[MC-125400] Bubble columns spawn inconsistently

The first time I tested bubble columns, I made a 2x2x2 cube of water source blocks over magma blocks. One out of the 4 columns produced a bubble column. But repeating this, none seem to, even with the exact same setup. It seems bubble columns spawn only inconsistently.

EDIT After some more testing, this seems to be related to block updates. If you have a 1x1x3 column of water sources (the 3 is 3-tall in the Y axis) over a magma block, contained by glass, you'll properly get a bubble column. If, however, you break one block of glass at the bottom of the column, letting the water flow out, half the time you'll get a bubble column with no flowing water, the other half you'll get just a regular column of water with the water flowing out. And you can change between these simply by updating the magma block underneath. The expected behavior would be that, regardless of block updates, you'd have a bubble column and then flowing water out the side.

EDIT 2 After some more testing, I was able to reproduce the issue in a consistent manner. Screenshots of the process are attached. It's a 1x1x3 column of all water sources, a magma block below, and a contained 1-block outlet on the side of the bottom water source.

"Starting" shows how the column looks normally – notice it's water and not bubbles.

"First Placement" shows what happens when I click once with a water bucket on the magma block, thus placing a fresh water source at the bottom of the column. Notice the water now flows out properly, but it's still not bubbles.

"Second Placement" shows what happens when I click again in the same place with a water bucket. The bottom source turns into bubbles and it stops flowing out (you can see the outlet water starting to diminish).

"AutoReset" shows that, once the outlet water disappears completely, suddenly the column turns back into water sources and the bubbles disappear, resetting everything to the initial starting state.

I'm starting to think this has less to do with block updates, and more to do with the way the water source at the bottom interacts with water around it. Either way, now that I've found a consistent reproduction, you can build it yourself and see the odd and surely unintended behavior.

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Comments 19

_zombiehunter 2018-02-15T11:05:37Z

Can confirm this, found this issue too when trying to build a simple item elevator with soul sand producing an upward bubble column. It works in some cases, sometimes not. Placing/removing water source or solid blocks diagonal above the soul sand block sometimes activates or deactivates the bubble column while above the soul sand there's still the required minimum of 2 blocks of water. This feature is undoubtedly one of the most useful additions of this update and allows people to create very efficient and compact upward/downward transportation systems for entities, although I would really expect this to work more consistent in all cases.

_zombiehunter 2018-02-15T13:01:51Z

Update: See the comment of Agnes Larsson in MC-125409. Right now, bubble column generation depends on neighbour blocks (including the corner blocks), and they don't form if air blocks are present amongst them. This should explain most of the observed issues with bubble column generation.

[Mod] redstonehelper 2018-02-15T14:39:59Z

@@unknown, on MC-125409:

Bubble column generation depends on all the neighbor blocks (including corner neighbors). A bubble column can't for example generate if any of the neighbor blocks are air.

With this being said, I agree we should look into bubble column generation.

Irbis 2018-02-15T15:08:01Z

@redstonehelper - you mentioned about different person, I guess... @FruBasilicum is not @Excited

[Mod] redstonehelper 2018-02-15T15:10:54Z

Oops, had too many profiles open at the same time. Fixed, thanks.

9 more comments

Agnes Larsson 2018-02-15T15:26:54Z

I made a fix that should be consistent. However, this will probably change when we have the real water fixes in. Current bubble column rules (might change!):

No horizontal neighbor is allowed to be air
At least one horizontal neighbor must be a pure WATER block

This can give ugly looking things i.e. when placing bubble columns in water falls. This is planned to be fixed with the other water fixes.

Irbis 2018-02-15T19:19:56Z

@@unknownSo we can't make 3x3 waterbubble column?

_zombiehunter 2018-02-15T20:58:07Z

@Michał Tried a 3x3 column, the center column (which has no water source blocks as neighbours) still creates a bubble column, seems to work fine to me. I guess having other bubble columns as neighbours instead of water sources works too. You just need to have one column with water source blocks as neighbours to begin with.

UPDATE:
Tried 2x1 and 3x1 column configurations, can confirm this. With the first one, only one bubble column activates, the other one remains as water source blocks. Expading it to 3x1 activates all three of them.

I still think the dependency on neighbouring blocks should be removed completely, it would make bubble columns even more flexible and easier to build. At least the current mechanics allow players to build some "relatively" compact 2x1 column item elevators, already tested some which work totally fine. Single column elevators would be preferable for making actual pipe systems though.

Irbis 2018-02-15T21:30:12Z

@@unknownIt's "fixed for future version, not 18w07b.

_zombiehunter 2018-02-15T22:08:46Z

@Michał I know, I can read. I answered your question and dropped a short opinion on how the columns would preferably work in the future compared to their current state. It wasn't a complaint about anything benig broken in 18w07b, I've even mentioned that I got some item elevators to function properly 😛

Aaron Rhodes 2018-02-16T19:49:50Z

The current behavior of needing at least 1 pure water block next to the column causes severe issues if you have a magma block under water surrounded on all four sides by other magma blocks; i.e. a plus shape. A bubble column is not allowed to form in the center, because it is surrounded by four bubble columns and no pure water blocks. Then, since magma blocks randomly evaporate water above them, the center magma block will at some point do that. Now, in that brief moment that the water evaporates and becomes air, the four surrounding bubble columns become invalid, do to no horizontal block being allowed as air. This causes the four surrounding magma blocks to now evaporate the water above them, and given the fact that water source blocks will be reformed indefinitely in the right circumstances (bottom of the ocean), this behavior continues to loop until one of the magma blocks is removed. Adding more magma blocks outward makes the effect more problematic. Adding screenshots that show the behavior.

[Mod] redstonehelper 2018-02-16T21:14:29Z

@@unknown: Please create a separate ticket for this issue.

MukiTanuki 2018-02-17T02:35:52Z

This appears to possibly still be an issue? Bubble columns will still form somewhat inconsistently and sometimes form and deform at will. This might be partially due to this bug: https://bugs.mojang.com/browse/MC-125723

Aaron Rhodes 2018-02-17T02:49:08Z

Scroll up in the comments on this ticket and read the fix that agnes larsson added. The fix to this issue is that bubble columns require an adjacent block of water to form, and this behavior is subject to change. Technically, the ticket you made is the intended behavior at the moment, but it will likely be changed for reasons similar to the one I gave.

Irbis 2018-02-19T13:10:48Z

Still this is highly inconsistent: I can't guess if in Lshaped columns of water with soulsand/magma on bottom it will create one or two bubblecolumns.
I made a test. Created L shape columns with soulsand. After adding water - center was bubblecolumn. After destroying and placing back soulsand - edges were bubblecolums. Inconsistant. Screenshots of this attached.

Aaron Rhodes 2018-02-19T14:12:51Z

It isn't inconsistent depending on the order that you set this up in. If you place soulsand in one of the 2 corners first, then place soulsand in the center, then soulsand in the remaining corner, you will have 1 bubble column in the center. The same happens if you place soulsand in the center to begin with. If you place soulsand in the 2 corners first, then place soulsand in the center, you will have two bubble columns. The order in which you placed the water has the same effect. You will get consistent results if the same bubble column gets activated first each time.

Irbis 2018-02-21T14:44:08Z

@@unknown How about /fill or moving all soulsand with pistons at once? Will it remain unchanged or change or random?

Aaron Rhodes 2018-02-21T14:58:39Z

I would assume it would update starting from the north-west corner all the way to the south-east corner. Given a big enough area, the chain reactions that start can get complicated and cause a seemingly random occurrence. If you repeat the same setup and the same method for changing the blocks a few times and get inconsistent end results, then it could still be considered an issue.

Andy (Romaq) Smith 2018-04-09T04:06:37Z

It would be very handy to get solid confirmation on "intended behavior". It appears the current behavior is to require 1x2 minimum with one column having bubbles and the other still, preferably for player elevators on the side away from the entrance. I'd prefer a single column of water, but I found I could do a "dead-fall" diagonally with a "still-water" buffer directly adjacent to both the bubble column and the "dead-fall" column. This would allow a way to break going up or down to use more than just a "bottom" and "top" floor. It's a solution I can live with. If anyone finds a screenshot necessary, I'll put something together on Minecraft Forum. Otherwise, clarification on "intended behavior" would be quite welcome once this is firmed up for the 1.13 release.