[MC-149827] Mob jumping favors x-axis

Whenever a mob's AI tells it to jump, it will heavily favor the x-axis. This can easily be seen with spiders and cave spiders, as they will jump whenever they get close to you. You can also view it in wolves, but it is a little more complicated to set up. Other mobs may be affected, but I cannot find reliable ways to test them.

Steps to Reproduce in Spiders

Create a Redstone Ready Superflat world.
Spawn a spider/cave spider and aggro it
Run along the z-axis – the spider will jump at you
Run along the x-axis – the spider will frequently jump in place
Run diagonally along both axis – the spider's jump will heavily skew towards the x-axis.

Steps to Reproduce in Wolves

Create a Redstone Ready Superflat world.
Spawn a skeleton and splash it with a slowness potion
Spawn a wolf to chase the skeleton
Note that the wolf jumps similarly to the spiders above

Mobs also tend to rotate their bodies a lot when jumping, this may be related to this bug.

Attachments

caveSpiderJump.mp4

spiderJump.mp4

wolfJump.mp4

Comments 3

ProPork 2020-05-03T02:46:16Z

You can even do this as a player, I've seen this already in 1.12.2 and 1.15.2

ampolive 2021-07-17T14:26:55Z

Can confirm in 1.17.1.

[Mod] Jingy 2024-06-23T22:18:29Z

Affects 1.21, though the spider's position when it jumps is far less (if at all) skewed towards the x-axis. The direction the entity faces however will still noticably face along the x-axis when jumping, which does not look natural.