1.17 underwater fog is incorrect/broken

[ruvaldak]

1.17 changed underwater fog to linear fog, and no longer supports fogDensity. While Optifine has code to emulate density on linear fog, this doesn't exist (yet) on Iris, which causes fog to be entirely gone underwater. Might be best to rework the fog in the shader rather than relying on the shader mod to convert the deprecated fogDensity to linear fog.

[ruvaldak]

As a preliminary, changing

float fog = (isEyeInWater>0) ? 1.-exp(-gl_FogFragCoord * gl_Fog.density):
clamp((gl_FogFragCoord-gl_Fog.start) * gl_Fog.scale, 0., 1.);`

in gbuffers_clouds.vsh to

float fog = clamp((gl_FogFragCoord-gl_Fog.start) * gl_Fog.scale, 0., 1.);

allows fog to be rendered underwater again, though not accurate to vanilla w/o shaders, and a little buggy visually

[ruvaldak]

While this issue may be exclusive to Iris for now, until they get code in to emulate fog density, it is likely preferable to not rely on emulation in 1.17. Another issue related to fog in Iris with XorDev-Default is that fog beyond loaded chunks can sometimes be solid black. This may be related to only exponential fog, as this doesn't exist above the water in the overworld.

Other issues in Iris but not OF include: Beacon beam being solid black, block breaking decal not supporting any form of alpha