Flashing lights in volumetric fog when attenuation is above 3

[AngryCyboot]

Tested versions

• Reproducible in 4.2 and 4.2.1

System information

Godot v4.2.1.stable - Windows 10.0.22631 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 960 (NVIDIA; 31.0.15.4617) - Intel(R) Core(TM) i5-10400F CPU @ 2.90GHz (12 Threads)

Issue description

Lights with a high attenuation flicker when placed in a volumetric fog (effect appears both in scene view and when I run the project).
The effect seem to change randomly depending on the distance to the point of view.
Here the attenuations are 1;3;4 in order for those three lights.

Recording.2024-01-25.132018.mp4

Steps to reproduce

• Create a scene 3d
• create a WorldEnvironment and activate volumetric fog
• create an omnilight and increase it's attenuation above 3
• (optional) move the light relative to the point of view, it makes the effect more noticeable

Minimal reproduction project (MRP)

LightsFlashInVolFogMRP.zip

[Calinou]

This is likely due to high-frequency data being present in the froxels, so temporal reprojection is unable to smooth it out. We may need to cap light attenuation in the volumetric fog shader to prevent this (perhaps we can decrease energy past that value to compensate instead).