@rulecad/model-link

Share a printable model as a link. The model is compressed into the URL's #fragment, which browsers never send to the server, so a public web page can open a private design and nothing is uploaded. It also writes STL files, and 3MF files in Bambu Studio's project layout with each part on its own filament (AMS) slot. No dependencies: it uses the browser's own CompressionStream, which Node 20+ has too.

import { fromParts, encode, decode, stl, threemf } from '@rulecad/model-link';

const model = {
  title: 'Soap tray', version: '1.0.0',
  ...fromParts([
    { name: 'tray', triangles },                                  // [[[x, y, z] ×3], …], mm, Z up
    { name: 'logo', triangles: logoTriangles, slot: 2 },          // printed in the AMS's second filament
  ]),
};
const link = `https://your-viewer.example/#m=${await encode(model)}`;

const back = await decode(link.split('#m=')[1]);
const stlBytes = stl(back);              // Uint8Array, binary STL
const zip = await threemf(back);         // Uint8Array, a .3mf (one object, two parts on slots 1 and 2)

• Precision: corners are snapped to a grid about 1/5000 of the model's size, and shared corners are stored once.
• Many copies of one shape (nine keycaps): fromShapes() stores each shape once and a transform per copy, and decode() expands them.
• Things that move: a model can carry motion: its items, the joints between them (fixed, revolute, prismatic, cylindrical, ball, path), named poses, and which item each part moves with. jointValues(motion, pose) gives every joint's values, followers included, and placeItems(motion, values) gives where each item is. The page uses these for its sliders, and cad uses the same functions to place an assembly, so both agree. The format is described at the top of the motion section in model-link.mjs.
• Safety: links are data, never code. decode() checks the format and sizes (LIMITS), refuses damaged links, and refuses links from a newer format version.
• Short links: parseHash(location.hash) also reads #s=<id>, a GitHub Gist holding the data, and fromGist(id) fetches it without signing in.
• The file says who made it: stl(m, keep, { generator }) and threemf(m, keep, { generator }); the default is rulecad.
• Reproducible files: a 3MF records the day it was made; bambu3mf(objects, { date: '2026-10-14' }) fixes it, so the same model gives the same bytes.
• bambu3mf([{ name, parts: [{ name, triangles, slot }] }]) writes a 3MF from triangles directly. It has been checked by loading the files back into Bambu Studio; other slicers read the same file as plain objects.
• zip([[name, text], …]) writes a ZIP of text files, with the platform's own compression (no library).