shape-analysis

name

shape-analysis

description

Enrich a short or vague 3D-object prompt into a detailed, print-ready design brief before modeling. Use when the user asks for an object in a few words — "phone stand", "wall hook", "pen holder", "planter", "GoPro mount" — and the request lacks dimensions, features, style, or ergonomic detail. Analyzes the intended shape and returns a structured brief with popular, well-considered defaults so the generated object comes out refined and appealing rather than generic.

Shape Analysis — prompt enrichment for 3D parts

Purpose

A short prompt like "phone stand" underspecifies the object: it says nothing about angle, phone size, cable routing, footprint, or style. Modeling it literally yields a bland box. This skill turns a terse description into a detailed design brief — the shape, the dimensions, the popular features people actually expect for that object — so the downstream CAD step produces something refined and appealing.

This is a read-only, no-artifact skill. It writes no files and generates no geometry. Its only output is one enriched design brief, which the user (or the cadcode skill) then turns into a model.

When to use

• The user names an object in a few words with no dimensions, features, or style.
• The prompt is ambiguous about intended use, target fit (a phone, a bike rail, an M3 bolt), or aesthetic.
• The user explicitly asks to "make it nicer / more polished / more popular".

Do not use it when the user already gave a complete spec, is editing an existing .py part, or asked for an exact literal shape ("a 20 mm cube").

Workflow

1. Classify the object. Map the prompt to a known object category (stand, mount, holder, tray, hook, enclosure, planter, adapter, bracket, …). If the category is unclear, pick the most common reading and state the assumption.

2. Infer the target it must fit. Many objects exist to hold or attach to something else. Resolve real reference dimensions:

   • Consumer devices → typical real sizes (a modern phone ≈ 75 × 160 × 8 mm).
   • Fasteners / rails / standards → look them up rather than guessing.
   • When a fit dimension drives the whole part, call it out explicitly and add a printing clearance (0.2–0.4 mm for FDM slip fits).

3. Add the popular features. For the category, list the features that make the object genuinely useful and that most well-liked versions include — e.g. a phone stand gets an adjustable viewing angle (~60°), a cable channel, a lip to stop the phone sliding, and a stable weighted base. Prefer features that are printable without supports.

4. Set concrete dimensions. Give real numbers, not "medium". Include overall envelope, wall thickness (≥ 2 mm for structural FDM), and any critical internal dimension. Keep the footprint stable (wide base, low center of mass).

5. Choose a style. A short aesthetic direction: minimal / geometric / organic / utilitarian. Note fillet radii on handled or visible edges (2–4 mm reads as "finished", sharp reads as "prototype").

6. Respect print reality. Flag overhangs > 45°, thin unsupported spans, and anything needing supports. Prefer a flat, large first-layer face and a single-piece design unless a split obviously helps.

7. Emit one brief in the format below and stop. Do not model anything.

Output format

Return exactly one fenced ```design-brief block containing the enriched spec as JSON, followed by a 2–3 sentence plain-language summary. Keep every dimension in millimeters.

{
  "object": "phone stand",
  "category": "stand",
  "fits": { "target": "modern smartphone", "ref_mm": [75, 160, 8], "clearance_mm": 0.3 },
  "envelope_mm": [90, 80, 70],
  "wall_mm": 2.4,
  "features": [
    "60° viewing angle",
    "front lip 8 mm to retain the phone",
    "rear cable channel 12 mm wide",
    "wide weighted base for stability"
  ],
  "style": "minimal, geometric, 3 mm filleted visible edges",
  "print": { "orientation": "base flat on bed", "supports": false, "notes": "no overhang > 45°" },
  "assumptions": ["single phone, portrait orientation", "PLA on an FDM printer"]
}

Then: a short summary the user can approve or tweak, e.g. "A minimal 90×80 mm portrait phone stand at a 60° angle, with a retaining lip, a rear cable channel, and a wide base for stability — printable flat with no supports. Adjust the angle or add a landscape slot if you like."

Handoff

This skill is standalone: it produces a brief, not a model. When the user wants the object built, hand the enriched brief to the cadcode skill as the design input — its concrete dimensions and feature list are exactly what cadcode needs to generate a good .py part on the first pass. If the user only asked for analysis, stop after the brief.

Guidance

• Default to popular, safe, printable choices; call out every assumption so the user can correct it in one message.
• Never invent a precise reference dimension you are unsure of — look it up or mark it as an estimate.
• Keep briefs tight. More detail than a modeler can act on is noise; aim for the handful of decisions that most change how the finished object looks and works.