Sky color depends on absolute height in world and changes abruptly

1.16 pre3 in a superflat custom dimension

1.16 pre5 still has this problem

Is this a bug or a feature?

1.16 rc1

Cnfirmo que este bug pasa en mundos superplanos en la 1.16.1

This issue is especially annoying when using "Floating Islands" World Type. Perhaps add a setting where the user can adjust the horizon per world?

This is cave fog/underground fog.

I made a void data pack recently and realized the sky goes black due to this still... I wish this would fixed... Maybe link it to ocean height or have it as its own parameter in world gen.

Can confirm in 1.17.1 and 21w38a (very good decision to reopen this issue).

Can confirm in 21w39a.

Can confirm in 21w41a.

Can confirm in 21w42a.

Can confirm in 21w43a.

Can confirm in 21w43a.

Can confirm in 1.18 Pre-release 1.

Can confirm in 1.18 Pre-release 2.

Copying over my general fix suggestion from MC-214813 and MC-215387 as they were resolved into this, implying working on all three of these is planned:
It's probably a good idea to get rid of the "sky goes black" effect in its entirety. Instead, the lush caves and dripstone caves should specify their own sky and fog colors in the json files to get an equivalent effect. As for caves which are neither of these, a new generic "minecraft:caves" biome could be added, which defines fog and sky colors as well. This would also stop other biome effects from bleeding underground, as well as surface builders going down too deep.
This should make customization much easier since the black sky is no longer hardcoded.

I should also note that there's a similar sky darkening effect that can be seen below min_y, which is apparently a void fog leftover, so can also be removed for similar reasons.

I'm not sure if this approach may require some extrra biomes, however, such as a "mountain caves" biome for underground emerald generation handling, a "swamp/desert caves" biome for fossil generation as well as a "badlands caves" with extra gold.

Going into feature request territory at this point, but perhaps slime chunks could be replaced with a "slime caves" biome, allowing for their spawning to be configured like other biomes do rather than another hardcoded world thing. This is getting out of scope at this point, though.

Affects 22w03a.

Another approach to maybe consider is to have the darkness slowly envelop the skybox as the player descends. At sea level the sky would begin to darken about 5 degrees below the horizon, fading into a dark gray at 20 degrees downwards. At min_y the transition begins at 30 degrees above the horizon and ends at 15 degrees above, while the color itself darkens into pitch black. Below that the angle increases rapidly, with darkness covering the entire sky at min_y - 32.

In tandem with this, fog color could use a gradient from light blue to dark gray, and this gradient would be evaluated at a point based on the percentage of the screen exposed to the open (i.e. blue/overcast/starry) sky. I don't know how tricky/expensive it would be to calculate this percentage, but if it's a heavy lift the number can be updated once every so often as opposed to every frame. This approach could lead to unexpected fog colors when chunks or parts of chunks don't render (i.e. the cave ceiling is high and the render distance is low), but I imagine the fittingness of the fog color would scale proportionally with hardware capabilities. This would also require a new setting to toggle fog fading in either the dimension or biome JSON files.

Affects 22w11a (edit: and 22w12a, 22w14a, 22w15a, 22w16b and 22w17a).

This is really jarring for any skyblock worlds. 

Seems to be fixed as of 1.19.2. See screenshot 'fixed.png'.