SDFGI visual banding / Regression in Godot 4.4 beta RC1

[TheDamocles]

Tested versions

In the current 4.4 beta RC1, SDFGI encounters visual banding and more light leaking compared to the same scene rendered in 4.3 stable (and previous version 4.2).

The problem did not appear in 4.4 dev 7 yet. So some change after that release must cause it.

System information

Linux Mint 22, AMD Ryzen 7 7840HS w/ Radeon 780M Graphics × 8 + GeForce RTX 4060 Max-Q / Mobile

Issue description

Light leaks more prominently through thinner walls, and the shadows create visual horizontal bands that where not visible in 4.3.
Also the light looses energy quicker, resulting in darker bounces.

The scene uses a simple imported glb mesh for the walls and windows in the scene.

The only change to SDFGI I can see recently was about handling custom sky rotation.

Godot 4.3 stable:

Godot 4.4 beta 1

Steps to reproduce

Should be reproducible with SDFGI on any more complex scene with thinner walls that can cause light leaking and angled surfaces.

Minimal reproduction project (MRP)

none attached

[Calinou]

Please upload a minimal reproduction project¹ to make this easier to troubleshoot.

Footnotes

1. A small Godot project which reproduces the issue, with no unnecessary files included. Be sure to not include the .godot folder in the archive (but keep project.godot).
   
   Drag and drop a ZIP archive to upload it. Do not select another field until the project is done uploading.
   
   Note for C# users: If your issue is not C#-specific, please upload a minimal reproduction project written in GDScript. This will make it easier for contributors to reproduce the issue locally as not everyone has a Mono setup available. ↩

[TheDamocles]

A minimal test, created with Godot 4.3 stable
SDFGI_Test_Minimal.zip

I use C#, but that just for the ingame camera controller. You can delete the "actor" node if needed.
The visual issues can be seen already in the editor itself.

The scene looks still fine in 4.4 Dev 7, the issues crop up in the Beta 1 build. (Im using the mono builds here)

[matheusmdx]

I'm able to reproduce the issue, i'll bisect.

[matheusmdx]

Bisected to #100441, @StaydMcMuffin

[clayjohn]

Cc @StaydMcMuffin must be a problem with the normal we write out for SDFGI

[StaydMcMuffin]

Cc @StaydMcMuffin must be a problem with the normal we write out for SDFGI

I'm actually stumped by this one. Assuming the normals that get written out are from the normal_output_buffer/normal_roughness_output_buffer variables assigned in the MODE_RENDER_MATERIAL/MODE_RENDER_NORMAL_ROUGHNESS blocks at the end of the shader, there should be no real difference from my changes, as these seem to just pack the final shading normal.
Granted I'm not very familiar with the SDFGI side of things, so someone more knowledgeable than I should probably take a look. Perhaps there's a discrepancy between what's being output and what the SDFGI shaders expect?

[clayjohn]

Solved! We were using the geo_normal for writing out the normals for SDFGI instead of using the normal_interp. So we were wrongly flipping the normal direction based on gl_FrontFacing when we shouldn't have

[TheDamocles]

Thanks for solving this issue. Looking forward to 4.4