How to make blocks like "redstone" working in a minecraft-like game when the chunks are not loaded

Question

I'm working on a 2D minecraft-like game, I use chunks to save my world and each chunk has 128*128 blocks in it. And infinite chunks can create an infinite world.

Memory should never be infinite and only several chunks near the character are shown on the screen and loaded into memory. How can I handle logic based blocks like red stone signals when they are in chunks far away and so not loaded in memory?

Answer 1

What you need to do is separate terrain from live blocks. For example you could store the live blocks in a dictionary that uses a point as key. And then unload the terrain. This way your live blocks stay in memory in a way you see fit, and you can still look them up based on position, but the terrain is stored on disk for later retrieval.

This will increase memory a bit, but you can't avoid it entirely.

Answer 2

In Minecraft, circuits in unloaded chunks simply do not work. Especially with pistons and other ways of interacting with the environment, it could get expensive quickly to keep far-away circuits running in an infinite world.

I see three main possible choices for your game:

• Keep all chunks loaded. This is just a big nope.
• Keep nearby chunks loaded. For chunks too far away, save the state of the chunk. When coming close to the chunk, load the state again.
  • This means that the circuit will continue where it left off. Complex circuits won't break this way.
  • On the downside, the circuit won't run when the player is too far, though this is generally acceptable.
• Store active components separately. For chunks too far away, unload the terrain data but keep circuitry active.
  • This will cause things such as sensors, timers, etc... working all the time.
  • Bigger resource hit. An infinite world means possibly infinite circuits constantly running.
  • This would only work if circuits cannot interact with the terrain, or if they can only interact with the terrain within proximity of the player.

Of course there may be other ways to work around this, but those are likely going to be some form of hybrid between these ideas.

Answer 3

Tekkit (a popular minecraft mod) does this by allowing players to build anchors that keep a few blocks around them in memory regardless of player proximity.

It might be a good choice if there is clear distinction between dynamic blocks that require the presence of the player (an automatic door) and others that don't (a generator of some sort).

http://tekkitclassic.wikia.com/wiki/World_Anchor

Answer 4

Just an idea on a way to handle this without it bogging the game down too much.

What you could do instead is enforce a game mechanic that only runs that "redstone block" when it is connected to some sort of rare or hard to craft "Power" block, suggesting that the presence of the player powers the "redstone" and is required to run it.

I believe that how it actually works is dependent on what your "redstone" does. Does it physically move the block and do you handle moving blocks in unloaded chunks? What if it throws TNT into 10 chunks away, how would the "redstone" handle that?

I believe that to get a serious suggestion on a particular issue the question about the logic will have to be more specific.

Answer 5

I will just focus on just one topic in this answer: If you want to unload distant circuits to save CPU time and/or memory, what will happen to complex circuits that spred across multiple chunks?

1. Igore this problem. Easy to implement, but unsatisfactional behaviour.
2. Let player be aware of this problem, and give him a tool to display chunk bounds. I think there was such item in one of Minecraft's mods. Player then can build circuits only on one chunk if he needs to.
3. Create some connective block, when placed, it will guarantee that all circuits in a set redius will be always loaded/unloaded at the same time. Assuming that radius is smaller than chunk size, one such block will connect maximally 4 chunks together. However overusing these blocks can lead to infinitely many connected chunks.
4. In Tekkit mod, there was World Anchor block, that kept surrounding chunks loaded all the time. Good choice if you want to have some machinery running away from player.

Summary: Depends on what you need, I wouldn't be afraid of combining 2, 3 or 4 (or all) together, you can also nerf 3 to connect maximally N chunks.