version: "1.0.0" name: blender-assembly-structure description: Plan, build, place, and validate physically meaningful Blender object assemblies, including manufactured part boundaries, mechanical seams, mounting interfaces, pivots, hierarchy, constraints, instancing, modular grids, connector planes, and precision snapping. Use when several objects must form one product, machine, architectural module, vehicle, furniture item, mechanism, or environment structure without incorrectly welding independent parts, eyeballing alignment, or leaving continuous shells as overlapping primitives.

Blender Assembly Structure

Own object-level construction and scene assembly. Do not claim topology fusion merely because objects share a parent, collection, material, or object container.

Suite Authority

Follow ../blender-production-router/references/production-protocol.md and ../blender-production-router/references/native-component-contract.md. The Router alone owns route, stage, budgets, rollback, and pauses. This skill owns object boundaries, interfaces, placement, and assembly evidence only; it cannot restart analysis, reroute, or delete a project.

Use a provisional Part Graph for reversible Blockout. Require an approved Part Graph only when entering formal_production or committing Functional Parts. Emit local repair requests instead of creating a second state machine.

Required Part Graph

Before assembly, classify every buildable part in construction_graph.json:

• physical function and form level;
• continuous or separate manufacturing state;
• reason for separation;
• construction method and final object name;
• combination level A, B, C, or D;
• connection or interface method;
• pivot, motion, constraint, material, modifier, instance, and export ownership;
• bevel class and clearance policy.

Difficulty is never a valid reason to split one continuous shell into several penetrating objects. Run scripts/validate_part_graph.py before formal production and again before Functional Parts.

Derive part boundaries from manufacturing, independent motion, a real material/transparent interface, instancing, modifier/export ownership, or a visible seam. Do not split by reference color blocks, convenience, or local modeling difficulty. A complex continuous shell remains one topological responsibility even when several temporary construction objects help create it.

Read references/assembly-production.md for the complete assembly and interface protocol. Read ../blender-direct-surface-modeling/references/construction-method-playbook.md when the assembly uses modular grids, snapping, repeated modules, host openings, or path-generated parts.

Combination Levels

• A_VISUAL_GROUPING: transforms, parenting, or collection organization; valid for Blockout or

already independent parts, never topology proof.

• B_OBJECT_JOIN: one object container with possibly several disconnected mesh islands; use only

when one data container is useful and the islands remain semantically independent.

• C_PHYSICAL_ASSEMBLY: separate manufactured or moving parts with seams, mating surfaces,

clearances, mounts, fasteners, pivots, or constraints.

• D_TOPOLOGY_FUSION: one continuous volume or shell created through shared topology, Bridge,

Weld, Boolean Union plus cleanup, remesh, or reconstruction. Hand this route to blender-direct-surface-modeling.

Assembly Protocol

1. In reversible_blockout, record provisional part roles and interfaces before mutation; approve

the affected Part Graph before formal production.

1. After Blockout, replace or convert proxies and send every D_TOPOLOGY_FUSION part to

blender-direct-surface-modeling before assembly detail.

1. Build primary load-bearing parts and receiving interfaces first.
2. Establish mating surfaces, wall thickness, recesses, sockets, pivots, and scale-derived clearance.
3. Establish grid units, module origins, connector planes, snap element/base/orientation, and

target ownership before placing repeated architectural or product modules.

1. Add hinges, fasteners, latches, seals, handles, or constraints only when their function and

attachment are defined.

1. Organize collections by production role: model, cutters, controls, fasteners, glass, collision,

simulation, lighting, cameras, and export.

1. Test open/closed or extreme mechanical states where parts move.
2. Validate every visible contact and every unexplained overlap from front, side, top, hero, and

wireframe views.

Hard Rules

• Join Objects does not weld vertices or remove disconnected islands.
• Parent and Collection do not create physical interfaces.
• A shared material does not make objects one manufactured part.
• Do not push a button, handle, bearing, or panel through its receiver without a recess, mount, or

documented hidden tolerance.

• Do not Boolean-union parts that must move, be replaced, remain transparent, or preserve a seam.
• Do not keep a continuous shell fragmented because one local transition is difficult.
• Do not use fasteners as decoration before the mounting logic exists.
• Do not create Functional or Detail parts before Primary, Structural, and Transition gates pass.
• Do not eyeball modular alignment or accumulate repeated transform drift. Snap one source or

instance from a declared origin/connector convention and measure the resulting gap.

Completion Gate

Require mapped final objects, valid collection ownership, classified combination levels, intentional mesh-island counts, mating interfaces, seam/clearance evidence, tested pivots or constraints, and no unclassified visible intersections. Send continuous topology to blender-direct-surface-modeling and final checks to blender-geometry-validation.