/render — 3D Model Skill for Claude Code

A Claude Code skill that generates 3D models from text descriptions using build123d and renders them in a browser viewer.

/render a gear with 12 teeth
/render a phone case with rounded corners
/render a torus knot

Claude writes the parametric Python code, executes it, and the model appears in your browser within seconds. Open the code panel to tweak parameters and re-render with Ctrl+Enter.

Install

# Clone into your Claude Code skills directory
git clone https://github.com/YOUR_USER/claude-render-skill.git ~/.claude/skills/render

# First run installs build123d automatically (~30s)

That's it. Type /render a box with a hole in any Claude Code session.

How it works

you: "/render a gear"
        │
        ▼
   Claude Code writes build123d Python code
        │
        ▼
   Executes → exports .glb to viewer/models/
        │
        ▼
   Three.js viewer auto-loads the model
   http://localhost:3123

The viewer starts automatically on first render. It includes:

• Three.js 3D viewport with orbit controls
• Hamburger (☰) menu in the top-right with all toolbar actions
• Code editor panel (</> code) for tweaking parameters, Ctrl+Enter to re-render
• Model gallery (▦ models) to browse previous renders
• Render mode toggle (solid / wireframe / x-ray)
• Dimension overlay (□ dims) with a bounding box and W/D/H labels
• Cross-section slice (✂ slice) — X/Y/Z axis, position slider, flip
• STEP export (⬳ STEP) for sending to a slicer or CAD tool
• Edit mode (✎ edit) — drag a box on the model, type an instruction, Claude applies it
• Auto-reload on new models

By default, render("model", shape) exports the authored build123d geometry exactly. For a quick shell/infill preview, use render("model", shape, printable=True) or render_printable("model", shape).

Region-based edits (✎)

Click ✎ edit in the menu, drag a rectangle over the part of the model you want to change, type an instruction ("make this hole bigger", "replace this grid with dots", "add a Ø3 mm hole here"), and press send. The viewer captures a screenshot with the red selection rectangle and queues it under viewer/edits/pending/.

Claude picks up queued edits in one of two ways:

• On-demand: type /render apply pending edits — Claude processes every queued edit, modifies the relevant viewer/models/<name>.py, re-runs it, and the viewer reloads.
• Hands-free: run /loop /render apply pending edits once per session. Claude re-checks the queue about every 60s until you stop the loop.

Every applied edit is echoed back in chat as 📝 Edit prompt: "..." so you can see exactly what you asked for before the change lands.

Files

├── SKILL.md           # Skill definition + build123d API reference
├── setup.sh           # One-time bootstrap (creates .venv, installs build123d)
├── viewer/
│   ├── index.html     # Three.js viewer, hamburger menu, edit/slice tools
│   ├── serve.py       # Local HTTP server (port 3123) + /api/edit endpoint
│   ├── render.py      # render() helper: exports .glb + .step + .stl and
│   │                  # saves a copy of the model script next to them
│   ├── models/        # Generated .glb / .step files + scripts
│   └── edits/
│       ├── pending/   # Queued ✎ edits waiting for Claude
│       └── processed/ # Applied edits (kept for history)
└── README.md

Requirements

• Python 3.10+
• Claude Code

No other Python dependencies: setup.sh creates an isolated venv and installs everything. The viewer page itself loads three.js from jsdelivr, so the first load needs network access.

Manual usage

You can also use the viewer standalone without Claude Code:

# Start the viewer
~/.claude/skills/render/.venv/bin/python3 ~/.claude/skills/render/viewer/serve.py

# Write a script
cat > ~/.claude/skills/render/viewer/models/script.py << 'EOF'
from build123d import *
from viewer.render import render

box = Box(10, 10, 10) - Cylinder(4, 12)
box.color = Color("steelblue")
render("model", box)
EOF

# Run it
PYTHONPATH=~/.claude/skills/render ~/.claude/skills/render/.venv/bin/python3 ~/.claude/skills/render/viewer/models/script.py