LightmapGI appears too saturated with static colored lights since 4.4.beta1

[Calinou]

Tested versions

• Reproducible in: 4.4.beta1, 4.4.beta2
• Not reproducible in: 4.3.stable, 4.4.dev7

System information

Godot v4.4.beta (cb460ad) - Fedora Linux 41 (KDE Plasma) on X11 - X11 display driver, Multi-window, 1 monitor - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 4090 (nvidia; 565.77) - 13th Gen Intel(R) Core(TM) i9-13900K (32 threads)

Issue description

Lightmaps appear too saturated when baking colored lights that have the Static global illumination mode:

4.3.stable up to 4.4.dev7

4.4.beta1 onwards

This affects both directional and non-directional lightmaps, regardless of their texture's compression mode (i.e. it's not caused by VRAM compression). Maybe a sRGB/linear conversion is missing somewhere?

I bisected the regression to cb460ad. cc @Geometror

Steps to reproduce

• Bake lightmaps with colored lights that have the Static global illumination mode.

Minimal reproduction project (MRP)

test_lightmap_directional_compress.zip

LightmapGI nodes are in static.tscn and static_directional.tscn.

[SpockBauru]

Changed the hundred trees MRP in order to have a reduced VRAM footprint while baking:

playble_terrain.zip

There is indeed something wrong with static light colors, they are more saturated on 4.4.beta1:

4.3	4.4.dev7	4.4.beta1

Not only colors, there's also something wrong with the shadows. If I bake with Shadowmask enabled and dynamic DirectionalLight, the shadows are a way more detailed and easier to see. But with static DirectionalLight, shadows are barely noticeable and look like a blob:

Dynamic DirectionalLight + Shadowmask	Static DirectionalLight

Edit: Shadow comparison with Static DirectionalLight between dev7 and beta1

4.4.dev7	4.4.beta1