Room themes

✅ Available

A room theme is the palette + decoration set the worldgen feature uses to build the dungeon room around the hanging cage. Each theme is a single JSON file at data/<namespace>/tiedup_room_themes/<name>.json. When the structure generates, the server picks one theme at random (weighted) and uses it to paint the room: walls, floor, ceiling, pillars, scatter clutter, and scripted decoration blocks.

This page documents every field a theme file can contain.

Server-authoritative — no client sync

Room themes are used only during server-side worldgen. Unlike furniture, there is no client sync — the theme is consumed on the server. A theme is a JSON file under data/; you don’t ship any texture for it. The placed result is just vanilla blocks, so clients see it through normal chunk sync with no extra wiring.

Loading is fail-soft (mostly)

Bad palette entries are skipped and the theme still loads. A theme is hard-rejected (skipped entirely) only if it is missing or has an invalid wall_palette, floor_palette, ceiling_palette, wall_shell, wall_accent, or pillar_palette — or if any required palette lacks a default condition. When a room looks wrong, check the server log on /reload for a warning. If every theme is rejected, worldgen falls back to a plain stone-bricks room rather than crashing.

Minimal theme

The smallest valid definition — the six required palettes/blocks, each with a default condition:

{
  "wall_palette":    { "default": [{ "block": "minecraft:stone_bricks" }] },
  "floor_palette":   { "default": [{ "block": "minecraft:stone_bricks" }] },
  "ceiling_palette": { "default": [{ "block": "minecraft:stone_bricks" }] },
  "wall_shell":      "minecraft:stone_bricks",
  "wall_accent":     "minecraft:chiseled_stone_bricks",
  "pillar_palette":  { "default": [{ "block": "minecraft:stone_brick_wall" }] }
}

The file name is the theme id: data/mypack/tiedup_room_themes/crypt.json registers as mypack:crypt. The namespace comes from the folder, and the path after tiedup_room_themes/ (minus the .json suffix) becomes the id.

Top-level fields

Field	Type	Req?	Notes
weight	int	optional (default 10)	Random selection weight across all themes. Clamped to [1, 1000]. Higher = more likely.
wall_palette	palette	required	Wall blocks. Conditions: default, bottom_row.
floor_palette	palette	required	Floor blocks. Conditions: default, edge, corner.
ceiling_palette	palette	required	Ceiling blocks. Only default is read.
wall_shell	block string	required	Single block for the outer wall shell (the structural backing behind the wall face).
wall_accent	block string	required	Single block for trims/frames/accents.
pillar_palette	palette	required	The four corner pillars. Conditions: default (shaft), cap (top & bottom).
scatter_palette	palette	optional	Random floor/ground clutter (cobwebs, candles…). If present but invalid it’s ignored (check the log) and the theme still loads.
decorations	object	optional	Scripted block placements (corners, midpoints, furniture, lighting flags). See Decorations.

`weight` is theme selection, not block selection

The top-level weight chooses which theme the room uses (across all loaded themes). The per-entry weight inside a palette chooses which block within that palette. They are separate weighted rolls — don’t confuse them.

Palettes

A palette is a JSON object mapping condition names to arrays of weighted block entries. Every required palette must contain a default condition — it is the fallback used when a more specific condition has no entries.

"wall_palette": {
  "default": [
    { "block": "minecraft:cracked_deepslate_bricks", "weight": 0.20 },
    { "block": "minecraft:deepslate_bricks",          "weight": 0.80 }
  ],
  "bottom_row": [
    { "block": "minecraft:mossy_cobblestone", "weight": 0.30 },
    { "block": "minecraft:deepslate_bricks",  "weight": 0.70 }
  ]
}

Conditions per palette

The worldgen feature requests a specific condition depending on where in the room the block is being placed. If a palette has no entries for the requested condition, it transparently falls back to default. So you only need to define the extra conditions you actually want to vary.

Palette	Conditions	When each is used
wall_palette	default, bottom_row	bottom_row at the lowest wall row (floor-level course); default for every other row.
floor_palette	default, edge, corner	corner at the four room corners; edge along the perimeter; default for the interior.
ceiling_palette	default	Only default is sampled.
pillar_palette	default, cap	cap at the top and bottom of each pillar; default for the shaft in between.
scatter_palette	default	Only default is sampled.

Define only `default` if you don't want variation

A palette with just default is valid and is used for every position. Adding bottom_row / edge / corner / cap is purely optional polish.

Weighted block entries

Each entry in a condition’s array is an object:

Field	Type	Default	Notes
block	block-state string	—	Required. Uses vanilla blockstate syntax, so it supports state properties, e.g. minecraft:candle[lit=true]. No NBT (a {...} data tag is rejected).
weight	float	1.0	Relative weight within the condition. Must be > 0 — a non-positive weight skips the entry (check the log).
random_property	object	none	Optional. Expands this one entry into several, varying an integer block-state property over a range. See below.

Within a condition the picker rolls proportionally by weight. Weights are relative — they do not need to sum to 1.0 (using fractions that sum to 1 is just a readable convention).

random_property expansion

random_property is sugar for “this block, but pick a random integer property value”. It expands a single entry into one entry per value in [min, max], splitting the parent weight evenly across them.

{
  "block": "minecraft:candle[lit=true]",
  "weight": 0.30,
  "random_property": { "name": "candles", "min": 1, "max": 3 }
}

The example above produces three entries — candles=1, candles=2, candles=3 — each with weight 0.30 / 3 = 0.10, so the combined chance of a lit candle stays 0.30.

Field	Type	Default	Notes
name	string	—	The block-state property to vary. Must be an integer property on that block, or it falls back to the base state (check the log).
min	int	1	Lowest value (inclusive).
max	int	min	Highest value (inclusive). If max < min the base state is used (check the log).

Values must be legal for the block

Each value in [min, max] that the property does not actually accept is skipped. For example minecraft:candle only allows candles 1–4, so max: 5 would silently drop the fifth. Only integer properties are supported — lit (a boolean) or facing (an enum) cannot be randomized this way; set those directly in the block string instead.

Decorations

The optional decorations object places scripted, positioned blocks on top of the painted shell. Every field here is optional; omit the whole object for a bare room.

"decorations": {
  "corner_decorations": [
    { "block": "minecraft:cobweb", "y_offset": 1 },
    { "block": "minecraft:cobweb", "y_offset": 9 }
  ],
  "wall_midpoint_blocks": [
    { "block": "minecraft:soul_lantern", "y_offset": 3 }
  ],
  "first_corner_special": {
    "block": "minecraft:water_cauldron[level=3]",
    "x_offset": 1, "y_offset": 1, "z_offset": 1
  },
  "furniture_cluster": [
    { "block": "minecraft:barrel", "y_offset": 1 },
    { "block": "minecraft:brewing_stand", "x_offset": 1, "y_offset": 1 }
  ],
  "use_torch_lighting": false,
  "has_ceiling_chain": true
}

Field	Type	Default	Notes
corner_decorations	positioned-block[]	[]	Blocks placed at each of the four room corners. Typically used in pairs (a low + a high cobweb).
wall_midpoint_blocks	positioned-block[]	[]	Blocks placed at the four wall midpoints (e.g. wall sconces/lanterns).
first_corner_special	positioned-block	none	A single block placed only at the first corner — good for a one-off feature (cauldron, skull).
furniture_cluster	positioned-block[]	[]	A small grouped arrangement (barrel + brewing stand, lectern + candles…).
use_torch_lighting	bool	false	Whether the room is lit with torches.
has_ceiling_chain	bool	false	Whether a decorative chain hangs from the ceiling.

Positioned blocks

Each decoration entry is a block string plus integer offsets from its anchor position:

Field	Type	Default	Notes
block	block-state string	—	Required. Same rules as palette block (state properties OK, no NBT).
x_offset	int	0	Horizontal offset along the room’s local X.
y_offset	int	0	Vertical offset from the floor (the most common one — height of the decoration).
z_offset	int	0	Horizontal offset along the room’s local Z.

Offsets are room-local

Offsets are applied relative to each placement’s anchor (a corner, midpoint, or the cluster origin), and the horizontal axes are oriented to the room — so the same definition mirrors correctly regardless of which way the structure spawned. The interior runs roughly 1–11 on each horizontal axis and the wall rises ~10 rows, which is why the shipped themes use y_offset values like 1 (floor level) and 9 (just under the ceiling).

Full example

A complete shipped theme — data/tiedup/tiedup_room_themes/oubliette.json — exercising every feature (multi-block palettes, bottom_row / corner variation, random_property candles, a scatter palette, and a full decoration block):

{
  "weight": 10,
  "wall_palette": {
    "default": [
      { "block": "minecraft:cracked_deepslate_bricks", "weight": 0.20 },
      { "block": "minecraft:deepslate_bricks",          "weight": 0.80 }
    ],
    "bottom_row": [
      { "block": "minecraft:mossy_cobblestone",         "weight": 0.30 },
      { "block": "minecraft:cracked_deepslate_bricks",  "weight": 0.14 },
      { "block": "minecraft:deepslate_bricks",          "weight": 0.56 }
    ]
  },
  "floor_palette": {
    "default": [
      { "block": "minecraft:cobblestone",     "weight": 0.15 },
      { "block": "minecraft:deepslate_tiles", "weight": 0.85 }
    ],
    "corner": [
      { "block": "minecraft:mossy_cobblestone", "weight": 1.0 }
    ]
  },
  "ceiling_palette": {
    "default": [
      { "block": "minecraft:cracked_deepslate_bricks", "weight": 0.20 },
      { "block": "minecraft:deepslate_bricks",          "weight": 0.80 }
    ]
  },
  "wall_shell": "minecraft:deepslate_bricks",
  "wall_accent": "minecraft:polished_deepslate",
  "pillar_palette": {
    "default": [
      { "block": "minecraft:deepslate_brick_wall", "weight": 1.0 }
    ],
    "cap": [
      { "block": "minecraft:polished_deepslate", "weight": 1.0 }
    ]
  },
  "scatter_palette": {
    "default": [
      { "block": "minecraft:cobweb", "weight": 0.40 },
      { "block": "minecraft:candle[lit=true]", "weight": 0.30, "random_property": { "name": "candles", "min": 1, "max": 3 } },
      { "block": "minecraft:moss_carpet", "weight": 0.30 }
    ]
  },
  "decorations": {
    "corner_decorations": [
      { "block": "minecraft:cobweb", "y_offset": 1 },
      { "block": "minecraft:cobweb", "y_offset": 9 }
    ],
    "wall_midpoint_blocks": [
      { "block": "minecraft:soul_lantern", "y_offset": 3 }
    ],
    "first_corner_special": { "block": "minecraft:water_cauldron[level=3]", "x_offset": 1, "y_offset": 1, "z_offset": 1 },
    "furniture_cluster": [
      { "block": "minecraft:barrel", "y_offset": 1 },
      { "block": "minecraft:brewing_stand", "x_offset": 1, "y_offset": 1 }
    ],
    "use_torch_lighting": false,
    "has_ceiling_chain": true
  }
}

Selection & loading

1. Drop the JSON in data/<namespace>/tiedup_room_themes/ inside your addon pack (see Packaging for the full folder layout). The file name (path after the folder, minus .json) becomes the theme id.
2. Run /reload (or restart the server). The log reports how many themes loaded and how many were skipped.
3. The next time the structure generates, the server rolls across all loaded themes by their top-level weight and paints the room with the winner.

Themes apply at generation time only

A theme is chosen and baked into the world when the chunk generates. Editing or /reload-ing a theme does not repaint rooms that already exist — only newly generated structures pick up the change. Two themes with the same id (across packs) collide: the last one loaded wins (you’ll see a warning in the log).

Related pages

Furniture & pets

The other worldgen-adjacent datapack registry — but furniture does sync to clients. See Furniture & pets.

Bones & regions

Reference tables for the rest of the data-driven systems. See Bones & regions.

Item JSON

The block-state string syntax (block[prop=value]) is the same one used here. See Item JSON.