GCodeOverlay/README.md

G-Code Overlay

Overlays a G-code toolpath on the CNC router's live camera stream, so you can reality-check a job before/while it runs and see where the tool will and won't go (e.g. for placing screws/clamps).

Pure client-side static web app — TypeScript + Vite + Canvas 2D, no backend. The G-code file is parsed locally in the browser; nothing is uploaded.

Develop

• npm install
• npm run dev — local dev server
• npm test — run the unit tests
• npm run build — type-check + production build to dist/

Deploy

Serve the built dist/ as static files. Configure via public/config.json (bundled into the build):

• streamUrl — the camera stream URL. The page shows it in an <img> element, which works directly for an MJPEG stream. If the stream is HLS or WebRTC, swap the <img id="stream"> in index.html for a <video> element and add the appropriate playback wiring (e.g. hls.js for HLS).
• calibration — produced once via the in-app Calibration panel (see below). Paste the generated JSON here to persist it for all viewers. Calibration is stored in normalized [0,1] camera-frame coordinates, so a single calibration works for every viewer regardless of screen size.
• renderDefaults — cutColor, rapidColor, lineWidth for the overlay.

Use

1. Open a local G-code file with the Open G-code button.
2. Calibrate (one-time, persisted in config.json): jog the CNC spindle to a known X/Y, enter those coordinates, then click the spindle tip in the video. Repeat for at least 10 well-spread points including the table corners (distortion is worst there). A good target is a "box + #" — lines at the thirds of each axis — giving 16 points (12 on the perimeter + 4 interior crossings); jog-and-mark each so the coordinate is exact. Pick the polynomial Degree (default 3, which compensates wide-angle barrel distortion; drop to 2 for sparse calibration), click Compute warp — the per-point error (px) flags any misclick — and paste the generated JSON into public/config.json.
3. Align the toolpath to the material: drag it to move, Shift-drag to rotate, use Set origin by clicking video, or type a numeric X/Y/rotation. Then reality-check the overlay against the live cut.

Notes

• Calibration uses a bivariate polynomial warp (machine-mm ↔ normalized image), not a plain perspective homography. A homography keeps straight lines straight, so it cannot follow the curvature a wide-angle lens introduces; the polynomial's cubic terms model that barrel distortion (which is a degree-3 effect on position), so the overlay tracks the bowed bed edges instead of drifting at the corners. The forward map draws the overlay; an independently-fit inverse map powers click-to-set-origin and dragging.
• Supported G-code: G0/G1/G2/G3 motion, G90/G91, G20/G21 units, arcs via I/J or R. Cutting moves are drawn solid, rapids dashed.