cadrs

A parametric, feature-based CAD app written in Rust, with a Bevy UI and an OpenCASCADE modeling kernel. Its workflow follows Onshape's: sketch on a plane, constrain and dimension, build parts from features, put them together in assemblies, and make drawings from them.

Status: early and moving fast. cadrs works through the Onshape Learning Center's CAD Basics courses exercise by exercise, but it is not yet a finished tool. Expect rough edges, and file formats that may still change.

Features

• Sketching: lines, rectangles, circles, arcs, splines, Bézier curves, ellipses, polygons, slots, points and text. Snapping and inference to points, midpoints, centres, intersections, alignments and part edges. Geometric constraints and driving dimensions, with a least-squares solver that keeps the sketch consistent while you drag. Trim, extend, split, offset, mirror, patterns, and Use (project) of part edges.
• Part Studios: extrude, revolve, sweep, loft, fillet, chamfer, shell, draft, hole (counterbore, countersink, tapped; ISO and ANSI tables), linear and circular patterns, mirror, booleans, Transform, planes, mate connectors, thicken, fill and helix. Every feature can be edited later, and the part rebuilds.
• Assemblies: instances, fastened, revolute, slider, cylindrical, planar and other mates, a triad to move parts, mate connectors, exploded views and a bill of materials.
• Drawings: standard and projected views, sections, dimensions, annotations, callouts and BOM tables.
• More: versions and history, derived parts and linked documents, a variable table and expressions, measurement and mass properties, linear static simulation (FEA), a path-traced renderer, PCB Studio with IDF import and export, and STEP, IGES and STL import and export.
• Onshape import: bring your own Onshape documents across with their feature history instead of dead STEP geometry (tools/onshape).

From sketch to part to PCB, in one document. Watch the 90-second demo.

Building

You need a stable Rust toolchain (rustup), CMake and a C++ compiler. The first build compiles OpenCASCADE from source, which takes several minutes; later builds are incremental.

On Debian or Ubuntu, Bevy also needs these:

sudo apt install cmake g++ pkg-config libasound2-dev libudev-dev libwayland-dev libxkbcommon-dev

Then:

git clone https://github.com/rvdende/cadrs
cd cadrs
cargo run --release

Documents are stored in your platform's data folder (on Linux, ~/.local/share/cadrs/).

A Windows build can be cross-compiled from Linux with MinGW: cargo build --release --target x86_64-pc-windows-gnu.

Using it

The mouse and keys follow Onshape's: right-drag orbits, middle-drag pans, and the wheel zooms toward the cursor. Shift+S starts a sketch, Shift+E an extrude, N views normal to the sketch plane, Shift+7 gives the isometric view, and F zooms to fit. Shift+/ (or Help › Keyboard shortcuts) lists the rest.

AI assistants (MCP)

cadrs has an MCP server (Model Context Protocol), so an AI assistant on your machine (Claude Code, Claude Desktop, Cursor, …) can drive the running app: create documents, draw sketches, add and edit features, read back faces and edges, export STEP and take screenshots. Turn it on in Preferences › AI assistants (MCP); the app then serves Streamable HTTP on http://127.0.0.1:7680/mcp (loopback only; the port is a preference). Every tool call runs through the command layer, so the assistant's steps show in the feature list and undo like your own.

The repository's .mcp.json registers the server with Claude Code for this project (approve it with /mcp the first time; claude mcp list shows whether it is connected). Elsewhere, claude mcp add --transport http cadrs http://127.0.0.1:7680/mcp does the same, and other clients take the URL in their MCP settings.

The tools: create_document, open_document and get_document; add_part_studio; add_sketch (rectangles, circles, polygons, lines and arcs on a default plane, a part face or a Plane feature); extrude; add_feature, edit_feature, get_feature and delete_feature for any feature type from JSON; list_faces and list_edges for the references fillets, chamfers and sketches take; import_step and export_step; screenshot; run_scenario for scripted UI steps; and undo. crates/cadrs_mcp is the server and the tools' schemas; crates/cadrs_app/src/mcp.rs runs the calls on the app.

Development

cargo test --workspace                    # all tests
cargo clippy --workspace --all-targets    # lints
cargo run -- --headless --scenario <name> # run a scripted scenario, saving screenshots

Scenarios (scenarios/*.ron) drive the real app with synthetic input and write PNGs to target/scenarios/<name>/. The golden tests in crates/cadrs/tests/golden.rs compare them with baselines kept on your machine (tests/golden/, not committed); the first run records them, and CADRS_BLESS=1 saves new ones.

Layout

crates/cadrs_kernel/README.md describes the modeling layer: the kernel API, persistent face and edge naming, and the OpenCASCADE backend. The notes in reference/onshape/ record how Onshape behaves, which is what cadrs is measured against.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Third-party parts keep their own licenses: the Inter font is under the SIL Open Font License (assets/fonts/OFL.txt), and OpenCASCADE under the LGPL 2.1 with the OCCT exception.

Disclaimer

cadrs is an independent project. It is not affiliated with, endorsed by or sponsored by PTC or Onshape. Onshape is a trademark of PTC Inc. cadrs uses its own icons, font and branding.