Changing Modpacks?

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Wannabeuk

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Jul 29, 2019
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Hey guys,

I've never actually asked this, I've just assumed that if i wanted to change a modpack i would have no way of keeping the current world.

However i just wanted to check what options i actually have, we're in the usual position of wanting new mods, but having people who do not want to lose current projects in the world. So, what would actually happen if i removed mods from a map? Would the world go "poof" and corrupt, or would it be able to handle this is some way?

Sorry if this is a stupid question, but i was hoping something could be done.
 

Wannabeuk

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Jul 29, 2019
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Well, more towards a custom setup of a pack, from horizons (obviously we will have to keep the biomes mods) more like removing rotarycraft and a few others, and adding a bunch of mods in.

Or if possible, perhaps moving to something like direwolf20.
 

Kahless61

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Jul 29, 2019
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Changing versions of mods can sometimes cause ID issues from blocks changing ID, and then some other block taking its ID. This is why they'll often recommend a map reset for certain versions. This can even lead to chunk corruption. Usually updates are not this severe - and they'll usually warn when this happens.
As for removing a mod, it's usually a pretty harmless process. Any blocks (worldgen, machines, etc) from the mod will simply disappear (usually causing lighting issues where the blocks used to be and they don't get proper lighting updates since it still thinks there's a block there. Oregen can/will also leave little holes in your world where the ore used to be). Any items in any inventories from the mod will also disappear pretty gracefully.
One other thing to note is that newly generated chunks can be a grab-bag - don't be surprised to see sudden vertical cliffs where one chunk just ends suddenly and the next chunk begins at a different level. These are harmless - although it can mess with structures.


So it's possible, it can just be risky. That's why step number 1 is backup your world - because we expect that it's probably going to corrupt (and as a result, feel a little relief when it doesn't). Then prepare the new modpack, copy over your world, try to boot the server, and if it actually boots, you're off to a good start. Next step is to try to log in and fly around and assess the damage.
 
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Pied_Piper_11

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Jul 29, 2019
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it really depends on the mods that you have things in your world from. And the item id's matter too.
See above
 

Wagon153

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Jul 29, 2019
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In the new 1.6 packs, as long as you were using the universal configs in the previous pack, and are using them in the new, you should have no problems with a transition, unless you remove a mod with tons of worldgen(Like Project Red or Metallurgy)
 

Wannabeuk

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Jul 29, 2019
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This is better news than i was expecting. I was worried about removing blocks causing the world to just die. I guess my next question is, How hard is it to regenerate parts of the world? say i did remove some worldgen. Could i selectively regenerate chunks avoiding the chunks with peoples structures?
 

ThatOneSlowking

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Jul 29, 2019
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This is better news than i was expecting. I was worried about removing blocks causing the world to just die. I guess my next question is, How hard is it to regenerate parts of the world? say i did remove some worldgen. Could i selectively regenerate chunks avoiding the chunks with peoples structures?
Im not sure of other ways, but if you have ICBM installed you could use the missiles that regenerate chunks and then remove the mod.
 

The Mobius Archives

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Changing mods, especially from Custom to another set of configs can be a bit difficult due to ID changes. For this I use mIDas or mIDas gold to switch from one ID set to another. This can be time consuming and you may miss a few ids but you'll be able to keep most of your world with the caveat that "something" may be missing.
 

Kahless61

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Jul 29, 2019
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Could i selectively regenerate chunks avoiding the chunks with peoples structures?
If you install the WorldEdit plugin, you can use //chunk to select a chunk and //regen to regenerate the selection to the seed. Again, if worldgen changed, you may suddenly have an entire chunk that literally sticks out (or sticks in), and may disrupt structures that run through that chunk (dungeon, mineshaft, stronghold, village).

If you have entire regions of chunks that you would like to reset (see minecraft "region"), you should be able to simply delete that region file and it will regenerate the next time someone ventures into it.