[3.x] Tweak default sky appearance to avoid blue tint in shadows in new projects

[Calinou]

3.x version of #57993.

This change only affects projects created after this PR is merged, as only the initial default_env.tres file contains the new values. Creating a new ProceduralSky in the editor or via code will keep using the old defaults for compatibility reasons.

Given the above precaution is taken for backwards compatibility, I think this is safe to try out for 3.5. Performance should be identical compared to before, as we're only tweaking default colors. We can consider further changes to the default environment for 3.6 (such as using ACES Fitted by default like in #49736).

Testing project: environment_tweaks_3.x.zip

Applying to existing projects

If you wish to apply the new defaults in an existing project:

• Close the Godot editor.
• Open default_env.tres (located at the project root) with a text editor.
  • If you've changed the default environment project setting, the path may be different or nonexistent. In this case, create a new default_env.tres file. You can specify its path later in the Project Settings.
• Replace its entire contents with the following:

[gd_resource type="Environment" load_steps=2 format=2]

[sub_resource type="ProceduralSky" id=1]
sky_top_color = Color( 0.385, 0.454, 0.55, 1 )
sky_horizon_color = Color( 0.646, 0.656, 0.67, 1 )
sky_curve = 0.15
ground_bottom_color = Color( 0.2, 0.169, 0.133, 1 )
ground_horizon_color = Color( 0.646, 0.656, 0.67, 1 )
sun_angle_max = 30.0
sun_curve = 0.15

[resource]
background_mode = 2
background_sky = SubResource( 1 )

• Save the file and open the Godot editor.

Preview

GLES3, no GI, Linear tonemapping

Before	After

GLES2, no GI, Linear tonemapping

Before	After

GLES3, no GI, ACES Fitted tonemapping (whitepoint set to 6.0)

Before	After

GLES3, GIProbe (propagation set to 0.0), Linear tonemapping

Before	After

Comparison between 3.x and 4.0

No GI and ACES Fitted tonemapping on both screenshots.
3.x appears brighter, as the fallback material in 3.x is much brighter than it is in 4.0. We could compensate for this by decreasing the default sky contribution to 0.6, but users would then have to set it back to 1.0 after loading a custom sky. We can also tweak the fallback material appearance instead.

3.x	4.0	3.x (sky contribution set to 0.6)