Shadow Caster Mask does not affect LightmapGI baking for lights with Static bake mode

[Calinou]

• Related to Vulkan: LightmapGI always bakes direct light shadows (for fully baked lights), even for lights that have shadows disabled #56611.

Tested versions

• Reproducible in: 4.4.dev 7187c25

System information

Godot v4.4.dev (7187c25) - Fedora Linux 41 (KDE Plasma) on X11 - X11 display driver, Multi-window, 1 monitor - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 4090 (nvidia; 560.35.03) - 13th Gen Intel(R) Core(TM) i9-13900K (32 threads)

Issue description

The Light3D Shadow Caster Mask property does not affect lights with Static bake mode when baking lightmaps.

Like #56611, this may be considered to be intended (as disabling shadow casting for certain objects may be done for performance reasons, which is a moot point for an offline baking process). However, this can be an issue if the shadow casting is disabled for aesthetic reasons or for accurate shadowmask baking (for DirectionalLight3D).

Real-time light

Baked light with Static bake mode

Notice how some objects that previously didn't cast shadows now cast shadows.

Steps to reproduce

• Create meshes, some on visual layer 1, some on visual layer 2.
• Create lights with shadows enabled. Set their shadow caster mask to affect only layer 1.
• Set lights to Static bake mode. Before baking, notice that certain objects don't cast shadows (which is expected).
• Bake lightmaps. Notice how all objects cast shadows now.

Minimal reproduction project (MRP)

test_shadow_caster_mask_lightmap.zip