Crystal Spikes

A NeoForge 1.21.1 mod that adds a highly configurable, datapack-driven crystal spike worldgen feature with geode-style block providers and a custom placement modifier for finding terrain undersides.

Feature: crystalspikes:crystal_spike

Configured feature JSON (data/<namespace>/worldgen/configured_feature/<name>.json):

Notes:

• All BlockStateProvider fields accept any vanilla provider, e.g. simple_state_provider or weighted_state_provider for mixed blocks within one spike.
• Decorators are only placed where they can survive (canSurvive), so e.g. sea pickles only land on coral blocks and floor fans never float sideways.

Example

{
  "type": "crystalspikes:crystal_spike",
  "config": {
    "core": {
      "type": "minecraft:simple_state_provider",
      "state": { "Name": "minecraft:calcite" }
    },
    "outer_layer": {
      "type": "minecraft:weighted_state_provider",
      "entries": [
        { "weight": 4, "data": { "Name": "minecraft:amethyst_block" } },
        { "weight": 1, "data": { "Name": "minecraft:budding_amethyst" } }
      ]
    },
    "surface_decorator": {
      "type": "minecraft:weighted_state_provider",
      "entries": [
        { "weight": 3, "data": { "Name": "minecraft:amethyst_cluster" } },
        { "weight": 1, "data": { "Name": "minecraft:large_amethyst_bud" } }
      ]
    },
    "base": {
      "type": "minecraft:simple_state_provider",
      "state": { "Name": "minecraft:basalt" }
    },
    "base_radius": { "type": "minecraft:uniform", "min_inclusive": 2, "max_inclusive": 4 },
    "direction": ["up"],
    "min_angle": 0.0,
    "max_angle": 20.0,
    "slope_angle": { "type": "minecraft:uniform", "min_inclusive": 22.0, "max_exclusive": 30.0 },
    "root_depth": 4,
    "decorator_chance": 0.1667,
    "decorator_face_chance": 0.5
  }
}

Examples

Complete working datapacks (configured feature, placed feature, biome modifier, anchor tags) are in example/datapack/

Placement modifier: crystalspikes:under_island

Finds anchor blocks on the underside of terrain (blocks in anchor_tag with air/water/lava below them) — made for hanging spikes under floating islands, without vanilla's 32-step environment_scan limit.

Example

{
  "feature": "example:my_spike",
  "placement": [
    { "type": "minecraft:rarity_filter", "chance": 8 },
    { "type": "minecraft:count", "count": { "type": "minecraft:uniform", "min_inclusive": 4, "max_inclusive": 8 } },
    { "type": "minecraft:in_square" },
    { "type": "crystalspikes:under_island", "anchor_tag": "example:end_stones", "min_y": 0, "max_y": 128 },
    { "type": "minecraft:biome" }
  ]
}

For surface placement, vanilla's heightmap + environment_scan (down) works fine. See the coral spikes in the example datapack.