Chunksmith

Chunksmith

Pre-generate your world -- and see it.

Chunksmith generates chunks ahead of time so players never wait on worldgen. What makes it different is that the same pass also builds the distant-horizon data for Distant Horizons or voxy. One run, two results: a world that loads instantly, and a world you can see to the edge of.

Originally derived from Chunky by pop4959; developed independently since. Everything Chunky did, Chunksmith still does.

Full documentation is on the wiki -- every setting, every command, and walkthroughs for pregenerating, trimming, and getting multiplayer LOD working.

Report a bug or ask a question

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What Chunksmith adds

It builds your LOD data while it pregenerates

No second pass. No re-reading region files. No separate LOD pregen afterwards. Install Distant Horizons or voxy, run a pregen, and the distant terrain is simply there.

It turns itself on. If a renderer is installed, LOD generation is on. There is no config key to hunt for.

Already pregenerated? Run the same pregen again. Chunksmith builds LODs from the chunks it already has -- it does not regenerate them, and it skips everything already done. Pregenerate today, install a renderer next month, lose nothing.

Multiplayer LOD, with no companion mod. Players joining your server download the pregenerated LOD data and see the whole world at distance without ever having walked it. The same jar is both halves -- server and client. The Paper/Spigot plugin serves it too, so a modded client against a plugin server works.

LOD without the disk (4.4.0). /cs horizon <radius> pregenerates normally inside the radius and, past it, builds the LOD and throws the chunk away instead of saving it. A world that would have been hundreds of gigabytes keeps only the area people actually play in, and the distant terrain still shows -- in single-player and for every player who joins. Chunks a player goes near are always kept. Not available with Moonrise; on Paper, the fully generated chunks are dropped but some partly generated ones at the edges are still written.

It keeps generating while people are playing

Most pregenerators make you choose between speed and a playable server. Chunksmith measures what it adds to tick time rather than steering on absolute tick time -- so a server already running hot for its own reasons doesn't throttle Chunksmith to nothing for load it didn't cause.

Every online player shrinks the allowance further, so an empty server runs flat out and a busy one actively gives ground. If the server still can't sustain it, the run pauses itself with a stated reason and resumes when things recover. Your /cs pause always outranks it.

It is measurably faster

dispatchMaxConcurrent controls how many chunk requests stay in flight, and it scales to your CPU instead of a fixed cap. On an 8-core dedicated server, raising it from the old fixed 50 to 200 measured +39% -- 31.6 to 43.9 chunks/sec. Settable live.

Other mods' structures actually get built

A pregenerator that drops each chunk the instant it's generated breaks every mod that reacts to "a new chunk appeared" and then builds on a later tick -- the ground is already gone by the time it looks. Measured with Millenaire on a 1.21.1 pregen: 309 placement attempts, 309 deferrals, zero villages.

Chunksmith holds each chunk until all eight neighbours exist, then releases it. Nothing here is mod-specific -- the rule is about chunks, so anything that builds on new land benefits.

It tells you when worldgen misbehaves

Overreach detection and structure-fault attribution, so a broken worldgen mod is something you can identify rather than something you merely suffer.

Everything is live

Every setting is readable and settable live -- no restart, no editing files, no server downtime. Server settings are /cs set; the ones that belong to your own client are /csclient set. That's a rule the project holds itself to, with a test that fails if a setting is added without a command for it.

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Everything Chunky did

Flexible shapes (square, circle, diamond, triangle, star, and more), centred on coordinates, world spawn, or the world border. Multi-world. Live progress, rate, ETA and an optional boss bar. Pause, continue, cancel, and continue-on-restart. World trimming. A developer API for progress and completion events.

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Installing

Required on the server -- or in single-player, where your own game is the server. The client install is optional.

You only need it on the client for multiplayer LOD: to see pregenerated distant terrain on a server you haven't walked. Pre-generation alone needs nothing on the client.

Ships as a Fabric, Forge, and NeoForge mod and a Paper / Spigot plugin. (Folia is not supported. From 4.0.0 the plugin will not load on Folia at all -- it no longer declares folia-supported, so Folia refuses it rather than running a platform nothing tests. An unverifiable claim is worse than an absent one.)

Server and client must run the same major version. 4.0.0 changed the LOD wire protocol, and a mixed 3.x/4.x pair turns LOD off in both directions: the client will not fetch and the server will not serve. Everything else keeps working -- it is the distant terrain that stops arriving, and both sides say so plainly rather than failing strangely.

Worth knowing before you update: a launcher will offer 4.0.0 to anyone on 3.x, so a client can be updated into that mismatch without the server being touched. Move both together.