How a resource pack turns it on in Transparent

A pack opts in with one small file at assets/transparent/transparent.json:

{
  "armor_stand": true,
  "player_armor": true,
  "player_cape": true,
  "painting": true,
  "end_crystal": true,
  "end_crystal_beam": true,
  "beacon_beam": false
}

Every key is optional; anything left out keeps its default. The file is read whenever resource packs reload, so switching packs or pressing the reload key applies the change straight away — no restart needed.

When several packs are active, the switches are combined: if any enabled pack asks for an option, that option is on. That way a pack that only retextures paintings does not accidentally switch off the transparent armour a pack below it provides.

The file alone changes nothing visible. The pack also has to ship textures whose pixels are actually partly transparent — a normal fully-opaque texture stays fully opaque no matter what the switches say.