Note: This bug is NOT related to MC-119 or MC-10 as far as I can tell.
When the following conditions are given entities will fall though the floor:
The entity needs to be able to walk up a slab
It needs to stand on the ground (NBTTag OnGround:true)
It needs to move upwards and to the side
It needs to hit a block which it wouldn't hit if it was only moving up or only moving to the side
How to reproduce:
1. Put down a mob and a block on offset on top of it (Screenshot)
2. Punch the mob (easiest way to get a sideways upwards motion) against the block.
3. The mob will fall through the floor now.
The source of the bug is in the method which moves an entity in Entity.java.
In MCP: public void moveEntity(double x, double y, double z). Sure you will find it 🙂
This shows what needs to be changed to fix it (with some context): https://gist.github.com/Panda4994/9d83d261f5edffc3037e/revisions
I will also describe the problem and fix here:
https://www.youtube.com/watch?v=3aUqTmhn-50
And here:
So the problem is the part of the code which calculates the moving up slabs.
When a entity hits a block while moving sideways it will be called.
Then the game will make a list of all bounding boxes it could collide with when moving up by the step height of the entity (0.6 for normal mobs, 1.0 for enderman and horses) and the given amount in x and z direction.
This will not get the floor below the entity.
Now in this part of code a bounding box (BB from here on) will get moved to the position where it could go if no blocks were in the way.
Then the BB will get moved up till it hits something but at max the step height.
In the case described further up it will not move up the full step height.
Some other calculations follow.
Then the entity gets moved down till it hits a block but at max the step height.
It uses the list it created earlier for this check. So if the entity wasn't moved up by the step height it will get moved below the floor because the floor is not in the list.
An easy fix would be to just set the maximum it would get moved down to how far it got moved up.
Related issues
is duplicated by
MC-68081
irongolems- sinking threw blocks
MC-68231
Mob problem when you punch them
MC-68454
Mobs glitch through floor (upon being hit or chunk reload)
MC-69080
When Mobs are hit, they glitch halfway into the ground.
MC-69440
Mobs ocasionally drop 1 block after being hit.
MC-69518
Iron golems phaseing through blocks when hit
MC-70898
Mobs Sink Into Block Underneath Them When Hit
MC-71921
Mobs can fall through blocks when hit
MC-71989
New Doors mob 'sink' bug
MC-73449
armor stands "sinking" to lower levels of building
MC-74679
Mobs overpassing ground if hit in front of a specific wall shape
relates to
Attachments
Comments
migrated
migrated
Dupe of MC-119
migrated
not really, Sonic, this is something specific
migrated
Can confirm described behaviour/bug.
Panda4994
MC-68081, MC-68231, MC-68454, MC-69067, MC-69080, MC-69440, MC-70898, MC-71921 acutally describe the same issue but I didn't find them because they are falsely marked as duplicate of MC-119.
The listed ones should be connected to this one not to MC-119. There might even be more. The list of duplicates on MC-119 is long (And I bet full of more wrong duplicates. There can be more than one reason for mobs falling though the floor.).
migrated
@Sonic He said "This bug is NOT related to MC-119 or MC-10". Watch his video here: https://www.youtube.com/watch?v=3aUqTmhn-50 Read, or watch, before making a 'Dupe of mc-#' report. MC-119 is nowhere related to this, as mobs sink by them self, by walking in the bug MC-119, while he states thats mobs try to move by amount of their step height, if near a block, down, and the bound-hitbox can't see the block below the creeper, so the creeper moves into the block, and if chicken, or other 1-high face mobs, suffocate in land, and try to escape, if passive-type. So, any mobs that have a step height of 0.6 or higher, they get stuck in slabs, of on the lower side. Does that explain more to you?
Also, MC-71921, MC-70898, MC-69440, MC-69080, MC-68454, MC-68231, and MC-68081 is reporting a bug that is the same as this, and has been mistaken as bug dupe of MC-119, and should be possibly reopened, or changed.
@Panda MC-69067 looks like it is really a MC-119 dupe report, though very hard to be sure of.
Also, NOT a dupe of MC-119. Look carefully! Hopefully, this bug can be fixed, because who wants creepers in their floor, after hitting it? Want a little bit more on what happens on the 1.8 side of things, and what mobs can have the effect in a way? Look here: http://youtu.be/RXsK9MmAxMc (Note, Video may contain wild lightning, and Nether Mobs w/ Lightning Damage bug)
kumasasa
Relinked the named tickets (except MC-69067) to this one.
Panda4994
@KJP12 and @Kumasasa
The reason why I think MC-69067 is also caused by this bug is that the screenshot is showing exactly the conditions I described.
https://bugs.mojang.com/secure/attachment/79961/2014-08-23_15.35.46.png
Thank you for relinking the tickets 🙂
Sonicwave
Indeed confirmed. MC-119 is purely visual while this is actual falling through the ground.
Panda4994
michael