Скачать или смотреть Softlock by Clipping a Full Block by 0.00001m

technically it’s within 0.00000005m but who cares numbers are useless at that scale

This has been haunting my mind since I worked on la machine budget scattershot ripoff(I swear I'll give an update on that soon the server is just scary). But recently I finally figured out why it happens so now we can all enjoy it together c:

Basically, there's a 0.0000001m range where you can get yourself just completely stuck inside a full block's hitbox. There's probably some way to escape it with lag or something, but "softlock" sounds cooler and gamery, and I couldn't find any way to get out without smthn external(dying, mobs breaking blocks, spectater mode) so idk. Seems to have been added in 1.16, and still exists in 1.20. (seems to be "fixed" in 1.21.2! Doesn't seem like they fixed the causes, but if the infinite loop isn't as aggressive, and you can walk out before the server gets mad it seems.)

Anyway, this small range(where your hitbox lies 0.0000100m-0.0000101m within a full block's hitbox) lies right on the border of what the server deems "trying to clip into a block." And as a result of some small precision inaccuracies, it'll think you're trying to move into the block, even though you're standing still. This creates an infinite loop where the client and server get stuck constantly telling each other to reset your position/rotation to the same thing. So if you're not looking in the right direction to mine it yourself, you're just kinda stuck.

The "precision inaccuracies" in question is just a shortcut in the collision check specifically for full blocks, which is why this is exclusive to them. Usually collision checks give you 0.0000001m of leniency where you can clip into it without it caring. But occasionally for performance they'll just check the raw hitbox of full blocks, which accidentally(?) forgoes that leniency. I'm pretty sure 1.16 is when this shortcut was introduced in some places(but not all), which is why this bug happened.

Specificallyy(this is basically just my notes now),,,, when you send a position to the server, it first checks to see what blocks you're already colliding with(assuming your hitbox is shrunk by 0.00001m, which doesn't matter, but is why it's 0.00001-0.0000101m not 0-0.0000001m). It doesn't use any shortcuts to do this, so it'll miss any blocks you're just barely clipping. It then checks to see what blocks you'd be colliding with at your new position. If it finds any new blocks here that it didn't before, it'll assume you're trying to move to inside of a block, and tp you back to your previous position to try and fix it. The issue is that(in 1.16+) this check /does/ use the shortcuts, so it'll catch any blocks you're just barely clipping, even tho the other check wouldn't. This leaves a 0.0000001m range on every full block where even if you're standing still it'll think you're moving into a block, and send a packet to the client to tp you back. And once that tp is complete it immediately sends a new packet to the server to redo the check, but since you haven't moved, it just creates this loop.

Now, since the loop all happens within packets it doesnt require any ticks to pass, so in turn it just constantly runs as fast as it can. Even if the game is completely paused and there's no ticks happening. You can use this to interact with certain blocks infinitely many times instantly(   • Infinite Block Collisions from Clipping a ...   ), but sadly it doesn't let you eo anything super fun like infinitely jump(but if you could get something like this oscillating between two positions maybe?)

Also to actually do it in game, I just found some inputs that move me by 0.0000100-0.0000101m, and then lined myself up against the wall. Wayyyyy easier than I was expecting it to be tbh. Inputs were just sneak forward at yaw 119.735 for a tick, then at yaw 306.290 for another, then let go of everything and wait for momentum to stop. Cuz who doesn't love when your yaw needs to be accurate by +/-.005. Mordern game tasing is so dumb why does everything have to be a 64 bit float... Also the jump isn't necessary but I thought it was more funner.