Ladder/Vine bug

[henniboy321]

Right now there's a bug in minecraft where if you drop from certain heights you won't be able to catch a ladder or vine.

(the gold blocks are the heights that are affected)
We have tested for drops up to a height difference of 55 blocks to see which drops are affected (thanks chayos). [11, 16, 19, 22, 24, 27, 29, 31, 34 , 36, 38, 40, 42, 44, 45, 46, 48, 50, 52, 53, 55] As you can see, the bug starts affecting jumps from a height difference of 11 blocks and gets more frequent the higher you go.

Not only is this to inform you that this bug exists but if you encounter a map where a drop of this height is present, please let us know so we can fix this.

 

[Fire]

I'm pretty sure this has been in the game for a very long time. It's one of many unfortunate quirks of this game's really weird physics. Jumping into 2-block-high gaps with the same way until 1.14 made players' crouch hitbox smaller, having some really weird fall distances at which it was impossible to land one, one of the most notable being one-eighth of a block upwards: from a chest into one straight ahead.

I'll keep an eye out for any impossible drops, but since all maps are tested by their creators, I doubt there are any of issue. Some drops might have these heights (like the infamous one in Corrupt, not sure), but are doable because you also have forwards momentum hitting the ladder.

 

[Squidyerser]

Just saying, you can't jump from a chest into a 2bc (Which is at least 2 blocks away) before 1.14 because the game calculates your position every tick, and from the chest's y level (.875), you would fall past y=.2 to y=.0 (Which is the y level needed to fit in 2bc) in one tick, which is why it becomes impossible, because there isn't a tick where your y level is between that range when jumping off a chest, although 1.9+ reduces the player's hitbox by .15 when crouched. The reason is the same for long drops into 2bc, -3 is one of the more popular ones. (Your position would be .0<y<.2 of the block 3 blocks down when you jump down, so you can "fit in")
This also applies to jumps with positive tiers, e.g. 4+.1875 (4b with trapdoor) is the same as 4+.4375 (4b from carpet to slab). Because the tick before you land, your position is y>.4375, but 1 tick later, your position would be y<.1875, therefore 4+.1875 is the same as 4+.4375. These all revolves around the fact that the game calculates your position once every tick only
(It might also explain the ladder/vine "glitch" that henni was talking about, ill try to test it if I have time)

 

[Squidyerser]

Alright I've played around with it. This "bug" has the same reasoning as what I said above. I'm gonna take the one 11 blocks down as an example.
Let's assume the ladder is at y=100, so I'm walking down from y=111.
17 ticks (850ms) after walking down, your position would be y=100.19347, and at the 18th tick, your position would be y=98.9984.
To catch the ladder, your position has to be 100.0<y<99.0, and since in 2 consecutive ticks your position is y=100.19347, then y=98.9984, it completely misses the range of 100.0<y<99.0, hence you are not able to catch onto the ladder 11 blocks down.
If you were 0.0017 blocks higher, you can catch onto the ladder though. (Same explanation but different values for other heights)
So this is not a bug/glitch, it's just how the game mechanics work

 

[Hex]

I might label that as a glitchy mechanic myself, I highly doubt it's like that by intention, regardless of it not coming from an error in code. Thanks for the sleuth work!