jewelry-parametric-engine

name: jewelry-parametric-engine description: Strict rules and constraints for generating valid parametric jewelry geometry using CadQuery and OpenCascade.

PURPOSE

This skill defines the authoritative rules for generating parametric jewelry geometry.

All geometry produced must:

• Be manufacturable
• Be structurally valid
• Use millimeters as the only unit
• Export clean STL and GLB files
• Be manifold and watertight

This skill overrides any default geometric assumptions.

GLOBAL UNIT RULE

All dimensions are in millimeters (mm).

The system must:

• Never use inches
• Never mix units
• Never auto-scale silently

If unit uncertainty exists → default to millimeters.

JEWELRY JSON SCHEMA (AUTHORITATIVE)

All geometry must be generated from this schema:

{ "ring_radius": float, "band_width": float, "band_thickness": float, "center_stone": { "type": "round" | "oval" | "emerald" | "pear", "diameter": float, "height": float, "prongs": int }, "setting_type": "prong" | "bezel", "side_stones": [ { "type": string, "diameter": float, "count": int } ] }

No geometry should be generated without structured parameters.

PARAMETER RANGES (STRICT LIMITS)

Ring

• ring_radius: 7.0 – 12.0 mm
• band_width: 1.5 – 6.0 mm
• band_thickness: 1.5 – 3.5 mm

Center Stone

• diameter: 3.0 – 12.0 mm
• height: 40–70% of diameter
• prongs: 3–8 only

If values exceed limits → clamp safely.

PRONG CONSTRAINT RULES

Minimum prong thickness: 0.8 mm
Recommended prong thickness: 1.0–1.3 mm

Rules:

• Prongs must taper toward the tip
• Prongs must intersect stone at crown level
• Prongs must extend at least 0.5 mm above stone girdle
• Prongs must not intersect each other

Prong base must be fused to band using fillet (≥ 0.3 mm radius).

STONE SEAT DEPTH RULE

Seat depth must be:

15–25% of stone height.

Too shallow: → Stone instability

Too deep: → Light performance degradation

Auto-correct outside range.

BEZEL SETTING RULES

If setting_type == "bezel":

• Bezel wall thickness: ≥ 0.8 mm
• Bezel height: 20–30% of stone height above girdle
• Must include internal seat lip
• No sharp internal corners

SYMMETRY RULE

All rings must be symmetric across vertical center plane.

Side stones:

• Must be evenly distributed
• Must mirror across axis

No asymmetrical placement unless explicitly requested.

MANUFACTURABILITY RULES

Minimum wall thickness anywhere: 1.0 mm
Minimum structural support thickness: 0.8 mm

Disallowed:

• Floating geometry
• Self-intersections
• Zero-thickness surfaces
• Non-manifold edges
• Inverted normals

All edges joining structural components must use fillet radius ≥ 0.2 mm.

MESH EXPORT RULES

Before STL export:

• Validate solid is closed
• Remove internal faces
• Recompute normals outward
• Confirm watertight mesh
• Confirm single solid body

If invalid: → Auto-correct where possible → Otherwise reject generation

CAD GENERATION RULES

• Use parametric construction only
• No freeform sculpting
• No mesh boolean hacks
• All geometry must be built from solids
• Always maintain feature tree logic

Preferred operations:

• revolve()
• extrude()
• loft()
• fillet()
• boolean union (clean only)

ERROR HANDLING

If parameters are invalid:

1. Clamp to safe manufacturing value
2. Log correction
3. Continue generation

Never silently produce invalid geometry.

OBJECTIVE

The goal is not artistic approximation.

The goal is:

• Manufacturable
• Constraint-valid
• Parametric
• Customizable
• Cleanly exportable geometry

Accuracy > aesthetics. Structural validity > visual exaggeration.