Procedural objects are structures Iris builds from JSON parameters instead of loading from .iob files. Six families exist, all under proceduralObjects on a biome or a region: trees, fungi, coral, crystals, formations, ruins.

Trees have their own page: 17b - Procedural Trees. This page covers the shared model, the other five families, and sapling overrides.

Related: 12 - Regions, 13 - Biomes, 15 - Caves & Carving, 16 - Surfaces, Decorators & Deposits, 18 - Structures Overview, 19 - Objects, 20 - Object Placement, 35 - Vanilla Passthrough.

Each entry generates variants different shapes from its settings and seed. Increase variants for more shapes, or change seed for a different set.

With unchanged settings and the same Iris build, each variant retains its shape, accents, and attachments across server restarts and parallel generation.

chance controls how often an entry places in a chunk. density is the number of attempts in a chunk that passes. chance: 0.5, density: 4 gives four attempts in half the chunks.

Surface biome, region, and cave biome lists all contribute. A biome-owned CARVING_ONLY entry places only in that cave biome. Region-owned entries apply throughout the region. Use the object placement settings to control terrain support and anchoring.

Snippet key: procedural-objects. Valid on biomes and regions.

{
  "proceduralObjects": {
    "trees": [ { "...": "..." } ],
    "crystals": [ { "...": "..." } ]
  }
}

Every family supports these placement fields. Defaults differ per family and are noted where they diverge.

Only CARVING_ONLY entries take the cave path. Those search the chunk for an anchor using the active cave profile's defaultObjectAnchor, anchorScanStep, anchorSearchAttempts, and objectMinDepthBelowSurface; an entry that finds no anchor is skipped for that attempt. Dry entries reject water, explicit lava, and ordinary carved cells at or below the dimension cave-lava height. Set underwater: true only when a procedural object is intentionally allowed to anchor in cave fluid. The profile's defaultObjectPlaceMode overrides the entry mode, but only when the entry left mode at the default CENTER_HEIGHT. See 15 - Caves & Carving.

plausible is a tree-only field. Every other family places with decay prevention active.

Snippet key: fungus. A stem column with a cap grown on top, or a sideways shelf bracket.

Snippet key: coral. Defaults to underwater: true and waterlogged: true, so it grows from the seafloor and stays alive.

Snippet key: crystal. A budding base blob with tapered shards radiating from it. Defaults to carvingSupport: CARVING_ONLY and chance: 0.2, so it needs carved cave space to place at all. See 15 - Caves & Carving for the anchor settings that govern it.

Snippet key: formation. Natural and magical landmarks. Default chance: 0.02 — these are meant to be rare, and they are the family most likely to widen the pack's mantle radius.

When a procedural cave placement resolves to FLOOR, its lowest occupied block rests in the first open cell above the supporting floor. Alignment accounts for rotation; configured translate and random Y offsets still apply afterward. Ceiling, CENTER and surface placements keep their own anchor behavior.

For room-scaled formations, set carvingSupport: "CARVING_ONLY" and roomHeightFraction, for example 0.25. The selected room supplies the local floor and ceiling after anchoring; placements still respect its protected solids and passage. A formation that cannot fit is skipped. Feature-owned continuous pillars are configured separately with pillarSpacing in Authored Subterrain Features.

ICEBERG combines a low, wide body with independently varied summits. FISSURE keeps its shards disconnected so the cracks remain real negative space. SPIRAL sweeps a tightening helix with an open center. OVERHANG grows vertically before curling outward and down. ARCH sweeps one connected bridge between independently shaped feet, its configured height is the actual top bound, and the opening stays traversable. A pointed SPIRE always retains its final tip even at a zero-width top.

Snippet key: ruin. Man-made shapes that are weathered, eroded, and partly buried. Default chance: 0.05 and mode: MIN_HEIGHT.

Snippet key: ruin-decorator.

IrisTree lives on object placements (IrisObjectPlacement.trees), not under proceduralObjects. It maps a grown sapling to that placement's objects. This is a gameplay growth replacement, not worldgen scatter, and it never touches procedural trees.

Vanilla sapling growth continues until this is on. The enable recipe is 35 - Vanilla Passthrough Task 4.

Dimension treeSettings gates the whole feature:

1. Pick the family that matches the shape: trees for forests, fungi for mushroom biomes, coral for warm oceans, crystals for cave biomes, formations for deserts and coastlines, ruins for sparse land.
2. Add one entry with a single material, chance: 1, density: 1, variants: 4, and a fixed seed. Focus the biome and generate.
3. Get the silhouette right before you touch frequency. Dimensions, profile, and roughness change what the thing is; chance and density only change how often you meet it.
4. Add palettes, accents, and decorators once the shape holds up from several angles.
5. Match carvingSupport to the environment. Cave props also want a stilt place mode, either on the entry or through the cave profile's defaultObjectPlaceMode.
6. Drop chance to production values, remove the dimension focus, and verify the family stays inside the biomes and regions that declare it.