Vulkan: Volumetric Fog is reflected too much in SSR

[CheesecakeCG]

Godot version

4.0 beta 2 and also #66756 rebased against master (57ffc4d)

System information

Arch Linux, KDE 5.25.5, NVIDIA GeForce GTX 1060 6GB, NVIDIA Driver 515.76 Kernel 5.19.12-zen1-1-zen

Issue description

It seems to get brighter the further you zoom away from the surface.

Steps to reproduce

Enable Volumetric Fog and SSR in the same scene.

Minimal reproduction project

ssr_volumetric_fog_bug.zip

[BastiaanOlij]

Hmmm, this seems to me a problem in the order we do things, if SSR is applied after volumetric fog, then SSR simply won't work because the algorithm isn't suitable for reflecting fog. Not sure if this is fixable seeing SSR is a post process while volumetric fog is applied much earlier I think.

@clayjohn your ideas on this?

[clayjohn]

I've been thinking for awhile that we should move SSR earlier in the pipeline and calculate it at the same time as GI and using last frame's radiance like we do for SSIL.