LightmapGI: Environment sky intensity is not taken into account for ambient light baking when physical light units are enabled

[Calinou]

• Related to LightmapGI doesn't take CameraAttributes into account when baking indirect light in lightmaps (and only partially for direct light) #74139,
  SDFGI Skylight Won't Respect Camera Attribute Exposure #74899
  and Camera exposure adjustments cause changes in ambient lighting contribution #104174.

Tested versions

• Reproducible in: 4.5.beta 71a9948

System information

Godot v4.5.beta (71a9948) - Fedora Linux 42 (KDE Plasma Desktop Edition) on X11 - X11 display driver, Multi-window, 1 monitor - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 5090 (nvidia; 575.64.03) - AMD Ryzen 9 9950X3D 16-Core Processor (32 threads) - 62.33 GiB memory

Issue description

Environment sky intensity is not taken into account for ambient light baking when physical light units are enabled. Only the non-physical sky energy parameter is taken into account instead.

Edit: After some testing, it appears to work but is inconsistent. Further testing is

Energy Multiplier = 1.0, Intensity = 300 nt

Energy Multiplier = 1.0, Intensity = 30,000 nt

Lighting appears different due to brighter IBL, but the lightmap is too bright in both cases.

Energy Multiplier = 0.01, Intensity = 300 nt

Ambient light is more suitable now, but it's too bright compared to the sky.

Energy Multiplier = 0.01, Intensity = 30,000 nt

Also notice how the brightness of dynamic object lighting on the sphere of the left is now brighter for some reason.

Steps to reproduce

• Configure the Environment resource in the WorldEnvironment node to adjust sky light energy and intensity. Try different values that should compensate for each other, then bake lightmaps in the MRP and compare results on static and dynamic objects.

Minimal reproduction project (MRP)

Lightmap_dark.zip