Spontaneous chunk reversion?

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MisterFister
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Spontaneous chunk reversion?

Post by MisterFister »

What causes chunks to spontaneously regenerate from seed? I've been spending... dear lord, at least the last 12 in-game hours underground customizing subterranean chambers (a multi-level glass-roof farm, shroom farms, an artificial squid farm, etc.)

LOTS of diamond-tech terraforming on the surface had been completed, including wholesale removal of a nearby mesa-biome abandoned village save for one hut used to house my nether portal. Shelved off a lagoon, removal and controlled source-block flooding of at least 30 chunks-area of island. Extensive cave torching. Very large rudimentary-design tree farm and cocoa farm (cocoa farm generates approximately half a large chest of overflow seeds with each manual till, which takes approximately 2 in-game days to harvest and re-plant.

800-block length tunnel in the nether to a river-navigable series of villages, accounting for at least a mating pair of each caste (yet to relocate them all to a central outpost for controlled breeding and trading purposes.)

....

I emerged to the surface, armed with 9 diamond shovels, intending to visit my nearby desert to go harvesting a few chests worth of sand to smelt into glass. Ruined. The chunk housing my nether portal, gone, reverted to original virgin-seed terrain. Other chunks, haphazardly arranged, with original 12-high terrain that I'd previously terraformed down to sea level. Original trees spawned, my tree farm cut in half with leaves exposed but their trunks missing within the corrupted chunks.

No CLUE what has happened below ground. Easily 1400 hours in this SSP. No idea if the issue affects the nether, or my remote outpost with my villages. I have a Dropbox archive that took several snapshots of my save from many hundreds of gameplay hours ago. I haven't catalogued them yet, but the date stamps are not encouraging.

What causes this?

~~~ Screenies to follow.
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Gilberreke
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Re: Spontaneous chunk reversion?

Post by Gilberreke »

It's caused by chunk corruption. Since I haven't seen a BTW bug do this in ages, I assume you had a small disk error or something like that. Not sure.

That sucks though :/

I know some people regularly back their worlds up to stop this.
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ion
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Re: Spontaneous chunk reversion?

Post by ion »

happens sometimes. one way is to open the save game in mcedit and check if the chunks where swapped around
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MisterFister
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Re: Spontaneous chunk reversion?

Post by MisterFister »

Gilberreke wrote:It's caused by chunk corruption. Since I haven't seen a BTW bug do this in ages, I assume you had a small disk error or something like that. Not sure.

That sucks though :/

I know some people regularly back their worlds up to stop this.
Ok, so some good news is that my Dropbox backups are somewhat more detailed and inclusive than I thought. I have a LOT of slogging and cataloguing to do with them, but there remains a non-zero chance that I can at least pinpoint where the most crucial chunks became corrupted. This still has the potential to ruin dozens of conceivably hundreds of very tedious hours getting my very-OCD underground alignments in order (my underground farm first involved laying a patterned glass-brick roof at my shelved-floor of my lagoon approximately 25x80 blocks, followed by excavating a footprint of ~28x85 to a depth of 25 -- through caves, gravel-filling and removing two lava pools, a zombie spawner (!!) bridging the gap over a concealed lava-level ravine, and under-lighting the irrigation channels without glowstone.) Generated approximately 10 full chests of cobble and consumed at least 4 chests of glass brick and five chests of stone brick. Easily recycled through three or four dozen diamond pickaxes. Consumed two chests of sandwiches, three chests of poached egg (I track food consumption because the project involved tearing out both my preexisting farm AND my chicken coop and I WOULD be just about ready to redesign and relocate it at this point but for having discovered the chunk issues.)
ion wrote:happens sometimes. one way is to open the save game in mcedit and check if the chunks where swapped around
I'm aware of this from some YT vids, but I haven't the foggiest idea how to go about this. I'll know more if I catalogue through my archive of saves.
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MisterFister
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Re: Spontaneous chunk reversion?

Post by MisterFister »

Update: I did do some creative-mode exploring and flying around in that overworld section (no experiment efforts involved rebuilding my portal to explore possible nether damage or damage to my remote outpost location.) Poking around underground did indeed provide no surprises when I confirmed that the chunk corruption was entirely carried underground, likely down to bedrock.

A series of multiple very low-probability items of good fortune resulted in me finding a seemingly uncorrupted save version that "only" results in the loss of a few hours work, if the in-game "time" command is any indication (to say nothing of a walkthrough observation of my build progress.) I shall have to continue poking around in the nether and at my outpost to confirm this.

Based on the Windows timestamps of where in the chain the corrupted chunks appear... I think I can report an illustrating symptom. My practice is to exit to the main menu screen when I go afk for bathroom breaks and whatnot (and from this point forward, I shall incorporate into that practice a new emphasis on backing up the save folder at that point as well.) It's difficult to tell with any certainty, but I do distinctly recall three or four instances of loading back into my save to be in some kind of in-game distress, suffocating in Gloom and unable to move and rapidly losing health, amid a black screen. Panic-exiting and reentering the game, at the time, seemed to have solved the problem with no other lasting evidence of a problem, except for the lost health which regenerated over time anyway. This happened about half a dozen times on a specific gaming day over the span of a few hours.

I'd care for others' input or speculation here, but I wonder if that was literally the result of spawning into solid rock well below-ground in a then-newly-corrupted chunk, whereby exiting and reentering spontaneously cured the problem, at least with respect to that specific chunk I was working within. Since I was so deep underground and for such an extended period, I have no way to confirm that this correlates to the other chunks I discovered corrupted and re-generated from original seed. That said, since it was apparently the entire chunk and not just the surface terraforming that was corrupted, my theory here does seem to be a working one.
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Yhetti
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Re: Spontaneous chunk reversion?

Post by Yhetti »

Just a thought, if you've got a world that you've used deco addons in, don't start that world without any of those deco addons, otherwise you risk corruption. If you want to do this anyways, please backup your world before doing it.
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MisterFister
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Re: Spontaneous chunk reversion?

Post by MisterFister »

Yhetti wrote:-snip-
I run default graphics, but thank you, as this possibility of graphics overlay causing issues would never have occurred to me.
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CrimsonStorm
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Re: Spontaneous chunk reversion?

Post by CrimsonStorm »

Another thought--do you actually have your active save in your dropbox folder? If that's the case, I wouldn't be surprised if that's the source of your corruption. Dropbox is a pretty good backup service, but isn't perfect--and especially for large numbers of files with frequent changes (or large files that have small frequent changes) there is a fairly increased chance of things getting messed up.

My recommendation, if you want to use Dropbox to backup your worlds, is that you have your actual save data outside of your Dropbox folder and have some script (or manually) copy it over at some regular interval.
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MisterFister
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Re: Spontaneous chunk reversion?

Post by MisterFister »

CrimsonStorm wrote:Another thought--do you actually have your active save in your dropbox folder? If that's the case, I wouldn't be surprised if that's the source of your corruption. Dropbox is a pretty good backup service, but isn't perfect--and especially for large numbers of files with frequent changes (or large files that have small frequent changes) there is a fairly increased chance of things getting messed up.

My recommendation, if you want to use Dropbox to backup your worlds, is that you have your actual save data outside of your Dropbox folder and have some script (or manually) copy it over at some regular interval.
Apologies for the necro-reply, but this is the first time I'd seen this.

Indeed, I concur with your advice not to nest game-active file copies within a folder that is also Dropbox-active. My own troubleshooting with Dropbox for other issues suggests to me that the problems coming from such a practice would result in other types of errors, or at least other in-game symptoms such as my above-described occurrences of loading into the game instance suffocating in solid rock, whereupon my experience with that symptom only recurred a handful of times across a few real-world hours of a single play session. Conversely, Dropbox-created issues in a live save folder would suggest that my symptoms would've been spread out over more than just a single discrete game session. This is all, of course, presuming that my chunk-corruptions correlated with my suffocating-spawn symptoms, which I cannot categorically confirm or eliminate based on my troubleshooting and data-timeline I was able to create, but cest la vie.

In reply to your advice, however, my MC save folder is in the default location, and I use an external widget(?) to periodically snapshot key folder locations (such as my MC saves) INTO my Dropbox folder through use of the archive-flag attributes within Windows itself. Thus, the Dropbox connectivity transactions are performed on usage-inactive copies of the files, which creates the added side benefit of creating versioned backups of my BTW save -- and that side benefit was entirely unanticipated and unintentional to why I set things up the way I did.

Final result: all is well in my SSP. :D
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