popkern

popkern is an open-source parametric boundary-representation (BRep) CAD kernel written in Rust, developed by the popkern-dev organization. Parts are defined with short Rhai scripts and can be built in the browser through popkern live or on a local machine. The project describes itself as early and experimental.

What It Is

popkern is a geometry engine for solid CAD: the math that builds and edits precise solid models, plus accessible ways to use it. Users write scripts instead of drawing in a traditional CAD interface, and the project says its algorithms are based on published CAGD research. Outputs include .pkn documents, STEP files, STL meshes for slicers, rendered images and films.

How Parts Are Built

Every part is a Rhai script. Larger parts are organized as projects: a folder of numbered migration scripts, each continuing from the previous one, similar to database migrations. A later step can change an earlier feature, and a history scrubber replays the part one step at a time. Projects are git friendly. The popkern build command converts a project into a .pkn or STEP file, and popkern run, popkern render and popkern film handle STEP/STL export, images and turntable or scripted films from the command line.

Modeling Capabilities

The README lists booleans on exact solids that either succeed completely or fail cleanly, fillets and chamfers with smooth corner patches, sweeps, revolves, lofts, shelling, offsets, and sketches with a 2D constraint solver. It also lists watertight tessellation, STEP import and export, a full feature tree with rollback, suppression, reordering and undo, assemblies, threads, fasteners, hinges, and structural and thermal simulation inside popkern live.

Agent and MCP Workflow

popkern serve runs a local server on your projects folder and also exposes an MCP server, so an AI agent can list, edit, build and export the same projects. The project says popkern's code is written by AI agents under human direction, and that changes must pass thousands of automated tests and kernel validation, with results cross-checked against OpenCASCADE where comparable.

Current Status and Licensing

The README states this is experimental software: complex parts can be slow, and some shapes still fail, such as certain hole arrangements and fillets meeting at awkward corners. The kernel is AGPL-3.0-only with an additional permission covering user scripts and produced geometry, so scripts, models and STEP files belong to the user.