I dug up my old save from when I first started playing and was going to indulge in some nostalgia, play it again with the old 1.4.7. Unfortunately, last time I played it was on 1.8, and apparently the save is incompatible with older version (1.4.7 crashes when trying to load it). I remember that loading 1.8 saves in 1.7 emptied inventories and chests, too.
I loaded it up in NBTExplorer and manually fixed some of the playerdata by comparing it to a new world I created in 1.4.7 and moving around a few tags (mostly from playerdata/<my uuid> to level.dat/Player) but it still doesn't work. Anybdoy got some helpful clues on how to manually make a map work with an older version again?
I know ^^ but I figured with a bit of messing under the hood, it should be possible. Far as I know, map format hasn't really changed since forever, only big change I remember is username-to-UUID, so I'm hoping it's feasible to do.
If you really want to manually revert every single chunk - a process that will take probably months - you can look up the data formats and attempt to do it.
The only thing that changed in the save format between 1.4.7 and 1.8 is the conversion of numerical item IDs to strings, which would explain the crashing as the game is trying to read a string as a numerical value (the error probably says something like "ClassCastException: ck cannot be cast to cj"). Also, the last time I did this, loading a world created in 1.8 in 1.6.4, I found that the game only crashed when there were items in the player's inventory; however, any chunks with items were reset (with a lot of the aforementioned errors, which are caught during chunk loading so they don't crash the game but this aborts loading the chunk, hence they get reset). Otherwise, invalid blocks and entities will be safely removed (the game checks for and deletes invalid blocks and unknown entities are skipped) and unknown biomes will turned into plains (only affecting biome colors and precipitation).
The main issue is removing/replacing all invalid items, including in every dungeon and mineshaft chest, which are very common in older worlds; however, I did some looking around and found a filter for MCEdit that somebody made which converts 1.8 item IDs into numerical IDs; note that it only works on blocks and minecarts (you need to select the area to convert), not player/villager/etc inventories (you can put your inventory, including your ender chest, which is part of the player inventory, into chests):
You may also want to use MCEdit to delete 1.8 chunks entirely as these chunks will clash with older chunks due to changes in world generation, and this will help ensure that any 1.8 content will be removed (aside from item IDs, which are automatically updated when you load a world in 1.8. It is also possible that ocean monuments, which can generate in existing chunks, were generated where there would be deep ocean in 1.8, regardless of the actual biome, which will leave holes behind when their blocks disappear, so if you find any you can do a fill/replace to replace them with stone/dirt/etc).
Note that you also need to run 1.4.7 in its own profile with its own game directory - running different versions in the same directory, especially when there is a large gap between versions, is a leading cause of game malfunctions/crashes (you could also delete options.txt when you switch versions but that would probably become tiresome after a while).
The only thing that changed in the save format between 1.4.7 and 1.8 is the conversion of numerical item IDs to strings, which would explain the crashing as the game is trying to read a string as a numerical value (the error probably says something like "ClassCastException: ck cannot be cast to cj"). Also, the last time I did this, loading a world created in 1.8 in 1.6.4, I found that the game only crashed when there were items in the player's inventory; however, any chunks with items were reset (with a lot of the aforementioned errors, which are caught during chunk loading so they don't crash the game but this aborts loading the chunk, hence they get reset). Otherwise, invalid blocks and entities will be safely removed (the game checks for and deletes invalid blocks and unknown entities are skipped) and unknown biomes will turned into plains (only affecting biome colors and precipitation).
The main issue is removing/replacing all invalid items, including in every dungeon and mineshaft chest, which are very common in older worlds; however, I did some looking around and found a filter for MCEdit that somebody made which converts 1.8 item IDs into numerical IDs; note that it only works on blocks and minecarts (you need to select the area to convert), not player/villager/etc inventories (you can put your inventory, including your ender chest, which is part of the player inventory, into chests):
You may also want to use MCEdit to delete 1.8 chunks entirely as these chunks will clash with older chunks due to changes in world generation, and this will help ensure that any 1.8 content will be removed (aside from item IDs, which are automatically updated when you load a world in 1.8. It is also possible that ocean monuments, which can generate in existing chunks, were generated where there would be deep ocean in 1.8, regardless of the actual biome, which will leave holes behind when their blocks disappear, so if you find any you can do a fill/replace to replace them with stone/dirt/etc).
Note that you also need to run 1.4.7 in its own profile with its own game directory - running different versions in the same directory, especially when there is a large gap between versions, is a leading cause of game malfunctions/crashes (you could also delete options.txt when you switch versions but that would probably become tiresome after a while).
I got 1.4.7 running in its own subfolder already. I'll have to take a look at that MCEdit stuff. Chunks should be fine, IIRC I only briefly opened it in 1.8 a while back but only moved within sight of already generated chunks so that should not be an issue.
I dug up my old save from when I first started playing and was going to indulge in some nostalgia, play it again with the old 1.4.7. Unfortunately, last time I played it was on 1.8, and apparently the save is incompatible with older version (1.4.7 crashes when trying to load it). I remember that loading 1.8 saves in 1.7 emptied inventories and chests, too.
I loaded it up in NBTExplorer and manually fixed some of the playerdata by comparing it to a new world I created in 1.4.7 and moving around a few tags (mostly from playerdata/<my uuid> to level.dat/Player) but it still doesn't work. Anybdoy got some helpful clues on how to manually make a map work with an older version again?
Downgrading never was, never is and never will be supported.
I know ^^ but I figured with a bit of messing under the hood, it should be possible. Far as I know, map format hasn't really changed since forever, only big change I remember is username-to-UUID, so I'm hoping it's feasible to do.
If you really want to manually revert every single chunk - a process that will take probably months - you can look up the data formats and attempt to do it.
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The only thing that changed in the save format between 1.4.7 and 1.8 is the conversion of numerical item IDs to strings, which would explain the crashing as the game is trying to read a string as a numerical value (the error probably says something like "ClassCastException: ck cannot be cast to cj"). Also, the last time I did this, loading a world created in 1.8 in 1.6.4, I found that the game only crashed when there were items in the player's inventory; however, any chunks with items were reset (with a lot of the aforementioned errors, which are caught during chunk loading so they don't crash the game but this aborts loading the chunk, hence they get reset). Otherwise, invalid blocks and entities will be safely removed (the game checks for and deletes invalid blocks and unknown entities are skipped) and unknown biomes will turned into plains (only affecting biome colors and precipitation).
The main issue is removing/replacing all invalid items, including in every dungeon and mineshaft chest, which are very common in older worlds; however, I did some looking around and found a filter for MCEdit that somebody made which converts 1.8 item IDs into numerical IDs; note that it only works on blocks and minecarts (you need to select the area to convert), not player/villager/etc inventories (you can put your inventory, including your ender chest, which is part of the player inventory, into chests):
https://www.reddit.com/r/Minecraft/comments/231tyj/can_someone_do_a_mcedit_filter_to_change_item/cgso6z7
https://twitter.com/TexelElf/status/447525430963081216
You may also want to use MCEdit to delete 1.8 chunks entirely as these chunks will clash with older chunks due to changes in world generation, and this will help ensure that any 1.8 content will be removed (aside from item IDs, which are automatically updated when you load a world in 1.8. It is also possible that ocean monuments, which can generate in existing chunks, were generated where there would be deep ocean in 1.8, regardless of the actual biome, which will leave holes behind when their blocks disappear, so if you find any you can do a fill/replace to replace them with stone/dirt/etc).
Note that you also need to run 1.4.7 in its own profile with its own game directory - running different versions in the same directory, especially when there is a large gap between versions, is a leading cause of game malfunctions/crashes (you could also delete options.txt when you switch versions but that would probably become tiresome after a while).
TheMasterCaver's First World - possibly the most caved-out world in Minecraft history - includes world download.
TheMasterCaver's World - my own version of Minecraft largely based on my views of how the game should have evolved since 1.6.4.
Why do I still play in 1.6.4?
I got 1.4.7 running in its own subfolder already. I'll have to take a look at that MCEdit stuff. Chunks should be fine, IIRC I only briefly opened it in 1.8 a while back but only moved within sight of already generated chunks so that should not be an issue.