Pre-Determined or Roll on Opening Loot?

[RainyBasil]

I've been playing on a server with a few friends, we've gotten to a pretty good point in progression that we've started installing a few extra mods. There's a crafting recipe in one of these mods that has a schematic in it that can be found in ruin loot. I'm wondering if loot is pre-determined for a world seed, or rolled the moment you open a container. I don't want to end up searching for hours for something that won't happen so im hoping its rolled on opening.

[Bumber]

I would assume it's determined when the chunk is generated. I'd check in areas generated after the mods were installed to be safe. You don't need to create a new world.

There are also commands for regenerating chunks that have fewer than a given number of player edits (so you don't wipe your base or regenerate ore):

/wgen autogen 0
/db prune 5 confirm
/db vacuum

Where 5 is the number of edits. Haven't used these yet, personally, so IDK if you need to manually turn autogen back on afterwards so chunks will generate. Create a backup before doing something like this, obviously.

Edited March 30 by Bumber

[ifoz]

In the creative inventory there are 'randomizer stack' items that let you generate loot from the in-game loot tables when they are placed into a container.
This leads me to believe it's generated upon opening.

Still, I'd search new chunks or regenerate old ones. Better safe than sorry.

[Thorfinn]

Pretty sure it's on open. Tested this several versions ago, by making a backup copy of a world, opening either a chest or a vessel, I don't remember which, exit and load the backup world, and there was a different drop.