partforge (pixiteapps)

partforge is the engine behind a forge: a self-contained web app for one part, with a 3D viewer, a control panel holding just the parameters that matter, and STL, STEP and 3MF export. Describe a part to an AI agent and get a forge to share, so anyone can dial in their own version and print it. A forge is not a frozen STL: it is open-source code that renders and regenerates the model live, so the part stays editable.

The user, or an agent, writes one part definition: geometry build functions plus a parameter schema. partforge renders everything else: the 3D viewer, the control panel, the geometry workers, and the export buttons. Two geometry backends run in Web Workers, and partforge routes each part to whichever it needs: Manifold for fast preview meshes and STL and 3MF, including mesh-native fillet and chamfer, and Replicad, OpenCASCADE in WebAssembly, for exact B-rep, STEP, shell, and automatic fallback for blend geometry Manifold cannot handle. The viewer is three.js.

Because a part is just code, an agent can build it and check its own work: testing helpers measure volume and bounding box, probe geometry, detect self-overlap between sub-parts, and render the model so a multimodal agent can see what it made. A part can also declare a verify block, a manufacturing profile plus design-intent assertions, that flags problems like a too-thin wall or a part that will not fit the print bed before anyone hits export.