World fluids

A fluid can leave its tanks and pipes: poured from a bucket, it flows, swims and looks like its own liquid, with its own textures, fog, physics and effects. Players need no mod: the look comes from MachineEngine's resource pack.

Making a fluid placeableCopy Anchor Link

Any fluid resource type can be placeable. Add a fluid: section to its definition (see Resources):

resource-types:
  mypack:fluid/oil:
    category: machineengine:fluid
    color: '#2A2238'
    fluid:
      world: placeable
      look:
        texture:
          {source: recolor, pattern: lava, from: '#0A080E', to: '#4E3E60'}
        opacity: 0.96
        fog: '#0B0806'
      physics:
        viscosity:
          {speed: 0.5, gravity: 1.6, jump: 0.5, damping: 0.35, entity-drag: 0.3}
        spread: {ticks: 15, range: 5}
        infinite-source: false
      mixing:
        - {with: water, result: stop}
        - {with: lava, result: block, block: minecraft:obsidian}
      effects:
        - {type: potion, effect: minecraft:slowness}

Only world: placeable is needed: everything else defaults to water. A fluid without textures is the water texture in its menu color. Unknown fields are refused at startup with their path, so typos show in /machineengine report.

LookCopy Anchor Link

A texture is a resource pack key, such as mypack:block/oil_still, or a map with a source:

Fluids that look the same share one look on the client, so 22 placeable fluids with 22 different looks fit, and more if some look alike.

PhysicsCopy Anchor Link

Gravity and jump need 1.20.5 or later. Players' speed, gravity and jump are attributes their client predicts, so they feel smooth; damping is applied by the server and can stutter a little.

MixingCopy Anchor Link

Rules for where it flows into another fluid. The first rule that matches decides; without one, both stop where they meet.

EffectsCopy Anchor Link

Effects run every 10 ticks on whoever is inside.

Mobs and items feel effects and drag too, unless entity-effects is off.

Changing a fluid without a restart: fluids.ymlCopy Anchor Link

plugins/MachineEngine/fluids.yml overrides any placeable fluid, including those of addons such as Mekanized. On first start it lists every placeable fluid with its current values, ready to copy. Write only the fields to change:

fluids:
  mekanized:fluid/brine:
    look: {tint: '#E8DDB5', opacity: 0.8}
    physics:
      viscosity: {speed: 0.8}

/machineengine reload fluids applies it:

world and bucket can't be changed there: set them in the definition and restart.

The resource packCopy Anchor Link

MachineEngine writes the fluids' textures and a patched water shader into CraftEngine/resources/machineengine/resourcepack, so CraftEngine sends them with its pack. It builds them from the official Minecraft client jar, which it downloads from Mojang once and keeps in plugins/MachineEngine/cache.

After changing looks, rebuild and resend the pack:

/machineengine reload fluids
/ce reload pack

Players' renderersCopy Anchor Link

textures: auto (the default) picks the texture grid on 26.2 and later, where Sodium reads the pack's shader, and tint only before, so nobody sees the grid.

SettingsCopy Anchor Link

Under world-fluids: in config.yml. Restart marks settings that need one; pack marks those that apply after the pack is rebuilt.

CommandsCopy Anchor Link

All need machineengine.admin. Except info, they act on what you look at and are for players only.

How it works, and its limitsCopy Anchor Link

A placed fluid is vanilla water underneath: it flows, swims and drowns like water, and MachineEngine remembers which water blocks hold which fluid (saved in the chunk). Players see the difference because MachineEngine colors that water with a code, and the resource pack's shader turns each code into its fluid's look.

The client colors water by 4-block areas (biome cells) and blends the areas around each block. That sets the rules:

• Two different fluids keep a gap (fluid-gap). Blended together, two codes are no fluid at all, so the blocks between them would show plain water. Placing a fluid too close to another is refused, and fluid show tells you where it may go.
• A fluid and plain water don't share an area under conflict: stop: a fluid stops where plain water uses the area, and the other way round.
• Biome Blend (Video Settings) spreads colors a few blocks. With Sodium, each corner also blends the blocks around it, so the tip of a fluid pointing at another pool may fade a little. fluid-gap: 3 removes that. Very wide Biome Blend (15×15) needs a wider gap.

TroubleshootingCopy Anchor Link

A fluid shows as waterCopy Anchor Link

Set debug-colors: true, then /machineengine reload config, /machineengine reload fluids and /ce reload pack. Water faces show what the shader read:

/machineengine fluid info, looking at the block, tells you what the server sent for it and the 8 blocks around. Set debug-colors back to false and rebuild the pack when you are done.

Players see a grid on all waterCopy Anchor Link

Their renderer does not read the pack's shader (Sodium before 0.9, OptiFine, a shader pack). Use textures: tint, or keep auto on versions before 26.2.

The pack is not builtCopy Anchor Link

The first build downloads the client jar from Mojang (and Sodium from Modrinth). Without internet access, set client-jar (and sodium-jar) to the path of a jar. The console tells you what was written.

For developersCopy Anchor Link

The same fluids can be made in code: FluidType.builder(key).placeable()…build() from fr.robie.machineengine.api.resource.fluid. WorldFluids (fr.robie.machineengine.api.paper) reads, places and takes fluids in the world, and WorldFluidPlaceEvent, WorldFluidRemoveEvent and EntityFluidEvent (enter, leave) tell you when that happens. Your own effect, mixing result and texture types register like other MachineEngine types.