I move it around, I guess this is because of lumen update speed.

I know I can up the lumen update speed in exchange of performance but sounds overkill to do this just for one type of light. (I actually don’t know how much performance is lost if I increase the update speed)

Does anyone know if I can have a moveable Lightsource (flashlight) casting volumetric light, without the light trail when using lumen?



  • GlowingPotato
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    GlowingPotato polycounter lvl 10

    Well. turns out this is a limitation of Unreal. They use a heavy temporal filter to smooth out the fog. but its really bad with moving lights.

    WE can turn this filter off, but other stuff will break.

    I managed to do what I want by tweaking the volumetric gain of the light and its intensity.

    So, kinda solved.

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