Block Geometry

Block geometry

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The advanced automatic model-block APIs on this page target Minecraft 26.2, Fabric and NeoForge. They read packaged Java block-model elements and prepare server-safe shapes. Use the target's API rather than copying imports to another Minecraft version.

Choose AABB or OBB

Identifier model = Identifier.fromNamespaceAndPath("examplemod", "block/slanted_prop");
ModelShapeProvider.prepare(model);
VoxelShape detailed = ModelShapeProvider.shape(
        model, Direction.NORTH, BlockShapeMode.OBB);
VoxelShape axisAligned = ModelShapeProvider.shape(model, BlockShapeMode.AABB);

ModelShapeProvider and BlockShapeMode are in com.kltyton.bedrockruntime.api.block.shape. The other types are the 26.2 native Identifier, Direction and VoxelShape.

Run preparation during registration/setup. Return the prepared shape from the block's normal shape/collision methods.

• OBB preserves the rotated convex geometry.
• AABB encloses that geometry with native axis-aligned bounds.
• Shape queries read prepared data; rendering callbacks and movement queries do not parse model files.

Automatic multi-block structures

Use your loader's normal block and BlockItem registration. After assigning the properties their correct registry key, construct:

AutoModelBlock block = new AutoModelBlock(blockId, properties, BlockShapeMode.OBB);

AutoModelBlock shows the selected occupied cell's outline; AutoWholeModelBlock shows the whole structure. Subclass AutoPartShapeBlock / AutoWholeShapeBlock when you need custom origin interaction, placement, block entities or drops.

flowchart LR
    A[Packaged model elements] --> B[Rotate and clip geometry by occupied cell]
    B --> C[Validate all placement cells]
    C --> D[One block ID with origin offsets]
    D --> E[Render only the origin]
    D --> F[Forward interaction and linked removal to origin]

Loading

The model convention is assets/<namespace>/models/block/<block path>.json. One registered block ID represents the structure; state offsets identify the origin. Placement checks the occupied cells, world boundaries, replaceability and entity obstruction.

Each axis may extend at most four cells from the origin; model coordinates are clipped to the supported [-4, 5] block interval. Prepare models within those bounds.

AutoShapeDataProvider can generate the automatic blocks' orientation/origin blockstates and item definitions through your existing data-generation entrypoint. Original model JSON, textures, language files and loot remain authored by your mod.

Server configuration

Edit the loader-generated kltyton_bedrock_runtime-server.toml:

vanillaSlantedBlockObb = true
forceAllBlockObb = false
blockModelWhitelist = []
blockModelBlacklist = []

Setting	Behavior
vanillaSlantedBlockObb	Use packaged model geometry for native slanted models
forceAllBlockObb	Enable the model OBB path for allowed blocks; default false
blockModelWhitelist	Empty means unrestricted; a nonempty list restricts eligibility
blockModelBlacklist	Exclusions take priority over the whitelist

Entries support namespace:id, namespace:* and *. Block tags and arbitrary-position wildcards are not supported. A whitelist restricts scope; it does not enable a mode by itself.

forceAllBlockObb = true
blockModelWhitelist = ["minecraft:*"]
blockModelBlacklist = ["minecraft:chest", "minecraft:trapped_chest"]

For forced mode, KBR uses packaged model elements where available and the block's own finite collision pieces otherwise. Originally empty collision stays empty. The lists also apply to KBR model OBBs; excluded model geometry uses its model AABB path.

Client resource packs, animated renderers and visual model overrides do not automatically change the server's block-physics model.

Parsing existing element arrays

The 26.2 API also exposes ModelShapeCache.buildForElements(JsonArray, Direction) and its ShapeSet/Cell results for callers that already hold model elements.

See the block-shape reference for provider registration, origin hooks and detailed configuration behavior.