The bug
The particles minecraft:cloud (naturally shown when placing a wet sponge in the nether and when a raid starts) and minecraft:sneeze (naturally shown when a panda sneezes), move very fast towards the ground when a player is nearby.
This looks rather weird because the particles do not collide with blocks and just "fall through" the ground. During this they also become dark / black when they fall through a solid block.
Note: Despite looking similar, death particles are of type minecraft:poof and are not affected.
Reproduction steps
Summon two repeating command blocks with the appropriate commands already inputted inside of them by using the commands provided below.
/setblock ~1 ~ ~1 minecraft:repeating_command_block{Command:"particle minecraft:cloud ~2 ~1 ~ 0 0 0 0 10",auto:1b}/setblock ~1 ~ ~1 minecraft:repeating_command_block{Command:"particle minecraft:sneeze ~2 ~1 ~ 0 0 0 0 10",auto:1b}Move close towards the particles
❌ They fall through the ground
Attachments
Comments 24
Confirmed for 14w33c. Strange.
Here's a video example of the cloud particle adding unwanted downward motion (you can add the link to your description if you want).
Confirmed for 1.8. Quite strange as particles (except for mobappearance) should not be affected by player position/movement.
EDIT: Mob deaths aren't affected by this since according to the wiki they use the "explode" particle instead of "cloud":
http://minecraft.gamepedia.com/Particles
As it turns out, when the particles are ticked it looks for any player entity in close proximity and immediately changes its Y-velocity.
Can confirm in 1.18.2 and 22w11a. You can execute the following commands to make reproducing this much simpler.
/setblock ~ ~ ~ minecraft:repeating_command_block{auto:1b,Command:"particle minecraft:cloud ~2 ~1 ~ 0 0 0 0 10"}/setblock ~ ~ ~ minecraft:repeating_command_block{auto:1b,Command:"particle minecraft:sneeze ~2 ~1 ~ 0 0 0 0 10"}
Screenshots don't really show this bug well, but I did my best.