Exponential Height Fog and Local Fog Blending

Development Rendering
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1

Hello,

Recently, we encountered a visual problem when working with local fogs.

We noticed that it always renders on top of local fog, which appears to be a visual bug. It is obvious with a large world, with local fog standing out on the horizon.

Are there any commands or options to avoid this scenario? Maybe you have other workarounds?

Looking for any suggestions,

Bartłomiej Gadzała

2

Steps to Reproduce

  1. Make an empty scene with sky and directional light
  2. Add Exponential Height Fog with high density
  3. Add Local Fog with high density and low falloff
  4. Observe that local fog is always rendered on top of local fog, regardless of distance.
3

Hello,

Thank you for reaching out.

I’ve been assigned this issue, and we will be looking into Local Fog Volume blending for you.

4

Hello,

This is intended behavior.

When Volumetric Fog is disabled, Local Fog Volumes are composited on top of Exponential Height Fog.

https://dev.epicgames.com/documentation/en\-us/unreal\-engine/local\-fog\-volumes\-in\-unreal\-engine

When Volumetric Fog is enabled, and “r.LocalFogVolume.RenderIntoVolumetricFog=1”, then the Local Fog Volumes will be composited into the Volumetric Fog.

Please let us know if this helps.

5

Hello,

Thank you for the answer. Unfortunately for us, volumetric fog is not an option. It is too expensive, and we can’t have it enabled on all graphic settings quality levels. We were thinking more of replacing the Material Instance, which will allow us to blend with distance.

6

Hello,

Both Exponential Height Fog and Local Fog use FGlobalShaders, not Materials.

  • Exponential Height Fog: “FExponentialHeightFogPS” from “HeightFogPixelShader.usf”
  • Local Fog: “FLocalFogVolumeTiledRenderPS” from “LocalFogVolumeSplat.usf”

What Material (Instance) were you intending to replace?