The bug
When a liquid gets randomly ticked, it flows. That seems strange, since flow should always be predictable. To illustrate this, here is a gif of this behavior with 300 random tick speed: http://gfycat.com/NiftyInnocentElver
Notice the flow being uneven throughout, whereas a random tick speed of 0 is completely even:
http://gfycat.com/PrestigiousAdorableBeardeddragon
(Actually, there is a slight inconsistency to the right, but I believe that's a separate issue).
How to reproduce
In order to see the effects, run /gamerule randomTickSpeed 1000 and place some water or lava. Note that this behavior can still happen at the default random tick speed, it's just unlikely and difficult to see.
Code analysis
By @unknown in this comment.
Linked issues
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Comments
Can confirm for 1.9.4.
Here is a fix (MCP names) :
-Open BlockDynamicLiquid.java
-Add "this.setTickRandomly(false);" to the constructor.
That's not very hard to figure out, so I see three possibilities :
-Nobody reported this before
-It works as intended
-The devs are really lazy
@redstonehelper :
Is lava decay supposed to use random ticks ? If so, also add
if (materialIn==Material.lava)
{
[REPLACE THIS WITH A TAB]this.setTickRandomly(true);
}
to the constructor to fix this bug for water, but keep it for lava.
NeunEinser
Yeah, can confirm that for 1.10, noticed it myself when doing some test.
gaspoweredpick
MC-93468 is caused by water sometimes generating extra blocks while flowing.
confirmed for 16w44a.
I think everybody would like to see this fixed
I should point out that removing random ticks from flowing liquids would also affect liquid dissipation. More specifically, it would slightly slow the already-relatively-slow dissipation, though it would make the rate more predictable (in which case it might make for some interesting medium-period clocks).
The effect of the random ticks is almost negligible though. The effect is at least 100 times less than the predictable behaviour. I don't think it's worth keeping it, since the effect can't be observed anyway.
NeunEinser
Can confirm for 1.11.2
If it's intended for liquid DISSAPATING, then you can change code like this: don't generate water when ticked, remove it instand when needed.
wobst.michael
Should be fixed in 1.12.2 pre-1. Please check if it's fixed as expected.
tryashtar
Confirmed fixed! Thanks!
Fix got reverted.
why was it reverted?
Because of MC-120709, it isn't as simple to fix without delaying 1.12.2's security issue fix for too long.
Irbis
@Grum: You can disable random tick for water/lava that already updated within last 7(water) or 30(lava) ticks. Something similar was made for turning on redstone torches - random tick will not turn it faster even if burned out redstone torch can be turned on by random tick.
Nice, in the latest snapshot 17w50a it has been fixed. I don't know if that is going to stay but I hope it does.
MC-120709 got fixed as well in this snapshot, so there's no reason this fix shouldn't stay
tryashtar
The asymmetrical flow also appears to be fixed as of 18w10c.
tryashtar
Erik Broes
Could have to do with how random ticks are used for lava decay.