Corruption containment question

[the5thrider]

I'm sorry if this was answered in the past but I've honestly tried looking for the answer and keep on getting different answers (I think some of the ideas are from earlier versions). The wiki stats corruptions/hallow cnanot spread more than 3 blocks. Why then do most of the guides recommend 4 air blocks? Wouldn't 3 air blocks work?

A couple of sources I think suggest that thorns can spread corruption but wouldn't a singe wood wall against the side of 1 of the walls of the 3 air block hellovator/shaft be enough?

Any thoughts would be appreciated and sorry agin if it is addressed elsewhere

[Drag]

Yes, this is true. 3 blockis is the max range and 3 open air blocks would be enough to prevent the spread. However, if throns grow over the gap, it'll spread past your nice opening. 4 blocks makes it even harder for this happen, and I personally reccomend 5 and then also lining your hellevators.

Before hardmdoe even started I completely cut off my crimson from everything with a 5 block wide space. Of course, this does nothing when you smash demon alters and cause a single, random block to be corrupted somewhere int he world... For the same reasons, I've also cut off my town and a small area around it.

[the5thrider]

But thorns can't get through a single layer of wood right? So in theory lining one of the walls should be enough... I read that the thorns can't grow on wood and I don't think they can penetrate wood either.

I'm still not sure I understand why 4 would be better especially if you line the walls. I understand the thorn theory but the lined walls should stop thorns right? Is the 4 just to be safe or is there another reason?

[the5thrider]

Thanks for the help by the way. I'm trying to contain my world before I go to hardmode but it's a lot of work so I want to make sure if I do it I'm not wasting my time making ineffective containment

[ShadeDaystar]

Originally posted by the5thrider:

But thorns can't get through a single layer of wood right? So in theory lining one of the walls should be enough... I read that the thorns can't grow on wood and I don't think they can penetrate wood either.

I'm still not sure I understand why 4 would be better especially if you line the walls. I understand the thorn theory but the lined walls should stop thorns right? Is the 4 just to be safe or is there another reason?

Thorns may be able to be stopped with a simple barricade, but the blocks that spread corruption start being able to skip over blocks (in a limited radius) once the world enters hardmode. A lot of people feel "Better Safe than Sorry", so they use wider barriers to make it even less likely that the corruption spreads.

If you think 3 is going to work for your world, go with 3. There's no hard and fast rule about any of this. If you try 3 and find some leaks, then you can always go back and widen the barriers.

Edit: Just read your last post. When you defeat the Wall of Flesh, a huge swath of both Hallow and Corruption gets generated. So that'd be another one to deal with. Then, when you go and smash Demon Alters to generate your new ores, each one smashed has a chance of turning a random stone block into either Pearlstone or Ebonstone/Crimstone. Which could generate yet another patch of the biome.

Anything you do now is either stop-gaps or busywork. Because once you enter Hardmode, there's no guarentee that what you've done won't be completely undone.

[Celator]

Yes, you can make a 3-block gap and then cover one or both sides of it with an incorruptible block, and it'll stop the corruption. The incorruptible block will stop the thorns, and the corruption blocks won't be able to spread across the 3-block gap (which can include the incorruptible blocks, natch).

[the5thrider]

"If you think 3 is going to work for your world, go with 3. There's no hard and fast rule about any of this. If you try 3 and find some leaks, then you can always go back and widen the barriers."

I guess my question would be there should be a hard and fast rule based on the programming right? According to the wiki it should be 3 blocks but I wanted to see if anyone tested this.

"Yes, you can make a 3-block gap and then cover one or both sides of it with an incorruptible block, and it'll stop the corruption. The incorruptible block will stop the thorns, and the corruption blocks won't be able to spread across the 3-block gap (which can include the incorruptible blocks, natch)."

This is what I think too, but so many guides recommend 4 or even 5 blocks I started having doubts.

As to the hardmode swath and the new spawns, I realized that these would happen. My plan was to make a giant grid across my world to limit the spread (I'm only on a small world). The random spawning would only take out one slot in the grid and could be later more easily be converted. Plus I figured if the world was bad enough, I could always use the hellavators to completely purify the world.

[Zemecon]

The reason they say "four blocks" when the Corruption can only be stopped by three is because when you are counting how many blocks to remove you always consider the one your standing on. So you go "one block (the block you're standing on), two block, three block, four block," and then leave the fifth block alone. So you do wind up with a gap that is three blocks wide. Which should be enough.

Consider it this way: A corrupted block will affect whatever is touching it and what is beside it, but nothing beyond it. A non-corrupted block will pick up corruption from the block touching it as well as the block beside it but not beyond it. So that second block in the centre of your 3-block gap acts like a buffer.

It is much easier to explain with a diagram or a screenshot. but you can also use tree saplings as an analogy. Each sapling requires the block it will be planted on to be free (obviously) but it also requires both blocks on each side to be completely free, too. And they can't overlap with the free block beside other saplings, either. So imagine that one sapling is the very tip of the corruption and the sapling beside it is the very tip of your uncorrupted area.

So a 3-block gap should theoretically be enough to stop Corruption from spreading. Of course in practice means you'll have to try it out and see what happens.

[ShadeDaystar]

Originally posted by the5thrider:

I guess my question would be there should be a hard and fast rule based on the programming right?

Technically, there can be. But there's also the possibility of RNGs. And without looking at the coding yourself, all you're going on is other people's advice and observations. Some people prefer smaller buffers, some prefer larger ones "just to be safe". Honestly, you're really making this more difficult than it has to be.

[Celator]

Originally posted by Zemecton:

Consider it this way: A corrupted block will affect whatever is touching it and what is beside it, but nothing beyond it. A non-corrupted block will pick up corruption from the block touching it as well as the block beside it but not beyond it. So that second block in the centre of your 3-block gap acts like a buffer.

That's not true. It's more or less true for normal mode, excepting vines and thorns, but in hardmode a block of corruption can infect any block within a 3-block radius around it, whether it's touching it or not. That's why you have to be extra careful when cleansing the corruption in hardmode, because oftentimes corruption blocks will be scattered around rather than in continuous swaths.

Originally posted by the5thrider:

I guess my question would be there should be a hard and fast rule based on the programming right? According to the wiki it should be 3 blocks but I wanted to see if anyone tested this.

It is three blocks, it's been thoroughly tested and proven. The reason some guides recommend more could be because they were confused by corruption springing up due to other factors (thorns, vines, smashing demon altars), but three is really all you need.

[Zemecon]

Originally posted by Over8001:

Originally posted by Zemecton:

Consider it this way: A corrupted block will affect whatever is touching it and what is beside it, but nothing beyond it. A non-corrupted block will pick up corruption from the block touching it as well as the block beside it but not beyond it. So that second block in the centre of your 3-block gap acts like a buffer.

That's not true. It's more or less true for normal mode, excepting vines and thorns, but in hardmode a block of corruption can infect any block within a 3-block radius around it, whether it's touching it or not. That's why you have to be extra careful when cleansing the corruption in hardmode, because oftentimes corruption blocks will be scattered around rather than in continuous swaths.

Umm, I never said that corrupted blocks only spread to the blocks touching them. They also spread to whatever is two blocks away. Any "air block" touching them can also spread corruption. That's why I said the minimum length for a corruption-preventing gap needed to be three blocks wide. That's also why I said you need a buffer block between the air block touching a corrupted block and an air bloch touching a normal substrate block.

[Celator]

Originally posted by Zemecton:

Umm, I never said that corrupted blocks only spread to the blocks touching them. They also spread to whatever is two blocks away. Any "air block" touching them can also spread corruption. That's why I said the minimum length for a corruption-preventing gap needed to be three blocks wide. That's also why I said you need a buffer block between the air block touching a corrupted block and an air bloch touching a normal substrate block.

Oh, I'm sorry, I misinterpreted you and thought meant the blocks beside the original corrupt blocks (I wasn't sure why you were being redundant). That makes more sense.

However, that's still not entirely correct, since corrupt blocks can spread up to 3 blocks away (i.e. across 2-block gaps), not just 2 blocks away.

[Zemecon]

Originally posted by Over8001:

Originally posted by Zemecton:

Umm, I never said that corrupted blocks only spread to the blocks touching them. They also spread to whatever is two blocks away. Any "air block" touching them can also spread corruption. That's why I said the minimum length for a corruption-preventing gap needed to be three blocks wide. That's also why I said you need a buffer block between the air block touching a corrupted block and an air bloch touching a normal substrate block.

Oh, I'm sorry, I misinterpreted you and thought meant the blocks beside the original corrupt blocks (I wasn't sure why you were being redundant). That makes more sense.

However, that's still not entirely correct, since corrupt blocks can spread up to 3 blocks away (i.e. across 2-block gaps), not just 2 blocks away.

From the Terraria wiki[terraria.gamepedia.com]:

Originally posted by terraria.gamepedia.com:

In order to stop the spread of Corruption in Hardmode, the player must create a gap of at least three tiles containing empty space or non-corruptible blocks.

I'm not necessarily denying what you said but maybe you could post some screenshots.

[Celator]

Originally posted by Zemecton:

From the Terraria wiki[terraria.gamepedia.com]:

Originally posted by terraria.gamepedia.com:

In order to stop the spread of Corruption in Hardmode, the player must create a gap of at least three tiles containing empty space or non-corruptible blocks.

I'm not necessarily denying what you said but maybe you could post some screenshots.

Um... That literally is agreeing with what I just said. Corruption can spread up to 3 blocks away, that's why you need a 3-block gap to stop it.

[Light]

Grass can spread up to 5 blocks away I believe. My trench was 6 lol.

[Zemecon]

Originally posted by Over8001:

Originally posted by Zemecton:

From the Terraria wiki[terraria.gamepedia.com]:

Originally posted by terraria.gamepedia.com:

In order to stop the spread of Corruption in Hardmode, the player must create a gap of at least three tiles containing empty space or non-corruptible blocks.

I'm not necessarily denying what you said but maybe you could post some screenshots.

Um... That literally is agreeing with what I just said. Corruption can spread up to 3 blocks away, that's why you need a 3-block gap to stop it.

No, it doesn't agree with what you just said. I said Corruption could only spread across two blocks - both the corrupted bloch and the air block directly beside it can transmit corruption to whatever touches them - so you need one air block beyond the corrupted air block to act as a buffer. You therefore only really need a three-block-wide gap. If I'm wrong then i'm wrong but I don't think I typed anything in there that agrees with what you said. I don't think the wiki said anything that agrees with you, either, aside from requiring a three-block-wide gap. I didn't read anything in that article that said the corruption could spread across three blocks, only that it required a three-block-gap in order to stop it.

If the corruption really does spread across three blocks then you'd need a gap that is wider than three blocks - I'd give it about five or six - in order to contain it.

Originally posted by Cowboymaniac19:

Grass can spread up to 5 blocks away I believe. My trench was 6 lol.

That doesn't explain why the dirt houses in my world aren't completely covered in grass by now after being only three or four blocks away from the ground, which has grass on it.