On devices not yet using Render Dragon (currently iOS and Android), when the start point of fog in a resource pack is set closer to the player through custom fog values, the transition is abrupt in the overworld - with no fog for a few chunks close to the player, and then sudden appearance of full-strength fog approximately halfway to the edge of the render distance. This makes custom fog definitions useless for any resource pack that requires full cross-compatibility across devices. This issue used to be present on other platforms such as Windows 10, but got resolved with the introduction of Render Dragon. However it was never fixed for other devices.

Importantly, low fog_start values in resource packs do work properly in the Nether dimension, even on non-Render Dragon devices, confirming that it is not a technical or performance limitation of the engine or device - but rather a bug that seems likely easily fixed.

How to reproduce: create a resource pack with custom fog definitions. Set the "fog_start" to a low number. Apply the resource pack on a non-Render Dragon device, and view in the overworld dimension.

Expected Behavior: Fog transitions slowly, from low opacity near the player to full opacity at the edge of the render distance. This is how it behaves on Render Dragon devices.

Actual Behavior: There is a sharp cutoff, where the fog goes from 0% opacity to full opacity.