6. Server admins

Versions

Fysik must be on the server and on every player, with exactly the same version: every player who owns part of a structure must calculate it exactly as the others do. Players without it, or with another version, cannot join. Update the server and tell your players to update at the same time.

Who calculates

Only players calculate. Whoever owns a piece (the player near it, as in vanilla) solves the whole structure and decides that piece's fate; the calculation gives the same result on every machine, so owners of different parts of one structure agree, and a crack is synced to everyone through the piece. Each player and cart tells everyone which pieces it rests on, so moving loads are the same for all.

To check that two players agree, both aim the hammer at the same structure and type fysik hash in the console: it prints the number of pieces, a fingerprint of the result and the most loaded piece. With both players close enough to have the whole structure loaded, and nobody building or moving on it, both must see the same fingerprint. If they differ, send both players' dumps (Ctrl+F8) in an issue.

The dedicated server calculates nothing. It relays, syncs the settings and hands the pieces near the centre of the world, which it would otherwise keep, to the nearest player. It needs no extra CPU.

Settings

Settings marked server in the configuration table on the mod page are enforced by the server and synced to every player. An admin can change them in game with a configuration manager (F1); changing a structure, weight or material setting recalculates every structure. The ones worth knowing:

• Structure.Mode: Physics, Sandbox or DisplayOnly (see Getting started).
• Structure.Difficulty: Relaxed makes materials 50% stronger, Strict 30% weaker.
• Failure.CrackWarningSeconds: the warning before a piece just past its limit falls (5 s).
• Failure.DamageWeakens: off, damage never changes a piece's strength.
• Structure.WorldBuildings: whether world buildings are simulated (below).
• Weight.LiveLoads: off, chest contents, players, carts and snow weigh nothing.
• Weight.Contents, Weight.Player, Weight.Snow: how much stored items, players and a full layer of snow weigh. Weight.Snow = 0 turns only the snow off.
• Weight.Wood, Stone, MetalBar, Nail, PerItemWeight: what objects weigh per material.
• Material.<type>: density and strengths of each material, for fine calibration.

World buildings

By default, stone towers, abandoned houses, villages, ruins, fortresses and every other piece no player placed keep vanilla support, show in grey and are never brought down by Fysik; a player build resting on one is held as if on rock. With Structure.WorldBuildings = Physics they are simulated like player builds. This changes the world for good: many of them were not built for real forces and crack and fall as soon as someone comes near. Pieces spawned with console commands, or by mods that do not record a builder, count as world buildings.

Big bases

Structures of up to Structure.MaxFrameBodies pieces (2000 by default, 500 to 5000) get the full calculation, on a worker thread: about 0.5 s for 2000 pieces, 2 s for 5000. Larger ones use a simpler model that does not recognise arches; the hammer then adds simplified model. Raise the limit if your players build arches into big bases. A structure that reaches beyond every player's loaded area is never brought down.

Worlds and modifiers

• A world where buildings never fall (NoBuildingFall) keeps that rule: Fysik shows the forces but brings nothing down.
• A world without heavy snow (NoHeavySnow) has no snow weight. A world with heavy snow on every piece (AllHeavySnow) puts snow on tarred roofs and the stave church pieces too.

Moving an existing world to Fysik

1. Back up the world.
2. Start with Structure.Mode = Sandbox, so nothing falls, and let players look over their bases with the X-ray (F7) and shore up what is red.
3. Switch to Physics.

Other mods

Mods that change structural integrity (NoBuildIntegrity, Forever Build, Balrond Better Build and the like) conflict with Fysik. Pieces added by other mods get conservative default materials, with a warning in the log for each unknown material; their objects weigh their recipe.

Console

With the game started with -console, F5 opens the console: fysik stats shows solver statistics and who owns the pieces around you, fysik recalc recalculates everything, fysik dump writes the structure under the hammer to BepInEx/fysik-dump.txt and fysik hash prints the fingerprint of its result (see Who calculates).