Foxtrot

Foxtrot is a fast viewer for STEP files, a standard interchange format for mechanical CAD. It is an experimental project built from the ground up, including new libraries for parsing and triangulation.

This repository includes a simple native GUI:

(demo model source)

In addition, the same code can run in a browser (click to see the demo):

(demo model source)

For more background on the project, check out this writeup by one of the main authors.

Quick start

(Prerequisite: install Rust and Cargo, and clone this repository)

cargo run --release -- examples/cube_hole.step

WebAssembly demo

(Prerequisite: install wasm-pack and clone this repository)

cd wasm
wasm-pack build --target no-modules
python3 -m http.server --directory deploy # or the simple server of your choice

Then, open the local server's URL (typically 127.0.0.1:8000) and select a sample file from the list.

Subsystems

• cdt: Constrained Delaunay triangulation (standalone)
• express: Parser for EXPRESS schemas files and a matching code generation system
• experiments: Experiments with trait systems (unused)
• step: Auto-generated STEP file parser. This take a very long time to compile, so it is isolated into this crate.
• triangulate: Converts a file loaded by step into a triangle mesh, using cdt as its core
• nurbs: A handful of NURBS / B-spline algorithms used by triangulate
• gui: GUI for rendering STEP files, using WebGPU
• wasm: Scaffolding to run in the browser using WebAssembly

Code generation

step/src/ap214.rs is automatically generated from 10303-214e3-aim-long.exp, which is available via CVS here (check out the APs folder).

To regenerate, run

cargo run --release --example gen_exp -- path/to/APs/10303-214e3-aim-long.exp step/src/ap214.rs

Regression testing

The test_assets/ directory contains STEP files used for tessellation regression testing. To add components from a KiCad board:

pip install zstandard  # one-time dependency
python3 scripts/ingest_kicad_pcb.py path/to/layout.kicad_pcb

This extracts embedded 3D models, deduplicates them into test_assets/, and regenerates test_assets/baseline.json. You can pass multiple .kicad_pcb files at once. After running, commit the new assets and updated baseline.

To run the regression suite against the baseline:

cargo run --release --example regression_test -- --compare test_assets/baseline.json

License

© 2021 Formlabs

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.

Contribution

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

Disclaimer

Foxtrot is a proof-of-concept demo, not an industrial-strength CAD kernel. It may not work for your models! Even in the screenshots above, there are a handful of surfaces that it fails to triangulate; look in the console for details.

This isn't an official Formlabs project (experimental or otherwise), it is just code that happens to be owned by Formlabs.

No one at Formlabs is paid to maintain this, so set your expectations for support accordingly.

References

STEP Integrated Definitions