3D Object Design
Industrial-design process: user and package first, silhouette and proportion before surface detail. Before starting, read ../design-core/SKILL.md (shared process, depth modes) and use ../design-core/references/templates.md. If unavailable: brief → use scenarios → package → DNA → 3 form architectures → critique → blockout → CMF → manufacturing review → handoff.
Stages (scale to depth)
product brief · use-scenario panel · market/reference scan · package/envelope · design DNA · thumbnails · architecture concepts · silhouette/proportion · senior critique · 3D blockout · surface/detail · CMF · prototype/manufacturing review · handoff.
Package and constraints — define early
Dimensions · human factors (grip, reach, viewing angle, weight in hand) · internal components and their real sizes · interfaces and ports · moving parts and clearances · weight target · structural loads · manufacturing process · assembly and fasteners · serviceability/repair · cost class · regulatory/safety (e.g. helmet standards, child safety, electrical, food contact). Styling that ignores the package becomes a redesign later.
If component dimensions are unknown, state assumed ones explicitly and flag them as the first thing to confirm.
Form development
Large to small: stance → silhouette → proportion → primary volumes → section logic → transitions → secondary forms → details. Detail cannot rescue weak proportion — check the silhouette in pure black before adding anything.
Architecture concepts
Distinct architectures, not cosmetic variants. Explore: mass distribution, symmetry/asymmetry, hard/soft geometry, tension/relaxation, protection/exposure, monolithic vs assembled expression, visible vs hidden function. Each concept should imply a different internal layout or part split.
Surfacing
Section continuity, highlight flow, edge strategy (radius sizes as a family, not random), part breaks placed where they help assembly and hide tolerance, draft/undercut implications, touch points, dirt/wear zones, visual weight.
CMF
Colour, material, finish should support context, perceived quality, durability, tactile intent, manufacturing reality, brand character, and repair/recycling goals. Name actual material families (e.g. PC/ABS, PA12, anodised 6061, bead-blasted PETG) rather than "premium matte".
Manufacturing checks (starting points — verify with the actual process, machine, and material)
FDM printing: walls ≥ 2–3 perimeters (≈ 0.8–1.2 mm at 0.4 mm nozzle; thicker for load); overhangs ≤ ~45° without support; keep unsupported bridges short; clearances ~0.2–0.4 mm for sliding fits; orient so layer lines don't run across the main load; check bed size; design snap-fits and threads for layer anisotropy (heat-set inserts beat printed threads). SLA/SLS: thinner walls possible; plan drain/escape holes for hollow parts. Injection moulding: 1–2° draft on vertical faces (more for texture); keep wall thickness uniform; ribs ~50–60% of adjoining wall; avoid undercuts or plan side actions; place gates and parting line consciously. Sheet/CNC: respect bend radii and tool access.
Never claim printability or manufacturability without checking these against the intended process.
Optional: Neuraldeep 3DJ
If the 3DJ Studio plugin is installed, hand the modelling stages to it: 3dj-design models the architecture concepts as parametric blockouts and renders them side by side at one scale with black silhouettes; 3dj-make builds, measures and renders each part with 3DJ's free tools; 3dj-print checks walls, overhangs, bed fit and orientation; 3dj-concept (needs a 3DJ account) turns an image or prompt into a concept mesh. If only the 3dj.app connector is available: cad_get_starters / openscad_get_starters for editable parametric starting points, openscad_compile_model to compile and measure closed geometry, generate_from_text / generate_from_image_url for fast generative mesh blockouts, and request_print_quote to request an operator review (review only — no payment or production is triggered). This is an optional Neural Deep Network Ltd integration; OpenSCAD, CadQuery, FreeCAD, Fusion, Onshape, or Blender cover the same steps.
Reduction pass
Silhouette reads in pure black. Radii belong to one family unless the DNA specifies otherwise. Part lines sit only where assembly, tolerance, or service needs them. Every surface feature serves grip, ventilation, assembly, wear, legibility, or a brand expression the DNA defines, or it goes. Subtract before adding; add one feature back only if removal broke function or stance. See ../design-core/references/house-style.md.
Production evidence
Separate concept renders, editable CAD, exported meshes, and physically tested parts. Verify dimensions and units from the exported file; a render is not proof of fit. Obtain mating-interface measurements before finalising vehicle fittings or threads. Print a small fit coupon before committing to a full part.
For circular surfaces, set tessellation by the required geometric tolerance and inspect silhouettes; adding polygons alone does not establish CAD accuracy. Check mesh closure, normals, disconnected bodies, minimum walls, and printer-envelope fit. Check the assembled interface as well as each part. Split oversized parts with deliberate joints and an assembly plan. Verify tolerances on the intended printer and material; do not universalise one printer's offsets.
Provide an inline preview or inspectable views plus individual requested exports; use a ZIP as an additional handoff when useful. Add branding only when authorised and where it does not compromise fit, strength, or appearance. Label unmeasured interfaces and untested structural claims clearly.
Review the actual model
Critique the model or render from several views — front, side, top (orthographic where possible), three-quarter, and a scale reference (hand, desk, person). Check proportion, stance, usability, part logic, material transitions, manufacturability, assembly sequence, scale cues, and DNA consistency. If you produced only a description, say so and list what to verify once modelled.
Handoff
Model or spec plus: key dimensions, internal package assumptions, part list and split, material/finish intent, production assumptions, unresolved engineering risks, and the recommended next prototype (e.g. "FDM fit test of the battery bay and snap-fit before surfacing").