Vulkan Mobile: LightmapGI sampling is not disabled on lights with Static bake mode, causing double lighting to appear

[Calinou]

Godot version

4.2.beta1 (first version to be able to sample lightmaps correctly with Mobile), 4.2.rc1

System information

Fedora 38, GeForce RTX 4090 (NVIDIA 535.129.03)

Issue description

LightmapGI sampling is not disabled on lightmapped meshes with Static bake mode, causing double lighting to appear:

Forward+	Mobile

The dynamic object rendering issue is tracked in #84846.

Steps to reproduce

• Create meshes with Static bake mode that have UV2 (you can use Add UV2 in PrimitiveMesh for this).
• Add some lights, enable shadows on them and set their bake mode to Static.
• Bake lightmaps and look at the scene's appearance.
• Switch to the Mobile rendering method and compare visuals.

Minimal reproduction project

test_lightmapgi_mobile.zip

[clayjohn]

To clarify, the problem here is that the light is still drawn dynamically despite using the static bake mode right? If a light is statically baked, my expectation is that only the lightmap will be used. I wouldn't expect the lightmap to be disabled.

I noticed while working on something else that the dynamic light is added to the lightmap even when the light is statically baked

[Calinou]

To clarify, the problem here is that the light is still drawn dynamically despite using the static bake mode right? If a light is statically baked, my expectation is that only the lightmap will be used. I wouldn't expect the lightmap to be disabled.

Yes, I expect it to render like in Forward+ and Compatibility where the real-time light is skipped on the lightmapped surface (since it's already been baked).

This does not apply to surfaces that don't have a lightmap due to not having been baked (or not having UV2 generated), even if the light uses the Static bake mode.

[clayjohn]

To be clear, in the Forward+ backend, the dynamic light is still added on lightmapped surfaces. So this issue must exist in both backends.

Forward+ also has an unitialized memory error because the bake mode is only passed to the shader if the light is using shadows.