MC-259666Reloading a resource pack that has a custom texture atlas for a second time causes severe FPS lag on the client
This issue affects rejoining Tubnet, Hypixel, MCC Island, and any server using a pack that may use a custom atlas, though those three are among some of the most prevalent. Hence, if you join a server that uses custom server resource packs such as Tubnet and leave, and then join again, you will notice severe FPS lag. This issue also affects singleplayer when reloading such resource packs on a Mac M1/M2 machine, as pointed out by @Caden Kriese.
To reproduce:
1. Join Tubnet or MCC Island (Tubnet lets you join for free)
2. Leave Tubnet and join again
Results: Severe FPS lag on the second login.
Expected results: No additional FPS lag no matter when you join.
Note: Joining either of those servers for the first time, and then logging off to join another server using a resource pack also causes lag. For example, you get lag if you leave Tubnet to join MCC Island and vice versa.
Environment
Apple M1 Max
Linked Issues
Created Issue:
Joining a server that uses a custom server resource pack for a second time causes severe FPS lag on the client (Affects Tubnet and MCC Island)
If you join a server that uses custom server resource packs such as Tubnet and MCC Island, leave, and then join again, you will notice severe FPS lag. Doesn't seem to affect Hypixel's lobbies that uses custom resource packs, so it probably has to do with the server being on the newer versions too.
To reproduce:
1. Join Tubnet or MCC Island (Tubnet lets you join for free)
2. Leave Tubnet and join againResults: Severe FPS lag on the second login.
Expected results: No FPS lag no matter when you join.Note: Joining either of those servers for the first time, and then logging off to join another server using a resource pack also causes lag. For example, you get lag if you leave Tubnet to join MCC Island and vice versa.
Attachments2
If you join a server that uses custom server resource packs such as Tubnet and MCC Island, leave, and then join again, you will notice severe FPS lag. Doesn't seem to affect Hypixel's lobbies that uses custom resource packs, so it probably has to do with the server being on the newer versions too.
To reproduce:
1. Join Tubnet or MCC Island (Tubnet lets you join for free)
2. Leave Tubnet and join againResults: Severe FPS lag on the second login.
Expected results: No additional FPS lag no matter when you join.Note: Joining either of those servers for the first time, and then logging off to join another server using a resource pack also causes lag. For example, you get lag if you leave Tubnet to join MCC Island and vice versa.
![[Mod] violine1101](../../../data/avatars/users/92858.png){kind=small}
Apple M1 Max
If you join a server that uses custom server resource packs such as Tubnet and MCC Island, leave, and then join again, you will notice severe FPS lag.
Doesn't seem to affect Hypixel's lobbies that uses custom resource packs, so it probably has to do with the server being on the newer versions too.To reproduce:
1. Join Tubnet or MCC Island (Tubnet lets you join for free)
2. Leave Tubnet and join againResults: Severe FPS lag on the second login.
Expected results: No additional FPS lag no matter when you join.Note: Joining either of those servers for the first time, and then logging off to join another server using a resource pack also causes lag. For example, you get lag if you leave Tubnet to join MCC Island and vice versa.
Joining a server that uses a custom server resource pack for a second time causes severe FPS lag on the client (Affects TubnetandMCC Island)Joining a server that uses a custom server resource pack for a second time causes severe FPS lag on the client (Affects Tubnet, Hypixel, MCC Island, and any server using a custom pack)
Important![[Mod] markderickson](../../../data/avatars/users/18946.svg){kind=small}
![[Mod] Avoma](../../../data/avatars/users/86198.png){kind=small}
If you join a server that uses custom server resource packs such as Tubnet and
MCC Island,leave, and then join again, you will notice severe FPS lag.To reproduce:
1. Join Tubnet or MCC Island (Tubnet lets you join for free)
2. Leave Tubnet and join againResults: Severe FPS lag on the second login.
Expected results: No additional FPS lag no matter when you join.Note: Joining either of those servers for the first time, and then logging off to join another server using a resource pack also causes lag. For example, you get lag if you leave Tubnet to join MCC Island and vice versa.
This issue affects Tubnet, Hypixel, MCC Island, and any server using a custom pack. If you join a server that uses custom server resource packs such as Tubnet and leave, and then join again, you will notice severe FPS lag.
To reproduce:
1. Join Tubnet or MCC Island (Tubnet lets you join for free)
2. Leave Tubnet and join againResults: Severe FPS lag on the second login.
Expected results: No additional FPS lag no matter when you join.Note: Joining either of those servers for the first time, and then logging off to join another server using a resource pack also causes lag. For example, you get lag if you leave Tubnet to join MCC Island and vice versa.
Joining a server that uses a custom server resource pack for a second time causes severe FPS lag on the client(Affects Tubnet, Hypixel, MCC Island, and any server using a custom pack)
![[Mojang] Bartosz Bok](../../../data/avatars/users/10122.svg){kind=small}
[Mojang] Bartosz BokJoining a serverthatuses a customserver resourcepackfor a second time causes severe FPS lag on the clientReloading a resource pack that has a custom texture atlas for a second time causes severe FPS lag on the client
This issue affect
sTubnet, Hypixel, MCC Island, and any server using acustom pack. If you join a server that uses custom server resource packs such as Tubnet and leave, and then join again, you will notice severe FPS lag.To reproduce:
1. Join Tubnet or MCC Island (Tubnet lets you join for free)
2. Leave Tubnet and join againResults: Severe FPS lag on the second login.
Expected results: No additional FPS lag no matter when you join.Note: Joining either of those servers for the first time, and then logging off to join another server using a resource pack also causes lag. For example, you get lag if you leave Tubnet to join MCC Island and vice versa.
This issue can affect rejoining Tubnet, Hypixel, MCC Island, and any server using a pack that may use a custom atlas, though those three are among some of the most prevalent. If you join a server that uses custom server resource packs such as Tubnet and leave, and then join again, you will notice severe FPS lag.
To reproduce:
1. Join Tubnet or MCC Island (Tubnet lets you join for free)
2. Leave Tubnet and join againResults: Severe FPS lag on the second login.
Expected results: No additional FPS lag no matter when you join.Note: Joining either of those servers for the first time, and then logging off to join another server using a resource pack also causes lag. For example, you get lag if you leave Tubnet to join MCC Island and vice versa.
This issue
canaffect rejoining Tubnet, Hypixel, MCC Island, and any server using a pack that may use a custom atlas, though those three are among some of the most prevalent.If you join a server that uses custom server resource packs such as Tubnet and leave, and then join again, you will notice severe FPS lag.To reproduce:
1. Join Tubnet or MCC Island (Tubnet lets you join for free)
2. Leave Tubnet and join againResults: Severe FPS lag on the second login.
Expected results: No additional FPS lag no matter when you join.Note: Joining either of those servers for the first time, and then logging off to join another server using a resource pack also causes lag. For example, you get lag if you leave Tubnet to join MCC Island and vice versa.
This issue affects rejoining Tubnet, Hypixel, MCC Island, and any server using a pack that may use a custom atlas, though those three are among some of the most prevalent. Hence, if you join a server that uses custom server resource packs such as Tubnet and leave, and then join again, you will notice severe FPS lag.
To reproduce:
1. Join Tubnet or MCC Island (Tubnet lets you join for free)
2. Leave Tubnet and join againResults: Severe FPS lag on the second login.
Expected results: No additional FPS lag no matter when you join.Note: Joining either of those servers for the first time, and then logging off to join another server using a resource pack also causes lag. For example, you get lag if you leave Tubnet to join MCC Island and vice versa.
This issue affects rejoining Tubnet, Hypixel, MCC Island, and any server using a pack that may use a custom atlas, though those three are among some of the most prevalent. Hence, if you join a server that uses custom server resource packs such as Tubnet and leave, and then join again, you will notice severe FPS lag. This issue also affects singleplayer when reloading such resource packs on a Mac machine, as pointed out by @Caden Kriese.
To reproduce:
1. Join Tubnet or MCC Island (Tubnet lets you join for free)
2. Leave Tubnet and join againResults: Severe FPS lag on the second login.
Expected results: No additional FPS lag no matter when you join.Note: Joining either of those servers for the first time, and then logging off to join another server using a resource pack also causes lag. For example, you get lag if you leave Tubnet to join MCC Island and vice versa.
This issue affects rejoining Tubnet, Hypixel, MCC Island, and any server using a pack that may use a custom atlas, though those three are among some of the most prevalent. Hence, if you join a server that uses custom server resource packs such as Tubnet and leave, and then join again, you will notice severe FPS lag. This issue also affects singleplayer when reloading such resource packs on a Mac M1/M2 machine, as pointed out by @Caden Kriese.
To reproduce:
1. Join Tubnet or MCC Island (Tubnet lets you join for free)
2. Leave Tubnet and join againResults: Severe FPS lag on the second login.
Expected results: No additional FPS lag no matter when you join.Note: Joining either of those servers for the first time, and then logging off to join another server using a resource pack also causes lag. For example, you get lag if you leave Tubnet to join MCC Island and vice versa.
MC-259666 doesn't seem to be fully fixed. The stall still occurs, though only when reloading such resource packs in a certain order.
To reproduce this issue, you need to have another resourcepack (that doesn't have a custom atlas) already loaded, and then load the Hoplite resource pack first before loading the MCC Island resourcepack. Presumably, because the Hoplite pack is smaller than the latter.
Steps to reproduce:
1. Load a resourcepack.
2. Load Hoplite's resourcepack.
3. Load MCC Island's resourcepack after unloading Hoplite's.
Result: Severe micro stutters would occur. Only way to fix this is to reopen the game. 
Alternatively:
2. Load MCC Island's resourcepack first.
3. Load Hoplite's resourcepack after unloading MCC Island's.
Result: No micro stutters at all, no matter what order you load these resource packs afterwards. 
New video demonstrating the issue: https://youtu.be/RAHWb9uYSi4
I have the same issue - might just be on Apple M1/M2 computers, as I have the same issue and am using an M1 Mac Mini. I've tested this out on non-modified 1.19.2 and 1.19.3 and it only happens on 1.19.3
edit: happens on ANY server with a custom resource pack - just tested Minehut as well
Moved part of the title to the description since it's much more fitting here.
This only happens with resource packs using custom texture atlases in their resource pack. It also happens on singleplayer if you disable and re-enable a resource pack with texture atlases (F3+T does not work). I can reproduce since 22w46a.
Updated summery and description based on Caden Kriese's comment.