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Custom Fluids

experimental
intermediate
scripting
Custom Fluids

FORMAT & MIN ENGINE VERSION 1.21.20

This tutorial assumes an advanced understanding of blocks and the execute command. Check out the blocks guide before starting.

EXPERIMENTAL

Requires Holiday Creator Features for use of block tag Molang queries and to trigger block events.

Requires Beta APIs to use @minecraft/server module version 1.6.0-beta.

Creating fluids that are identical to vanilla fluids is not currently possible, but you can make something similar! This template/tutorial is designed to assist you in creating a custom "semi-fluid".

Flow Logic ​

  • The fluid block has states defining whether it is a source and its depth.
  • If there is air beneath fluid blocks, it will be converted into falling fluid.
  • Fluids with a depth above 1 will spread horizontally with decreasing depths.
    • This will not occur if there is falling fluid below.
  • Flowing fluid block must have another fluid block adjacent to survive.
  • Source blocks do not need to have other fluid blocks surrounding themselves.

This implementation does not include face culling due to its current complexity.

Source Fluid Block ​

Below is the code for a custom fluid. Copy and quick replace custom_fluid with your fluid's name. When the source block detects air in its surroundings, it replaces it with the outer fluid blocks. If the source block detects air beneath it, it will also place a falling fluid block underneath.

Download Custom Fluid Geometry
Custom Fluid Block JSON
BP/blocks/custom_fluid.json
json
{
    "format_version": "1.21.20",
    "minecraft:block": {
        "description": {
            "identifier": "wiki:custom_fluid",
            "menu_category": {
                "category": "none"
            },
            "states": {
                "wiki:source": [true, false],
                // Depth of fluid - default to 4
                "wiki:depth": [4, 5, 3, 2, 1]
            }
        },
        "components": {
            "minecraft:light_dampening": 0,
            "minecraft:collision_box": false,
            "minecraft:selection_box": false,
            "minecraft:destructible_by_explosion": false,
            // Trigger fluid spread
            "minecraft:queued_ticking": {
                "looping": true,
                "interval_range": [20, 20], // Fluid speed in ticks
                "on_tick": {
                    "event": "wiki:flow"
                }
            },
            "minecraft:material_instances": {
                "*": {
                    "texture": "custom_fluid", // Shortname defined in `RP/textures/terrain_texture.json`
                    "render_method": "blend",
                    "ambient_occlusion": false,
                    "face_dimming": false
                }
            },
            "minecraft:loot": "loot_tables/empty.json",
            "tag:custom_fluid": {}
        },
        "events": {
            "wiki:flow": {
                "sequence": [
                    // Dry out
                    {
                        "condition": "!q.block_state('wiki:source') && ((q.block_state('wiki:depth') == 5 && !q.block_neighbor_has_any_tag(0, 1, 0, 'custom_fluid')) || (q.block_state('wiki:depth') == 1 && !(q.block_neighbor_has_any_tag(1, 0, 0, 'custom_fluid_2') || q.block_neighbor_has_any_tag(-1, 0, 0, 'custom_fluid_2') || q.block_neighbor_has_any_tag(0, 0, 1, 'custom_fluid_2') || q.block_neighbor_has_any_tag(0, 0, -1, 'custom_fluid_2')) || q.block_state('wiki:depth') == 2 && !(q.block_neighbor_has_any_tag(1, 0, 0, 'custom_fluid_3') || q.block_neighbor_has_any_tag(-1, 0, 0, 'custom_fluid_3') || q.block_neighbor_has_any_tag(0, 0, 1, 'custom_fluid_3') || q.block_neighbor_has_any_tag(0, 0, -1, 'custom_fluid_3'))) || (q.block_state('wiki:depth') == 3 && !(q.block_neighbor_has_any_tag(1, 0, 0, 'custom_fluid_4', 'custom_fluid_5') || q.block_neighbor_has_any_tag(-1, 0, 0, 'custom_fluid_4', 'custom_fluid_5') || q.block_neighbor_has_any_tag(0, 0, 1, 'custom_fluid_4', 'custom_fluid_5') || q.block_neighbor_has_any_tag(0, 0, -1, 'custom_fluid_4', 'custom_fluid_5'))))",
                        "die": {}
                    },
                    // Spread
                    {
                        "condition": "q.block_state('wiki:depth') == 4",
                        "run_command": {
                            "command": [
                                "execute if block ~~~1 air run setblock ~~~1 wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=3]",
                                "execute if block ~~~-1 air run setblock ~~~-1 wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=3]",
                                "execute if block ~1~~ air run setblock ~1~~ wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=3]",
                                "execute if block ~-1~~ air run setblock ~-1~~ wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=3]"
                            ]
                        }
                    },
                    {
                        "condition": "q.block_state('wiki:source') && q.block_neighbor_has_any_tag(0, 1, 0, 'custom_fluid')",
                        "set_block_state": {
                            "wiki:depth": 5
                        }
                    },
                    {
                        "condition": "q.block_state('wiki:source') && !q.block_neighbor_has_any_tag(0, 1, 0, 'custom_fluid')",
                        "set_block_state": {
                            "wiki:depth": 4
                        }
                    },
                    {
                        "condition": "q.block_state('wiki:depth') == 3",
                        "run_command": {
                            "command": [
                                "execute if block ~~~1 air unless block ~~-1~ air unless block ~~-1~ wiki:custom_fluid run setblock ~~~1 wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=2]",
                                "execute if block ~~~-1 air unless block ~~-1~ air unless block ~~-1~ wiki:custom_fluid run setblock ~~~-1 wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=2]",
                                "execute if block ~1~~ air unless block ~~-1~ air unless block ~~-1~ wiki:custom_fluid run setblock ~1~~ wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=2]",
                                "execute if block ~-1~~ air unless block ~~-1~ air unless block ~~-1~ wiki:custom_fluid run setblock ~-1~~ wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=2]"
                            ]
                        }
                    },
                    {
                        "condition": "q.block_state('wiki:depth') == 2",
                        "run_command": {
                            "command": [
                                "execute if block ~~~1 air unless block ~~-1~ air unless block ~~-1~ wiki:custom_fluid run setblock ~~~1 wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=1]",
                                "execute if block ~~~-1 air unless block ~~-1~ air unless block ~~-1~ wiki:custom_fluid run setblock ~~~-1 wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=1]",
                                "execute if block ~1~~ air unless block ~~-1~ air unless block ~~-1~ wiki:custom_fluid run setblock ~1~~ wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=1]",
                                "execute if block ~-1~~ air unless block ~~-1~ air unless block ~~-1~ wiki:custom_fluid run setblock ~-1~~ wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=1]"
                            ]
                        }
                    },
                    {
                        "condition": "q.block_state('wiki:depth') == 5 && q.block_neighbor_has_any_tag(0, 1, 0, 'custom_fluid')",
                        "run_command": {
                            "command": [
                                "execute if block ~~-1~ wiki:custom_fluid [\"wiki:depth\"=3] run setblock ~~-1~ wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=5]",
                                "execute if block ~~-1~ wiki:custom_fluid [\"wiki:depth\"=2] run setblock ~~-1~ wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=5]",
                                "execute if block ~~-1~ wiki:custom_fluid [\"wiki:depth\"=1] run setblock ~~-1~ wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=5]",
                                "execute unless block ~~-1~ air unless block ~~-1~ wiki:custom_fluid if block ~1~~ air run setblock ~1~~ wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=3]",
                                "execute unless block ~~-1~ air unless block ~~-1~ wiki:custom_fluid if block ~~~1 air run setblock ~~~1 wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=3]",
                                "execute unless block ~~-1~ air unless block ~~-1~ wiki:custom_fluid if block ~-1~~ air run setblock ~-1~~ wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=3]",
                                "execute unless block ~~-1~ air unless block ~~-1~ wiki:custom_fluid if block ~~~-1 air run setblock ~~~-1 wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=3]"
                            ]
                        }
                    },
                    // Fall
                    {
                        "run_command": {
                            "command": "execute if block ~~-1~ air run setblock ~~-1~ wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=5]"
                        }
                    },
                    {
                        "condition": "q.block_neighbor_has_any_tag(0, -1, 0, 'flowing_custom_fluid')",
                        "run_command": {
                            "command": "setblock ~~-1~ wiki:custom_fluid [\"wiki:source\"=false,\"wiki:depth\"=5]"
                        }
                    }
                ]
            },
            "wiki:pick_up": {
                "die": {},
                "decrement_stack": {},
                "run_command": {
                    "command": "give @s lava_bucket",
                    "target": "other"
                }
            }
        },
        "permutations": [
            {
                "condition": "q.block_state('wiki:source')",
                "components": {
                    // Enables the block to be picked up by an item of choice
                    "minecraft:selection_box": {
                        "origin": [-7.5, 0.5, -7.5],
                        "size": [15, 13, 15]
                    },
                    "tag:custom_fluid_source": {}
                }
            },
            {
                "condition": "!q.block_state('wiki:source')",
                "components": {
                    "tag:flowing_custom_fluid": {}
                }
            },
            {
                "condition": "q.block_state('wiki:depth') == 5",
                "components": {
                    "minecraft:geometry": "geometry.fluid.5",
                    "tag:custom_fluid_5": {}
                }
            },
            {
                "condition": "q.block_state('wiki:depth') == 4",
                "components": {
                    "minecraft:geometry": "geometry.fluid.4",
                    "tag:custom_fluid_4": {}
                }
            },
            {
                "condition": "q.block_state('wiki:depth') == 3",
                "components": {
                    "minecraft:geometry": "geometry.fluid.3",
                    "tag:custom_fluid_3": {}
                }
            },
            {
                "condition": "q.block_state('wiki:depth') == 2",
                "components": {
                    "minecraft:geometry": "geometry.fluid.2",
                    "tag:custom_fluid_2": {}
                }
            },
            {
                "condition": "q.block_state('wiki:depth') == 1",
                "components": {
                    "minecraft:geometry": "geometry.fluid.1",
                    "tag:custom_fluid_1": {}
                }
            }
        ]
    }
}

Fluid Bucket ​

To place your custom fluid you need a custom bucket item. Below is the JSON for the custom bucket. Replace any instance of custom_fluid with your fluid's name.

Custom Bucket Item JSON
BP/items/custom_fluid_bucket.json
json
{
    "format_version": "1.21.20",
    "minecraft:item": {
        "description": {
            "identifier": "wiki:custom_fluid_bucket",
            "menu_category": {
                "category": "items"
            }
        },
        "components": {
            "minecraft:max_stack_size": 1,
            "minecraft:icon": {
                "texture": "custom_fluid_bucket" // Shortname defined in `RP/textures/item_texture.json`
            },
            "minecraft:block_placer": {
                "block": "wiki:custom_fluid"
            }
        }
    }
}

Scripts ​

The fluids use a script to add the ability for the player to float/sink in the fluid. The script also adds fog. To add your fluid to the script, put the ID of your new fluids in the fluids string array.

BP/manifest.json
json
{
  "modules": [
    ...
    {
      "type": "script",
      "language": "javascript",
      "entry": "fluids.js",
      "uuid": ...,
      "version": [1, 0, 0]
    }
  ],
  "dependencies": [
    {
      "module_name": "@minecraft/server",
      "version": "1.6.0-beta"
    }
  ]
}
Fluid Movement & Fog Script
BP/scripts/fluids.js
javascript
import { system, world } from "@minecraft/server";

const fluids = ["wiki:custom_fluid"];

system.runInterval(() => {
    const players = world.getPlayers();

    for (const player of players) {
        // Fluid effects
        if (
            fluids.includes(
                world
                    .getDimension(player.dimension.id)
                    .getBlock({ ...player.location, y: player.location.y + 1 }).typeId
            ) ||
            fluids.includes(
                world.getDimension(player.dimension.id).getBlock(player.location).typeId
            )
        ) {
            player.addEffect("slowness", 3, { amplifier: 2, showParticles: false });
            player.addEffect("slow_falling", 4, { showParticles: false });
            if (player.isJumping) {
                player.addEffect("levitation", 3, { amplifier: 2, showParticles: false });
            }
        }
        // Fluid fog
        if (
            fluids.includes(
                world
                    .getDimension(player.dimension.id)
                    .getBlock({ ...player.location, y: player.location.y + 1.63 }).typeId
            )
        ) {
            player.runCommand("fog @s push wiki:custom_fluid_fog fluid_fog");
        } else {
            player.runCommand("fog @s remove fluid_fog");
        }
    }
});

Result ​

By the end your BP folder should look like this:

      • 📝custom_fluid.json
      • 📝custom_fluid_bucket.json
      • 📝fluids.js
      • 📝custom_fluid.json

Download Example Pack ​

If anything goes wrong, or if you require all of the template files, they are available for download here. The pack includes everything necessary for a functional fluid.

Download MCADDON
Edit Custom Fluids on GitHub