Vulkan: LightmapGI exhibits light bleeding through occluded areas and face edges

[WickedInsignia]

Godot version

4.0 Alpha 12

System information

Windows 10, GTX1080, i7 6700

Issue description

Godot 4 LightmapGI exhibits light bleeding through completely occluded spaces and on the edges of faces.
The latter has the appearance of insufficient padding or texel resolution but seems to happen regardless of resolution.

Edge Leaks:

These seem to happen regardless of what resolution the meshes are brought in as. Even in this small scene, an atlas resolution of 2048x2048 wasn't enough to resolve. Both shots from Godot 4.

Edge Leaks, Godot 3 vs 4:

Godot 3's mapper doesn't really exhibit the same leak issues, so this seems to be a regression.

Occluded Areas, Godot 3 vs 4:
Completely occluded areas also seem to struggle. In this area where the object intersects with the plane, light bleeds through even with Godot 4's mapper set to Ultra.

Steps to reproduce

MRP provided. Settings in both projects are matched.

Minimal reproduction project

Godot 3:
LightmapQualityExampleG3.zip

Godot 4:
LightmapQualityExampleG4.zip

[Calinou]

I can confirm this on 4.0.alpha 5fec0d2 (Linux, NVIDIA 510.68.02). I could notice increased lightmap bleeding when updating the global illumination demo to readd lightmaps, but haven't found any combination of settings that resolves it.

Edit: Still reproducible as of 4.0.beta6. Remember to remove the .godot/ folder from the MRP before opening the editor, so that all 3D scenes are forced to be reimported to fix octahedral compression issues.

[sietse85]

Is this the same issue? Godot 4.1 Mono on Linux

[Calinou]

Is this the same issue? Godot 4.1 Mono on Linux

This appears to be just vertex normals lacking detail due to the mesh not being subdivided enough, so this is an unrelated issue that can't be fixed by Godot.

[jcostello]

#81872 seems to fix this issue. I would like someone else to verify @WickedInsignia

[lander-vr]

It seems like I'm still experiencing this in 4.2.1 and #81872 does not seem like a solution to this issue. Pixels that should be completely occluded still receive light, which ends up showing as light leaking/bleeding after denoising. This is also discussed in #75440

Modular environment, using 1 bounce:
With denoising:

Without denoising, no bleeding/leaking shows:
(Ignore the weird pattern that shows up in the bounced light, I'm currently trying to investigate when/why this happens, but it is not related to this issue)

Inside a wall section:

Inside a different wall section:

Whether geometry is completely intersecting or just overlapping (which is the case in my environment) doesn't seem to make any difference. These screenshots use medium quality, but with quality set to ultra the same issue persists with the same severity.

[Calinou]

@lander-vr Please open a new issue with a minimal reproduction project attached.