Clear color is lighter on mobile renderer

[ChibiDenDen]

Godot version

4.1.1

System information

windows 11, mobile renderer

Issue description

On Mobile Vulkan renderer, the clear color is 50% lighter than expected

See steps to reproduce and Minimal reproduction project below.

The box and background have the same color on Forward+ and compatibility, but not on Mobile
happens also in runtime on exported project, not only in editor preview

Images of the same scene from
compatibility:

Forward+:

Mobile:

Steps to reproduce

• add a CSGBox3D with "unshaded" shading, and albedo of #545454
• add environment with Background = Custom color and color of #545454

Box and background are not the same color

Minimal reproduction project

bg_color.zip

[clayjohn]

This looks like a linear->sRGB conversion issue somewhere in https://github.com/godotengine/godot/blob/master/servers/rendering/renderer_rd/forward_mobile/render_forward_mobile.cpp

[ChibiDenDen]

I think it has more to do with the _render_buffers_get_luminance_multiplierset to 2 in the mobile renderer here:

godot/servers/rendering/renderer_rd/forward_mobile/render_forward_mobile.cpp

Line 342 in 41a7f6b

float RenderForwardMobile::_render_buffers_get_luminance_multiplier() {

adding a .darkened(0.5) at the end of this line fixed it for me:

godot/servers/rendering/renderer_rd/forward_mobile/render_forward_mobile.cpp

Line 935 in 41a7f6b

c.push_back(clear_color.srgb_to_linear()); // our render buffer

not sure if its the correct solution, I would love to create a pull request if you say it sounds right to you

[AndrewShobbrook]

Yeah it seems like they forgot to multiply the colours by 0.5 in this specific case (Comment in _render_buffers_get_luminance_multiplier says that it gets multiplied by 2 due to using a UNORM buffer and they just multiply by 0.5 when rendering)

[clayjohn]

I think it has more to do with the _render_buffers_get_luminance_multiplierset to 2 in the mobile renderer here:

godot/servers/rendering/renderer_rd/forward_mobile/render_forward_mobile.cpp

Line 342 in 41a7f6b

float RenderForwardMobile::_render_buffers_get_luminance_multiplier() {

adding a .darkened(0.5) at the end of this line fixed it for me:

godot/servers/rendering/renderer_rd/forward_mobile/render_forward_mobile.cpp

Line 935 in 41a7f6b

c.push_back(clear_color.srgb_to_linear()); // our render buffer

not sure if its the correct solution, I would love to create a pull request if you say it sounds right to you

Ya, that sounds right

[ywmaa]

I am having the same issue :

as you see a clear color is provided, still the actual color is brighter, and it messes my whole scene, so it makes it a totally different color than the forward plus

Scene in Vulkan Mobile :

Scene in Forward Plus :