mojira.dev
MC-265084

Entity position is not visually accurate when Motion NBT tag is changed too early after the entity is summoned

Put a repeating command block with the following command:

summon minecraft:snowball ~ ~ ~1 { Motion: [1d, 1d, 0d], Tags: ["TestEntity"] }

You get a nice flow of snowballs thrown to the east.

Now add 2 chain command blocks behind the first one with the following commands:

execute as @e[tag=TestEntity] run data merge entity @s { Motion: [0d, 1d, 1d] }
tag @e[tag=TestEntity] remove TestEntity

Visually, the flow now starts by being thrown to the east before being magically teleported to its expected route to the south.

If you place yourself in the east snowballs flow, you don't get hit because they are not actually here, they are at the south even if invisible.

The issue also occurs at least for dragon fireball, egg, ender pearl, experience bottle, experience orb, eye of ender, falling block, fireball, item, llama spit (which is even stranger), potion, small fireball, and to a lesser extent for arrow, spectral arrow and TNT.

Linked issues

Attachments

Comments

j_p_smith

Thank you for your report!
We're actually already tracking this issue in MC-139548, so this ticket is being resolved and linked as a duplicate.

However, that ticket has been resolved as Won't Fix, which means that although this is considered a bug, it will not be fixed.

Please be sure to use the search feature before creating a ticket to see if the issue has already been reported.

Quick Links:
📓 Bug Tracker Guidelines – 🛠 Community Support – 📧 Mojang Support – ✍️ Feedback and Suggestions – 💬 Mojira Discord

AHL

The problem is that you can't summon an entity and calculate it's motion in the same tick it's been summoned to let it have a nice trajectory. The summoned entity must have it's trajectory already set in it's summon command or it will be completely messed up if changed afterward. But since we can't put variables as values in commands, we have no other choice.
Besides, Searge's answer about the non-resolution of thig bug is from 2014. Maybe their mind has changed since then?

AHL

(Unassigned)

Unconfirmed

(Unassigned)

23w33a

Retrieved