Build Engine lighting inconsistent/No lighting outside fog

[Orangestar]

In OpenGL mode, setting the "Sector Light Mode" in the Hardware Rendering Options menu to "Build" does not work if "Fog mode" has been set to "Off". The scene is rendered fullbright instead.

Fog Mode: Standard

Fog Mode: Off


If the sector has its sky set to F_SKY1, the lighting will flash oddly on the walls and floor, unrelated to each other's position, in that sector as you move about.


Some adjacent sectors will also be affected, and have lighting inconsistencies. You can see this in DOOM2.WAD's first level - the end of the hallway in front of your starting position is lit differently than the floor it surrounds.


This seems to be due to the first level's secret being rendered and using F_SKY1: walking in and out of the bend in that hallway will cause the lighting to flicker.


It looks like in sectors with a sky, the walls are lit either none or all while the floor is lit normally. In sectors without when the sky is being rendered, it does the opposite: floors are lit or unlit while walls are variable.

GZDoom 4.7.1. I'm on Manjaro and using the version that came with my package manager, which is labeled as "GZDoom g4.7.1-m - 2021-10-20 08:18:37 +0200 - SDL version", but I have confirmed the issue on the Windows build with a similar header ("GZDoom g4.7.1 64-bit (2021-10-20 08:18:37 +0200)") with my laptop.

Wads:
gzdoom.pk3, 666 lumps
game_support.pk3, 2514 lumps
DOOM2.WAD, 2919 lumps (or DOOM.WAD, 2306 lumps)
game_widescreen_gfx.pk3, 216 lumps

Desktop specs, as reported by GZDoom:
OS: Manjaro Linux, Linux 5.15.21-1-MANJARO on x86_64
CPU Vendor ID: AuthenticAMD
Name: AMD Ryzen 5 3600 6-Core Processor
Family 23 (23), Model 113, Stepping 0
Features: SSE2 SSE3 SSSE3 SSE4.1 SSE4.2 AVX AVX2 F16C FMA3 BMI1 BMI2 HyperThreading
GL_VENDOR: NVIDIA Corporation
GL_RENDERER: NVIDIA GeForce GTX 1060 6GB/PCIe/SSE2
GL_VERSION: 4.6.0 NVIDIA 510.47.03 (Core profile)
GL_SHADING_LANGUAGE_VERSION: 4.60 NVIDIA

Laptop specs, as reported by GZDoom:
OS: Windows 10 (NT 10.0) Build 19044
CPU Vendor ID: GenuineIntel
Name: Intel(R) Core(TM) i7-10510U CPU @ 1.80GHz
Family 6, Model 142, Stepping 12
Features: SSE2 SSE3 SSSE3 SSE4.1 SSE4.2 AVX AVX2 F16C FMA3 BMI1 BMI2 HyperThreading
GL_VENDOR: NVIDIA Corporation
GL_RENDERER: NVIDIA GeForce MX330/PCIe/SSE2
GL_VERSION: 4.6.0 NVIDIA 472.47 (Core profile)
GL_SHADING_LANGUAGE_VERSION: 4.60 NVIDIA

[Rachael]

Not a bug. All the light modes need fog in order to work properly. Disabling fog is intentionally disabling fog which is how some of these more "vanilla" (or rather, distance fading) light modes work.

[Graf Zahl]

Not all light modes work well with this. The main reason that the option still exists is debugging, so it's left in to help mappers if they need it.

[Nash]

I wonder; is there actually any legitimate reason why disabling fog is exposed to the user, considering how broken the game would be without it? The performance hit can't be that significant...

Ah just saw Graf's reply about it being a debug aid for modders. Ok yeah, makes sense.

[Orangestar]

Then is fog just broken in sectors with skies? I don't understand why this was labeled as wontfix when the lighting is clearly not working correctly with fog on in sky sectors.

[Graf Zahl]

Consider the Build light mode mostly experimental. It was meant more as a gimmick than a really useful feature.