A Claude Code skill for building parametric, 3D-printable models that are numerically verified, not eyeballed — with build123d / OpenCascade + trimesh. Covers the verify loop (render → section → MEASURE), the OCC geometry gotchas that bite silently (winding-sets-extrude-direction, offset-on-scaled-sphere, blanket-mirror regressions), snap-fit retention math, FDM support-free printability math, and reverse-engineering a part's geometry from photos via a credit-card scale ruler + known-hole-pattern homography.
Distilled from a series of real builds — caps, covers, cradles, enclosures, and stands (worked examples linked below).
A 3D render that "looks solid" proves nothing — a hollow with no occlusion looks identical. Every constraint (fit, clearance, retention, printability) must become a falsifiable number (trimesh proximity, a true 2D section, a volume-drop assertion), not a vibe. That's the whole discipline.
git clone https://github.com/evnchn-agentic/agentic-3d-modeling.git \
~/.claude/skills/agentic-3d-modelingEach is one model built end-to-end with this discipline:
- coin-stand — shelf-edge coin-display clips with a Slant3D-style designed snap-off support (a 1.2×0.2 mm bridge line)
- connector-cap — a commercial robot's connector-panel cover, reverse-engineered from photos because no CAD exists
- gimbal-base-cover — a two-part clamshell engineered to print fully support-free
- power-board-enclosure — a tray-and-lid enclosure built before the board arrived, via homography on its mounting holes