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unfamily edited this page Sep 30, 2026 · 4 revisions

Structure System

Requires Iskandert's Utilities 3.0.0.0.0 or newer (datapack load/ layout).

Multi-block structures defined in JSON: place with Structure Placer items, the Structure Placer Machine, monouse reward items, or OP commands. Patterns use a 3D character grid; each character maps to block alternatives in key.

Related

Topic Page
Stages (gates on structures) Home — Internal Stages
Stage actions Stage-Actions

Datapack locations

Two JSON types, both under data/<namespace>/load/:

Type "type" field Typical folder
Structure definitions iska_utils:structure load/iska_utils_structure_definitions/
Monouse items iska_utils:structure_monouse_item load/iska_utils_structures_monouse/

Or data/<namespace>/load/<file>.json with the correct "type" (routed like other IskaUtils load files).

  • One file, many structures: the structure array can hold several definitions in the same JSON file.
  • Many files: all definitions from all matching files are loaded and merged.

Reload: /reload, /iska_lib_dev reload, or /iska_utils_structure reload.

Overwritable

Value Behaviour
"overwritable": true Later packs / reloads may replace this definition when merging the same id
"overwritable": false Protected from overwrite — use for pack content you want to keep

Structure definition (iska_utils:structure)

{
  "type": "iska_utils:structure",
  "overwritable": false,
  "structure": [
    {
      "id": "my_mod-my_structure",
      "name": "My Custom Structure",
      "description": "Tooltip text",
      "icon": {
        "type": "minecraft:item",
        "item": "minecraft:diamond_block",
        "count": 1
      },
      "pattern": [[["AAA"], ["ABA"], ["AAA"]]],
      "key": {
        "A": {
          "display": "minecraft.stone",
          "alternatives": [
            { "block": "minecraft:stone" },
            { "block": "minecraft:cobblestone" }
          ]
        },
        "B": {
          "display": "minecraft.chest",
          "alternatives": [{ "block": "minecraft:chest" }]
        }
      }
    }
  ]
}

Fields per structure

Field Required Default Description
id yes — Unique id: modid-name (used in commands and monouse place)
name yes — Display name
pattern yes — 3D layout (see Patterns)
key yes — Maps pattern characters to blocks
description no — Tooltip
icon no — Item icon in machine GUI (type, item, count)
can_force no false Allow shift+place on placer item and place … force command
can_replace no [] Blocks/tags/tokens that may be overwritten (see Replacement)
slower no false 5-tick delay between blocks
place_like_player no false Place as player (events, mod hooks)
refresh no false Schedule one block tick after each placement (redstone, observers)
stages no [] All listed stages required (/iska_lib_stage)
machine no true Show in Structure Placer Machine GUI
hidden no false Commands only; hidden from normal placement

Patterns

pattern is a 3D array [Y][Z][row] (each inner string is one row along X):

Axis Meaning
Y Layer index (height), bottom to top
Z Row index (north–south)
Characters in a row West → east
Character Meaning
@ Structure center (anchor for placement / machine)
space Skip (no block)
any other Must exist in key

Pattern example — 3×3 platform

"pattern": [
  [["AAA"], ["AAA"], ["AAA"]]
],
"key": {
  "A": {
    "display": "minecraft.stone",
    "alternatives": [{ "block": "minecraft:stone" }]
  }
}

Pattern example — vertical stack with center

"pattern": [
  [[" @ "], [" A "], [" B "], [" C "]]
],
"key": {
  "A": { "display": "minecraft.stone", "alternatives": [{ "block": "minecraft:stone" }] },
  "B": { "display": "minecraft.iron_block", "alternatives": [{ "block": "minecraft:iron_block" }] },
  "C": { "display": "minecraft.gold_block", "alternatives": [{ "block": "minecraft:gold_block" }] },
  "@": { "display": "minecraft.air", "alternatives": [{ "block": "minecraft:air" }] }
}

Pattern example — 5×5 foundation

"pattern": [
  [["CCCCC"], ["WWWWW"], ["WWWWW"]],
  [["CCCCC"], ["W   W"], ["W   W"]],
  [["CC@CC"], ["W   W"], ["W   W"]],
  [["CCCCC"], ["W   W"], ["W   W"]],
  [["CCCCC"], ["WWWWW"], ["WWWWW"]]
],
"key": {
  "C": { "display": "minecraft.cobblestone", "alternatives": [{ "block": "minecraft:cobblestone" }] },
  "W": { "display": "minecraft.oak_planks", "alternatives": [{ "block": "minecraft:oak_planks" }] },
  "@": { "display": "minecraft.cobblestone", "alternatives": [{ "block": "minecraft:cobblestone" }] }
}

key entries

Each letter in the pattern points to:

Field Description
display Tooltip/GUI label (minecraft.stone style)
alternatives Ordered list; first valid block is preferred when placing

Each alternative:

{ "block": "minecraft:oak_stairs", "properties": { "facing": "north", "half": "bottom" } }

Multiple wood types (one pattern letter)

"W": {
  "display": "minecraft.planks",
  "alternatives": [
    { "block": "minecraft:oak_planks" },
    { "block": "minecraft:birch_planks" },
    { "block": "minecraft:spruce_planks" }
  ]
}

Replacement (can_replace)

A position is cleared only if the existing block matches an entry in can_replace (unless can_force / aggressive applies).

Form Example
Block id "minecraft:dirt"
Tag "#minecraft:flowers"
Token "$replaceable", "$air", "$fluids", "$plants", "$dirt", "$logs", "$stone", "$ores", …

Match order: exact block → $ tokens → # tags. If nothing matches and can_force is false, placement stops at that cell.

can_force example

{
  "id": "my_mod-force_structure",
  "name": "Bulldozer Structure",
  "can_force": true,
  "can_replace": [
    "minecraft:dirt",
    "minecraft:grass_block",
    "$replaceable",
    "#minecraft:flowers"
  ],
  "pattern": ["..."],
  "key": { "..." }
}
  • Structure Placer item: shift + right-click (second click) to force within can_replace rules.
  • Command: /iska_utils_structure place <id> <x> <y> <z> force — requires can_force: true; overwrites every cell in the pattern.

Other placement flags

Flag Effect
refresh: true Tick each placed block once (redstone contraptions)
slower: true 5 ticks between blocks
place_like_player: true Player placement semantics (slower, mod-compatible) 
{
  "id": "my_mod-redstone_gadget",
  "refresh": true,
  "place_like_player": true,
  "pattern": ["..."],
  "key": { "..." }
}

Stages

"stages": ["chapter_1_complete", "has_nether_star"]

All listed stages must be satisfied for the player placing the structure. Empty array = no requirement.

Monouse items (iska_utils:structure_monouse_item)

Right-click consumable: gives items, places a structure, consumes the stack.

{
  "type": "iska_utils:structure_monouse_item",
  "overwritable": false,
  "structure": [
    {
      "id": "iska_utils-wither_grinder",
      "place": "iska_utils-wither_grinder",
      "aggressive": false,
      "give": [
        { "item": "minecraft:wither_skeleton_skull", "count": 3 },
        { "item": "minecraft:soul_sand", "count": 4 },
        { "item": "iska_utils:wither_proof_block", "count": 26 }
      ]
    }
  ]
}
Field Description
id Entry id in this file
place Structure id to place (must exist in a structure definition)
give Items granted on use
aggressive If true, place over any existing block (can destroy builds). Unlike can_force, no can_replace filter

Placement in-game

Method Notes
Structure Placer item Manual placement at targeted block
Structure Placer Machine Automated; RF/FE per block (server config); pulls materials; respects stages
Monouse item One-shot reward + place
Commands OP — see below

Structure Placer Machine

Topic Detail
Energy RF/FE per block placed (configurable; 0 disables consumption)
Materials Uses alternatives order from key
Redstone Ignore / low / high / pulse modes
GUI Lists structures with machine: true and met stages

Commands (OP 2)

Command Description
/iska_utils_structure list List loaded structure ids
/iska_utils_structure reload Reload definitions and sync clients
/iska_utils_structure info <id> Size, center, flags
/iska_utils_structure place <id> <x> <y> <z> Place respecting can_replace
/iska_utils_structure place <id> <x> <y> <z> force Overwrite all pattern cells (can_force: true required)

Examples

1. Simple wooden house

{
  "type": "iska_utils:structure",
  "overwritable": false,
  "structure": [
    {
      "id": "example-simple_house",
      "name": "Simple Wooden House",
      "description": "Starter house",
      "icon": { "type": "minecraft:item", "item": "minecraft:oak_planks" },
      "can_replace": ["$replaceable", "$air", "$plants"],
      "pattern": [
        [["WWWWW"], ["W   W"], ["W @ W"], ["W   W"], ["WWWWW"]],
        [["WWWWW"], ["W   W"], ["W   W"], ["W   W"], ["WWWWW"]],
        [["WWWWW"], ["W   W"], ["W   W"], ["W   W"], ["WWWWW"]],
        [["RRRRR"], ["RRRRR"], ["RRRRR"], ["RRRRR"], ["RRRRR"]]
      ],
      "key": {
        "W": {
          "display": "minecraft.oak_planks",
          "alternatives": [
            { "block": "minecraft:oak_planks" },
            { "block": "minecraft:birch_planks" },
            { "block": "minecraft:spruce_planks" }
          ]
        },
        "R": {
          "display": "minecraft.oak_slab",
          "alternatives": [
            { "block": "minecraft:oak_slab", "properties": { "type": "bottom" } }
          ]
        }
      }
    }
  ]
}

2. Redstone machine (stages + force)

{
  "type": "iska_utils:structure",
  "overwritable": false,
  "structure": [
    {
      "id": "example-redstone_machine",
      "name": "Automated Redstone Machine",
      "description": "Pistons and dispensers",
      "icon": { "type": "minecraft:item", "item": "minecraft:redstone" },
      "can_force": true,
      "slower": true,
      "place_like_player": true,
      "can_replace": ["$replaceable", "$air", "$dirt"],
      "stages": ["redstone_engineer"],
      "pattern": [
        [["SSSSS"], ["S   S"], ["S@RRS"], ["S   S"], ["SSSSS"]],
        [["     "], ["  P  "], ["  D  "], ["  H  "], ["     "]]
      ],
      "key": {
        "S": {
          "display": "minecraft.stone",
          "alternatives": [
            { "block": "minecraft:stone" },
            { "block": "minecraft:cobblestone" }
          ]
        },
        "R": {
          "display": "minecraft.redstone_wire",
          "alternatives": [{ "block": "minecraft:redstone_wire" }]
        },
        "P": {
          "display": "minecraft.piston",
          "alternatives": [{ "block": "minecraft:piston", "properties": { "facing": "up" } }]
        },
        "D": {
          "display": "minecraft.dispenser",
          "alternatives": [{ "block": "minecraft:dispenser", "properties": { "facing": "up" } }]
        },
        "H": {
          "display": "minecraft.hopper",
          "alternatives": [{ "block": "minecraft:hopper", "properties": { "facing": "down" } }]
        }
      }
    }
  ]
}

Troubleshooting

Symptom Likely cause
Structure not in list JSON syntax error, wrong "type", or failed load — check log
Blocks skip / stop mid-build Block not in can_replace and can_force false
Wrong block state Fix properties on the alternative
“Cannot place” with stages Player missing a stage in stages
force command fails Structure lacks can_force: true

After editing datapacks: /iska_lib_dev reload or /iska_utils_structure reload.

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