LightmapGI doesn't take CameraAttributes into account when baking indirect light in lightmaps (and only partially for direct light)

[Calinou]

• Related to VoxelGI does not preserve CameraAttributes across scene reloads #74134.

Godot version

4.0.rc6

System information

Fedora 37, GeForce RTX 4090 (NVIDIA 525.85.05)

Issue description

LightmapGI doesn't take CameraAttributes into account when baking indirect light in lightmaps (and only partially for direct light, i.e. when using Static bake mode).

DirectionalLight3D bake mode set to Dynamic

Regardless of the presence of a CameraAttributes resource in the LightmapGI's properties, this is the result after baking.

DirectionalLight3D bake mode set to Static, LightmapGI with CameraAttributesPhysical

This works as expected, but changing exposure parameters then baking again doesn't affect light brightness at all even after rebaking lightmaps (be it aperture, shutter speed, ISO or multiplier).

Also note that using a CameraAttributesPractical results in the same lighting, which is unexpected.

DirectionalLight3D bake mode set to Static, LightmapGI without CameraAttributesPhysical

This is overly bright as expected (which shows that the presence of the CameraAttributes is taken into account by LightmapGI somehow).

Steps to reproduce

• Follow Physical light and camera units documentation to enable physical light and camera units in a project.
• Set up LightmapGI then bake it.

Minimal reproduction project

physical_light_camera_units_lightmap.zip

[clayjohn]

I'll take a deeper look soon. But it doesn't look like there is a bug here. The Camera attributes that is used by GI (both Lightmap and Voxel) is only used for adjusting the dynamic range when baking. At render time, the exposure will be adjusted to match the CameraAttributes that is used at render time.

You want the bake-time exposure to be as similar to the render-time exposure as you can to reduce banding.