Mob Spawning is currently broken, but I did some testing in creative and noticed a few things that might help to hopefully further diagnose it:
1) The surface cap appears to be 16. Looks like both cave/surface spawn caps have combined.
2) In creative, the mobs spawned immediately at ground level on a superflat world. Mobs barely spawned in any elevated platform.
3) Mobs seem to spawn at a higher freqeuncy when BELOW the player level. Seems the lower elevation was prioritized vs. the previous spawn mechanics of 25-55 blocks from the player in a sphere. (which was ideal - please revert it back). On surface level you can clearly see the 25 blocks around the player. At any other elevation (even with open sky access) mobs appear to want to spawn directly below the player as a preference.
4) Mobs spawning on single blocks seems to be have been nerfed. Spawning was increased when rows of 2-3 blocks were put together, instead of single lines with a gap/repeat. Even is multiple rows were present with single gaps between them, mobs tending to spawn on solid surfaces more often (in groups of 2-3).
5) Creeper farms are useless with the current cave spawning issues. To target the creeper with a trap door above it is now broken due to the cave spawning rules. There is no way to only target gunpower drops.
This appears to be more than a single cave/surface spawn change. Many more mechanics including the frequency and the priority of mobs spawn appear to have been changed unintentionally.
Comments 4
You have not given enough detail to justify your conclusions, such as the exact setup and steps to reproduce. Moreover, it is not clear what you think the bug here actually is.
I have been testing hostile spawns myself using 1-chunk platforms centered over 9x9 chunk lava oceans, and I have observed none of the behavior you describe.
I suspect that the results you describe can be explained simply by the fact that more mobs will spawn where there are more available valid spawn locations. That is a direct consequence of the algorithm choosing random x,z coordinates to attempt spawns.
The bug is that cave spawning appears to be broken still, with Mobs not spawning effectively in Mob farms. Moreover, I wasn't claiming my testing was conclusive which is why the opening statement of the above post reads "noticed a few things that might help to hopefully further diagnose it...".
My testing was down at both Y=4 and Y=70. Single rows with a 1 block wide x 16 block length. Space between. Repeated for an entire chunk (8 platforms). This was with two levels. In addition, creepers did not spawn in the only viable locations, (buttons beside an open spawn space with a trap door above making the height 2 1/2 blocks tall, indicating that creeper revisions made in the last update had been reverted/removed.
It's hard to tell if that's specifically creepers, but I can confirm in my realm that my creeper farm no longer works, despite the workaround or replacing the 1/2 slabs with carpet.
Does that help @goldenhelmet?
Yes it is more clear now, sorry for the delay in my reply. I happen to have recently built a button/trapdoor creeper farm like you describe. With just 1 level, my farm is very slow. However, I think this design will be slow even with many levels. Consider that with 1-wide rows with 1-wide air between and buttons on every other block, it allows only 1/4 of the blocks in the chunk to be viable spawn spots. Since the spawn algorithm picks random x, z coordinates to attempt spawns, this is going to make the spawning in the farm go at 1/4 the rate of a solid 16x16 platform. I just tested a 1-level setup like this in creative and got 1 creeper in about 2 minutes. When I use solid platforms for testing other things spawning is much faster.
You mentioned 2 1/2 height–did you mean 1 1/2? I believe the trapdoor on the ceiling should make the available space 1.8, and creepers are 1.75 blocks tall, while other mobs are 1.95. When I build it, I do get only creepers spawning.
Are you alternating the button locations on different levels? That could double your available x, z coordinates available for spawning within the farm, and increase the rates.
I can assure you that cave and surface caps are not combined. Sometimes they are not applied like you might expect though (I've been experimenting with that and created MCPE-61721, MCPE-62030, and MCPE-60552 as a result.)
As far as I can tell the spawning in a sphere 24-54 blocks away from the player is still how it works.
I think there could be something to the preference for wider than 1 block spaces, as I have noticed in my witch hut testing that structure witches only spawn if blocks adjacent to the spawning block are also solid with air above. But I do see creepers spawn in the farm with buttons on every other block, so I know it works (just slowly!)
You don't mentioned spawn-proofing the density check area, but you do mentioned spawns on the ground and solid platforms below. To get the farm to work you do have to spawn-proof all 80 chunks around (9 x 9).
Just had a phantom spawn below the player in a creative world. Also appears to confirm the issue with prioritizing spawns lower than the player.