source_color not working properly

[huwpascoe]

Tested versions

tested in 4.3 and 4.4 dev builds

System information

Godot v4.3.stable - Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 960 (NVIDIA; 32.0.15.6636) - Intel(R) Core(TM) i5-6600K CPU @ 3.50GHz (4 Threads)

Issue description

Instantiating a new ShaderMaterial results in the default uniform values marked source_color to skip the sRGB-to-linear transform.

• If the same scene is saved and reloaded, the correct color is rendered.
• If the uniform parameter is set in the inspector or by set_shader_parameter(), the correct color is rendered.

Workaround: manually set the uniform to it's own default after instantiating.

material.set_shader_parameter(p_name, RenderingServer.shader_get_parameter_default(material.shader.get_rid(), p_name))

Steps to reproduce

• Create a MeshInstance3D of a plane
• Assign a new ShaderMaterial
• Assign a shader that displays a uniform vec3 of source_color

shader_type spatial;
render_mode unshaded;

uniform vec3 test_color: source_color = vec3(0.2, 0.5, 0.2);

void fragment() {
	ALBEDO = test_color;
}

Note that the color looks washed out.
Save the scene and reload, it now looks correct.

Minimal reproduction project (MRP)

source_color_bug.tscn.zip

[huwpascoe]

#70927 maybe related