Prior to 24w19a, projectiles with the 'power' tag could reliably be accelerated by the player using e.g. bubble columns or pistons. The replacement of 'power' with 'acceleration_power' introduced probably accidental but significant changes to how this acceleration works, and it's likely that setups built by players will no longer function (or worse, blow up surroundings) in 1.21 unless the difference is rectified.
Attached is a 1.20.4 WDL with two example setups including signs indicating where projectiles end up in 24w18a and older versions as well as where they'll end up in 24w19a+.
Steps to reproduce:
Download the attached world
Load it in 24w18a or earlier
Note where the projectiles land (marked by signs for both behaviors anyway)
Load the same world in 24w19a and later
Observed result:
The projectiles land in different places in 24w19a and above compared to 24w18a and earlier. 24w19a changes introduced additional weird behavior. One example is shown in the WDL, and two other examples are shown in the attached short clips provided by jjl21.
Expected result:
The projectiles land in the same place as they did in 24w18a and earlier and don't behave weirdly.
Linked issues
is duplicated by 3
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Comments 8
At this point I assume it's too late for the issue to be addressed before the 1.21 release. In that case it's probably for the best that the change be kept whether accidental or purposeful, since people will soon start building things with the new physics, and reverting the change in the future would just break all those new things.
All I would ask is that in the future significant entity physics changes be given more explicit patch notes instead of being hidden away as side effects of changes to NBT data, in order that players interested in such changes might find out about them in a more timely fashion. I only found out by chance, and apparently too late to make a bug report that could affect the release. The relative consistency of Minecraft's sandbox mechanics is in my opinion one of the game's core strengths, so it's unfortunate whenever parts of that sandbox are changed without note and players are left to guess if the change was accidental or if there was some good reason for it.
> In that case it's probably for the best that the change be kept whether accidental or purposeful, since people will soon start building things with the new physics
I disagree, the amount of machines we have now and that were being developed as this change happened is much bigger than what we might develop within a few updates, not to mention that current behaviour just makes less sense, at least in my opinion, with ptojectiles being redirected or stopped by pistons or water.
I disagree, the amount of machines we have now and that were being developed as this change happened is much bigger than what we might develop within a few updates, not to mention that current behaviour just makes less sense, at least in my opinion, with ptojectiles being redirected or stopped by pistons or water.
Fair enough. If there's a quick point release with a reversion to the old behavior I guess that shouldn't be too disruptive. Regardless it would be nice to hear if this was inadvertently chanaged or if not, hear what the rationale was. If you want to make a clip or a WDL showing off some more of the weird behavior I can attach it to the report.
We consider the bubble column pushing wither skulls as working as intended. However, the second issue of them being deflected oddly is a separate issue due to the bounding box of the wither skull not being set up properly when it spawns tracked here: MC-262112.
Oops, somehow missed the WAI marking when going to update the report. Unfortunate but understandable. Hopefully it won't destroy too many player creatiions.
Please update the description to include steps to reproduce this issue, as well as expected VS observed results.
Please also attach any needed datapacks, resourcepacks, screenshots, videos or worlds needed to help reproduce this issue.