djl

This happened to me too last night in 21w44a.

Seed: 4959143000471432977

We found a lush cave with no hanging vegetation in a world on our multi-player server testing 21w41a in survival.

Seed: -202766726466362800

Coordinates: -1821, 55, -1374

Checking the biome at various y levels, we noted that it is lush_caves from 55 to 65, then dark_forest from 66 to 84 (the roof). Biome on the surface is dark_forest too (of course).

So, it would seem that the reason for no cave vines, spore blossoms, etc. in this cave is that most of the cave volume with downward facing block surfaces is not lush_cave biome.

I created a single player world with the same seed to do some more investigation. In it, there is a small region in one corner of the cave that has some hanging moss and cave vines. They span the y=65-66 change to dark_forest biome, presumably due to biome blending.

I wonder if this is really a bug? Is the entirety of a cave volume expected to be lush if some part of it is? It feels like that should be so vertically in caves like the one we found. But how far does that reasoning extend horizontally? Our cave has other caves connected to it via small passages near the top. Should all of that be lush too? Looks to me like 3D biomes raise some interesting design questions.

Update (after another play session):

We dug deeper in the world on the multi-player server and found multiple caves, large and small, with hanging vegetation in the same lush_cave biome.