minecraft-world-generation
Create and debug Minecraft 26.x and legacy 1.21.x world generation for datapacks, NeoForge, or Fabric, including biomes, dimensions, features, structures, and biome modifiers. Use for worldgen data or registration, not general gameplay systems.
Install
npx skills add https://github.com/Jahrome907/minecraft-agent-skills/tree/main/.claude/skills/minecraft-world-generation
claude plugin marketplace add https://llmmart.ai/marketplace.json && claude plugin install jahrome907-minecraft-agent-skills@llmmart
git clone https://github.com/Jahrome907/minecraft-agent-skills.git
The skills CLI installs just this skill, for any of its supported agents. Claude Code installs the whole jahrome907/minecraft-agent-skills collection as a plugin from our marketplace. Git is the plain clone.
Skill manifest
Minecraft World Generation
Use this skill for biome, dimension, feature, or structure data and their
registration. Use minecraft-datapack for non-worldgen data and
minecraft-modding for non-worldgen gameplay code.
Routing Boundaries
Use when: the task changes worldgen data, registration, or injection.Do not use when: the task is non-worldgen datapack work (minecraft-datapack).Do not use when: the task is non-worldgen mod systems (minecraft-modding).
Choose the delivery path
| Approach | Best When | Platform |
|---|---|---|
| Datapack JSON | Change data supplied by a pack | Vanilla, any server |
| Mod + Datagen | Registering new biomes/dimensions, code-driven | NeoForge / Fabric |
| Biome Modifier (NeoForge) | Adding features/spawns to existing biomes | NeoForge |
| BiomeModification API (Fabric) | Adding features/spawns to existing biomes | Fabric |
Worldgen registries are datapack registries: their files load at world load and their registry path determines the data path. Read the NeoForge registry guide before choosing a mod-specific registry path.
Version boundary
Use Minecraft 26.x for new work. Use Java 25 and start each JSON schema from the exact target's vanilla data or generated output. Do not copy a 1.21 shape into a 26.x pack merely because it parses as JSON.
Preserve an established 1.21.x project on Java 21 and its matching schema unless the task explicitly includes an upgrade. Keep examples matched to the project version.
The 26.1 migration primer
removes minecraft:random_patch and minecraft:no_bonemeal_flower. It replaces
the random-patch pattern with a separate minecraft:simple_block configured
feature and placements for count, random offset, and block-predicate filtering.
Inspect the relevant primer section before migrating code or data.
Read legacy 1.21 JSON patterns only when the project targets that version. Those examples are not release artifacts for 26.x.
Data layout and reference graph
data/<namespace>/
├── worldgen/
│ ├── biome/
│ │ └── my_biome.json
│ ├── configured_feature/
│ │ └── my_ore.json
│ ├── placed_feature/
│ │ └── my_ore_placed.json
│ ├── noise_settings/
│ │ └── my_dimension_noise.json
│ ├── structure/
│ │ └── my_structure.json
│ ├── structure_set/
│ │ └── my_structures.json
│ ├── processor_list/
│ │ └── my_processors.json
│ ├── template_pool/
│ │ └── my_pool.json
│ └── carver/
│ └── my_carver.json
├── dimension/
│ └── my_dimension.json
├── dimension_type/
│ └── my_type.json
├── tags/
│ └── worldgen/
│ └── biome/
│ └── is_forest.json
└── neoforge/
└── biome_modifier/ (NeoForge mod only)
└── add_ores.json
Build and review the graph from its leaves upward:
- Define a configured feature, then its placed feature.
- Reference placed features from a biome or biome modifier at the intended decoration step.
- Define a structure, then its structure set; a jigsaw structure also needs a template pool, processor list, and structure template.
- Define a dimension type and noise settings before a dimension that references them.
Use fully qualified identifiers across namespaces. An external minecraft: or
dependency reference is valid when that dependency supplies the registry entry;
do not create a local copy merely to satisfy static checking. If the same pack
contains that external namespace and registry directory, treat it as local and
verify the target exists.
Biomes and dimensions
For 26.x biome and dimension data, use the exact target's vanilla data or
datagen output as the schema source. The older effects and dimension-type
fields do not model newer environment behavior. The 11 decoration steps still
organize placed features; choose the semantically appropriate step and keep ore
placement in underground_ores.
The version-labeled 1.21.5 biome and dimension examples are in legacy 1.21 JSON patterns.
26.x feature pattern
For the 26.1 replacement for a simple random patch, the migration primer shows
a simple_block configured feature and a placed feature with count, random
offset, and a block-predicate filter. Adapt the exact values and block state to
the target release's generated data.
At data/<namespace>/worldgen/configured_feature/my_plant.json:
{
"type": "minecraft:simple_block",
"config": {
"to_place": {
"type": "minecraft:simple_state_provider",
"state": { "Name": "minecraft:sweet_berry_bush", "Properties": { "age": "3" } }
}
}
}
At data/<namespace>/worldgen/placed_feature/my_plant.json:
{
"feature": "<namespace>:my_plant",
"placement": [
{ "type": "minecraft:count", "count": 96 },
{
"type": "minecraft:random_offset",
"xz_spread": { "type": "minecraft:trapezoid", "min": -7, "max": 7, "plateau": 0 },
"y_spread": { "type": "minecraft:trapezoid", "min": -3, "max": 3, "plateau": 0 }
},
{
"type": "minecraft:block_predicate_filter",
"predicate": {
"type": "minecraft:all_of",
"predicates": [
{ "type": "minecraft:matching_block_tag", "tag": "minecraft:air" },
{ "type": "minecraft:matching_blocks", "blocks": "minecraft:grass_block", "offset": [0, -1, 0] }
]
}
}
]
}
NeoForge biome modifiers
Biome modifiers load from
data/<modid>/neoforge/biome_modifier/<path>.json. They can target a biome id
or tag and add or remove placed features, among other changes. The current
Biome Modifiers guide
documents their schemas, decoration steps, and datagen.
For neoforge:add_features, features accepts a placed-feature id, list, or
tag. Vanilla placed features may be referenced in biome JSON or added with a
modifier, but NeoForge cautions against doing both because feature-order cycles
can crash world loading. Prefer a copy under the mod namespace when an injected
vanilla feature would create that risk.
When targeting a biome from an optional dependency, put the target in a biome
tag entry with required: false, then use that tag in the modifier. This lets
the pack load when the dependency is absent.
Structures and dimensions
For any current release, derive structure, template-pool, dimension, and dimension-type JSON from that release's vanilla data or datagen output. Confirm the reference graph before launching a test world:
structure_setreferencesstructure.- Jigsaw
start_poolreferencestemplate_pool; each single-pool element references its structure template and processor list. dimension.typereferencesdimension_type; a noise generator's stringsettingsreferencesworldgen/noise_settings.
For Fabric registration or mod datagen, use the exact loader and API version's documentation rather than copying 1.21 code into a 26.x project.
The detailed 1.21 structure and dimension examples are in legacy 1.21 JSON patterns.
Development Workflow
- Create or edit worldgen JSON files in
data/<namespace>/worldgen/(or equivalent mod resources path). - Run the bundled validator to catch JSON and cross-reference errors before loading:
./scripts/validate-worldgen-json.sh --root /path/to/datapack-or-mod-resources # Strict mode treats warnings as failures: ./scripts/validate-worldgen-json.sh --root /path/to/datapack-or-mod-resources --strict - Fix any reported errors and re-validate until clean. The validator checks:
- JSON validity for
worldgen/**andneoforge/biome_modifier/** - Cross-reference integrity for
placed_feature -> configured_feature - Cross-reference integrity for
structure_set -> structureand biome/biome_modifier feature targets - Cross-reference integrity for
jigsaw structure -> start_poolandtemplate_pool -> structure template / processor_list
- JSON validity for
- Compare biome and dimension-type JSON against the exact target's vanilla
registry shape before in-game testing. The helper does not run Mojang codecs:
valid JSON and local references do not prove that fields such as
carvers,effects, or dimension settings match that release's schema. - In-game biome and structure testing:
/locate structure <namespace>:my_structure /locate biome <namespace>:my_biome /place feature <namespace>:my_oreplace featuretakes a configured-feature ID, not its placed-feature wrapper. See Mojang's place command reference in the 1.19 release notes. - For dimension testing, use
/execute in(dimension must exist at world load, not added via/reload):execute in <namespace>:my_dimension run tp @s 0 100 0 - Check
latest.logfor worldgen errors (missing biome references, malformed noise settings). - Note:
/reloadrefreshes datapack JSON but does not re-generate already-generated chunks. Test new worldgen in a fresh world or newly generated chunks. For existing test worlds, use a disposable copy and a purpose-built chunk reset/regeneration workflow;/fillonly replaces blocks and is not a substitute for world generation.
References
- Minecraft Wiki — World generation: https://minecraft.wiki/w/Custom_world_generation
- Minecraft Wiki — Biome: https://minecraft.wiki/w/Biome/JSON_format
- Minecraft Wiki — Features: https://minecraft.wiki/w/World_generation/Configured_feature
- NeoForge Biome Modifiers: https://docs.neoforged.net/docs/worldgen/biomemodifier/
- Fabric BiomeModifications: https://wiki.fabricmc.net/tutorial:biomemodification
- misode's data pack generator (worldgen UI): https://misode.github.io/worldgen/
Files (minecraft-agent-skills)
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references
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legacy-1.21-worldgen-json.md 4.6 KB
# Legacy Minecraft 1.21.5 Worldgen JSON These examples target Minecraft 1.21.5. For another 1.21.x release, compare each registry with that exact release's vanilla data or datagen output before adapting it. Minecraft 1.21.11 and 26.x change worldgen and environment data; the broad label "1.21.x" does not establish JSON schema compatibility. ## Biome and feature chain Biome `features` has 11 arrays, one for each `GenerationStep.Decoration` index. Ores belong at index 6, `underground_ores`. Each entry is a placed-feature id. At `data/<namespace>/worldgen/biome/my_biome.json`: ```json { "has_precipitation": true, "temperature": 0.7, "downfall": 0.8, "effects": { "sky_color": 7907327, "fog_color": 12638463, "water_color": 4159204, "water_fog_color": 329011 }, "spawners": {}, "spawn_costs": {}, "carvers": [], "features": [ [], [], [], [], [], [], ["<namespace>:my_ore_placed"], [], [], [], [] ] } ``` At `data/<namespace>/worldgen/configured_feature/my_ore.json`: ```json { "type": "minecraft:ore", "config": { "targets": [ { "target": { "predicate_type": "minecraft:tag_match", "tag": "minecraft:stone_ore_replaceables" }, "state": { "Name": "minecraft:emerald_ore" } } ], "size": 4, "discard_chance_on_air_exposure": 0.0 } } ``` At `data/<namespace>/worldgen/placed_feature/my_ore_placed.json`: ```json { "feature": "<namespace>:my_ore", "placement": [ { "type": "minecraft:count", "count": 8 }, { "type": "minecraft:in_square" }, { "type": "minecraft:height_range", "height": { "type": "minecraft:trapezoid", "min_inclusive": { "above_bottom": 0 }, "max_inclusive": { "absolute": 64 } } }, { "type": "minecraft:biome" } ] } ``` ## Dimension and dimension type At `data/<namespace>/dimension_type/my_type.json`: ```json { "ultrawarm": false, "natural": true, "coordinate_scale": 1.0, "has_skylight": true, "has_ceiling": false, "ambient_light": 0.0, "monster_spawn_light_level": { "type": "minecraft:uniform", "min_inclusive": 0, "max_inclusive": 7 }, "monster_spawn_block_light_limit": 0, "piglin_safe": false, "bed_works": true, "respawn_anchor_works": false, "has_raids": true, "logical_height": 384, "height": 384, "min_y": -64, "infiniburn": "#minecraft:infiniburn_overworld", "effects": "minecraft:overworld" } ``` At `data/<namespace>/dimension/my_dimension.json`: ```json { "type": "<namespace>:my_type", "generator": { "type": "minecraft:noise", "biome_source": { "type": "minecraft:fixed", "biome": "<namespace>:my_biome" }, "settings": "minecraft:overworld" } } ``` Use `minecraft:multi_noise` only with a complete set of climate parameters from a known-good 1.21 source. Keep the dimension type, noise settings, and every referenced biome in the same Minecraft version. ## NeoForge biome modifier At `data/<namespace>/neoforge/biome_modifier/add_ores.json`: ```json { "type": "neoforge:add_features", "biomes": "#minecraft:is_overworld", "features": "<namespace>:my_ore_placed", "step": "underground_ores" } ``` For a legacy `remove_features` modifier, `steps` is an array; for `add_features`, use the singular `step`. Verify the exact minor version's NeoForge documentation before hand-authoring other modifier types. ## Jigsaw structures At `data/<namespace>/worldgen/structure/my_structure.json`: ```json { "type": "minecraft:jigsaw", "biomes": "#<namespace>:my_biome_tag", "step": "surface_structures", "terrain_adaptation": "beard_thin", "start_pool": "<namespace>:my_pool/start", "size": 6, "max_distance_from_center": 80, "use_expansion_hack": false, "spawn_overrides": {} } ``` At `data/<namespace>/worldgen/template_pool/my_pool/start.json`: ```json { "fallback": "minecraft:empty", "elements": [ { "weight": 1, "element": { "element_type": "minecraft:single_pool_element", "location": "<namespace>:my_structure/start", "projection": "rigid", "processors": "minecraft:empty" } } ] } ``` At `data/<namespace>/worldgen/structure_set/my_structures.json`: ```json { "structures": [ { "structure": "<namespace>:my_structure", "weight": 1 } ], "placement": { "type": "minecraft:random_spread", "spacing": 32, "separation": 8, "salt": 12345678 } } ``` The pool's `location` needs a matching `data/<namespace>/structure/my_structure/start.nbt`; use a processor list other than `minecraft:empty` only when its JSON exists and has been tested.
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scripts
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jq-shim.mjs 7.3 KB · in bundle
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validate-worldgen-json.sh 18 KB
#!/usr/bin/env bash set -euo pipefail PASS='[PASS]' WARN='[WARN]' FAIL='[FAIL]' ROOT='.' STRICT=0 while [[ $# -gt 0 ]]; do case "$1" in --root) ROOT="${2:-}" shift 2 ;; --strict) STRICT=1 shift ;; --help|-h) cat <<'USAGE' Usage: validate-worldgen-json.sh [--root <path>] [--strict] Checks worldgen JSON integrity: - validates JSON under data/**/worldgen, data/**/dimension, data/**/dimension_type, data/**/tags/worldgen, and data/**/neoforge/biome_modifier - validates key directory conventions - validates local cross-references: dimension -> dimension_type + noise_settings placed_feature -> configured_feature structure_set -> structure jigsaw structure -> template_pool template_pool single_pool_element -> structure template + processor_list biome and biome_modifier feature references -> placed_feature USAGE exit 0 ;; *) echo "$FAIL unknown arg: $1" >&2 exit 1 ;; esac done if ! command -v jq >/dev/null 2>&1; then SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)" JQ_SHIM="$SCRIPT_DIR/jq-shim.mjs" if command -v node >/dev/null 2>&1 && [[ -f "$JQ_SHIM" ]]; then jq() { node "$JQ_SHIM" "$@" } else echo "$FAIL jq is required" exit 1 fi fi if [[ ! -d "$ROOT" ]]; then echo "$FAIL root path does not exist: $ROOT" exit 1 fi FAILURES=0 WARNINGS=0 pass() { echo "$PASS $*"; } warn() { echo "$WARN $*"; WARNINGS=$((WARNINGS + 1)); } fail() { echo "$FAIL $*"; FAILURES=$((FAILURES + 1)); } strip_cr() { printf '%s' "${1%$'\r'}"; } json_query_raw() { local filter="$1" local file="$2" if command -v jq >/dev/null 2>&1; then jq -r "$filter" "$file" else node "$JQ_SHIM" -r "$filter" "$file" fi } TOTAL_SUPPORTED_FILES=0 declare -A VALIDATED_JSON_FILES=() declare -A INVALID_JSON_FILES=() declare -A CONFIGURED_FEATURES=() declare -A PLACED_FEATURES=() declare -A STRUCTURES=() declare -A TEMPLATE_POOLS=() declare -A PROCESSOR_LISTS=() declare -A STRUCTURE_TEMPLATES=() declare -A DIMENSION_TYPES=() declare -A NOISE_SETTINGS=() declare -A VANILLA_TEMPLATE_POOLS=( ["minecraft:empty"]=1 ) declare -A VANILLA_PROCESSOR_LISTS=( ["minecraft:empty"]=1 ) declare -A VANILLA_DIMENSION_TYPES=( ["minecraft:overworld"]=1 ["minecraft:overworld_caves"]=1 ["minecraft:the_nether"]=1 ["minecraft:the_end"]=1 ) declare -A VANILLA_NOISE_SETTINGS=( ["minecraft:overworld"]=1 ["minecraft:large_biomes"]=1 ["minecraft:amplified"]=1 ["minecraft:nether"]=1 ["minecraft:end"]=1 ["minecraft:caves"]=1 ["minecraft:floating_islands"]=1 ) DATA_ROOT="$ROOT/data" BIOME_FILES=0 BIOME_MODIFIER_FILES=0 to_id() { local file="$1" local rel ns path noext rel="${file#"$ROOT/data/"}" ns="${rel%%/*}" path="${rel#*/}" path="${path#worldgen/}" noext="${path%.json}" noext="${noext%.nbt}" echo "$ns:${noext#*/}" } split_ref() { local default_ns="$1" local ref="$2" if [[ "$ref" == *:* ]]; then echo "$ref" else echo "$default_ns:$ref" fi } check_json() { local file="$1" if jq empty "$file" >/dev/null 2>&1; then unset 'INVALID_JSON_FILES[$file]' pass "valid JSON: ${file#$ROOT/}" else INVALID_JSON_FILES["$file"]=1 fail "invalid JSON: ${file#$ROOT/}" fi } check_json_once() { local file="$1" if [[ -n "${VALIDATED_JSON_FILES["$file"]+x}" ]]; then return fi VALIDATED_JSON_FILES["$file"]=1 check_json "$file" TOTAL_SUPPORTED_FILES=$((TOTAL_SUPPORTED_FILES + 1)) } should_validate_dimension_type_ref() { local source_ns="$1" local id="$2" local target_ns="${id%%:*}" if [[ "$target_ns" == "$source_ns" ]]; then return 0 fi if [[ "$target_ns" == "minecraft" && -n "${VANILLA_DIMENSION_TYPES[$id]:-}" ]]; then return 1 fi [[ -d "$DATA_ROOT/$target_ns/dimension_type" ]] } should_validate_noise_settings_ref() { local source_ns="$1" local id="$2" local target_ns="${id%%:*}" if [[ "$target_ns" == "$source_ns" ]]; then return 0 fi if [[ "$target_ns" == "minecraft" && -n "${VANILLA_NOISE_SETTINGS[$id]:-}" ]]; then return 1 fi [[ -d "$DATA_ROOT/$target_ns/worldgen/noise_settings" ]] } find_worldgen_jsons() { local category="${1:-}" while IFS= read -r -d '' worldgen_dir; do if [[ -n "$category" ]]; then [[ -d "$worldgen_dir/$category" ]] || continue find "$worldgen_dir/$category" -mindepth 1 -type f -name '*.json' -print0 2>/dev/null else find "$worldgen_dir" -mindepth 2 -type f -name '*.json' -print0 2>/dev/null fi done < <(find "$DATA_ROOT" -mindepth 2 -maxdepth 2 -type d -name worldgen -print0 2>/dev/null) } find_namespace_jsons() { local dir_name="$1" while IFS= read -r -d '' dir; do find "$dir" -mindepth 1 -type f -name '*.json' -print0 2>/dev/null done < <(find "$DATA_ROOT" -mindepth 2 -maxdepth 2 -type d -name "$dir_name" -print0 2>/dev/null) } find_neoforge_jsons() { local dir_name="$1" while IFS= read -r -d '' dir; do find "$dir" -mindepth 1 -type f -name '*.json' -print0 2>/dev/null done < <(find "$DATA_ROOT" -mindepth 3 -maxdepth 3 -type d -path "$DATA_ROOT/*/neoforge/$dir_name" -print0 2>/dev/null) } find_structure_templates() { while IFS= read -r -d '' dir; do find "$dir" -mindepth 1 -type f -name '*.nbt' -print0 2>/dev/null done < <(find "$DATA_ROOT" -mindepth 2 -maxdepth 2 -type d -name structure -print0 2>/dev/null) } find_tags_worldgen_jsons() { while IFS= read -r -d '' dir; do find "$dir" -mindepth 2 -type f -name '*.json' -print0 2>/dev/null done < <(find "$DATA_ROOT" -mindepth 3 -maxdepth 3 -type d -path "$DATA_ROOT/*/tags/worldgen" -print0 2>/dev/null) } find_invalid_tags_worldgen_jsons() { while IFS= read -r -d '' dir; do find "$dir" -mindepth 1 -maxdepth 1 -type f -name '*.json' -print0 2>/dev/null done < <(find "$DATA_ROOT" -mindepth 3 -maxdepth 3 -type d -path "$DATA_ROOT/*/tags/worldgen" -print0 2>/dev/null) } should_validate_template_pool_ref() { local source_ns="$1" local id="$2" local target_ns="${id%%:*}" if [[ "$target_ns" == "$source_ns" ]]; then return 0 fi if [[ "$target_ns" == "minecraft" && -n "${VANILLA_TEMPLATE_POOLS[$id]:-}" ]]; then return 1 fi [[ -d "$DATA_ROOT/$target_ns/worldgen/template_pool" ]] } should_validate_processor_list_ref() { local source_ns="$1" local id="$2" local target_ns="${id%%:*}" if [[ "$target_ns" == "$source_ns" ]]; then return 0 fi if [[ "$target_ns" == "minecraft" && -n "${VANILLA_PROCESSOR_LISTS[$id]:-}" ]]; then return 1 fi [[ -d "$DATA_ROOT/$target_ns/worldgen/processor_list" ]] } should_validate_structure_template_ref() { local source_ns="$1" local id="$2" local target_ns="${id%%:*}" if [[ "$target_ns" == "$source_ns" ]]; then return 0 fi [[ -d "$DATA_ROOT/$target_ns/structure" ]] } # A pack can reference vanilla or dependency-owned registry entries that are not # present in this source tree. Check own-namespace targets and any external # namespace that the supplied pack actually defines; leave the runtime to # resolve all other external entries. should_validate_worldgen_ref() { local source_ns="$1" local id="$2" local registry_dir="$3" local target_ns="${id%%:*}" if [[ "$target_ns" == "$source_ns" ]]; then return 0 fi [[ -d "$DATA_ROOT/$target_ns/worldgen/$registry_dir" ]] } echo "=== Worldgen Validator ===" if [[ ! -d "$DATA_ROOT" ]]; then fail "missing data/ directory" fi echo "Checking for legacy paths..." while IFS= read -r -d '' legacy_path; do fail "legacy path detected: ${legacy_path#$ROOT/}" done < <(find_neoforge_jsons 'biome_modifiers') while IFS= read -r -d '' invalid_tag_path; do fail "invalid worldgen tag path: ${invalid_tag_path#$ROOT/} (expected tags/worldgen/<registry>/...)" done < <(find_invalid_tags_worldgen_jsons) while IFS= read -r -d '' f; do check_json_once "$f" done < <( { find_worldgen_jsons find_namespace_jsons 'dimension' find_namespace_jsons 'dimension_type' find_tags_worldgen_jsons find_neoforge_jsons 'biome_modifier' } ) while IFS= read -r -d '' f; do id="$(to_id "$f")" CONFIGURED_FEATURES["$id"]=1 done < <(find_worldgen_jsons 'configured_feature') while IFS= read -r -d '' f; do id="$(to_id "$f")" PLACED_FEATURES["$id"]=1 done < <(find_worldgen_jsons 'placed_feature') while IFS= read -r -d '' f; do id="$(to_id "$f")" STRUCTURES["$id"]=1 done < <(find_worldgen_jsons 'structure') while IFS= read -r -d '' f; do id="$(to_id "$f")" TEMPLATE_POOLS["$id"]=1 done < <(find_worldgen_jsons 'template_pool') while IFS= read -r -d '' f; do id="$(to_id "$f")" PROCESSOR_LISTS["$id"]=1 done < <(find_worldgen_jsons 'processor_list') while IFS= read -r -d '' f; do id="$(to_id "$f")" STRUCTURE_TEMPLATES["$id"]=1 done < <(find_structure_templates) while IFS= read -r -d '' f; do id="$(to_id "$f")" DIMENSION_TYPES["$id"]=1 done < <(find_namespace_jsons 'dimension_type') while IFS= read -r -d '' f; do id="$(to_id "$f")" NOISE_SETTINGS["$id"]=1 done < <(find_worldgen_jsons 'noise_settings') while IFS= read -r -d '' _; do BIOME_FILES=$((BIOME_FILES + 1)) done < <(find_worldgen_jsons 'biome') while IFS= read -r -d '' _; do BIOME_MODIFIER_FILES=$((BIOME_MODIFIER_FILES + 1)) done < <(find_neoforge_jsons 'biome_modifier') if [[ "$TOTAL_SUPPORTED_FILES" -eq 0 ]]; then fail "no supported worldgen JSON files found under data/**/worldgen, data/**/dimension, data/**/dimension_type, data/**/tags/worldgen, or data/**/neoforge/biome_modifier" fi if (( ${#PLACED_FEATURES[@]} == 0 && (BIOME_FILES > 0 || BIOME_MODIFIER_FILES > 0) )); then warn "no placed_feature JSON files found" fi if (( ${#CONFIGURED_FEATURES[@]} == 0 && ${#PLACED_FEATURES[@]} > 0 )); then warn "no configured_feature JSON files found" fi echo "Checking dimension references..." while IFS= read -r -d '' dimension_file; do if [[ -n "${INVALID_JSON_FILES["$dimension_file"]:-}" ]]; then continue fi rel="${dimension_file#"$ROOT/data/"}" ns="${rel%%/*}" type_ref="$(jq -r '.type? // empty' "$dimension_file")" type_ref="$(strip_cr "$type_ref")" if [[ -z "$type_ref" ]]; then fail "dimension missing .type: ${dimension_file#$ROOT/}" else type_id="$(split_ref "$ns" "$type_ref")" if should_validate_dimension_type_ref "$ns" "$type_id"; then if [[ -n "${DIMENSION_TYPES[$type_id]:-}" ]]; then pass "dimension type target exists: $type_id" else fail "dimension references missing dimension_type: $type_id" fi fi fi settings_ref="$(jq -r 'if (.generator?.type? // empty) == "minecraft:noise" and (.generator?.settings? | type) == "string" then .generator.settings else empty end' "$dimension_file")" settings_ref="$(strip_cr "$settings_ref")" if [[ -z "$settings_ref" ]]; then continue fi settings_id="$(split_ref "$ns" "$settings_ref")" if ! should_validate_noise_settings_ref "$ns" "$settings_id"; then continue fi if [[ -n "${NOISE_SETTINGS[$settings_id]:-}" ]]; then pass "dimension noise settings target exists: $settings_id" else fail "dimension references missing noise_settings: $settings_id" fi done < <(find_namespace_jsons 'dimension') echo "Checking placed_feature -> configured_feature references..." while IFS= read -r -d '' pf_file; do rel="${pf_file#"$ROOT/data/"}" ns="${rel%%/*}" feature_ref="$(jq -r '.feature? // empty' "$pf_file")" feature_ref="$(strip_cr "$feature_ref")" if [[ -z "$feature_ref" ]]; then fail "placed_feature missing .feature: ${pf_file#$ROOT/}" continue fi if [[ "$feature_ref" == \#* ]]; then warn "tag reference not resolved in placed_feature: ${pf_file#$ROOT/} -> $feature_ref" continue fi feature_id="$(split_ref "$ns" "$feature_ref")" if ! should_validate_worldgen_ref "$ns" "$feature_id" 'configured_feature'; then continue fi if [[ -n "${CONFIGURED_FEATURES[$feature_id]:-}" ]]; then pass "placed_feature target exists: $feature_id" else fail "placed_feature references missing configured_feature: $feature_id" fi done < <(find_worldgen_jsons 'placed_feature') echo "Checking structure_set -> structure references..." while IFS= read -r -d '' ss_file; do if [[ -n "${INVALID_JSON_FILES["$ss_file"]:-}" ]]; then continue fi rel="${ss_file#"$ROOT/data/"}" ns="${rel%%/*}" while IFS= read -r sref; do sref="$(strip_cr "$sref")" [[ -z "$sref" ]] && continue sid="$(split_ref "$ns" "$sref")" if ! should_validate_worldgen_ref "$ns" "$sid" 'structure'; then continue fi if [[ -n "${STRUCTURES[$sid]:-}" ]]; then pass "structure_set target exists: $sid" else fail "structure_set references missing structure: $sid" fi done < <(jq -r '.structures[]?.structure? // empty' "$ss_file") done < <(find_worldgen_jsons 'structure_set') echo "Checking jigsaw structure and template_pool references..." while IFS= read -r -d '' structure_file; do if [[ -n "${INVALID_JSON_FILES["$structure_file"]:-}" ]]; then continue fi rel="${structure_file#"$ROOT/data/"}" ns="${rel%%/*}" structure_type="$(json_query_raw '.type? // empty' "$structure_file")" structure_type="$(strip_cr "$structure_type")" if [[ "$structure_type" != "minecraft:jigsaw" ]]; then continue fi start_pool_ref="$(json_query_raw '.start_pool? // empty' "$structure_file")" start_pool_ref="$(strip_cr "$start_pool_ref")" if [[ -z "$start_pool_ref" ]]; then fail "jigsaw structure missing .start_pool: ${structure_file#$ROOT/}" continue fi start_pool_id="$(split_ref "$ns" "$start_pool_ref")" if should_validate_template_pool_ref "$ns" "$start_pool_id"; then if [[ -n "${TEMPLATE_POOLS[$start_pool_id]:-}" ]]; then pass "jigsaw start_pool target exists: $start_pool_id" else fail "jigsaw structure references missing template_pool: $start_pool_id" fi fi done < <(find_worldgen_jsons 'structure') while IFS= read -r -d '' pool_file; do if [[ -n "${INVALID_JSON_FILES["$pool_file"]:-}" ]]; then continue fi rel="${pool_file#"$ROOT/data/"}" ns="${rel%%/*}" while IFS=$'\t' read -r location_ref processors_ref; do location_ref="$(strip_cr "$location_ref")" processors_ref="$(strip_cr "$processors_ref")" if [[ -z "$location_ref" ]]; then fail "template_pool single_pool_element missing .location: ${pool_file#$ROOT/}" else location_id="$(split_ref "$ns" "$location_ref")" if should_validate_structure_template_ref "$ns" "$location_id"; then if [[ -n "${STRUCTURE_TEMPLATES[$location_id]:-}" ]]; then pass "template_pool structure template target exists: $location_id" else fail "template_pool element references missing structure template: $location_id" fi fi fi if [[ -z "$processors_ref" ]]; then fail "template_pool single_pool_element missing .processors: ${pool_file#$ROOT/}" else processors_id="$(split_ref "$ns" "$processors_ref")" if should_validate_processor_list_ref "$ns" "$processors_id"; then if [[ -n "${PROCESSOR_LISTS[$processors_id]:-}" ]]; then pass "template_pool processor_list target exists: $processors_id" else fail "template_pool element references missing processor_list: $processors_id" fi fi fi done < <(json_query_raw ' .. | objects | select(.element_type? == "minecraft:single_pool_element" or .element_type? == "minecraft:legacy_single_pool_element") | [(.location? // ""), (.processors? // "")] | @tsv ' "$pool_file") done < <(find_worldgen_jsons 'template_pool') echo "Checking biome feature references..." while IFS= read -r -d '' biome_file; do if [[ -n "${INVALID_JSON_FILES["$biome_file"]:-}" ]]; then continue fi rel="${biome_file#"$ROOT/data/"}" ns="${rel%%/*}" while IFS= read -r fref; do fref="$(strip_cr "$fref")" [[ -z "$fref" ]] && continue if [[ "$fref" == \#* ]]; then warn "tag reference not resolved in biome file: ${biome_file#$ROOT/} -> $fref" continue fi fid="$(split_ref "$ns" "$fref")" if ! should_validate_worldgen_ref "$ns" "$fid" 'placed_feature'; then continue fi if [[ -n "${PLACED_FEATURES[$fid]:-}" ]]; then pass "biome feature target exists: $fid" else fail "biome references missing placed_feature: $fid" fi done < <(jq -r '.features[][]? // empty' "$biome_file") done < <(find_worldgen_jsons 'biome') echo "Checking biome_modifier feature/structure references..." while IFS= read -r -d '' mod_file; do if [[ -n "${INVALID_JSON_FILES["$mod_file"]:-}" ]]; then continue fi rel="${mod_file#"$ROOT/data/"}" ns="${rel%%/*}" while IFS= read -r ref; do ref="$(strip_cr "$ref")" [[ -z "$ref" ]] && continue if [[ "$ref" == \#* ]]; then warn "tag reference not resolved in biome_modifier: ${mod_file#$ROOT/} -> $ref" continue fi rid="$(split_ref "$ns" "$ref")" if ! should_validate_worldgen_ref "$ns" "$rid" 'placed_feature'; then continue fi if [[ -n "${PLACED_FEATURES[$rid]:-}" ]]; then pass "biome_modifier feature target exists: $rid" else fail "biome_modifier references missing placed_feature: $rid" fi done < <(jq -r 'if (.features? | type) == "array" then .features[]? else .features? // empty end' "$mod_file") while IFS= read -r ref; do ref="$(strip_cr "$ref")" [[ -z "$ref" ]] && continue rid="$(split_ref "$ns" "$ref")" if ! should_validate_worldgen_ref "$ns" "$rid" 'structure'; then continue fi if [[ -n "${STRUCTURES[$rid]:-}" ]]; then pass "biome_modifier structure target exists: $rid" else fail "biome_modifier references missing structure: $rid" fi done < <(jq -r 'if (.structures? | type) == "array" then .structures[]? else .structures? // empty end' "$mod_file") done < <(find_neoforge_jsons 'biome_modifier') echo "" if [[ "$FAILURES" -gt 0 ]]; then echo "$FAIL worldgen validation failed with $FAILURES error(s) and $WARNINGS warning(s)" exit 1 fi if [[ "$STRICT" -eq 1 && "$WARNINGS" -gt 0 ]]; then echo "$FAIL worldgen validation strict mode failed on $WARNINGS warning(s)" exit 1 fi echo "$PASS worldgen validation passed with $WARNINGS warning(s)"
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SKILL.md 10.3 KB
--- name: minecraft-world-generation description: "Create and debug Minecraft 26.x and legacy 1.21.x world generation for datapacks, NeoForge, or Fabric, including biomes, dimensions, features, structures, and biome modifiers. Use for worldgen data or registration, not general gameplay systems." --- # Minecraft World Generation Use this skill for biome, dimension, feature, or structure data and their registration. Use `minecraft-datapack` for non-worldgen data and `minecraft-modding` for non-worldgen gameplay code. ## Routing Boundaries - `Use when`: the task changes worldgen data, registration, or injection. - `Do not use when`: the task is non-worldgen datapack work (`minecraft-datapack`). - `Do not use when`: the task is non-worldgen mod systems (`minecraft-modding`). ## Choose the delivery path | Approach | Best When | Platform | |----------|-----------|----------| | Datapack JSON | Change data supplied by a pack | Vanilla, any server | | **Mod + Datagen** | Registering new biomes/dimensions, code-driven | NeoForge / Fabric | | **Biome Modifier (NeoForge)** | Adding features/spawns to existing biomes | NeoForge | | **BiomeModification API (Fabric)** | Adding features/spawns to existing biomes | Fabric | Worldgen registries are datapack registries: their files load at world load and their registry path determines the data path. Read the [NeoForge registry guide](https://docs.neoforged.net/docs/concepts/registries/) before choosing a mod-specific registry path. ## Version boundary Use Minecraft 26.x for new work. Use Java 25 and start each JSON schema from the exact target's vanilla data or generated output. Do not copy a 1.21 shape into a 26.x pack merely because it parses as JSON. Preserve an established 1.21.x project on Java 21 and its matching schema unless the task explicitly includes an upgrade. Keep examples matched to the project version. The [26.1 migration primer](https://docs.neoforged.net/primer/docs/26.1/) removes `minecraft:random_patch` and `minecraft:no_bonemeal_flower`. It replaces the random-patch pattern with a separate `minecraft:simple_block` configured feature and placements for count, random offset, and block-predicate filtering. Inspect the relevant primer section before migrating code or data. Read [legacy 1.21 JSON patterns](references/legacy-1.21-worldgen-json.md) only when the project targets that version. Those examples are not release artifacts for 26.x. --- ## Data layout and reference graph ``` data/<namespace>/ ├── worldgen/ │ ├── biome/ │ │ └── my_biome.json │ ├── configured_feature/ │ │ └── my_ore.json │ ├── placed_feature/ │ │ └── my_ore_placed.json │ ├── noise_settings/ │ │ └── my_dimension_noise.json │ ├── structure/ │ │ └── my_structure.json │ ├── structure_set/ │ │ └── my_structures.json │ ├── processor_list/ │ │ └── my_processors.json │ ├── template_pool/ │ │ └── my_pool.json │ └── carver/ │ └── my_carver.json ├── dimension/ │ └── my_dimension.json ├── dimension_type/ │ └── my_type.json ├── tags/ │ └── worldgen/ │ └── biome/ │ └── is_forest.json └── neoforge/ └── biome_modifier/ (NeoForge mod only) └── add_ores.json ``` Build and review the graph from its leaves upward: 1. Define a configured feature, then its placed feature. 2. Reference placed features from a biome or biome modifier at the intended decoration step. 3. Define a structure, then its structure set; a jigsaw structure also needs a template pool, processor list, and structure template. 4. Define a dimension type and noise settings before a dimension that references them. Use fully qualified identifiers across namespaces. An external `minecraft:` or dependency reference is valid when that dependency supplies the registry entry; do not create a local copy merely to satisfy static checking. If the same pack contains that external namespace and registry directory, treat it as local and verify the target exists. --- ## Biomes and dimensions For 26.x biome and dimension data, use the exact target's vanilla data or datagen output as the schema source. The older `effects` and dimension-type fields do not model newer environment behavior. The 11 decoration steps still organize placed features; choose the semantically appropriate step and keep ore placement in `underground_ores`. The version-labeled 1.21.5 biome and dimension examples are in [legacy 1.21 JSON patterns](references/legacy-1.21-worldgen-json.md). ## 26.x feature pattern For the 26.1 replacement for a simple random patch, the migration primer shows a `simple_block` configured feature and a placed feature with count, random offset, and a block-predicate filter. Adapt the exact values and block state to the target release's generated data. At `data/<namespace>/worldgen/configured_feature/my_plant.json`: ```json { "type": "minecraft:simple_block", "config": { "to_place": { "type": "minecraft:simple_state_provider", "state": { "Name": "minecraft:sweet_berry_bush", "Properties": { "age": "3" } } } } } ``` At `data/<namespace>/worldgen/placed_feature/my_plant.json`: ```json { "feature": "<namespace>:my_plant", "placement": [ { "type": "minecraft:count", "count": 96 }, { "type": "minecraft:random_offset", "xz_spread": { "type": "minecraft:trapezoid", "min": -7, "max": 7, "plateau": 0 }, "y_spread": { "type": "minecraft:trapezoid", "min": -3, "max": 3, "plateau": 0 } }, { "type": "minecraft:block_predicate_filter", "predicate": { "type": "minecraft:all_of", "predicates": [ { "type": "minecraft:matching_block_tag", "tag": "minecraft:air" }, { "type": "minecraft:matching_blocks", "blocks": "minecraft:grass_block", "offset": [0, -1, 0] } ] } } ] } ``` --- ## NeoForge biome modifiers Biome modifiers load from `data/<modid>/neoforge/biome_modifier/<path>.json`. They can target a biome id or tag and add or remove placed features, among other changes. The current [Biome Modifiers guide](https://docs.neoforged.net/docs/worldgen/biomemodifier/) documents their schemas, decoration steps, and datagen. For `neoforge:add_features`, `features` accepts a placed-feature id, list, or tag. Vanilla placed features may be referenced in biome JSON or added with a modifier, but NeoForge cautions against doing both because feature-order cycles can crash world loading. Prefer a copy under the mod namespace when an injected vanilla feature would create that risk. When targeting a biome from an optional dependency, put the target in a biome tag entry with `required: false`, then use that tag in the modifier. This lets the pack load when the dependency is absent. --- ## Structures and dimensions For any current release, derive structure, template-pool, dimension, and dimension-type JSON from that release's vanilla data or datagen output. Confirm the reference graph before launching a test world: - `structure_set` references `structure`. - Jigsaw `start_pool` references `template_pool`; each single-pool element references its structure template and processor list. - `dimension.type` references `dimension_type`; a noise generator's string `settings` references `worldgen/noise_settings`. For Fabric registration or mod datagen, use the exact loader and API version's documentation rather than copying 1.21 code into a 26.x project. The detailed 1.21 structure and dimension examples are in [legacy 1.21 JSON patterns](references/legacy-1.21-worldgen-json.md). --- ## Development Workflow 1. Create or edit worldgen JSON files in `data/<namespace>/worldgen/` (or equivalent mod resources path). 2. Run the bundled validator to catch JSON and cross-reference errors before loading: ```bash ./scripts/validate-worldgen-json.sh --root /path/to/datapack-or-mod-resources # Strict mode treats warnings as failures: ./scripts/validate-worldgen-json.sh --root /path/to/datapack-or-mod-resources --strict ``` 3. Fix any reported errors and re-validate until clean. The validator checks: - JSON validity for `worldgen/**` and `neoforge/biome_modifier/**` - Cross-reference integrity for `placed_feature -> configured_feature` - Cross-reference integrity for `structure_set -> structure` and biome/biome_modifier feature targets - Cross-reference integrity for `jigsaw structure -> start_pool` and `template_pool -> structure template / processor_list` 4. Compare biome and dimension-type JSON against the exact target's vanilla registry shape before in-game testing. The helper does not run Mojang codecs: valid JSON and local references do not prove that fields such as `carvers`, `effects`, or dimension settings match that release's schema. 5. In-game biome and structure testing: ```mcfunction /locate structure <namespace>:my_structure /locate biome <namespace>:my_biome /place feature <namespace>:my_ore ``` `place feature` takes a configured-feature ID, not its placed-feature wrapper. See Mojang's [place command reference in the 1.19 release notes](https://www.minecraft.net/en-us/article/the-wild-update-out-today-java). 6. For dimension testing, use `/execute in` (dimension must exist at world load, not added via `/reload`): ```mcfunction execute in <namespace>:my_dimension run tp @s 0 100 0 ``` 7. Check `latest.log` for worldgen errors (missing biome references, malformed noise settings). 8. Note: `/reload` refreshes datapack JSON but does **not** re-generate already-generated chunks. Test new worldgen in a fresh world or newly generated chunks. For existing test worlds, use a disposable copy and a purpose-built chunk reset/regeneration workflow; `/fill` only replaces blocks and is not a substitute for world generation. --- ## References - Minecraft Wiki — World generation: https://minecraft.wiki/w/Custom_world_generation - Minecraft Wiki — Biome: https://minecraft.wiki/w/Biome/JSON_format - Minecraft Wiki — Features: https://minecraft.wiki/w/World_generation/Configured_feature - NeoForge Biome Modifiers: https://docs.neoforged.net/docs/worldgen/biomemodifier/ - Fabric BiomeModifications: https://wiki.fabricmc.net/tutorial:biomemodification - misode's data pack generator (worldgen UI): https://misode.github.io/worldgen/
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